N1818 Elite only works plugged in

I bought a Novatech N1818 Elite laptop a few days ago, and it arrived yesterday. It’s a fantastic machine, but the only problem I have with it is that every time I unplug it from the AC adaptor, it shuts down immediately, even though the charge is showing 100% on the battery.

Any idea what could be causing this? I read in the instructions that the battery is locked until it’s plugged into the mains. Could it be linked to this?

I’ve tried updating the drivers and doing the usual unplug everything and hold down the power button, but no luck.

Any support would be greatly assisted.