Charge 12V battery with 5V USB C?
I want to connect 8×1.5V NiMh batteries in series (12V). I want to use them for a DIY circuit and then charge the batteries via a 5V USB-C mobile power adapter.
What kind of circuit board do I need?
It has to be transformed from 5v to 12v somehow and the charging current must not be too high.
And what would I need if I wanted to connect 4×3.7V Li-Ion batteries in series (14.8V) and charge them via USB-C.
I've seen that there are charging modules (18650) for individual Li-ion batteries. Can you just leave the batteries connected in series and connect one of these modules in parallel to each of the four batteries, or could that cause a fire?
I hope someone can help me
(2 votes)
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For the first time, 1.5v the maximum voltage of NiMH, 1.2v the nominal, and only at about 1V they are empty.
Most of the time you’re at nominal voltage, i.e. about 9.6V, and your device should work up to about 8V. You only have the 12 volts at the beginning for the first few seconds.
And with the li-ion batteries you have now taken the nominal voltage, the maximum voltage is 4.2V so you have at the beginning 16.8V.
To get back to the actual question, no, at NiMH is slow to load in series safe, at li-ions not. You need to have connections between the cells at li-ions so you can charge them all individually.
There are so-called BMSs. https://www.ebay.de/itm/233634393203 which also protect against short circuits and low discharge.
Then you need to load this one more boost converter https://www.ebay.de/itm/176214116980 then you set the voltage and the maximum ampere number and then is first charged with a maximum current, and then with a maximum voltage. This is the correct type of li-ion cells to load.
And good NiMH there are modules where you can connect directly 5v https://www.ebay.de/itm/275306057376
You can high-transform the voltage with a stepup converter. There are special charging circuits for charging. At NIMH you can probably turn all cells in series, but you need a detection when they are full (Leider drops the voltage at the end something again when they are fully charged, constant voltage is not ideal)
In lithium batteries, you need a charging electronics with balancers, which ensures that virtually every cell is charged separately even if the cells are connected in series (Balancer has connection to each battery)
Okay. That’s too complicated and too big.
My plan would now be to connect two Li-Ion 18650 batteries in parallel (due to the required capacity) and then connect a 18650 charging module in parallel with it or a battery with an integrated USB-C socket. My >=12v I need from a 3.7v to 12v step up converter. Gives a loss through the additional Step Up board, but I’d rather.
Balancers are also not compelling: e.g. https://www.ebay.de/itm/276009709866
Is there any other platinum…
Switching parallel is not so the yellow of the egg. Yes, it is partly also made in battery benches, but there is always the risk that a cell is broken earlier. Ideally, the batteries fit very well (same type, same wear, same characteristic…) A series connection with balancer is somewhat more uncritical.
Then only the question remains whether the 1000mA max charging current is sufficient for 2 batteries. Do you know that? If this is not enough, you can simply switch the same module again parallel to the batteries.
But what do you mean to switch 2 charging modules parallel to the 2 parallel batteries? If it’s going to work.
A charging module has max 1A charging current.
So I can increase the speed a little
In principle, the charging current then lasts correspondingly longer. Where generally the charging current should be adjusted to the cells (less is generally OK)