FVEAA Forums
Member EV Projects => Member Vehicles => Topic started by: john.emde on May 07, 2010, 12:18:44 PM
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Todd
Now that you have had a little time to test the difference between your 8 volt flooded lead acid batteries and your new LiFePO4 battery pack with Mini BMS, inquiring minds would like to know all the details. Besides being cleaner. Range? Charging ability? What is the difference in weight and can you notice any handling and performance difference? Would you/will you do it again?
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He tells me car requires less power due to reduced weight and has more power due to voltage more steady under load. Mini BMS as I understand is any cell too low sounds a buzzer or too high initiates charger shutdown sequence. Now Bug has unrelated mechanical problems.
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Thank you Howard - your assessment is generally correct.
As noted in the FVEAA message board, the bug has encountered mechanical coupling problems which we cannot fix until early next week. What this means for the committed 'very little or no gas usage' green guy is a lot of walking or riding the bicycle. Oh well, I could use the exercise.
So - more specifics on the Lithium pack. I've done some longer test runs in between shorter daily use. Below I note the test runs, and after all that show the PbA comparison.
Test run #1: approximately 27 miles (9 miles then 18 miles over 2 days) - to get the bug home from Pioneer conversions. No problems. Local surface roads, rough weather (rain/cold) in early April. BMS indicators hooked up, but not the buzzer. No red lights showing (red light on BMS = BAD - either over or under voltage). Energy back into the pack: approximately 9-10 kWh. Energy use - about 350 wH/mile.
Test run#2: 22 miles continual, mixed local surface and highway. Energy - 7kWh back into the pack. BMS hooked up - warning was a cheap Radio Shack 12V Fan! No problems. Energy - 330 wH/mile.
Test run #3: 32 miles (I see a pattern here!) - mixed surface roads and highway. Energy - 11kWh; 350 wh/mile. Replaced the 12V warning fan for the BMS with a buzzer.
More to follow -
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(more)
Test run #4: 42 miles (more pattern). Energy back - 14 kWh, about 340 wh/mile. Mixed hwy and surface.
Test run #5: 54 miles (hey I broke the pattern!) - 16 kWh, only 291 wh/mile! I had the wind at my back. Mostly hwy driving at 55-60mph. Car runs very smoothly at that speed. No warnings for low voltage whatsoever.
The theoretical pack value is about 24 kWh - so with 55 miles I used about 2/3 of the pack, meaning I would have a theoretical range of 83 miles! Of course, you don't want to push your batts to the limit, and you want to keep about 20%-90% SOC. So, maybe the range limitation is more like 70 miles or so.
It is important to note that I don't have an SOC at all. When I find one out there that I'm comfortable with, I will get it (I had the PakTrackr and that sucked - it didn't measure real SOC or amp usage worth a horse's ass).
Weight - I've dropped about 500 lbs. I need to get the car weighed - when it's back on the road.
The PbA system had a maximum range of 43 miles, when the T-875 (8V) Trojans were working good. The good period lasted about 5,000 miles or 1 year for me. After that, they went downhill in a hurry. I had a devil of a time with them this winter, and had to replace 5 of them just to keep the car running.
more to follow
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The PbA batts (18 of them) cost about $2,200 originally, and to replace 5 of them (I actually replaced 6 - 1 was covered under warranty) cost me about $800. So, total $3,000 into a pack that lasted me about 7,000 miles. Waste of $$! Very high per-mile cost. And, keep in mind, the last 2,000 of those miles were a major fight to keep them charged. Towards the end, I was able to do about 25 miles on a charge at best. I've heard of others having better experience (15k miles) with the T-890 batteries, so maybe I just had bad luck. PbA sucks nuts.
Another thing is that the PbA system would sag under acceleration loads, but you could take 800 amps out of the batteries. For the LiFePo, I haven't taken more than about 450 amps out of them, so acceleration is slower (you can't do any jack-rabbit starts). So that's the only drawback I've seen. And, to take care of the LiFePo (batts are 160 amp-hours), you don't want to draw more than 450amps for more than a couple seconds anyway, or else you will ruin them.
The PbA was a 144V system (18 8V in series). Top resting voltage was about 152 volts. With sag, even fully charged, they dropped below 120V often (momentarily). After about 10 miles, even when new, they would sag under lower current draws (but not bad), and you could feel them starting to run out of energy after about 20 miles, even when new. Later, when older, you would feel this after 10 miles. So, you could get 40 miles on a charge, but that's with no hwy, no heater, babying the accelerator, and even after all that you essentially limp for the last 10 miles. No fun. Again, PbA bites dingle-berries.
more to follow
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To summarize PbA, weight was about 1,100 lbs, I have heavy-duty custom springs in the back, but the bug still creaked like an 80 year old on a bike ride. The real practical range was close to about 30 miles when new if you wanted an enjoyable ride and much less when old.
Now comes along LiFePo. I have 48 LiFePo 160 aH in series. Resting voltage rated at 154V, true resting voltage at about 160V. Here's the kicker - NO SAG! With heavy draw on acceleration - maybe it drops to 150V. After 10 miles cruising down the road at 40mph - 150+ volts. After 20 miles - same. After 30 miles - same. After 40 miles - same. After 50 miles - same! You get the picture. No sag. Even with acceleration, I have not seen my volt meter needle drop below 144V EVER. These babies are like the Energizer bunny on Steroids. They are truly a technical marvel to use and drive with.
I won't be doing any hot-rodding due to the current draw limitations (you want these to last 100k miles if you can).
So I charge every night, and the BMS shuts the charger down (I have a Manzanita PFC-20) - actually, it goes into low current (3 amps or less) charging time-out for about 1/2 hour. This happens as soon as the first battery hits about 3.65 V. It will throw the red light. By the time the charger winds down, about 1/3 or so of the batts throw red lights - and upon measure, none are higher than 3.7V. For comparison, the maximum voltage you want to go is 4.2V and that is only on the 1st time to balance the batts.
More to follow.
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The under-voltage warning is through the BMS - the buzzer. If any battery goes below 2.6V, it throws a signal to the BMS control unit and sounds the buzzer. If that happens, you limp home at about 10mph or disconnect and bypass the offending battery. You will get a red light on the cell module if this happens (normal operation - green light).
