FVEAA Forums
EV Technology => Batteries => Topic started by: terry.kane on April 14, 2008, 07:44:00 PM
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I find all of the jargon in talking about batteries very confusing! In the last month, I've learned a lot but I'm still not confident. I'd like to propose that we try to standardize how we talk about batteries. I had previously proposed an "index" figure for pricing batteries based on "US$ per Ah @ 3V" but this does not take several things in to account, such as number of expected cycles in its lifespan and the actual useable Ah to recommended DOD. There is also the need for a BMS, temperature factors, Peukert values, etc.
I'd like to propose an index relating to US$/"true Ah"/Volt/Life cycles. We should have a contest to "name the unit". It's not difficult to do the math if you have the specifications on a cell. The number is more sensible if we multiply the result by 1,000.
For Example:
Nilar 9Ah/24V NiMH cell @ $250.
(250/9/24/2000)*1000 = 0.5787
Headway 10Ah/3.2V LFP
(19/10/3.2/2000)*1000 = 0.2968 (assumes 2000 cycles but I'm not sure on that)
The lower the number, the better the life-cycle cost, in raw terms.
You still have to factor in weight and up-front costs...
Comments?
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Good subject
From wikipedia the key parameters for a battery are:
For a Modern, high capacity NiMH rechargeable batteries
Energy/weight 30–80 Wh/kg
Energy/size 140–300 Wh/L
Power/weight 250–1000 W/kg
Energy/consumer-price 2.75 Wh/US$[1]
Cycle durability 500–1000
Nominal Cell Voltage 1.2 V
By referring specifically to AA NiMH (I dream to use them on a project). I will set the equation as follows:
(Energy X Cycles)/consumer-price = ((2.5 A-H x 1.2 Volts) x 500 cycles) / $ 1.0 = 1500
For a T105 :
(Energy X Cycles)/consumer-price = ((140 A-H x 6 Volts) x 300 cycles) / $ 130.0 = 1930
The bigger the number the better, I will think that the NiMH is much better when including the factor for weight
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For price, I would recommend a simple formula of dollars per Kilowatts.
For example, my Deka Dominator batteries in my Force cost about $250 each and are a 12Volt battery with a 57 Amp-Hour capacity at the 1 hour rate with an estimate of 600 cycles. Kilowatts = V * A * Cycles = 12 * 57 * 600 = 410.4 Kw. This translates to $0.61/kw. Since my Force uses about 137 Watts/mile, I spend about $0.08 per mile on batteries.