If it won't turn you need a battery change. By the time you have done that all the excess fuel will certainly have drained away.
Is there any advice about this in the flight manual? Always use that for the correct advice.
By the way, do be careful about flying with an almost flat battery (this can be done if you use an external power supply in a situation where you have already exhausted the battery power). If the generator fails in flight, you will lose all electrical systems very quickly indeed.