Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Pure fantasy right now but sounding board time :-) LOW power electric hybrid??

b13bliss · 12-06-2010, 02:10 AM

I like your thinking, especially the idea of using plug-in electric power for brief, high demand loads without needing to pack $20k worth of batteries around.

I'm no expert, but my understanding of C ratings on battery packs is that you multiply the C rating by the amp hour capacity to get the highest safe discharge rate in amps. A 5000mAH battery has 5 amp hour capacity times the C15 rating= 75 amp max rate of discharge. The total capacity of the battery is 37v x 5AH, so at a 75 amp discharge rate it would empty in 5/75ths of an hour (or 1/15 of an hour) which equals 4 minutes (4x15=60.) Your 4 battery pack would output about 11kw (148 volts times 75 amps). I don't think you would get acceptable acceleration from it, but I don't really know. You also don't want to use the battery's full capacity, so subtract 1 minute to leave the bottom 30% unused.

Cool idea, but the cost might still be prohibitive. I would really like to use batteries, but they're heavy and expensive and have a fairly short life span in terms of miles per dollar spent. If your metro cruises along using 10KW of power at 60 mph steady state, you would use about 9KWh to go your 54 miles
and would need at least a 13KWh battery pack. That would be about 70 of the batteries you mentioned at $150 each or $10,500. Say they were the greatest battery and you get 3000 cycles out of them, then you would go about 162,000 miles before replacing them. The cost of battery ownership would be about 6.5 cents per mile not including the electricity they use. Right now your cost of fuel at 50mpg is about 6 cents per mile. Electricity is cheap, but battries are not. That being said, I still would like to incorporate them into a reasonable scheme.

12-06-2010, 02:10 AM	#3 (permalink)
b13bliss EcoModding Lurker Join Date: Oct 2009 Location: Reno Posts: 4 Thanks: 0 Thanked 0 Times in 0 Posts	I like your thinking, especially the idea of using plug-in electric power for brief, high demand loads without needing to pack $20k worth of batteries around. I'm no expert, but my understanding of C ratings on battery packs is that you multiply the C rating by the amp hour capacity to get the highest safe discharge rate in amps. A 5000mAH battery has 5 amp hour capacity times the C15 rating= 75 amp max rate of discharge. The total capacity of the battery is 37v x 5AH, so at a 75 amp discharge rate it would empty in 5/75ths of an hour (or 1/15 of an hour) which equals 4 minutes (4x15=60.) Your 4 battery pack would output about 11kw (148 volts times 75 amps). I don't think you would get acceptable acceleration from it, but I don't really know. You also don't want to use the battery's full capacity, so subtract 1 minute to leave the bottom 30% unused. Cool idea, but the cost might still be prohibitive. I would really like to use batteries, but they're heavy and expensive and have a fairly short life span in terms of miles per dollar spent. If your metro cruises along using 10KW of power at 60 mph steady state, you would use about 9KWh to go your 54 miles and would need at least a 13KWh battery pack. That would be about 70 of the batteries you mentioned at $150 each or $10,500. Say they were the greatest battery and you get 3000 cycles out of them, then you would go about 162,000 miles before replacing them. The cost of battery ownership would be about 6.5 cents per mile not including the electricity they use. Right now your cost of fuel at 50mpg is about 6 cents per mile. Electricity is cheap, but battries are not. That being said, I still would like to incorporate them into a reasonable scheme.