I'm trying to make a relatively simple battery charger for a rechargeable 9V lithium ion battery.
I wanted to make a charger that will not cause overvoltage or damage to the battery and will also provide LED indicators that will show when the battery is being charged and when the battery has finished charging.
I've decided on using a Zener diode that will shunt current above the maximum battery voltage to ground and an LM317 configured as a constant-current source.
The idea is that once the battery reaches the charged voltage (around 8.7VDC), the "charged" LED will turn on.
When I breadboarded the circuit, being powered with a 12VDC power supply (as I intend for the final circuit to use) the LED is just always on. (The 100F capacitor on the output is only for simulation purposes.)
The following attached are the schematics and a chart from a voltage sweep simulation.
https://www.circuitlab.com/circuit/n533pn7gekzv/zener-charge-circuit-3/
Any help would be greatly appreciated!
Edit:
This is the type of battery I was testing with - I couldn't find an actual datasheet though: https://www.eblmall.com/product/ebl...t-lithium-ion-600mah-li-ion-batteries-4-packs. I took apart one of them, and I see that there are two Li-ion cells and what looks like a very simple battery management PCB which includes an 8205A Dual N-channel MOSFET (https://www.maritex.com.pl/product/attachment/91261/8205A.pdf) and an "20L8 K60S", which I can't find any info on. I'm not sure if/how this circuit actually has any bearing on how my charger circuit is designed though.
I wanted to make a charger that will not cause overvoltage or damage to the battery and will also provide LED indicators that will show when the battery is being charged and when the battery has finished charging.
I've decided on using a Zener diode that will shunt current above the maximum battery voltage to ground and an LM317 configured as a constant-current source.
The idea is that once the battery reaches the charged voltage (around 8.7VDC), the "charged" LED will turn on.
When I breadboarded the circuit, being powered with a 12VDC power supply (as I intend for the final circuit to use) the LED is just always on. (The 100F capacitor on the output is only for simulation purposes.)
The following attached are the schematics and a chart from a voltage sweep simulation.
https://www.circuitlab.com/circuit/n533pn7gekzv/zener-charge-circuit-3/
Any help would be greatly appreciated!
Edit:
This is the type of battery I was testing with - I couldn't find an actual datasheet though: https://www.eblmall.com/product/ebl...t-lithium-ion-600mah-li-ion-batteries-4-packs. I took apart one of them, and I see that there are two Li-ion cells and what looks like a very simple battery management PCB which includes an 8205A Dual N-channel MOSFET (https://www.maritex.com.pl/product/attachment/91261/8205A.pdf) and an "20L8 K60S", which I can't find any info on. I'm not sure if/how this circuit actually has any bearing on how my charger circuit is designed though.
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