The BMS consists of cell modules on each cell, the control unit, wiring to series string them altogether, and wires that go to the RJ input for the charger - Reg Bus pins #1 and #2. Even without the regbus, the charger would time out at about 172V (max - 3.6 V per battery).
The BMS costs about $650.
The charger is a Manzanita Micro - PFC 20 - I got it used for $1,275. New is about $2,000. You could use a Zivan, but would need to rig up a BMS to throw a signal if any battery hit 3.6V, to a relay contactor, which would then turn off the Zivan. The charger should be constant current - constant voltage, which I think the Manzanita and the Zivans are.
Batteries - about $10,300 for 50 of them. So, I have 2 extra if anyone wants to play and test.
more to follow
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Total system cost: $12,225, including charger. For comparison, the PbA cost $3,000 (noted earlier) + $1,000 for the Zivan HV charger, or about $4,000.
Without charger, system costs are about $11,000 for LiFePo and $3,000 for PbA. Oh another thing - you need to water PbA every month (pain), and you get HCL everywhere - burns holes in the car's carpet, your clothes, rags, gloves, you name it.
In one incident my PbA batts were so bad, they couldn't get near the max voltage that they used to, and the Manzanita happily pumped 15amps into the batts for about 12 hours, not cutting back because it wasn't approaching max voltage. I had battery acid water vapor that had condensed EVERYWHERE in the car - it took hours to clean up. I litterally ruined 3 pair of heavy-duty leather work gloves in the process. They had holes in them the next week (even after washing) the size of Manhattan. Never again with the lead!
So back to costs. The LiFePo batts are 3.6 x the cost of PbA. What do you get for your extra $$?
- longer range - 70+ real fun miles compared to 25 ok miles
longer life (assuming you take care of them) - 100k miles compared to my dismal 7k miles for PbA. Time will tell if this holds true.
more to follow
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Conclusion (yeah!)
So, the early going is that I'm totally happy with LiFePo. I no longer have range anxiety, at least for the wide swath of land we call the Chicago metro area. To all my friends and back, without needing an opportunity charge.
Handling - car weighs 500 lbs less - handles much better! Less squeaking in the back - but still a little, since I have about 400 lbs of LiFePo back there, still keeping the heavy duty springs.
Disadvantage over lead? Cost! However, COSTS FOR LIFEPO HAVE BEEN COMING DOWN AND WILL CONTINUE TO DO SO. There are thousands of large batteries that are shipped to the US each month for hobbyist and other industrial use. The world of Lithium is getting more competitive yet is still lucrative. I look forward to future costs decreasing, so more of my buds can do LiFePo (right Howard?)
Disadvantage over a new Nissan Leaf? Our cars still break down (my recent experience). I now have to install a permanent air cooling system for the motor, and may have to get it cleaned up or re-furbished (we'll see what damage 2 winters have done to it!)
Advantages over lead? Numerous! I've cited many reasons here. The biggest one - the LiFePo electric car acts very much like a gas car in what you would expect in performance and range, at least for daily and local use. It is a much better car to drive. Lithium batteries are the real deal!
SO, GO LITHIUM AND GO EVS!
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Great Job Todd!!! very exciting news.... have you recalibrated your controller to limit the current? Good luck with the coupler repair.
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No, not yet. But that's forthcoming.
By the way, the car used to get about 400 wH/mile. So efficiency has improved a lot.
Update: Jim Dawson had the motor and trans out today (thank you Jim!). The problem is the clutch disk - it broke and all the little spring parts disintegrated. Jim ordered a new one and will strengthen it via a MIG welder. The part will come in by Monday.
I'm trying to get an adaptor so that I can have the output airflow from the squirrel cage blower go to an input that will go to the motor. So, I need to rig up an adaptor for the connections. I went to Home Depot and bought a few things to try this.
With the increased range, John Emde recommends that we cool the motor at all times via a constant airflow.
I'll be back from a biz trip late Tuesday night and will try to pick up the car Wed. Hopefully it will get back on the road. Jim looked at the motor and it's not too bad (not too much debris in there) - so he blew out all the carbon, etc.
I'll keep everyone updated with further developments.
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More updates -
Jim did a good job getting the new clutch disk in. He also had it welded for strength. A special thanks to George Gladic for taking me out to Jim's garage last Saturday to see the work, and to Jim for doing the work.
He also wired the reverse lights (I had not done that), and mounted the band on the end of the WarP! 9" motor.
I was able to pick up the car on Wed. and drive it home. About 1/2 way there (8 miles), I stopped at a gas station (of all places) to check the motor - since I didn't have the blower cooler (squirrel cage) fan installed yet. The motor was ok - it was only about 52 degreees F that day. Off on my merry way, but alas - main contactor won't engage! Oh no - what now?
Turns out that a small wire to the Hairball for 12V in was loose at a fuse. So, I wiggled the fuse a bit until contact was made, and walla - everything worked and I got home.
I installed the squirrel cage blower and had rigged up an adaptor to go from the square output of the blower to the 2" input (hose) to the motor band. I took out the temp switch so that the blower is running when the ignition key is on.
Continued...
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The new blower works nicely, albeit may be too much cooling - I notice when the motor isn't running, the blower has a tough time trying to push stagnant air, so a lot leaks out at the junction. I haven't yet seen it in action when the motor is running.
Anyway, with the new band that seals up the intake air of the motor (except the tube opening), I shouldn't need to worry any longer about nasty salt, water, etc. getting into the motor - so I can ride all winter long!
One of the drawbacks with the blower is that there is now soo much crammed under my hood, that the intake hose butts up against some small yet important wires that go to the Hairball for the Zilla Controller. This could cause a problem (no starting), so I'm thinking of re-positioning some of the components. I may go to Jim's shop again tomorrow to get some advice on this. As an example, I have about 12 relays for all sorts of things, and it would make sense to consolidate all these into one space.
Thanks to Rich Carroll and John Emde for the motor band and their advice - it seems to be a good product and I look forward to many hours of motor-cooled EV driving with the Lithium.
More to follow -
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Another problem sprang up - on my way to the train station to work on Thursday am, the buzzer went off - the one to warn about a low battery - man is that sucker loud! So I was close to home, I gingerly went back home and disconnected the main pack and 12V battery and my wife drove me to the train station. After work that night, I checked all the batteries, even under load (with the heater on), and all were within 0.01V of each other, and all on, and all checked out ok (you gotta love the Lithium!)
