battery for mini solar panel

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Egg_

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Im trying to build a tiny solar charged energy source. Im a beginner at electronics so i need some help choosing batteries. Im only planning to spend a small amount of money so i figured i could use six 6v 250mah panels i found for really cheap(3s2p).So Im thinking of either building a 3s3p liion pack with the 3000mah 10c batteries i found (4$ each) or using 12v 7000mah dry akkumulator. Theres also these lifepo4 batteries with 6000mah 3c for around the same price but i cant really find any good bms for that voltage. What should i do? As i said i am a beginner with electronics and kinda know it would be inefficent to have solar in this price range but think it could be a cool thing to have.
 
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To avoid an explosion and fire you need a Lithium battery charger IC, set to match the recommended battery voltage and current. A cheap BMS is a protection circuit, usually with 25A current (!), not a charger circuit.
 
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For lithium cells, you need a protection IC or board (the "BMS board on ebay etc), plus, for series connected cells, that must include a "balance" function to maintain the cells all at equal voltage.

Then you need a charge controller set for the correct battery voltage and current limit.


A gel lead-acid type is simplest, as the only things you need with that are a fuse for safety, and a voltage regulator or limiter circuit which should be set to 13.8V for a 12V battery on long term float charge.

The cells also need a series diode to prevent them draining the battery when there is insufficient light to charge it.
 
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I also vote for an SLA battery as they are fairly tolerant of overcharge, easy to charge, and relatively cheap.
For the low solar panel currents you probably don't even need any kind of regulator (volage or current) and can just connect then directly (two in series connected in parallel with the others two pair) to the battery through a diode.
Use a high current (1A or larger) Schottky diode for minimum forward voltage drop when charging.
 
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