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geronimo-john avatar image
geronimo-john asked

12-12 30 Isolated/non-isolated... again... with a twist

My first post here.

I am planning on using my 2019 F-150 AGM/alternator to charge my three 100 Ah Battleborns in my travel trailer. Both my truck and trailer have chassis grounds and they are mechanically and electrically tied together. So far, if I understand correctly, that would suggest using the less expensive non-isolated 12-12 30.

Now for the harder part.

  • I use an Anderson WDH hitch which has two large chains that connect via a "Whale Bone" at the receiver and may have metal to metal contact most of the time on the trailer ends of the chains.
  • My hitch ball is greased to reduce ball wear from the Anderson weight distributing hitch. And the chains are connected to a polyethylene cone shaped sleeve that is also greased.
  • The Tow Vehicle has only a small wire ground via the 7-pin.

These paths all work just fine for the LED trailer lights and electric brakes.

But for a 30 amp load I have some concern that they are not sufficient for a 12-12 30 to provide a 100% consistently reliable ground path.

Am I over-thinking this? Or would it be prudent to order the isolated 12-12 30 and run both + and - from the truck battery to the 12-12 30 and lithium's? Thank you

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Mike Dorsett avatar image
Mike Dorsett answered ·

Hi, You could not rely on either the trailer hitch or the chains to provide any electrical connection. Trying to do so would cause continuous arcing - even if the hitch was not greased. The small wire in the lighting cable will be insufficient as you point out. However, you do NOT need to use an isolated charger, provided you do install a high capacity (45A) ground cable which is securely bonded to the appropriate grounds at both ends. This then calls for a high current plug and socket system for the charger cable - to allow easy disconnection. Amphenol make a suitable series of automotive power connectors, but as these are single pole, it will be necessary to ensure the charger is off before disconnecting any of the cables.....

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geronimo-john avatar image geronimo-john commented ·

Thank you for the excellent response. Good news on the non-isolated. Saves some nice $$$. :-) I am familiar with the Anderson plug connections, and will also check out the Amphenol line as well.


I'll be running two home run dedicated 4 AWG stranded cables, tied to the battery posts through 60 amp fuses at both truck battery terminals. Near the trailer hitch, I'll hard mount one side of an Amphenol/Anderson (120A (if available) or their 175A if not) two pole plug system. Run the home runs to the Victron 12 - 12 30 Non-Isolated, and ten to the Victron Shunt (- load side terminal) and the trailer lithium battery + terminal.

Any other suggestions of course would be welcomed.

Again, I appreciate you response.

Geronimo John

PS: I'll be looking only at two pole plugs.

PSS: Not sure how the likes/hides works yet, I was trying to like your response.

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