7 pin plug 12v direct current

Once you go solar you will never not have one, trust me....but the OP asked about "basically" the charge wire in a seven pin arrangement. It depends on the truck to start with....some have a built in solenoid, others you have to install an aftermarket one but a "HOT" wire at the plug is usually there. You can very easily get in trouble if it is hot all the time...you will pull power from the truck battery...a very bad thing. Best advise is to use a volt meter to check it at the plug to know what you have going on. The advantage is that if you don't have solar your battery will charge while you drive, but not a very reliable source as your alternator is not going to keep up in most cases.