On Tue, Feb 1, 2011 at 13:17, Lev Serebryakov <[email protected]> wrote: > Sealed, gelled lead-acid from modern UPS is very current :) Point taken, but the point I was making is that the basic chemistry of the NiMH batteries is perfectly current; you'd indicated NiMH was somehow outdated.
> 4xAA costs about $20 (if we speak about good ones -- Varta, Sanyo, I'm not sure where you buy yours, but the most I've ever spent for very good 2200-2700mAh NiMH cells is about $13 for a pack of 4, and the per-cell price goes down for higher quantities. > Typical "3rd party" UPS battery is 12V @ 7.5Ah for the same $20, which > gives 12*7.5/24 = 3.75 hours of work... Yes, it is much heavier... You're probably right, lead-acid is most often cheaper per Ah. However, I still maintain that NiMH is the way to go for an onboard charger. The cells are cheaper and less troublesome than LiPo, and can be mated with the onboard "power via 5v" option for a lightweight, seamless power backup. I'd venture a guess that most people interested in battery backup would be more attracted to a 10oz, in-case option that lasts 20-60 minutes as opposed to a 6lb external battery option that lasts 4-6 hours. Even so, we're just bikeshedding at this point; unless either of us is ordering thousands, Soren and his existing partners have spoken and it's going to be NiMH. >> An added bonus to the NiMH chemistry is simplicity of management. >> They're better off staying fully-charged than doing any discharge >> cycles like some chemistries want > But it is better to charge them with independent channels. It is not > clear, how many channels will have net6501 and which charging current > will be available. Nearly every chemistry is best charged by-cell, including lead-acid. That doesn't mean they can't be charged with a single channel, it's just less efficient. _______________________________________________ Soekris-tech mailing list [email protected] http://lists.soekris.com/mailman/listinfo/soekris-tech
