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Lithium Ion battery charging circuit for 12V battery scheme

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abe94

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I'm currently setting up a backup system whose output should be a constant 12v 1A. I plan to use several good 18560's I salvaged from a laptop battery and connect them in series-parallel to get the required voltage. Now I need to design a charger for this 12V pack. All the design I found online usually deal with one or two cells. For this I'd have to connect several of them in series-parallel to get the required voltage and amperage. Is there any circuit for such a voltage level and capacity ?
I could include a uC in there for sense and control and stuff but I'd prefer to keep the circuit as micro free as possible. Any inputs ? Thanks.
 

There is need for caution, because Lithium Ion type are in several news reports for causing fires and explosions.

Each cell's ought to be checked for good health. When you string them in series, each needs to match the others in performance.

I've heard some batteries come with a built-in circuit which controls charging, or limits voltage, etc. Do yours have this?
 

A Lithium-ion battery cell is 3.2V when it is almost dead and its load should be disconnected and is 4.20V when fully charged. Then its average discharging voltage is 3.7V. Three in series make 9.6V to 12.6V which is not a constant 12.0V. You could use a 12V voltage regulator and four battery cells in series.

The Ah rating is not its maximum current, it is how much current it can supply in an hour. It can probably supply 10 times or 30 times its Ah current for a short time.

You need a circuit that senses low voltage and disconnects the battery from the load. Then you need a "balanced 4-lithium cells charger" for the cells.
 

I would just use a completely standard Laptop battery with an unmolested Laptop charger.

Then build a custom switching power supply to convert that to the required constant 12.0 volts output.
 

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