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I'm trying to build a panel to charge a 12.8 volt lithium ion pack which needs 15 volts to charge. I calculated that using 28 cells would give the proper voltage but now I'm not sure because I think that there could be voltage lost to resistance in the circuit. I read that some people recommend using 36 cells to get 18 volts and charge 12 volt lead acid batteries but that doesn't make sense to me. These are the specs for the cells I'm using. Any insight would be appreciated. Thanks
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Hi 1sttime - Welcome to Solar Panel Talk!
Let us see what some of the members can tell you about your query!
Russ[SIGPIC][/SIGPIC] -
Dependent on other factors your going to want around 25+watts worth of panels.
And a charge controller of course, welcome to the area!But what if you use 12% and only get 8% energy return not filling a battery completely off the solar array- is this considered a cycle? Mmmmmmm mauh brain's sizzling
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[quote] If a pigeon had his brains it would fly sideways [/quote]Comment
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Well, I'm building the panel myself and the plan was to have it be 830 watts to charge a 4 kw/hr pack and power a circuit that's a constant drain. It's really pretty different from lead acid packs. I think someone with more experience with lithium packs could help more but thanks for your advice.Comment
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Thanks for posting more specifics, next time post that in your first post instead after someone try's to help please.
But what if you use 12% and only get 8% energy return not filling a battery completely off the solar array- is this considered a cycle? Mmmmmmm mauh brain's sizzling
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[quote] If a pigeon had his brains it would fly sideways [/quote]Comment
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You need to be more specific as their are at least a half dozen different lithium chemistry out there and each has its own unique voltage. You are also going to have to design and build a custom charge controller for them as the commercial ones for lead acid can destroy a lithium battery.
The panels have to produce several more volts than the battery they charge to overcome wiring losses, and the charge controller operating voltage drop.
To use lithium batteries in a solar system is going to require an over sized solar array which is going to add substantial cost to the system that can never be recovered. Typically with lead acid technology the max charge current is C/10 to C/8 so if you had a 100 AH lead acid battery the max applied is 10 amps which works out very well for renewable energy applications..
The sweet spot for lithium is a continuous C.5 to C.8 for 2 to 6 hours until the charge current tapers off to 3% of the rated charge current. So that same 100 AH battery requires 50 to 80 amps. So instead of using a 120 watt panel, you now need 1000 watts or more.MSEE, PEComment
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But what if you use 12% and only get 8% energy return not filling a battery completely off the solar array- is this considered a cycle? Mmmmmmm mauh brain's sizzling
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[quote] If a pigeon had his brains it would fly sideways [/quote]Comment
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[QUOTE=MarineLiner;16783]But what if you use 12% and only get 8% energy return not filling a battery completely off the solar array- is this considered a cycle? Mmmmmmm mauh brain's sizzling
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[quote] If a pigeon had his brains it would fly sideways [/quote]Comment
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