The culprit was the BMS - the 'loop' was disconnected at the last battery when I was installing the blower accidentally. Re-connection was a cinch, I tightened the female spade connector, and all was well. So, I chared up the car and she was ready for more fun and games.
Tonight my wife, a friend of the family, and myself went out to dinner in Oak Brook, via Elec Bug - no problems, smooth ride, no worries about range (about a 20 mi. ride; I also went about 10 mi. earlier today for lunch without charging). Our friend's comment was that the car drove like a normal car. What a relief it is to not have to worry about range!
So, I still need to continue on with my distance trials. The last one was 1-1/2 weeks ago (before the clutch disk problem), and I'm eager to try again. Last big run was 55 miles. I would like to try 65 - the last 5 mi. or so close to home. I'll let everyone know how it goes, and at some point I'll post pictures.
Happy EV trails!
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And now, for a new update -
Yesterday, I drove 69 miles in the Elec Bug. About 1/3 highway, over 2 separate trips. The batteries were fine at the end of the trip, and they were all about 3.25V - within about 0.02 V of each other. How's that for consistency!
The best news is enery use - just over 20kWh back into the pack. So, that works out to 293wH/mi.! The best ever.
Again, I don't have an SOC yet, but with the pack at a theoretical 25kWh, that means I may be able to get 80 miles or so on a charge. Sounds good to me!
LiFePo rocks!!!
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Sweeeeeeeeeeeeeeeeeeeeet Todd! i'm getting the urge to "go lithium" now :-) My t-125 pack is 4 years old now and starting to tire, so i'm considering a change in chemistry. Thanks for all the detailed information about your experiences!!
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My lead acid are approaching 2yrs old (sept) and I am also getting itchy my self. Keep posting updates when you have time.
tks mac
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More updates -
Yesterday I went to a client meeting, then back home to charge. Then to Lincoln Park for dinner and back. Total miles = 90! in one day! Total energy = 29kWh. Good mileage!
Today I went to a doc appt in Hoffman Estates and back - total miles = 64. Total energy = 17kWh. Great mileage!
Total for 2 days = 154 miles. A major record for any of my converted EVs. Total energy = 46kWh. Total efficiency = about 300Wh/mile. Good stuff!
It was mostly highway driving. I go 55-60mph. The challenge is that if traffic is light, everyone else is going 70mph. They pass me like I'm going backwards and give me dirty looks. I previously didn't drive much on the hghwy with the EVs, so I'll have to get used to it. Oh well - at least my fuel doesn't result in an oil spill!
More as time goes on -
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I'm guessing you are charging with 220v for this much driving, I read the chargers give the option either 110 or 220v depending on where you might be recharging. Whats the voltage of your sys, mine is 96v or 16 6 volt golf cart batts. The supplier talks about going over voltage due to size of basic unit (12v +/-) is your supplier Elite Power ?
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Robert -
Yes, I have a 220V outlet in the garage. My charger is a Manzanita Micro PFC-20. So, I'm charging at Level II. This charger is cabable of either 110V or 220V AC input. It's pretty sweet.
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side question, my motor is exposed under car, I avoid driving in the rain. One time it did act strange... Should I not drive in the rain
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You need to get a belly pan that will shield the motor from moisture. It's pretty easy to attach one - aluminum sheet metal cut to shape and bolted with 1/4" self-tap sheet metal screws to the frame will do the trick.
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Today I drove 52.4 miles, over 2 trips. Almost all highway driving, with an opportunity charge in between at home (even though it wasn't necessary). Total energy = 16kWh. Efficiency = 305Wh/mile.
So efficiency is ranging from about 290-350Wh/mile, and most runs are closer to 300Wh/mile.
With all the driving I'm doing, I should get to 1,000 miles soon. I have between 600-700 miles on these batteries so far.
Tomorrow will be another early morning run to Hoffman Estates for family planning. All highway and about 60 miles. It's nice to be able to rely on this car!
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More fun updates -
Yesterday, ran 64 miles, all hwy, and used 19kWh. So pretty good efficiency again.
However, it was raining in the morning. When we got back home, the car was soaking (outside). I plugged in the charger and turned it on, and went to close the trunk, and got a nasty shock! So, I turned off the charger, and unplugged the main breaker (Anderson connector) so the pack is totally isolated. Turned the charger back on, and POP! Something blew inside it. Current continued to flow out - very odd. So I turned off the charger to see what was wrong.
I disconnected the charger and opened it up - one of the 3 main capacitors blew like a cherry bomb! I called Manzanita and spoke with Rich Rudman. He mentioned that the capacitor quality wasn't that great with the older models (this charger is almost 8 years old). So, I shipped it UPS today back to him, and he will replace the capacitors and send it back for a modest fee. The good news is the capacitor replacements will be upgrades.
Rich is doing well - they just moved into a bigger shop/office, and he has a staff of 6 including a secretary. They can crank chargers out within 2-3 weeks from the order.
I fortunately have a backup Zivan charger that was adjusted to 174V (top voltage), and this voltage which works well for my LiFePos. I charged the pack up. It takes more time (only 16 amps out of the Zivan vs. 20 amps from the Manzanita), but works ok. It will be my backup until the Manzanita is back. The BMS 'warning' system still seems to work ok.
The original isolation problem has to do with the DC-DC converter. It seems to have capacitors in there. Anyway, not sure what can be done, but it does create some voltage leakage from the main pack because it is 'always on'. I'll have to see if anything can be done about this.
That's all for today -
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Yesterday I had my first and hopefully last panic about the LiFePo batteries. Since the Manzanita is being repaired, I've been using the Zivan. It was adjusted to 174V top-off, which was about where the Manzanita was. I had manually watched it a couple times. A number of regs went red (3.65V), but none triggered the alarm (3.8V). There charger went into shutdown mode after CC/CV just fine. So I drove to get our dinner (wife was still recuperating and I was in charge of 'cooking') and came back I knew I didn't have a full charge when I left, and after about 7 more miles, figured about a 2 hour total charge to top off the batts (the Zivan is about 20% slower than the Manzanita).
