You could Parellel it with one battery and it might help a little. But seems you have one or more bad batteries if That is all you got out of them. You should have gotten at least 4 hrs or more unless it was bad windy. Most get 6/8 hrs out of 31's and not that much difference in 29's. If you have a meter I'd sure check each battery after a full charge and check all connections real good.