Forum Discussion

tdhoch's avatar
tdhoch
Explorer
Jul 13, 2013

Charging camper battery with truck alternator?

We're in the process of buying a pickup truck and truck camper for off-the-normal-path explorations. I understand that it's common to have the rig set up so that the truck engine/alternator will keep the deep cycle battery in the camper charged while driving. The trucks voltage regulator should take care of keeping the truck starting battery properly charged (and not overcharged); but how does the system know when to charge and when to stop charging the deep cycle battery in the camper? How is the charge from the truck regulated? Is there a risk of over-charging the camper battery on long drives?

Thanks for lending a newbie a helping hand.
Truck Campers
  • trvsdad1's avatar
    trvsdad1
    Explorer
    Jul 13, 2013
    In my alpenlite I have two deep cycle batteries that will only charge "while driving" if the camper power switch is off. Power switch on, no charging while driving.
  • RoyB's avatar
    RoyB
    Explorer II
    Jul 13, 2013
    This is my proposed plan to charge a couple of deep cycle batteries that will be mounted in the back of my truck.

    These will normally get charged from the RV Trailer PD9260C 60AMP setup but for the times I am just running the truck hopefully I can re-charge them using the truck alternator.

    The risk as I can see it is the truck alternator big enough to handle more batteries being charged. Haven't done this protoype setup yet to see if it works or not...

    Drawing modified from the BLUE SEA home site doing something very similar...

    Look up the specs on the BLUE SEA SI-ACR smart relay shown in the drawing
  • tdhoch's avatar
    tdhoch
    Explorer
    Jul 13, 2013
    Thanks all of you for the help. Some is actually starting to rub off on me.. and before long I may understand it. Cewillis, the pics are very helpful, and it looks like the way to go.
  • cewillis's avatar
    cewillis
    Explorer
    Jul 13, 2013
    There is nothing for the alternator to 'know'. When the batteries (any of them) reach the alternator charging voltage (~14 - 14.2), charging stops. In other words, the 'feedback' is the battery voltage.

    Here's my charge circuit. 2 gauge wire.
  • romore's avatar
    romore
    Explorer II
    Jul 13, 2013
    That smart solenoid Jeff refers to also prevents draining the truck battery when the key is off so a boost won't be required in the morning.
  • Camper_Jeff___K's avatar
    Camper_Jeff___K
    Nomad III
    Jul 13, 2013
    There are a couple well detailed threads in the TC University section on installing dedicated large wire circuits from the alternator to the T C batteries.
    I would install 4AWG wire and a smart solenoid that separates thr TC and truck batteries or electrical systems to prevent the TC batteries from discharging back to the truck during high current demand situation conditions like night driving with the headlights, running lights, fan, and stereo all on. With the factory plug only, the alternator will never fully charge the TC batteries.
  • popeyemth's avatar
    popeyemth
    Explorer
    Jul 13, 2013
    Normally you don't get enough amperage to hurt the camper batt and the voltage/ charge rate is controlled by the truck alternator internal regulater.
    Voltage drop over the long wires means its basically a trickle charge system.

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