I went inside, ate dinner, and took a nap. After a total of about 1 hr and 20 min, I went out to check on the charger. As soon as I approached the garage I heard the dreaded sound - the alarm was going off! I was on the phone with a friend and had to hang up ASAP. I ran to the garage and threw open the door. 'I'll call you back Jesse - I have an emergency!" - and hung up right away. I can't remember all the details but I think the Zivan was at the CV phase where you get the blinking red light (CC phase is solid red). Almost every battery in the back box was showing red lights and the alarm was ringing all the way to China! Oh C#%p! What happened?
I immediately unplugged the charger in no time flat, before bothering to check the current output from it. If it was blinking red, (which I cannot recall with 100% accuracy), it would be pumping out about 5 amps. The next 10 mins. were a blur - like a bad car wreck.
Continued...
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I think the alarm went off within 1-2 mins, but again I cannot be sure. I got out a spot light and whipped out the meter to check where the batts were. Frantically testing the voltage, the highest I saw was 3.85V. Mind you, this was about 3 or 4 mins. after unplugging the Zivan. I tested others - 3.7V, 3.6V, 3.8V, 3.75V, etc. All of these were throwing red lights. But, one by one, the red lights start disappearing, which I took as a good sign. I felt the batteries - they were not warm (about room temp which was 80F). The regs on the other hand have small ceramic heat sinks and some of them were very hot. They were apparently disapating as much energy as possible. I didn't even know the regs could do this. Within 10 mins. or so (again, can't recall exactly), all the red lights were gone and the batts were settling down.
I removed the Zivan from the car and looked at the peak voltage setting switch - it was set on the next higher setting - about 194V! This would give 4.08V per batt, if they were all perfectly balanced (which of course they are not). Whoa!! How the heck did that happen? No wonder the alarm set off. I used a small screwdriver to dial it back down to 174V, which it did very easily - too easily! So that was the culprit - when the charger was in the back of the car, it was bouncing around when I got dinner. The peak voltage setting is a bit loose, and it must have jarred this to the next highest setting. Cripe! From now on NO CHARGERS IN THE CAR WHEN DRIVING!
Continued...
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After things cooled down a bit I went into the house and told my wife. She was worried and not happy about it. If these batts go bad, I cannot replace them.
So I decided to take a short trip to see if everything still worked. On the road near the house, I called a friend and asked what he thought. He was mentioning that heat build up can kill the batts, so advised that I head back home and let things cool for the night, which I did - but not after putting about 6 mi. on the car. No problems driving, and afterwards all batts were normal temp and a reasonable voltage (3.335V).
I called another FVEAA friend and asked what he thought about a warning system - ideally some way for me to hear the alarm if I'm in the house. Suggestion - get a baby monitor and put it near the back battery box so you can watch them and hear the alarm! Great idea! He even offered to loan me a spare one that he had.
No charging that night - I was too paranoid!
Back in the house, time to do some research. First the BMS - http://www.cleanpowerauto.com/MiniBMS.html to the website I go and study the manual. It's been updated in the short time since I originally installed it (about 1-1/2 months). Since I had the Manzanita, I had concentrated on it's wiring to the BMS. But there's a nice YouTube video of Dimitri (owner) showing how the BMS works with a Zivan.
Continued...
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So - watching the video and looking at the diagrams - What's this?? There is a way to hook up a relay to turn off the Zivan when any 1 cell hits 3.8V? This is the safety feature I didn't have! I only had the top off charger voltage, and that failed because it was jarred to a higher value. Silly me!
I spoke with Dimitri today and ordered the solid state AC relay (he sells them). 2 day shipped UPS from FL - more in shipping than the cost of the relay! But no charging until that baby is here and installed - which should be late Saturday.
His advice was that if the batts were damaged, heat doesn't do it - overcharging causes swelling. I need to look for gaps between the batteries. If they swelled, then they are damaged and have lost capacity.
So back home tonight I inspect - no noticable gaps except for 2 junctions (max. total 4 batts) - but there's nothing blatantly obvious - this could have been there before. Per another friend's advice, the only way to know for sure is to drive the car and charge it up - over time, to make sure it keeps and holds a charge and can perform.
As noted above, I won't charge until Saturday, but I decided to drive around to see if the batts hold a charge. Tonight was ideal driving weather.
Continued...
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I stayed off the highway - too risky for this test. I drove until I had 38 miles (6 were from last night). Dropped into my garage and tested the batts - no red lights! All within 0.012V of each other - 3.3301V-3.3313V. Not bad! So off to more testing I did. Another 18 miles, easy driving (no big acceleration). I'm amazed at how little energy is used to keep the car going at 40mph - sometimes < 50 amps!
So, total distance = 56 miles. Back home, checked the batts again, and they were all at 3.29V - all within 0.005V of each other! How's that for balanced?
Early conclusion - I didn't seem to damage the batts. Thanks be to the Lord on High!
Of course, time will tell - I need to charge the batts again (this time with safety shut off relay), and charge and discharge the car multiple times. Only over a long period will I be able to tell if any damage has been done.
So lesson learned - make absolutely sure about the BMS operation and safety shut-offs of the charger before charging! These batts don't forgive (I've been told).
Continued..
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I got the call from Manzanita today - repair bill was about $500. Yikes! New capacitors (ultra caps) and a new control board - Rich wasn't happy with the old board (this charger is about 8 years old!). So, I should get it back in about a week.
I'll keep everyone posted to let you know how the batts continue to perform.
Thanks to everyone who helped out with good advice - Rich Carroll, Jim Dawson, Ted Lowe, and Ken Simmermon.
Long live EVs and take care of those Lithiums!!!!
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Can you tell what companies supply these batts. The one I know of is elite power
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I got the call from Manzanita today - repair bill was about $500. Yikes! New capacitors (ultra caps) and a new control board - Rich wasn't happy with the old board (this charger is about 8 years old!). So, I should get it back in about a week.
I'll keep everyone posted to let you know how the batts continue to perform.
Thanks to everyone who helped out with good advice - Rich Carroll, Jim Dawson, Ted Lowe, and Ken Simmermon.
Long live EVs and take care of those Lithiums!!!!
