How do multi-channel Li-Po chargers work?

[meteor]

Howdy!


I'm looking for a basic explanation how a multi-channel Li-Po charger manages to individually charge 4 series-connected cells when powered from a single source.

Obviously there is some way to electrically isolate each charge circuit. Is it done with inductors or something like that?


Here's one, but the "Parallel Charge" label is a bit of a misnomer as that's not really how it works. (due to the tab connections, it would be impossible to parallel charge a 4S series pack, i.e. 4.2V 4C single output): http://www.commonsenserc.com/commonsenserc/index.php?cPath=38_29&osCsid=62b84077bde5175182c6292d9f160284



Thanks.

[kschauwe]

The only way I can think of, is to use a DC/DC converter, with multi secondary windings.

[Comatose]

You can do it with multiple regulators, with each regulator floating on top of the cell below it (ground references cell-1). For anything above 3s switching regulators are basically a must because of the votage drop experienced by the bottom regulators.

[osmium_192]

I dont get what you mean by a series charging, but if your refereing to a balancing charger, then it is possible.

Think of the balancing charger as 4 individual chargers connected to the same power source, like how you can have more than one bulb on a battery in parallel.

The individual chargers are connected to their own cell and so detect the voltage of that cell only. The charger can only detect the voltage between the two wires, and if these only connect to one cell then its that one cell it charges and detects.

I think you can make better sense of a drawing.

Owen

[coro]

Attached picture is correct in case that "chrgr" contains galvanic separation (transformer).
I expect that this charger uses single transformer with four separate secondary wirings, then graetz, capacitor, and simple CC/CV charger (four times, separate for every cell).