Lipo battery protection circuit!!!!

I have this Lipo battery with built in protection and it's connected to this circuit. Connection at the top, left is battery charger and right is step up converter.
As a test I drew around 40mA from this until it died assuming that the built in circuitry would protect it. It promtly died and is now on charge via the micro USB connection on the left. However, when I measure the voltage on the battery it's just 600mV which means it's not charging!! I can bypass the protection circuitry but would prefer to be able to recover from this situation without resorting to such drastic measures. Anyone any suggestions?

Mike.

Five hours later and still the same. I'm thinking of using two 1N4148s and a 100Ω resistor in series to bypass the charger circuit (Vdd to Vbat). Anyone see anything wrong with this?

Mike.

Update, bypassed the charger chip with two 1N4148s and a 180Ω resistor and all appears to be good now - battery showing 3.6V and appears to be charging. Will see in the morning if all is well.

From the drop on the resistor I think it was charging at 3mA. Maybe this was enough to get the battery voltage up to where the charger chip detected a battery and started charging. Time will tell.

Mike.

Pommie said:

... From the drop on the resistor I think it was charging at 3mA. Maybe this was enough to get the battery voltage up to where the charger chip detected a battery and started charging. ...

Click to expand...

Makes sense:

All fully charged now. I'm now thinking that, due to the built in protection, the charger circuit could just be a 20Ω resistor.

Mike.