Yes, yikes! This isn't a repair, it's an upgrade! i can see from his point of view... he'd rather not support his older designs. Ultracaps in an SMPS ? Perhaps to use fewer capacitors....???
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The regs on the other hand have small ceramic heat sinks and some of them were very hot. They were apparently disapating as much energy as possible. I didn't even know the regs could do this.
i looked at the miniBMS from the link you sent (http://www.cleanpowerauto.com/MiniBMS.html (http://www.cleanpowerauto.com/MiniBMS.html)). The ceramic items are power resistors, not heat sinks. Each miniBMS can only shunt up to 1 amp. i think their basic concept is to handle an overcharging event for short periods of time until the auto-shutoff or (human responding to the ERROR buzzer) can react. If 18amps of charging current is going in, a 1 amp diversion won't help much for long. It's a bit like a front bumper in a slow speed accident. The auto-shutoff (as you mentioned above) is the airbag though! Best wishes and thanks for keeping us posted on your bleeding-edge leadership!
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More on MiniBMS shunt regulator. Here's a picture of it:
(http://www.cleanpowerauto.com/images/MiniBMS%20Module%20Small.jpg)
This is a very simple circuit. When the battery voltage is too high, it diverts power past the battery. It's basic parts include: a power transistor (black rectangle lower middle), power resistor (big cream colored ceramic rectangle on left), voltage comparator (black rectangle in middle center), a shunt-regulator (small black rectangle on the top middle), and a diode (can't tell from too small of picture). i suspect the schematic/theory is very similar to this:
http://www.solorb.com/elect/solarcirc/shuntreg2/ (http://www.solorb.com/elect/solarcirc/shuntreg2/)
i'm curious how much power the regs consume while in normal charging mode? Do any of the components get warm in "green light" mode ? Thankx!
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Rob -
Elite Power is where I got the LiFePo batteries from.
Ted - during charging, the CMS modules are drawing about 0.7 amps. At 3.3-3.4V during most of the charging, that's 2.3-2.4 watts of power draw. Very minimal.
I do not notice any components getting warm during the 'green' mode - but I haven't checked very carefully.
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So I charged the batts up tonight while manually watching them. I got the relay (will install tomorrow) so the fail-safe will be implemented.
On my 56.1 mi. run yesterday, I put 17kWh back into the pack for a full charge. Total efficiency = 303Wh/mi. So - 2 good things: [1] the efficiency hasn't changed; and [2] the pack charged up again and seems to be holding a charge, so no immediate damage to the batts from the potential over-charge the other day.
I was manually watching the charger and it went into CV mode (wind-down) at 170V. Then I checked the current meter, and it went down to about 7 amps. I went inside for a few moments - when I came out again - Walla! Another buzzer warning! WTF?? So soon?
It must have just gone off - I saw the total pack voltage - 181V - how did it climb from 170V so quickly? Anyway, the charger was in the 'yellow' phase and the current wasn't very much (about 5-6 amps), so I unplugged it. The buzzer went off < 1 min., which is a good sign. All the red lights disappeared in about 3-4 min. (good sign). None of the resistors were warm (good sign). So I've learned more about the charger - even with the lower voltage setting, the shut-down feature will pump these batts up so that at least some of them will hit 3.8V (triggers the buzzer). That is why the sure-fire way to avoid overcharging with the Zivan is to get the relay - any batt hits 3.8V and Bammo! Off goes the charger.
I believe Ted - the relay is more like an airbag.
One other thing - some of my batt clusters shift around a bit - and the bolts were a bit loose! I inspected and tightened all of them - this is routine maintenance that I will have to do.
That's all for tonight!
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Today I installed the solid-state AC relay. I tested it and it works well. Now my Zivan backup charger is complete. There are a few things about this that make it less than ideal (compared to the Manzanita):
[1] The BMS kicks off the Zivan (via the relay) when the first batt reaches about 3.86V. That's a little too high for me - I'll have to see if it can be dialed-down.
[2] About 2/3 of the batts are throwing red lights by this time (over 3.65V).
[3] The current in the CV phase is about 4 amps - a bit too high for my taste.
[4] I have heard that if the solid-state relay fails, it does so in the open position - that's a headache you don't want (although there is another semi-safety feature that the CV phase starts at about 174V so about 3.6V for each batt; but it can creep up to 185 or 190V - hence the problem I had earlier).
For the Manzanita, no batt reaches 3.8V - the BMS signals the regbus and the charger goes into shutdown mode sooner - only a handful of regs are throwing the red lights. Also, the CV phase in the Manzanita pumps out 1-2 amps - much more palatable if you want to preserve the batteries.
I drove the car about 18 miles tonight to Sonic Drive In for Sundaes. No problems, and I think I'll let the batts rest - so no charging tonight. I would like to start doing more test runs to see how far my true range is.
That's all for tonight!
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Hey Todd, Is the Zivan specially programmed for using with LifePo bats? If not, it won't treat them well at all. For my Zivan NG3 configured for flooded lead batteries (120v):
Solid red LED = bulk = constant current until voltage hits a high mark (current here is about 18a)
Blinking red = consolidation = constant voltage at high mark while current decays to a lower value
Solid yellow = equalization = raise voltage very high with very little current (this is only needed for flooded bats, and when they emit their gases/bubble).
After a fairly long drive, bulk runs for 2-4 hours, consolidation for 10's of minutes and equalization for an 1-2 hours.
Hope your charger isn't trying to equalize your LifePo's!
i didn't quite get your meaning of the current consumed by the regs. Do you have a reg on each battery and a single CMS ? i'm curious about the efficiency of the whole charge using the shunt reg method.
The shunt reg method is simple and cheap, but i see two issues that are non-starters for my adoption: 1) diverted power is wasted as heat, and 2) provides only limited balancing.
However, i may be missing the function of your CMS.
Issue 2 is certainly the biggest concern as the bats age and some reach the 'auto shutdown mode' much sooner than others. The preferred (balancing) approach is to continue charging until the last battery hits the shutdown point (need to send less current to the already 'full' batteries in the string). This either requires regs that can handle much higher current or separate charge wires to each battery.
