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Building a NiCd battery pack | 6 comments (6 topical, editorial)

Re: Building a NiCd battery pack (3.00 / 0) (#3)
by Slingshot on Thu Sep 11th, 2008 at 10:02:58 AM MST
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That's interesting, and a good result.

I had always been under the impression that it is difficult to obtain good results when paralleling NiCads or NiMH cells. Because they are generally charged by controlling current, as opposed to a float voltage such as for lead-acid, presumably the cells would not charge-discharge uniformly in a parallel arrangement.

Anyone else?

Re: Building a NiCd battery pack (3.00 / 0) (#5)
by Bruce S (bruce(dot)stahl <at>gmail (dot)(com)) on Fri Sep 12th, 2008 at 07:37:12 AM MST
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Slingshot;
I will add a little to what Zap said. I have found that to keep cross cell problems to a minimum, it's best to match the cells as best as possible, then like he did watch them to make sure they become a cohesive pack.
By completely charging the set as an entire pack, then using them , then recharging the packs as a whole , helps the entire set become a "one" set pack . Rather than charging the packs as individual packs then having them used , will certainly lead to imbalances.
When these packs are tested at our office they go through a very structured testing.
When I built the packs up for our 48V e-bike they were then retested as a single pack. For us there has not been any problems yet.
So far I've built 2 packs doing this, one pack of 36Vdc rated at 32Ahr & the most recent pack being 48Vdc rated at 16Ahr. Both are still going strong . The first pack is now 2 years old the last being less then 4 months.

Hope this helps;
Bruce S

[ Parent ]

Re: Building a NiCd battery pack (3.00 / 0) (#6)
by zap (bell47g5a at comcast dot net) on Fri Sep 12th, 2008 at 11:24:47 PM MST
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One thing I forgot to say was that keeping the paralleled parts (and the pack as a whole) symmetrical goes a long way towards keeping the charge on all cells level.

If I was only pulling 500ma out of the pack I wouldn't worry much at all. Depleting the pack in a half hour is probably pushing things a bit too much... hence the reason I've been watching the pack closely for now.

zap
[ Parent ]

Building a NiCd battery pack | 6 comments (6 topical, 0 editorial)

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