Can a 600 Amp Hour Deep Cycle Battery in Truck Bed be Charged Using Tow Package Wiring on a Ram

Question:

Hello Etrailer Can you please advise on my plans to use a factory 230AMP engine alternator which serves a factory 800CCA engine battery, to charge a 600AH deep cycle RV battery located in the bed of a 2016 RAM 1500 truck. I plan to use your PNC56070 to extend the 7 pin plug wired from the factory rear bumper to the left front of the truck bed wall in order to plug in my camper, that’s the easy part. I am getting bogged down on wiring the charging circuit. I’d like to take advantage of the 230 alternator amps to charge the deep cycle. Since the black wire in the factory wiring I assume its 10 gauge? and the C56070 harness is 10 gauge, my gauge/amp/distance chart tells me after the current flows 18 feet there will only be 0-20 amps available. So I am considering clipping the black wire in the C56070 and routing a new 10 gauge wire from the center pin in the front of the bed to the engine compartment. This shortens the distance to 5 feet and provides between 20 and 60 amps per my chart to the deep cycle. Under the hood I am considering using your solenoid PK5231201 with 10 gauge on each end and a connection to an ignition switch controlled circuit on the 90 degree pole. If you approve to this point 1 where do I find the factory 10 gauge trailer power wire under the hood 2 where do I find an ignition switch controlled circuit under the hood and 3 This solenoid is only rated for 80 amps, is it too small? I would prefer an isolator such as DW08771 or larger or smaller? instead of the solenoid PK5231201 in a circuit similar to the above. However DW08771 is rated at 95 amps….1 Is this too small for the 230 amp alternator? 2 is it too big for the 10 gauge wire? Your knowledge is appreciated Thank You.

asked by: John S

Expert Reply:

The problem is that tow package wiring like that used in the factory 7-Wayas well as the in-bed 7-Way # C56070 is not large enough to handle the amperage that would be required to charge up a 600 amp hour deep cycle battery. At best it can maintain the current charge level of the battery but will not be able to up-charge it. Also, the factory tow package circuits won't be fused high enough (most likely) to handle the additional power pulled by the second battery and could blow.

However, 10 gauge automotive grade wire can handle up to 46 amps at a distance of 20 feet. My source is the Pocket Ref, Third Edition (Sequoia Publishing). At 6 feet the Pocket Ref suggests that a 10 gauge wire can handle up to 152 amps. This is assuming a 1/2 inch voltage drop across the length of the wire. The numbers will change if there is more or less voltage drop.

If the alternator is able to push back enough amperage to the battery in the truck bed as well as perform its other duties then this set up will work.

Regarding the battery isolation solenoid # PK5231201 the amp rating is only a factory when power is being pulled through it. So if the component connected to the isolator that is receiving the power, in this case a battery, is not drawing over 80 amps then the isolator will be fine. We do have a starter solenoid, # PK52331, rated for 200 amps.

In terms of where to find the various circuits under the hood on your truck the best thing to do is check the fuse panel lid so you can locate the fuses related to the various items you are looking for and tap into circuits that way. Otherwise you would have to try to trace wires and attempt to check for continuity to verify a wire at the back is the same as one at the front and so on. Not fun!