I have made long runs of the sewer line (as long as the slope continues downward, and I have had long runs of water hose longer than 100 ft, but I would never run electrical cords on the rig more than 30 to 50 feet because as the cord distance gets longer the worse the power gets that can actually cause some damage to some things. 150' on high amperage needs (like a trailer) is not a good idea and one must really know wire gauge and distance ramifications for electrical wiring, and it's more than an "if-the-cord-connects" mentality. You also need to know the big picture of what you're doing. Since I'm NOT that type of guy, I try and keep electrical wiring very simply in distance.
NCFishers, like many others is very good source of this type of advice and knowledge. I used to think H. John Kohl was as well, but he's just let out his secret.
H. John is still someone I'd listen to.
1retired06 does have good advice about having the batteries checked. You don't say what the voltage of the batteries was reading (isolate the batteries to get the proper reading). If the battery water level ever gets that low and over 5 years, just refilling the water might not fix things completely. It's a good idea to have the batteries checked to find out their condition going forward. This can be done at some autoparts stores for free or for a small fee.