Active stack balancer board dissection

[joeblack5]

I was curious about this 4 cell active balancer board. It has 4 transformers so it seems to be a stack balancer transforming the cell voltage back to the overall assembly voltage.
Tested a slightly unbalanced 280 ah 4 cell pack and it seems to work, some voltage came down and others went up.
So the question is how does it work under the coating.
Decided to sacrifice a unit for knowledge and scraped the coating.
See pic..
The transformer has three windings.

Below the transformer are two MOSFETs A07T. Then the circuits in front are same components.

The large component is an option coupler El3H7.

Above that a KL3 3 pin.

Above that and directly below the inducter is diode K14.

Then on the left next to the white connector.
A mystery chip C3J0.

Above the silver selector switch are two
7002 MOSFETs.

It looks like the pattern of the black coating is all the same..
That would mean that the control is in the mystery chip.

Any suggestions / interest.

johan

 

[joeblack5]

Without to much problem I was able to ohm out that each transformer has two out of three coils directly connected to the two MOSFETs and to one of the pins on the white connector.. so that would support the theory that each of them is powered by one cell. The opto would take care of the voltage shifts.
Later Johan

 

[joeblack5]

Anybody else have any experience with the board above.?