very odd

[dieselpower8]

so the other night i plug my extension cord into the truck but i forgot to plug the other end into the outlet so i go to start it the next day and it would not start. something drained my batteries so i had to charge them up. had the batteries tested and they are good. prior to this the truck was left plugged in for 12 hours a day. Now i havent even been pluggin it in at all and it will start fine in the mornings so nothing on my truck could have drained the batteries. can leaving the extension cord plugged into the truck and not the outlet drain ur batteries?

[NAFD86]

it shouldnt considering that there shouldnt be any electrical going out through the block