bq24200 (texas instruments) charger prob.

AilSnail

Flashlight Enthusiast
Joined
Jul 11, 2003
Messages
1,299
Location
Bergen, No
Hello, this little chip won't do as I tell it. Tried two times now, powered by 9v (open cirquit) cellphone charger. It is the version with the temp sens. The reference pin should be within 30-60% of Vcc. If there was an error there it should be flashing, which it doesnt, but it did when I used a 12v (o.c.) wart, which should be ok. I was using 10uF cer. caps but then put a large el.lyte (47uF 40v) on the input in addition.
The led shows it should be charging, but the cell stays at 3.98v.

The pcb gets quite hot, (and I tried heating it more to see if the ptc would kick in and shut it down, but no...), which could be the LED.
 
I rewired it and put a 2x 8.8kOhm resistor divider in place of the ptc network. And it now feeds from 2x li-ion cells. I changed the led and removed the elyt cap. it lights when Vin and Vout are connected, but it doesn't turn off when the cell is removed. It doesn't get hot. it doesnt charge either.
 
I made another one, powered from 2xLi-ion 123, but put 25 Ohm in series. I also put 1k in series with the LED. This one charges. :)
 
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