Towing RV with Lithium battery with my PB

[tim665214]

I am considering upgrading my RV battery to lithium. I have read that the higher voltages can damage a Tow Vehicle's alternator, and you would be advised to get a DC/DC converter. I was considering just removing the fuse that supplies 12v to the 7 pin connector to be safe, but since my Powerboost does not have an alternator, is this even necessary?

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[JEB]

I am considering upgrading my RV battery to lithium. I have read that the higher voltages can damage a Tow Vehicle's alternator, and you would be advised to get a DC/DC converter. I was considering just removing the fuse that supplies 12v to the 7 pin connector to be safe, but since my Powerboost does not have an alternator, is this even necessary?

I don’t think so. I tow with a pair of Battle Borns and haven’t experienced any issues. Plus, I think the issue is overhyped. Trailers with solar panels regularly maintain house batteries of all chemistries—not just lithium—at higher voltages.

A DC/DC converter is really only necessary if you you need more than a trickle charge at the 12v pin and are relying on the tow vehicle to charge your batteries in transit. With the PB, if you need in-transit recharging you might as well get that charge from the generator.

 

[tim665214]

A DC/DC converter is really only necessary if you you need more than a trickle charge at the 12v pin and are relying on the tow vehicle to charge your batteries in transit. With the PB, if you need in-transit recharging you might as well get that charge from the generator.

My RV has built in solar, so I don't need the 12v from the 7-pin. That is why I was considering pulling the fuse. I just want to make sure that the Lithium battery from the RV doesn't suck too many amps and burn something up.

 

[JEB]

My RV has built in solar, so I don't need the 12v from the 7-pin. That is why I was considering pulling the fuse. I just want to make sure that the Lithium battery from the RV doesn't suck too many amps and burn something up.

I misread. I thought you were concerned about the flow in the opposite direction.

I wouldn’t worry about lithiums pulling too much. The available current across the 12v pin is small—little more than a trickle. I don’t think any battery could pull enough through it to cause any damage to the truck’s electrical system. I haven’t had any problems.

 

[BLoflin]

The issue is really the opposite of what you are concerned with. Lithium batteries need a higher voltage to fully charge to 100%. That is why your RV charge controllers (whether the power source is coming from Solar panels or from 120VAC pedestals) need to have a Lithium setting to work with Lithium batteries.

You use a DC to DC voltage converter on the 12V line coming thru the hitch connector to raise the voltage up so you will get a full charge on your RV batteries. Otherwise the 12V coming from your truck will not fully charge (or top off) your RV batteries.

 

[brewduck]

I see my trailer pulling a little below 100 watts from the truck (PB) over the trailer plug. I let this charge the trailer when I'm towing, along with the solar panel (200 watts). I have 3 BB batteries in the trailer.

As you increase the voltage charging the lithium batteries it will try to pull more current; DC-DC converter are good to both limit this behavior (no more than 20amps for example), but also to raise the voltage before the batteries to increase the charge rate. Even if the truck is producing 14.4 volts up front, we do not see that back at the trailer with the batteries charging. It is a self-limiting system the way its setup and would require a DC-DC converter if you want to raise the charge rate.

With my previous truck I was looking at a 40amp DC/DC converter to get better charge while driving, but now with the PB I just wait and use the generator if I'm getting low.

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