Goal: Use exactly one 18650 charging board, like the TP4056, to charge several 18650 cells in round robin fashion. This has nothing to do with serial or parallel charging methods...just a brief round robin at each cell, independently charging one cell at time, in short cycles, from the single charging board.
Current thinking:
connect charging board positive and all cell positives to a positive power bus.
connect the cell negatives to the output pins of a bi-directional multiplex and then to negative bus.
loop thru the multiplexer output pins to connect a single negative at a time in the cycle.
What happens when a cell is fully charged (4.2volt).
A permanently connected charger senses that and stops charging until the cell drops below 4.1volt.
That might not happen for days if you're not discharging
AFAIK if you disconnect/reconnect, it starts charging again, until some detection time has passed.
Could be unhealthy for the battery to frequently be topped up to 100%.
Better investigate before you start this project.
Leo..
Leo, code oversees which cells to charge or skip in the charge loop. As a newbie to hardware, my struggle is how to physically make the circuit that uses a single charge board to give a small charge to cell 1, then cell 2, then to cell 3, and so on, only connecting to one cell at a time. How would you do that?
TP4056 charge boards are silly cheap so use one for each cell.
srnet, this circuit is a building block, a black box: one charge board must handle charge duty for its group of cells. Each cell in the group must be Independent of the other cells in the group, i.e. no serial and no parallel connections.
I just need guidance on the physical circuit for using one charge board to give cell 1 a charge, then cell 2 a charge and so on for its collection of cells.
Seems you're trying to re-invent the wheel.
"all cell positives connected to a bus, and switching batt negative" means that you're not trying to charge a stack.
A bunch of TP4056 modules (<$0.25 each shipped) seems a heck of a lot easier/cheaper than an Arduino switching logic level mosfets.
If you are trying to charge a stack, then neither solution will work.
Leo..
timpet:
I just need guidance on the physical circuit for using one charge board to give cell 1 a charge, then cell 2 a charge and so on for its collection of cells.
If you want to charge batteries in such a complex and expensive way, just use relays to switch the battery connections.
Although you have explained what you want to do, you have not said why you want to charge the batteries in this way.