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Connecting truck inverter to trailer?


jeffw

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We tow a car hauling trailer, and it's got a couple of batteries in it for the internal lighting, lifts and to start the generator. The trailer has a 120v minn-kota multiple battery charger installed.

 

The batteries seem to go flat pretty quickly (I'm suspecting I've got a parasitic drain when the trailer is left connected to the truck). I'd like to be able to charge the trailer house batteries when we're traveling in the truck, so I was thinking of running an extension cord from the truck inverter to the trailer to power the battery charger (and 120V lights).

 

What safety considerations do I need to be aware of? Suggestions for a nice 120V socket I can mount near the 5th wheel? Any other tips?

Thanks!

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Your idea has merit BUT it will only charge when you are traveling or plugged into S&B. Put a small solar panel and charge controller on it and you should be able to forget about it. Check that the charging is working occasionally and check the water in the batteries too. I have an enclosed trailer with a utility DC battery. I didnt go to the trouble of connectiing to tow vehicle circuit, just put on a panel and it stays in good condition, regularly exercising, which is more than I can say for myself. LOL

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We tow a car hauling trailer, and it's got a couple of batteries in it for the internal lighting, lifts and to start the generator. The trailer has a 120v minn-kota multiple battery charger installed.

 

The batteries seem to go flat pretty quickly (I'm suspecting I've got a parasitic drain when the trailer is left connected to the truck). I'd like to be able to charge the trailer house batteries when we're traveling in the truck, so I was thinking of running an extension cord from the truck inverter to the trailer to power the battery charger (and 120V lights).

 

What safety considerations do I need to be aware of?

Nothing special, other than don't let the cord drag.

Suggestions for a nice 120V socket I can mount near the 5th wheel? Any other tips?

I've used the cord ends at the bottom of this page with good results, but they are limited to 15 amp connections. 20 amp ends will swap in their place, but they aren't UL or CSA approved, or NEC approved as an assembly. Use at your own risk.

Thanks!

I think Mark(DMBruss) uses the same idea, maybe he'll come in.

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I installed a couple of cables from the truck alternator or battery bank to the trailer batteries with an isolator to prevent draining when truck is not running. Alternator is 135 amp, I'm told expect max 80% sufficiency so that is about 108 when going down the road. That way when I get to the destination the Inverter charger doesn't want to commandeer a whole circuit to charge the batteries at days end. I could tune the charge rate down though.

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Installing a DC line between the truck and trailer - as Roger mentions above - is problematic. The voltage drop in most installations makes them of limited benefit. But there ARE things you can do to mitigate the issues with DC.

 

Sending AC over to the trailer and using the charger already present works pretty well. Most of the chargers (certainly any converters) can handle very low voltage and dirty power just fine. So voltage drop issues in the AC circuit, and use of modified sine wave inverters to "generate" the power work OK. It's not real "efficient", but it will get a charge on your battery bank in the trailer, and in some sense the alternator in the truck provides "free" power to the truck battery bank - the source for the AC power going to the trailer. It "can" overwork the alternator in some scenarios, but that is relatively a minor issue.

 

Safety is not something to be taken lightly. You are sending AC across while in motion and a very high quality twist lock plug is REQUIRED. Plus a high quality protected cord. And you have to route the AC power through your bed to the rear of the truck, and protect THAT as well.

 

Overall, putting some solar on the trailer is a better solution, and it works when the trailer is "standalone" too.

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Jack, did you look at the link I provided?

Yes. That is great plug for non-moving applications, but it does not appear to be a twist lock. You want good retention in this application....but that does somewhat depend on the routing method.

 

BTW Bill B does this exact thing being discussed. I'm sure he will eventually comment.

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Yes. That is great plug for non-moving applications, but it does not appear to be a twist lock. You want good retention in this application....but that does somewhat depend on the routing method.

 

BTW Bill B does this exact thing being discussed. I'm sure he will eventually comment.

I understand Wanting a twist lock to hold it secure. But then again I think if the plug was to hang up on anything, would it not be better for it to come unplugged rather than pull the wires out causing a possible dangling live wire??

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