Do batteries charge while driving?

[cdoc83]

Hey all, I'm just getting into camping with a travel trailer and was wondering if the batteries "automatically" charge while attached to the tow vehicle? I have verified I have 12v+ at the correct pin on the 7 pole trailer plug but got wondering if simply plugging in is the equivalent of putting two batteries together of different charge levels (which, if I understand correctly, is really bad on the wiring and the batteries as they equalize)? Is there supposed to be some kind of inline resistance to ensure nothing bad happens, or is it fine to have a wire directly from the tow vehicle battery to the travel trailer battery (through the connector of course)?

[dodge_guy]

It’s more of a maintainer circuit than a charge circuit. So if you have an inverter running like I do for my small dorm fridge then it will keep the trailer battery at the proper voltage. However it would take quite a while to fully charge a dead battery through the circuit.

You also need to know if the vehicle side turns off power to the trailer when shut off so you don’t accidentally kill both battery’s.

[theoldwizard1]

cdoc83 wrote:
Hey all, I'm just getting into camping with a travel trailer and was wondering if the batteries "automatically" charge while attached to the tow vehicle?

I am sorry to say, that the other responders are very being very optimistic !

At best, you can expect that the trailer batteries is NOT discharge any further. They certainly will not re-charge if depleted !

Please read this DC-DC battery charger

[Old-Biscuit]

YES ......
Tow vehicle alternator will maintain/trickle charge trailer battery

Provided trailer battery disconnect switch (if so equipped) is ON
Otherwise trailer battery 'could' be isolated from charge circuit (depending on how disconnect switch is installed)

[kerrlakeRoo]

Most vehicles charge very slowly, in part because the wiring is limited.
To see if you are getting anything check the batteries voltage 3 times.
Once with the trailer disconnected, voltage at the battery.
Second with the tow vehicle connected but not running
Third with the engine running.
Your first and second voltages should be the same, the third after the tow vehicle has been running a few minutes should show an increase. If so, yes its charging as you drive.

[MFL]

The camper battery will charge from your vehicle alternator, but the line connecting truck and trailer is small, so takes quite a while.

Jerry