F350 Diesel WON'T FULLY CHARGE Trailer Batteries - Ford Forums

barley4beer · 10-13-2006, 14:43

Apparently, my 2005 F350 diesel truck will not sense the state of charge (SOC) of my towed 5th wheel, 12 volt deep cycle battery bank. This 400 amp hour bank can be highly discharged and the F350's alternator will not supply it with even close to a maximum charge. The truck's voltage/charge regulator must only look at the truck's starting battery system, keeping it fully charged regardless of the SOC of the trailer batteries. How do I modify the charging system so that I can get a high rate of charge going to the 5th wheel batteries when they need it, even if the starting batteries are fully charged? Thanks! JJ

jbawilliams · 12-02-2006, 07:33

I don't know how to fix it, but I have noticed a similar problem with my 96. I have not yet tried with my 99. We frequently primitive camp out on the family farm (all in CRP) down by the pond. We have made our own little private campground down there. I use 2 12v wired in parallel. We run the batteries down low, and when I plug in to let the batteries charge, they do not improve very much. I have found that when I hook jumper cables instead, I get a much better charge. I have always guessed that it was because of the size of the wire going back to the trailer. I think mine is 10 ga, but it could be 12 ga. My jumper cable are 4 ga. Perhaps a bigger guage wire would do the trick, as it would allow more truck battery charge to escape to the camper batts., and then the truck would charge truck batts. better.