Error 7 is for the key switch being turned off while in opperation but it is almost always a battery voltage problem. Try driving the unit while tilting back (ie have the battery under load) and see if the fault appears. Also check the battery voltage at the same time. You will probably find the the voltage is dipping under 35V. If it does load test each cell and see if there is a bad one or see if the whole battery is stuffed.
Cheers.
Matt
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