Thank you Dave and merci Alain!Originally Posted by mackrackit
This conversation about this matter and the the info you can find scattered around has brought myself to to new level of understanding the batteries.
Here is how I now will build it:
My PIC has 6*1.2V NiMH batteries and it measures the voltage of the batteries. A regulator (L4940) convert it to usable 5V.
The charging will work in the following way:
You plug 12V/800mAh to the batteries via a mosfet that will be on because the gate is connected via a resistor to the battery side and from the gate directly to a port of PIC so that it can cut off the charging even that the charger is still connected. How to continue from this point is slightly unclear at this point. There could be a small charge pulse for example 1s charge and 15s not, or measure the batteries all the time and wait them the drop a little and charge then until reached the previous "full" state.
So, during measuring of the battery woltage I will measure the voltage "curve" and wait until it does not grow any more (instead it drops a little) and that is the point to stop. On the other hand I will have two NTCs, one on the battery pack and the other as a reference (not near the batteries), I can so follow the heating up of the batteries and if they heat up too much, say 15 degrees PIC could cut off the charger by pulling the mosfet gate down. And keep on the this "batteries warm" mode until then charger is unplugged.
The only bad thing with this idea is that you can not shut off your PIC and the "battery usage" when your batteries are fully charged, but keep on this "after charging procedure" .
If you happen to have an idea how to plug the charger so that your PIC can notice that and turn off the charge when fully charged, please let me now....
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