PP9 Battery Substitute

Vintage transistor radios frequently need 9 Volt batteries called PP9. Not the little PP3 ones that are now commonplace. Unfortunately it's very difficult to find anywhere to buy a PP9 battery and even then they are very expensive.

The economical solution is to make one's own substitute, preferably rechargeable. Whatever you construct should be a close match for the size and shape of an original PP9 so that it fits in the radio without falling around when the radio is moved.

In this project I used a battery holder for 8 AA batteries (2x4 configuration with wires attached). The nominal voltage of a NiMH rechargeable is 1.2 volts so the total voltage is 8x1.2 making 9.6 Volts. When fully charged it's little higher and when near depleted it's a little lower. Your radio should work just fine.

If you prefer to use non-rechargeable AA batteries, get a holder for 6 batteries since they are each higher voltage than NiMH cells.

In theory you could charge the finished pack by applying