I found this PIC based charging circuit online. The full article is here NiCd Battery Charger
My question is how can PIC pin 18 get an accurate reading from the battery? The current to the battery is either that for full charge or trickle charge never off.
I will be charging a 750 mAh NiMh pack with 3AAA cells. Instead of the 1R0 5Watt resistor I will use a 16R 1/4 watt which should result in a charge current close to C/10.
Let me put it another way:
I am curious about the interaction of the voltage from the charger and the battery.
Since the battery voltage is read while being trickle charged what determines the voltage read by the PIC via the voltage divider.
I have been playing with the circuit on a BB. It looks like the 317 is following the battery voltage, maybe just a tad higher. But my old bench supply let out its magic smoke. Need to deal with that.
A big issue with charging batteries is to limit the initial charging current; both to protect the supply (transformer/rectifier/regulator) as well as to keep the max charging current in-line with the battery maker's specs. Write back if you want to add an electronic current limiter to your charger.