I have an old power tool that uses a NiCd 18 v battery. Both the tool and battery are barely used. I went to use it and water apparently got into the tray I had the charger for the battery setting in. It’s toast/ all corroded. Any ideas of a circuit design to charge the battery? I really don’t want to toss the whole thing. (Tried to find a replacement but discontinued quite awhile ago so no luck)
Thanks everyone

 

I have an old power tool that uses a NiCd 18 v battery. Both the tool and battery are barely used. I went to use it and water apparently got into the tray I had the charger for the battery setting in. It’s toast/ all corroded. Any ideas of a circuit design to charge the battery? I really don’t want to toss the whole thing. (Tried to find a replacement but discontinued quite awhile ago so no luck)
Thanks everyone

https://batteryuniversity.com/article/bu-407-charging-nickel-cadmium

 

https://batteryuniversity.com/article/bu-407-charging-nickel-cadmium

Ahhh…..Thanks but if you have a circuit design that would be great. Old tech I know but seemingly abandoned now and can’t seem to find anything I can use?

 

Ahhh…..Thanks but if you have a circuit design that would be great. Old tech I know but seemingly abandoned now and can’t seem to find anything I can use?

18V = 15 cells. You'll need to charge it to 1.4V a cell with a constant current, so if you have a 24V power supply that will be a good start.
Then you need a constant current source with I=0.1C, where C is the capacity of the battery
https://www.circuitlab.com/circuit/f646vh/2-transistor-constant-current-sink-01/
The battery goes where R3 is.

 

18V = 15 cells. You'll need to charge it to 1.4V a cell with a constant current, so if you have a 24V power supply that will be a good start.
Then you need a constant current source with I=0.1C, where C is the capacity of the battery
https://www.circuitlab.com/circuit/f646vh/2-transistor-constant-current-sink-01/
The battery goes where R3 is.

I have the original dc power adapter that plugged into the now defunct charger it has a labeled output of 20vdc and 400ma. It wasn’t where the charger was so it’s undamaged. I tested with a multimeter and it reads actual at 21.2vdc. I’ve tried to find the battery details but can only find the voltage, 18vdc. Capacity is a mystery for the moment. So… I see the schematic you site has a 5v supply. Changing the supply to the 20+ vdc will not require any of the other components to change? I have all the components shown.

 

Below are a couple charging circuits using a LM317 regulator to limit the current and stop the charge at 18V:
The first doesn't give the fastest charge, but it is simple.
The second adds a transistor for better current-limit control which gives a faster charge.

 

Below are a couple charging circuits using a LM317 regulator to limit the current and stop the charge at 18V:
The first doesn't give the fastest charge, but it is simple.
The second adds a transistor for better current-limit control which gives a faster charge.

View attachment 324132
View attachment 324134

Ok… in the first circuit I’m assuming you connect the battery to OUT and GND. Is the capacitor a 100uf (electrolytic) and is it needed across the battery?
Also R1&R2 are odd values…just get close?

In the location in the circuit where the battery connects, this cap neede?