We are towing a 2005 Toyota Highlander 4WD V6 Automatic using a Remco transmission pump. The car is placed in neutral and the key returned to the accessory position to keep the steering wheel unlocked. The brake assist is a BrakeMaster 9000 from Roadmaster connected to the air brake system on my Diesel pusher motorhome. We have towed it many times without a problem until recently.
We are on a trip to Alaska and have gone about 1500 miles so far, driving about 200 mile legs and have driven the car after each leg. On 2 of those legs the battery was drained and had to be jumpstarted. I am sure that everything, radio, heater, etc., was turned off. On this last leg the battery was down to 7 volts.
Any ideas as to what can be draining the battery? Can I or should I disconnect the battery while it is being towed?