John Veix wrote: "I have a customer with a hot air balloon (who) 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."
Mick says: If one recalls the YouTube videos of flaming notebook computers, that underscores the importance of proper management where the lithium chemistries are concerned. (I believe) a charge algorithm for lead batteries cannot safely be used with lithium. Southwest Electronic Energy: http://www.swe.com/default.aspx claims to have solutions for solar electric recharge of their lithium packs. This may be a good contact to pursue, but I have had no direct experience with SWE. For lithium, I think you should seek a supplier that can offer "single source accountability" where the cells, battery balance system and the solar charge controller all come from the same vendor. Otherwise if there are problems with these costly cells, the battery vendor could blame the control regimen and the manufacturer of the power electronics could blame the cell supplier. You want no finger pointing, no wiggle room and a single warranty for the combined bundle of lithium pack plus "battery management system"...and the "BMS" should include a solar charge control circuit for your described application. In terms of practicality, a 10 amp hour (12 volt nominal) lead battery only weighs about 9 pounds. If lithium technology could reduce that weight by 2/3 you'll save 6 pounds but your client will pay dearly for it, and you'll wind up with an exotic batch of gear that's not easy to service or plug in replacement parts. Is it worth it? Be sure & report back to the List so we can all learn... Mick Abraham, Proprietor www.abrahamsolar.com .
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