Battery drain using the Ladyada Lipo charger

Not that it is the end of the world, but the LiPo charger has a fault that kinda bugs me. When the LiPo is fully charged, the MCP73833 shuts off power to the battery. Since the battery and load are connected, the load pulls on the battery instead of getting its juice from the USB.

In my tests the battery ran from 4.20V down to 4.09V and then the charger kicks in again.

The appnotes for the chip 51746a and AN1149 describe using the Fairchild FFDFMA2P857 MOSFET/Diode to switch over so that when the USB is available, the load pulls on that and charges the battery. If the USB is removed, then it draws from the LiPo.

and when the USB is removed:

Sounds like a good addition.

 

BTW< the 2700mAh battery I’m using has a charge rate as 0.2C standard with a 1C max. 0.2C would be 540mA.

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