Li batteries are about 3.3 volts per cell, so the pack your client is looking at may be 4 or 5 cells in series.
It is probably important to buy a commercial pack, because most of these batteries need their terminals welded into their series-parallel connections -- not the sort of thing most wrenches are set up to do.
Also, most Li packs include battery management systems to keep them equalized and properly charged and discharged.
A123 Systems ( http://www.a123systems.com/#/applications/UPS/ ) has what they call "drop-in replacements" for 12 V lead-acid UPS systems, so maybe those packs are appropriate for solar charging. I recommend talking to applications engineers at the Li battery companies.
Aten Energy is also working on packs in 12 V nominal multiples.
http://www.atenenergy.biz/Foxx%20Specs.htm . A 12 V 10 AH pack weighs about 5 lbs. Their web site is lame and old, so you might have to find some other way of contacting them.
Here is an interesting product (11.4 AH) from the place where I buy my NiMH household cells:
http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4089
Prepare your customer for sticker shock.
John Veix wrote at 01:45 PM 8/24/2008:
Hi there,
I have a customer with a hot air balloon doesn't want to use F.L.A. deep cycle battery due to weight factors, but wants to use Li instead - and also wants to use PV to charge it.
I have never looked into this, but he seems to think the Li battery charges at 16.8v. The battery will be small, probably about 10 a/h and will be used for a transponder.
Can anyone enlighten me about the feasibility of this application.
cheers, John Veix, N.Z.
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