rhd
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I haven't seen one yet. Never really researched about it though. There is a balancer circuit in my site that used a voltage reference IC but it takes a bit of parts. Could be possible to make it smaller but with lower dissipation ability.
Or you can get a charger same as shown in here: Replacement 9 V battery - Náhrada baterie 9 V
I got one and it's basically three identical 4054 based single cell chargers with outputs all wired in series and the input to all charger ICs are isolated using a DC-DC converter.
There's always the simple but annoying way of using two isolated 4.2V CV sources too. If you're mains powering the thing just use two stepdown transformers instead of one. If you're planning on DC powering the whole thing then isolation becomes a bit trickier.
You know there are very inexpensive off the shelf solutions for such. While I always admire and recommend DIY when possible, sometimes economically it isn't worth the trouble.
I'm essentially trying to make a very tiny circuit for charging a 2S pack from a 16V DC source. At present, I'm just charging each cell separately, but that takes an extra step (switching from one cell to the next).
Yeah, size can be a problem. Perhaps a reverse engineering and DIY reproduction of a commercial unit would suffice?
DC 2-4S Lipo Balance Charger*
Is there any reason that a +/- 4.2V split rail setup wouldn't work? IE, my idea of regulating 8.2V output via voltage regulator, and then splitting it with an OP Amp to create a virtual ground at the midpoint?