I recently bought an old two-box metal detector that uses radio tubes and runs on the old radio batteries. There are two boxes, One is a transmitter box, the other is the receiver box. one with 6 tubes and one 45V battery (but has a third, center + connection, so is - + + the center plus terminal is 22.5V ) Then, there are two seperate 1.5V batteries also. The other box has two tubes and a 45V battery (no center 22.5V connection) and one seperate 1.5V battery also. My question is this: I am trying to change the battery system to rechargable batteries. I made a battery pack out of 5 nine volt batteries, but the rechargables charge up to 10 volts 50V total) initially each, then I made a separate battery pack for the 22.5V out of 1.2 AA batteries, which initally charge up to 1.364 volts each (16 come up to about 23.188V 15 to 20.46V) how can I run down the batteries to get to the correct voltage(s)? Or, does anyone know if these old detectors will take those over voltages? all batteries are connected "in Series". Also, do you think the rechargables probable higher mHa ratings(250 for 9V and 2,000 for 1.2V) could create any problems? This is the first time I have done this, so kind of new at it! I was going to use alkalines first, because the voltages are closer, but this machine eats batteries, so I am told and rechargable batteries are so much cheaper, in the long run. Thanks, Vance

I recently bought an old two-box metal detector that uses radio tubes and runs on the old radio batteries. There are two boxes, One is a transmitter box, the other is the receiver box. one with 6 tubes and one 45V battery (but has a third, center + connection, so is - + + the center plus terminal is 22.5V ) Then, there are two seperate 1.5V batteries also. The other box has two tubes and a 45V battery (no center 22.5V connection) and one seperate 1.5V battery also.

My question is this: I am trying to change the battery system to rechargable batteries. I made a battery pack out of 5 nine volt batteries, but the rechargables charge up to 10 volts 50V total) initially each, then I made a separate battery pack for the 22.5V out of 1.2 AA batteries, which initally charge up to 1.364 volts each (16 come up to about 23.188V 15 to 20.46V) how can I run down the batteries to get to the correct voltage(s)? 

Or, does anyone know if these old detectors will take those over voltages? all batteries are connected "in series". 

Also, do you think the rechargables probable higher mHa ratings(250 for 9V and 2,000 for 1.2V) could create any problems? This is the first time I have done this, so kind of new at it! 

I was going to use alkalines first, because the voltages are closer, but this machine eats batteries, so I am told and rechargable batteries are so much cheaper, in the long run.