Electrical – Can a diode prevent backwards current flow from a constant current source


I'm trying to make a AA battery replacement battery for a vintage computer because its actual battery has gone bad. Its of the NiMH type and I'm pretty sure those are charged with a constant current. I want to make sure that my alkaline batteries don't get accidentally charged if the AC adapter were to be plugged in. Would a diode prevent the constant current charger from charging my AA batteries?

Best Answer

It would (for all intents and purposes - there is always some leakage). However, a more significant issue is the fact that it will also drop almost half of you AA battery voltage - and thus waste half of the energy inside the battery. There are two options to mitigate this:

Battery protection circuits with some form of switch, such as a mosfet: These exist and use a circuit that will open a mosfet when power is applied from the output.

Alternatively, you could just use a NiMH battery and allow the system to charge it.