Hi everyone,
I am currently trying to design a very small power source for an embedded project. My current idea is to use a rechargable coin cell battery (e.g. Panasonic ML-1220).
A boost converter (e.g. tps61025) would provide system power. The load will be connected only for a few seconds per hour and draw about 2mA when connected. A capacitor will be used to mitigate spike current draw.
Maybe I would add something like bq27501 as a battery charge gauge.
My current problem is to design a charging circuit for this project. It must take power from USB, and recharge a 3V Manganese Lithium coin cell battery. All of the battery
charging controllers that I found aim at 4.2V charging voltage or higher, while a coin cell specification (http://industrial.panasonic.com/www-data/pdf/AAA4000/AAA4000PE17.pdf) requires 3.1V charging voltage.
Could someone advise some solution to recharge these batteries? If I use a voltage divider on the charging output of, say, bq24018 it would just draw current from the battery when idle and would completely undermine the performace.
Are there any smarter solutions to this problem?
Thanks for your help!
Vlad.
