I got a 1995 F-150. I tow a pop-up camper, and have added a battery to the camper. I want to be able to charge/top-off the battery on the trailer while I am going down the highway. Well, since its an old F-150, there is no nifty 7 plug rv connector already hard wired in, so I had to improvise. I ran 10 gauge primary wire from the starter solenoid (hot side from the truck battery) all the way to the trailer hitch. I put a fuse in the line right after the starter solenoid to protect from shorts on the frame of the truck. I used a standard 12v relay mounted on the rear bumper to only allow the wire active when the running lights are on (I was too lazy to do engine running, so I figured I always remember to turn the lights off when the engine is off). After the relay, the wire is run through the center plug on the 6-way plug for the camper (no brakes), and then through a two position switch, and one more fuse on the trailer battery before finally hitting that battery. Well, I also have a built in volt meter on that trailer to monitor battery voltage. With this rig, I cant get the voltmeter to register in the alternator/charging range, which is above the "full" level. With my voltmeter, I measured 13.1 V on the battery lead from the trailer. So its not enough to trip the alternator/charging level on my built in voltmeter (which is probably 14 v), is that a problem? Can I still get a good charge with 13 volts? If not, what can I do to get 14 volts on the trailer?

thanks