Serial charging 2/3*2S adapter case

The adapter was designed as a compact expander for serial charging of two or three 2S batteries with the possibility of switching.

IMPORTANT: You must to connect batteries of the same capacity and the same model to charging, with approximately the same charge.

To assemble the adapter, you need 3pcs of XH2.54 3P male connectors, 3pcs XT30 male connectors, 1pcs XT60 female connector, 1pcs of XH2.54 7P female connector, 1pcs SS12D10G5 type slider toggle switch, 8pcs M2*10 self-tapping screws, a flexible rubber shank, pieces of a breadboard with dimensions like on photo, wires, and heat shrink. It will be safer to fill the inside of the case with glue. The switch can tolerate a current of up to 3 Amperes in descriptions, but I would not trust this and would not exceed 0.5 A.
Before gluing and assembling the case, it is recommended to check the operability of the circuit: first test with a multimeter, then connect the batteries to the charger in the working position.

The holes in the bre