Trucks 12 volt power lead to trailer battery
How many amps can I expect to recover during a 8 hour drive. Say I use 30 amps per night boondocking and then hit the road again. I have a 150 amp alt. I have 2 twelve volt deep cycle batteries. The o...
Forum Discussion
Charging is controlled by voltage and current (amps).
Think of voltage like water pressure in a pipe, and amps (amp hours) live the volume of water you move from point A to point B.
To float the trailer batteries you want somewhere near 13.7 volts, to charge it in a hurry you need closer to 14.4 volts.
Imagine 2 55 gallon barrels 100 yards apart, connected by a good garden hose, lets put the full one at the top of a hill and the empty one at the bottom. you will move a lot of water in a hurry and fill the second one fast. Not imagine them on opposite ends of a football field, connected with 1/4 inch drip line. It is going to take all day to fill the empty one. Say we have a hose keeping the first one full (alternator) and the little drip line moving water to the second one. At first the second battle will seem to fill ok, but as the water level rises there is less and less difference between the height of the water in the two barrels.
Same issue with charging the trailer batteries. The alternator keeps the trucks battery at 14.x volts, but the long, small wire between it and the trailers battery limits the amount of power that can be transferred. As the trailer battery charges, the (driving) voltage difference between the two batteries shrinks, and the amount of current (amps) that passes drops as well.
A severely drained battery (8 or 10 volts) may pop a 30 amp fuse, a mostly charged battery (13+ volts) an amp or two may be all you get.
I have a 20 amp buck/boost converter on my trailer, set at 13.5 volts. No matter what the oncoming voltage from the truck is, it pumps it to 13.5 volts and a max of 20 amps into the trailer. When I was dry camping I set it to 14.2 volts, faster charge but higher possibility of overcharging the trailer batteries.
Think of voltage like water pressure in a pipe, and amps (amp hours) live the volume of water you move from point A to point B.
To float the trailer batteries you want somewhere near 13.7 volts, to charge it in a hurry you need closer to 14.4 volts.
Imagine 2 55 gallon barrels 100 yards apart, connected by a good garden hose, lets put the full one at the top of a hill and the empty one at the bottom. you will move a lot of water in a hurry and fill the second one fast. Not imagine them on opposite ends of a football field, connected with 1/4 inch drip line. It is going to take all day to fill the empty one. Say we have a hose keeping the first one full (alternator) and the little drip line moving water to the second one. At first the second battle will seem to fill ok, but as the water level rises there is less and less difference between the height of the water in the two barrels.
Same issue with charging the trailer batteries. The alternator keeps the trucks battery at 14.x volts, but the long, small wire between it and the trailers battery limits the amount of power that can be transferred. As the trailer battery charges, the (driving) voltage difference between the two batteries shrinks, and the amount of current (amps) that passes drops as well.
A severely drained battery (8 or 10 volts) may pop a 30 amp fuse, a mostly charged battery (13+ volts) an amp or two may be all you get.
I have a 20 amp buck/boost converter on my trailer, set at 13.5 volts. No matter what the oncoming voltage from the truck is, it pumps it to 13.5 volts and a max of 20 amps into the trailer. When I was dry camping I set it to 14.2 volts, faster charge but higher possibility of overcharging the trailer batteries.
