Battery Protection Circuit - is my voltage reading correct? Is this working?

Thread Starter


Joined Oct 3, 2022
I have created a circuit that can switch between series and parallel configurations for a pair of 9v batteries. To protect the batteries, I've added Schottky diodes on the + of each battery.

Now I want to test this circuit's function, and I'm confused by the result I'm getting. Specifically, in the "9v" configuration, when I remove one of the batteries and test the voltage across the battery leads, I'm reading 9v-ish. I would have expected that to be 0v because of the diode on the + leg. Where have I gone wrong in my understanding of this circuit? Also, what should I expect to read across that battery terminal in the 18v config?

I have verified that there is a relatively small current running through the open leads by placing an LED/resistor across the leads - I get a very dim illumination (likely corresponding to the 2mA leakage current of my Schottky diodes). So it seems the circuit is probably working as intended, but still confusing me as to why I read 9v across that open battery terminal.

Finally, if I'm reading 9v and getting 2mA of current through that battery, am I effectively protecting it from the possible damage/risk of reverse voltage? Or is that amount of voltage/current going to possibly damage the battery here if there are voltage imbalances?