ESP8266 Community Forum

- Tue May 12, 2015 5:32 am #17233

Hi

I'm hoping to use 2x 18650 3.7V (in parallel) and enable load share, i.e. if USB is plugged in, draw from USB - otherwise draw from battery. Does anyone know how load sharing in this setup could be accomplished?

Thanks

simplest way to do it is to add a small relay, energized when usb is plugged. relay contact will do the power selection switch. you can also add the 18650 charger from the link above, to charge your batt when
when usb is plugged.

but instead of relay, it be better if you use a mosfet to switch power from the batt. and transistor is cut offed when usb power is applied

Like this?

- Tue May 12, 2015 6:20 am #17235

Using something like these?

I've had a look at this one but I'm not quite sure what the output voltage is. Is it 3.7V?

In fact, would 3.7V need to be stepped down for the ESP?

Thanks!

I have some of those modules and have tested with a multimeter and it shows the output voltage reaches 4.19v when the LIPO is fully charged and the USB is connected. You can disconnect/reconnect the USB power and it switches automatically but doesn't go past 4.19v as long as there is a LIPO batter connected. Strictly speaking thats too high for an ESP but i power them with that and it seems to work ok. I guess if you're worried its too high you could put a diode in series to drop the voltage a bit, or a 3.3v regulator even i suppose.