General battery info

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russbost
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Joined: Tue Aug 30, 2011 11:19 pm

General battery info

Postby russbost » Fri Sep 02, 2011 8:58 pm

Following on from the "Poor Battery Life" thread - i will show my ignorance here as I had thought a 200 ah battery was just that, I didn't realise this was only the case at relatively low discharge rates - obviously not going to be generally applicaple to EV's. How do LiPo & LiFe compare in this respect?

Also if using something like a deep cycle leisure battery (is this what you guys use if using lead acid) are any guarantees (I see some batteries carry a 4 year warranty) going to be automatically invalidated.

Apologies if these are simplistic questions to you guys, but my learning curve needs to start somewhere!

GregsGarage
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Re: General battery info

Postby GregsGarage » Fri Sep 02, 2011 9:11 pm

From the wikipedia entry on Peukert's Law
Peukert's law, presented by the German scientist W. Peukert in 1897, expresses the capacity of a lead-acid battery in terms of the rate at which it is discharged. As the rate increases, the battery's available capacity decreases.


A couple of links;
http://en.wikipedia.org/wiki/Peukert%27s_law

http://www.smartgauge.co.uk/peukert2.html

All batteries suffer from the Peukert effect, but for lithium chemistries, it tends to be so low that you can ignore it for the most part. The practical effect is that an EV using lead acid batteries will see more range if driven conservatively, but with lithium you can accelerate faster without suffering the penalty caused by the Peukert effect. Hope that makes sense. :shock:
Greg Fordyce

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ChrisB
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Re: General battery info

Postby ChrisB » Sat Sep 03, 2011 9:23 pm

russbost wrote:Also if using something like a deep cycle leisure battery (is this what you guys use if using lead acid) are any guarantees (I see some batteries carry a 4 year warranty) going to be automatically invalidated.


Leisure batteries tend not to work that well in EV's due to the high levels of discharge going on, leisure units are more aimed at long slow discharges aka lights in carvans/tents etc
Generally you wont get any guarantee if you use a battery outside its design criteria

Traction batteries are really what you need when it comes lead acids.

ChrisB
I reject reality and substitute my own !!!!!!


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