# Are NIMH batteries available for use in EVs?



## willitwork (Apr 9, 2008)

Hmm, I did a search on NIMH in the forum, maybe the answer is located there, sorry about the dupe sounding post.


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## joseph3354 (Apr 2, 2008)

cobasys( a chevron subsidiary) produces large format nimh batteries,i have never even tried to get a price as they seem geared toward larger vehicles(buses mostly).due to patent restrictions(patent held by chevron)no one can produce a nimh battery larger than 9 amp hours.patent expires in 2015 i think not real sure of that could be sooner.


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## JRK5150 (May 18, 2008)

Wouldn't it be possible (though maybe not practical), to string lots of smaller NIMH cells together to reach the power rating needed?


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## Qer (May 7, 2008)

JRK5150 said:


> Wouldn't it be possible (though maybe not practical), to string lots of smaller NIMH cells together to reach the power rating needed?


Possible, yes. Practical, probably not. But definitely possible. I've been considering a bed of metal tubes filled with flash light NiMH-batteries, the problem is to get hold of 5000-10000 of them for a reasonable price...


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## JRK5150 (May 18, 2008)

If we were to use C cell NIMHs rated at 1.2 volts and 5500 milliamps, how many would we need to be roughly equivalent to a 72v system using 6 12v led acid batteries?


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## jwalin (May 7, 2008)

JRK5150 said:


> If we were to use C cell NIMHs rated at 1.2 volts and 5500 milliamps, how many would we need to be roughly equivalent to a 72v system using 6 12v led acid batteries?


Check out the Tenergy H cell battery. They have the highest ah rating I have found.

let me say this though....LiFePO is a better option. Nimh batteries have temperature instabilities when charging. And they explode if they get too hot or are overcharged. 

In 1998 I worked in the EV lab at IUPUI, called the Advanced Vehicle Technolog Institute. We were testing the EV-1 NimH batteries (Ovonics), and also some Panasonics that were in the RAV-4 EV's. We had an Aerovironment ABC-150 test center to test them.

We blew up quite a few. 

Jeff


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## joseph3354 (Apr 2, 2008)

nilar is making nimh for vehicles,again 9 amp hour and low discharge rates.this has to do with another aspect of the patent.the manufacturer of a vehicle with nimh can not provide more than 50 percent of the vehicles power.they sure tried to cover the bases didn't they?


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## weelliott (May 12, 2008)

JRK5150 said:


> If we were to use C cell NIMHs rated at 1.2 volts and 5500 milliamps, how many would we need to be roughly equivalent to a 72v system using 6 12v led acid batteries?


Assuming that you have 75 amp hours of capacity in a 72 volt system, that is 5400W hours, or 5.4KWH. 

To reach that with 1.2 volt 5.5amp hour batteries, calculate the Watt hour rating of each cell and divide. So 1.2V times 5.5 amp hour is 6.6WH, or .0066KWH. 

5400/6.6=818 cells.

In order to ensure that you are actually running a 72V system, divide 72 by 1.2, which yields 60, then make sure that the number of cells you have is a multiple of 60. So instead of 818, you'd need 840, or 780. This is because you'd be running 60 cells in series to get up to 72 volts.

I'm not sure how much 840 C cells would weigh, but I can't imagine more than 200 pounds. As for cost though...


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## JRK5150 (May 18, 2008)

WOW...84o huh! Yeah, that's a little out of my price range at the moment!  I checked out the Tenergy and LiFePO batteries too and again, way outa my league. Oh well, guess its good old lead acid for me, at least for a while. At least I shouldn't have to worry about them blowing up!


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## MitchJi (Dec 14, 2007)

Hi,

You could use Prius cells:
http://www.diyelectriccar.com/forums/showthread.php?p=40666

Mitch


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