To learn more about balancing, i'm running a small experiment with a 4 series pack of A123 cells that power my portable ipod dock boombox. i bought a DeWalt 36V pack with 10 A123 cells. i disassembled it and extracted the cells for other uses (like this experiment). i reassembled a 4 series pack and added a "balancing harness" connected to each intermediate connection point (5 wires for 4 cells). i bought the Thunder AC6 Dual Power charger (used by R/C hobbyists) which has LifePo and balancing algorithms. Once you plug in the "balancing harness" into the AC6, you can see the voltage of each cell through-out the charging process. If you configure the balancing option, it will back off on the more fully charged cells while the others come up. When it's done, each cell is typically within 2/100's of a volt of each other (3.59-3.61). i've only lightly cycled the experimental pack about 5 times so far, but look forward to more and deeper cycles to see how the balancing is affected over time.
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Ted -
From what you write, I can tell that you are a lot more knowledgable about this. However, I'll try to answer some of your questions as best I can:
[1] The Zivan is not specifically programmed for LiFePo. However, it is my understanding that the creator of BMS uses the same charger.
[2] The charger shuts off when the first batt hits 3.85V (not the last).
[3] By that time, about 2/3 of the regs are showing red lights (at least 3.65V, but they are all under 3.85V). I think the charger does CC/CV (I've measured this).
It is for reasons #2 and #3 above that I think the manzanita is better - it will shut down when the first cell hits 3.65V - thereby offering more protection against overcharge. However, 1-1/2 weeks with the Zivan (probably less than 6 charges) hopefully won't kill my batts.
As best I can tell, the regs take the heat when the batts are about 3.8V, so when the first batt hits 3.85V and shuts down the charger, the majority of the regs don't even get warm.
During blinking red phase, the charger is putting out 5-7 amps. During yellow phase, around 5 amps. The relay turns off the charger during the yellow phase, after about 10-15 mins. or so. The total pack voltage gets up to 181V (for 48 batts). I've also been watching this manually, like today, so I did not let the charger go into yellow phase - when the pack voltage got up to about 171V, I unplugged it.
Hope that helps!
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[1] The Zivan is not specifically programmed for LiFePo. However, it is my understanding that the creator of BMS uses the same charger.
Hmmmm... As long as the current and voltage thresholds are appropriately set for your battery pack, i think the CC/CV phases of the NG3 will be adequate as a backup charger, but i wouldn't use it all the time. The yellow phase should be avoided (LifePo charging specs specify the charge end at end of CV phase). i also remember reading that the yellow phase can be disabled (only set by factory technician unfortunately).
This leaves the issue of balancing unhandled though (by both the NG3 and MM charger too).
For our tried and true flooded lead acid bats, the yellow phase raises the voltage very high and that is when all the batteries in series are 'balanced'. We have much experience with this approach working.
For sealed lead acid (AGM), you can't use the yellow stage and we have a lot of anecdotal evidence that AGM packs fail prematurely due to uneven charging over time.
i'm afraid that without proper balancing, the same problem will occur with the LifePo cells. Much effort is put into preventing cells from overcharging, but no effort is put into undercharging. Eventually, the differences in the cells will become larger and ouch!
Does my argument seem right ?
Todd/Folks: please challenge my understanding !! Thanks!
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Ted:
I'm in general agreement with you on the balancing issue. I've also seen firsthand what the yellow sequence does.
When the Zivan enters the CV phase, blinking red, it cuts the power down from 16amps to about 5-7amps. What happens, however, is that the power isn't cut down enough, and after about 20 min. or so (I don't know exactly), the pack voltage starts to rise. The Zivan is set to go into blinking red at about 171V which works ok for my pack. To reiterate, the current during the CC phase (16a) and voltage that kicks in the CV phase (171V) are ok for my pack.
But, ultimately it climbs to 181 for yellow, which is why I prefer to manually watch this and shut off the charger before it gets to yellow.
The MM cuts down power a lot more ==> 1-2amps at 171V. So the 'finishing' charge, which you can set how long this is for, does a much better job at maintaining CV.
In terms of balancing, I think the MM does some kind of balancing, although I only have some vague anecdotal evidence of this. After maybe one or two dozen charge cycles, my batts are still very balanced at most stages of the charge/discharge cycle. Time will tell in the long run to see how this works after hundreds of cycles.
By the way, I have about 800 miles or so on the LiFePos. I hope to have 1,000 by the end of this week, and would ideally like to put 1,000 miles each month on the car.
I think this is a good discussion - perhaps we can do a presentation during one of our meetings on this subject?
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More fun at the EV OK Coral today -
On our way to another Doc visit via the expressway, the warning buzzer went off for a couple seconds. WTF? So I pulled over at Medieval Times (parking lot), and within 10 mins. checked all the BMS loop wires (none were loose) and the battery voltage (all was ok - 3.33V each). So, scratching my head, I thought this may be a false alarm and we continued on to our appointment.
On the way home, I took I-90 East to 294-S. Just before the Irving Park Rd. iToll plaza, the car dies out - first the ABS light comes on, then the ABS brakes pump on their own very briefly, then walla, a dead car. Fortunately I was in the far right lane and pulled over. A Chicago cop was behind me and pulled over as well, asking for help. He offered to call IDOT, but the IDOT tow trucks are not flat-beds (you need to only use a flat-bed with my VW New Beetle). I thanked the cop anyway, and he went off to deal with another emergency. I was grateful that he was there.
So I called a tow truck, the same company from Brookfield, same tow truck driver that I had about 5 weeks ago, and he remembered us. He towed us back to my house in N. Riverside. $130 poorer but back home safe. I was late for work so I had to deal with it later.
After work looked at everything up and down (limited time), spoke with John Emde (thanks John!), and diagnosed the problem - a failed IOTA DC-DC converter! I have the 55amp one. I mean, nothing was coming out of this and my 12V was dead on arrival! No wonder I died on the highway!
So, I need to look at the IOTA to see if there are any obvious problems. If not, I may need to get a bigger one - the 75amp model. With the motor blower on all the time, I may be pushing the IOTA to its limits (esp. w/ the power steering, which I use infrequently). Anyway, the car is out of action yet again (this is getting old and expensive!). I'll keep everyone posted.
I did get my refurbished Manzanita PFC-20 back today, which was the only good news I've had all week. It's been one unbelievably bad week for me. Thankfully I'm healthy, employed, and have my lovely wife, so I try to keep my head up.
