While down in Florida last January our converter went out and we had problems gettng the landing gear down. We hand cranked it down and then we disconnected the battery and hooked up a battery charger to the battery cables directly. We didn't put it on full charge but on the 2 or 10 amp setting and were able to run everything we needed until we had the converter replaced. Worked great for a temporary use anyway! Since we have a 2004 unit and it is a 30 amp unit we recharged the battery once the new converter was put in and haven't had a problems since! Knock on wood!
Dick's idea of the battery jumper unit is a good idea for a temp solution and at least you can crank the landing gear down and possibly the slides out without having to use the hand crank anyway!