I’ve now bought two of these cars. The second one because the first was missing the USB lead and I couldn’t charge the dead battery.
From what I’ve gathered (after hours of poking around with a multimeter and unsoldering wires), is the battery won’t charge at all once it’s dead. I can’t find any connection of power coming in to the VCC that the battery is wired up to.
In the end, I modified the car with a Sparkfun USB LiPoly Charger – Single Cell running the SYS OUT to the car’s main board, and then soldering the lipoly battery to the charging board (pic). Now the thing charges and works again.
For the record, I tried for a long time the technique of keeping the car on whilst charging the unit, but it didn’t make any difference, the power just didn’t seem to get to the battery. Here’s just an example of the power tests: power from mains to car, power getting to the unused VBAT and finally testing volate to the lipoly connection point – nothing (also tested the underside – same result).
So, this is a fun car, but be very wary of battery issues.