question on by pass diodes.

Thread Starter


Joined Oct 31, 2009
hi all,

I am wondering about a scenario on by pass diodes.

these can be placed across cells to stop reverse charging (battery depletion) and also prevent cells from damage.

I have a situation where I have 4 cells and 4 by pass diodes.

If i replaced the 4 individual diodes with 1 single diode across all cells would this protect all the cells.?

Ie the same protection but less real estate.

I am looking at a 36 cell battery stack also and its not really feasible to have that many byp ass diodes (4S 9P)

I am unsure on placing just 1 diode across a string of cells.?



Joined Mar 14, 2008
You need one diode across each cell (cathode to positive side) if you want to protect each cell from reverse charging. One diode will just prevent the whole battery from being reverse charged, not each cell.

Schottky diodes work best for this since they have a lower forward voltage drop.


Joined Jul 17, 2007
Well, I worked up this circuit for them before... and didn't hear anything more about it.

See the attached.

Lacking any information on the batteries aside from they are some variation of lithium chemistry, I simply threw together a schematic and simulation. The only thing really relevant about the simulation is that it shows the diode changes Vf over temperature.