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Batteries and charger? Answered

So I got one of those one cell battery bank that come also with a little crank generator. So far I took both of these apart to make one into a 2cell. So now these batteries are a parallel, my ? is if the voltage stays the same with the charging board and the mah is double this should not effect the board correct? and or the batteries. So far its been working both batteries reads the same voltage so the charging board must work. Now hear is the thing that I am concerned with, if I was to add 6 more into a parallel then all batteries would be the same MAH right. This should not damaged the board?

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Best Answer 3 years ago

Charging multiple batteries of the same nominal voltage ratings in parrelell shouldn't be an issue. The voltage between the 2 packs will always be the same once they are connected together like you say, however, you want to make sure the voltages are the same when you do connect them together. If one was partially discharged, at 3.7V, while the other was topped off @ 4.2V, there will be LOTS of current coming from the charged pack, going into the other one. With small voltage differences (like a few tens of mV), the current will be small, and thats not a big deal, and the cells will naturally balance out. However, with bigger V differences, damaging levels of current can flow. If you do not have a good accurate voltmeter or multimeter to test the voltages, use a 100 ohm resistor between the batteries for a few hours to let the charges ballence out slowly. Then proceed to connect them together.

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Once they are connected together like that safely, it does become effectively one larger capacity battery. The exact charge/discharge curve might be differently shaped, as it will be the sum of the separate cells, but with the same types of batteries, with the same nominal voltages, that will be insignificant, and no one usually worries about that unless it is a critical application where everything matters.

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Even if the capacities of the cells is wayyy different, but same type and same nominal voltages, then it doesn't really matter! The charge will always ballence between the 2, and the bigger battery will do more of the work, and the work both batteries do is proportional to their capacity/size. You shouldn't have any issues except maybe it taking much longer to discharge (good) and much longer to charge (bad) and obviously size and other physical constraints.

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However, batteries with different charge/discharge characteristics should NOT be connected together, like LiPo and NiMh. They have different fully charged voltages, and different fully-discharged voltages, so in this extreme case, if you were to charge the 2 up to maximim voltage for the NiMh battery, then LiPo battery voltage would be way too low, and probably be damaged from over-discharge, or charge it up to 4.2V and totally neglect and kill the NiMh. Either way, it will probably lead to a fire. So don't do that. Basicly, if you have to wire different types of batteries in parallel, do not charge it up beyond the limits of the lowest voltage battery, and discharge it beyond the limits of the battery with the highest cuttoff voltage.

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dominick.j.pezza

3 years ago

so I have an update...these EBL li-ion batts charged at 4.2v

the first pic was my tested batteries came out fine no over heating or on the board it self was very cool

sec pic I hooked up 4 EBL and its currently charging and the board is still doing awesome. ill just continue to monitor it.

Thanks for all your guys help and support

IMG_3278.JPGIMG_3279.JPG
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Samiran

3 years ago

If you add more batteries in parallel , each will experience same voltage across them and can be charged. BUT the charging process will be very slow since the crank output Power is a constant. Moreover if you use different manufacturer batteries and if their internal resistance does not match , a circulating current will flow which will over heat everything and also resist charging. Generally Linear ICs are used as boost converter and controller. You can eventually connect 4 instead of 2 Batteries but 6 will overkill the scenario, How ever your time to full charge all batteries will double. If you will ask me an advice I will charge 2 at once and again 2 & 2 after full charging or make a circuit for the same function.

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seandogue

3 years ago

The immediate problem I see with your idea is that if the cells aren't identically spec'd and aged (and even if they are), they may work against each other during charging or discharge, sometimtes even catastrophically.

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iceng

3 years ago

BTW knock out pictures, they are good enough for me to trace the wiring schematic if I needed to.

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Downunder35m

3 years ago

Damage will only happen if you use more output current than what the board is rated for.

Same if one of the batteries fail, but that should not affect the board if it is sealed off from the batteries.

The board will provide the output as it did before, I guess it is generic USB charger rated for 1A?

Keep in mind that using batteries in parallel is never the best solution.

Using a singe battery with more capacity is better.

Cranking to charge a big pack of batteries will also take much longer ;)
Might be easier to use a small 12V battery with 8 to 15AH and a step down converter to provide the 5V.