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I suppose the simple question here is, what's the best way to electronically connect and disconnect a 3.6V battery to a 4.2V source? So when the electronic switch is on, the battery gets charged from the 4.2V source, when the switch is off, the battery is disconnected completely and when tested with a volt meter, the battery V+ terminal shows the true voltage of the battery.
I had a voltage monitor connected from the battery to the mcu, but then I read that it wasn't required in 'Fast-charging' circuits where a temprature sensor is used to detect a full charge.
The reason I want to disconnect the battery from the microcontroller is because when it's charging, there will be a seperate 5V supply which will power the circuitry, MCU, and supply charging current to the battery. If I dont disconnect the battery when it's fully charged, it will never stop charging because V+ is shared by the battery and the charger.
This circuit should do, the rest is software.
Sounds a bit unsafe.
There's no need for a separate 5V supply, just run it off the battery while charging.When the battery goes some way down, reapply charge and if the charger is not connected, poll the pin every now and then. If the charger is on, you can see it by the battery voltage rising.
Okay so I figured it out, the original problem was in my first circuit where I was using 2 MOSFET's. 1 to enable and disable the battery to V+, and the other to enable and disable CH+ to the battery. I found that 1 MOSFET will work perfectly, the following schematic shows my new circuit:The voltage after the diode rests perfectly at 4.2V, and when the FET is disabled the battery holds charge and shows true voltage on my volt meter, which means it will be just perfect for the ADC as well because my Vref is 4.2V+ (Vdd).Thanks so much for your help and suggestion, I've been trying to re-design this for months now off and on, and I was set on the idea that I needed 2 FETs. Now I believe i have a perfectly functioning charging circuit with all monitoring capabilities necessary Cheers!
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