Large toy haulers stock batteries

A single battery is small capacity for a large unit, but as said above, should not die so quickly. It's probably just a bad battery. Some guys never add additional capacity on a toyhauler because most come with generators that get run every day which keep the battery topped up. We have the cheap interstate deep cycle/ starting half arse battery along with a second I transferred from my last trailer that is a 4 year old Walmart special cheapo. The two in parallel will take us all night with the heat on and still have plenty of capacity to get us through til morning generator hours and then start the generator. So, the fact that yours is dead while half way through unhooking means one of two things. It's shot or your truck is not charging it while traveling.