i have 5V current source and I want to charge 3 cell NiCd pack with it. Idea is to charge with voltage ~4.2 and current ~90mA. I know this circuit can be made with one transistor or less but i havn’t found anything useful yet. Can anyone help, povide schematics or ideas?
Charger
If the numbers are truly correct, all you would need is a .1 ohm resistor between your 5 volts and the battery pack. You need to drop a maximum of .8 volts at 90ma. Normally you would use a higher voltage and adjust your resistor value accordingly because you want some "overhead" in your circuit.
The ~8.7 ohm resistor did
The ~8.7 ohm resistor did the trick. Although nex time i will use ~6 ohm for a bit faster charging.
OOPS
You are correct…
I don’t know how I came up with that value and after thinking about it today I recalculated. Before I could post the correction…you had already done it.
Thanks