I had better add some detail now I know more.
The bike may not (as in isn't lol) be as new as the person I bought it from said.
The cover on the box that contains the electrics has an odd screw and the previous owner had taped some items up inside the box.
The bike is an izip aspen or aspen izip.
The battery is a 24v SLA unit and Has two batteries isnide the battery box.
When I first got this bike the battery power was being cut intermittently, but this was due to the front brake lever not being under enough tension to press the micro switch. The brakes needed tightening anyway and pulling 3mm of cable sorted that issue.
I charged the batteries until the charger said they were fully charged. It's a basic charger that only shows red for charging and green for charged.
Today was the first time the bike was actually ridden properly (it's for my son) and it randomly cuts out. The bike has three assistance settings and it will suddenly stop assisting with the pedals. Sometimes the battery power light will remain fully lit and sometimes it will go to its lowest level of one LED and flash. The power doesn't cut in the same way that operating the brakes cuts it as the motor seems to drag the rear wheel rather than simply freewheel. This is clearly dangerous when riding uphill as the bike comes to a standstill. It will do this on the flat or going uphill, and sometimes pedal assistance will restart after 2 or 3 seconds and sometimes it doesn't come back until you stop, turn off the power and start again.
Do any of you have any ideas on what could be wrong?
If any more info is needed to help then please ask