Q: Since the charger can’t distinguish between system current and charge current, is there any way to make auto charging work properly when the system is under load and the load current is variable or unknown? It seem that the termination criteria in this case will require system intervention to deal with the uncertainty is the charge current?
A: If you are using a AC charger you will not have a problem as the AC charger is capable to charge up to 600mA. Also, the charging threshold can be changed in software. The default end-of-charge is set at 80mA. You can change this in software if you can estimate the load on your system. It is difficult to say that automatic charging without any control is possible when you say that load is variable. You will have to have some software intervention to control the levels of charging.