I'll write as I make progress...
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On Saturday I opened up the Iota DLS-55 DC-DC converter-it was totally shot. Black carbon everywhere! All the fuses were ok, so the capacitors must have given out. Thanks to Rich (Pioneer), they had one in stock, and I bought it and installed it. He kept the old one - he may send it back to Iota, but if not, I wouldn't mind using it for 'show-and-tell' at the meeting. The new one has a relay installed which kicks the output to 14.4V once the ignition is on. I don't think that's what happened to my old one, but it helps all the same.
Due to the placement under the hood, the DC-DC replacement was a major pain. It took several hours!
Ken suggests that a 'pre-charge' circuit needs to be devised and installed before you turn on the main breaker (Anderson connector, in my case). A way around this, of course, is to leave the main break on all the time, which I will do for the time being.
I installed the Manzanita PFC-20 and adjusted the BMS to match. I had some minor wiring work, and the RegBus was working again. The PFC-20 is a far superior charger (CC/CV algorithim) than the Zivan, so I'll be using this at all times. One curious event - I was able to get the Manzanita up to 24 amps - and the current dial wasn't up all the way! Perhaps Rich R. threw in a Buck enhancer for 30 amps? I'll check with him - if so, that would be sweet!
My mileage remains very good. On the day that the car broke down (Friday) on I-294, I did 49.4 miles (all highway), and it took about 14.5kWh charge - for 293Wh/mile. Excellent consistent efficiency!
The batteries are holding up fine.
Back later!
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Hi Todd, I think the IOTA my need a pre-charge resistor if it's being disconnected on a regular basis, my 2 cents
Ken
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oops
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More updates -
Yesterday the temp was hot outside - 90 F per my car's temp gauge. I was stuck in Friday traffic for about 1-1/2 hours. With much stop and go. Even though my blower fan runs constantly, the motor temp was pretty hot as well - you could not keep your hand on it for too long after the trip. I let it run for about 45 min after I got home to cool it down.
I showed up at the Riverside Cruise Night on Thursday 6/10. There was a lot of interest in EVs and the Lithium batteries! I also ran the blower motor while the car was stationary for about 1 hour for demo purposes. Note to the club - where is the FVEAA signage? I would like to get some next time!
Over 3 days I drove 51.9 miles. Many of those were battling a strong wind from the south yesterday. So, the heat, wind, traffic, and 'idling' the car for a couple hours took its toll on the efficiency - I had about 20kWh for 51.9 miles - 385Wh/mile. Ouch! I think that stop and go traffic and the heat take their toll on efficiency!
The battery temps never got above 90 F so we're ok there. I have about 1,000 miles on the new pack. Hopefully it will last another 99,000! So far so good.
Go Lithium!!!
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Does this mean your fan for the motor is not good enough to cool the motor? Does the fan have to be mounted some place else to get more cooling fan air?
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Tim -
I think the fan is good enough to cool the motor - it's just that on 90+ F days, it is still going to get hot. If anything, my fan may be overkill.
Yesterday I drove to Ted's house and back, with a side trip for dinner (burritos). Total miles = 45.9, energy = 14kWh. Efficiency = 305wH/mi. That's more like it!
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Okay, great. I wish I could run the fan off of a separate (not attached to the auxilliary battery) rechargeable system that could be switch off in the car.
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So far, I have almost 1,200 miles on the Lithium pack. So far so good! I've saved about $115 in fuel costs over the last 2 months, based on my retail electricity rate ($0.13/kWh which includes all admin. charges) and today's gas prices. Over time, I'll save more as gas goes up and electricity costs stay the same.
As Steve G. mentioned in his post, we set the RPM and current limit in my Zilla to be more gentle on the batteries. That works fine so I'm happy with the results. It should result in longer lasting Lithiums.
Go Lithium!!!
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What kind/brand of speed sensor do you have on your motor and what RPM limit did you set?
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I think I got the speed sensor kit from EV Source in UT. If not there, then EV American in NH sold it to me. Check online - the websites will have this. The entire kit was made for the WarP! 9" motor.
RPM limit is 4800.
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On Monday 6/21 I went about 65 miles on a charge, almost all highway. I even drove through one of those major rain storms we've been having - a microburst in the South suburbs. Anyway, towards the end of my trip I was drawing high current (accidentally started off in 3rd gear) for a little too long and the alarm went off - for just a few seconds. I backed off and took it easy the rest of the way home (a few miles). Back in the garage I measured all the batts, and they were all within 0.011V of each other. No red lights - so I'm still not sure if I have a bad cell monitor or what.
Without knowing my true SOC (I don't have a meter yet), and without the ability to see the batt voltage as I'm driving, I really cannot tell if I'm pushing these batts or not. The lowest voltage was 3.269 (resting - with a very small load) when I got home, so no signs of any stressed batts.
On Thurs. 6/24 I went on my longest single run to date - 70.6 mi. on a charge! About 1/3 highway and 2/3 local, with lots of stop and go with heavy traffic. I've learned that even though you do a lot of acceleration, at speeds < 40 mph I can draw well under 40 a. At highway speeds, I draw 50 - 75 a, with some bursts at 100-200 a (acceleration, up a slight incline, etc.). So, the highway truly does use more power. I'm concluding that I may have about a 65 mi. range on the highway (in the summer) and probably 75+ mi. with local driving. But, I still don't know my ultimate range!
To date - I have about 1,400+ miles on the pack, used up 439kWh, for a cumulative efficiency of 305 Wh/mi - pretty good! I'm coming up on 9,000 mi. electric in the Bug. I'll let everyone know when I hit 10k.
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I know you are focusing on your batteries at this time, but do not forget the motor maintenance as well. I have been driving my car with the new rebuild, and have been amazed at the range I am getting. I am getting three times the range I got before the motor rebuild. I even sent an apology to the EXIDE battery sales manager because I had earlier said it was the batteries. I know I missed the meeting AGAIN because of the storm, but I really want to be educated as to how to drive and maintain the motor of these EV's. If the fan blower to the motor is the answer, I hope a kit comes out very soon.
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Tim,
If you have some interesting info on motors, perhaps you could write it up in the forums.... As you pointed out, not everyone can make it to the meetings.
Nathan.
