Electric Tounge Jack Question

Ok here is food for thought for you. I had my trailer in because my water pump wouldnt shut off. Long story short they told me it was fine when i picked it up. So I took the service centers word for it and put it into storage. When I went to pick it up the other day I see they left the pump and the battery shut off on. And the pump did start running and ran until it killed both batteries. The power jack was not going to move at this point and I had no clue how to manually do it. So since I was in the storage yard I had no way to charge the batteries. As luck would have it I plugged it into the truck to see if it would draw from it and it did.

So my point is I would wire it so that IF you have the same problem I did you wont be stuck.