Morris Minor Owners Club

I have no idea, and doubt it is that important...
however you dont get anywhere with a dead battery (especially on Ray's cars in the back yard, when he's in a rush and they are in the way)
The battery condition is one factor, but so is the Amp-hour rating. A bigger Amp-hour means it will go further when fully charged.
With a really big battery, you can probably go far enough to burn out the starter motor..

I read something on this once & they quoted 50 -100 yards or more.... enough to get you off the road out of the way if stalled at a busy road junction instead of holding up all the traffic...