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as well. I have been driving my car with the new rebuild, and have been amazed at the range I am getting. I am getting three times the range I got before the motor rebuild. I even sent an
WOW Tim!!! This is great news! i suspect i have a similar issue with my motor (range is poor and don't think it's all the batteries fault). What did your motor rebuild include? i'm a DIY type guy, so i'm interested in the details :-) Thanks!
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Update on Elec Bug and the Lithiums -
The summer drums beat on...
Temp has been in the 80s and 90s - the motor gets very hot during these days! Even with the blower motor cooling system, after driving for 45 mins. on the expressway the motor seems to really heat up.
During a trip to my company office in Lincolnshire (not my normal stomping grounds), the car died on Half-Day road, and again in the company parking lot. Both times I turned off the ignition and restared, and all was fine. It could be due to the heat, but I really cannot tell. Nothing obvious - no wires loose, etc. DC-DC seems to be ok, but there's no way for me to really test this part.
The other night I came back from about a 25 miles run (local roads), and notice some coolant leaking (the Zilla is liquid cooled). I needed to flush it out anyway to replace with phosphate-free coolant, so I spent a total of 5 hours underneath the damn car (again!) to try to flush out and fix the leak. I tightened all the hoses that I could reach (the leak is at the bottom of the reservoir tank) and filled away with the new pink coolant (VW G-12 - no phosphate). Most of it just drained right out to the garage floor - so I actually made the leak worse!! Oh well, I cannot fix it. Fortunately there's enough coolant in the reservoir (it didn't all leak out) so I could drive to the green fest and back today. I'll take the car into Jim Dawson's shop on Monday - he'll be able to fix the leak (the motor needs to come out in order to repair or replace the reservoir tank).
Total miles on Lithium - 1,839.5. I'm getting close to 2,000 miles. Total energy - 1,156 kWh. Average mileage - 309.6 wh/mile. Not bad at all! Longest run on 1 charge - 71 miles, and I still had a fair amount left in the batts. So, I don't know the range, but it's up there.
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Update -
After 2,100 miles and 4-1/2 months of Lithium battery use, it's time to balance. Note my BMS is really battery monitoring not battery balancing. Anyway, after a full charge, I notice that about 8 of the 48 batteries don't show a red light at the top of the charge - meaning they don't reach about 3.65V. So, I measure them, and they are all at the 3.4 - 3.5V level, and therefore starting to get out of balance.
I borrowed the battery monitoring system from Ted (thanks Ted for loaning it!). It is set to do either 1 or 4 cells at a time, and so I set it to 'balance' on 4 cells in series - that is, set it up so that it holds the voltage on the 3 of 4 which are all topped off, and put a charge on the 1 that needs to be brought up. Unfortunately, the system is not made to handle these large storage batteries, and after 2 hours and less than 1.0Ah, the thirsty battery didn't really have any more energy.
So, I bypassed and am charging the low batteries one at a time. I've been putting about 4-5Ah into them to bring them up to 3.62-3.66V, so the charger is topping these batteries off as best it can. With 1 battery at a time, I can pump up to 5A into them, so each one is taking about 1-1/2 hours or so (the charger automatically backs off when the batts reach about 3.5V and drops to about 2.5A).
This is quite a tedious process, and I've finished with 5 of them and am doing the remaining 3 batts tonight. You have to watch the system, although the battery charger knows when to quit.
Ideally I would like an automatic system that can balance all by itself.
I've ordered 2 individual chargers that can do 1 battery at a time, and bring the batts up to 3.8V using 3.0A. I'll let everyone know how that goes.
By the way - my average efficiency is 313.5Wh/mile. Not bad!!
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Another update - I apparently (slightly) over-charged some of the batts by 1-2 Ah - so I have to discharge a couple of them. This takes longer, since the max discharge rate is 1.0A.
Anyway, Maribel & I went for a nice long suburban drive in Elec Bug tonight. Mostly higway - from 55-60mph, and some local. Total distance - 80.2 miles! I noticed some minor sag in the battery performance towards the end, but otherwise no problems. The resting voltage was 3.23 - 3.24V for every battery, so they weren't out of juice! I could probably have gone another 10 miles if I wanted to, but I don't need to push it.
I still don't know the maximum range of this car but it is at least 80 miles! Can anyone say 100?
Lithiums are the best ever!
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Another update today - 90,000 miles on the VW New Beetle - 10,000 EV miles!
The Lithium batteries have about 2,700 miles on them - going strong!
I bought a parking pass (monthly) downtown at the garage that lets me charge for free - sweet!
Overall efficiency is 313.1Wh/mile - not bad and much better than lead acid!
Finally, I brought the last 2 'out of balance' batteries up to speed with my 'dumb' Lithium chargers - you have to watch them manually, but they work just fine. And very simple to use - they are user friendly!
GO LITHIUMS!!!!!
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With the winter weather setting in, I've sealed up the battery boxes with fiberglass and pink insulation as best I can. I made sure that all the battery warmers are working, and use them as needed. Similar to the PbA batteries, the back box is always the warmest, the middle box is next, and the front box the coolest.
I also noticed that my warning buzzer goes off if I punch the accelerator and hold it at 300+ amps for 5 sec. or so, even after a full charge. This didn't happen in the warmer weather, so I've been testing the batteries. I hooked up the multi-meter to each cell and note the resting voltage and the voltage when I accelerate and draw about 300 amps (close to 2C). I found the 'culprit' very early. In fact, I've not finished testing all 48 batteries yet. 1 battery drops to 2.4V at 2C! It's not supposed to do that, and since I have a couple spare ones, I'll swap it out in the next couple weeks when I get some time (it's not easy to get this battery out).
Another test was an endurance run that I just completed tonight (still have all the same batteries in there). I did 81 miles - a record! No heater running, so it was a bit chilly. About 75% highway driving, much of that against a stiff cold wind. I didn't accelerate too much. The warning buzzer never went off - so, if one of the batteries is not up to par, it only acts that way upon heavy load.
I'll probably take out the suspect battery and send it back to the distributor - he mentioned that I have a 1 year warranty on them. Anyway, I'm still vvery happy with the performance. I'm approaching 5,000 miles on the pack. Hopefully I can get another 95,000!
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Great News Todd Thanks for the update! ;D