I'm experimenting with MCP73871T-2CCI/ML charger for my Arduino project. I wanted to build one by myself based on datasheet.
I have build circuit on prototyping board, according to this schematic:
Unfortunately charging current for battery is very low. At maximum, my 1400mAh LiPo is charged with current 100 mA, MCP73871 does not switch do 1A charging at all. Even, when I discharged battery completely, it does not switch to high current charging.
I need to add, that I was soldering raw chip to the adapter board by myself, so it might be that I have either broke it or it is not soldered properly.
Could you be so kind to give me any ideas how I can diagnose the reason ?
Best Answer
Some improvements and checks you should make no matter what
Who are the main suspects?
R16: it may actually be 10k instead of 1k (thus limiting charging to about 100 mA). If \$V_{bat}\$ is well above 3.0V after the battery has been charging for a while at 100 mA, that may be the case.
Thermal regulation kicking in: a poor thermal bonding/heatsinking of the IC may be triggering the thermal regulation mechanism and throttling down the charging current. May have the same symptoms as above, but with a correct R16 value.
Bad battery: the battery may be faulty or may not be up to your needs. If \$V_{bat}\$ is well below 3.0V after the battery has been charging for a while at 100 mA, that may be the case. You could be stuck at the preconditioning state (10% of charge current) and not be able to switch to the full charge state.
Bad \$V_{batsense}\$ connection: may have the same symptoms as above, even with a perfectly fine battery.
Also, always have at hand these tables from the datasheet when troubleshooting: