So confused switching to Lifepo4 AlternatorBambi

[shannonc]

You'll be fine. I towed my previous trailer for 3 years with Lithium's and no 7-pin changes and never had any tow vehicle issues.

I think this video is helpful.

https://www.youtube.com/watch?v=WblbzIQgNRE

[JeffKim]

Originally Posted by richard5933

I'm not talking about mounting the DC-DC charger in the tow vehicle... That clearly should be in the trailer. I'm test talking about installing a designated supply line from the tow vehicle to feed the DC-DC rather than using the factory wiring.

Yes, thanks I'll take it under advisement. If I got the fancy Victron XS then I could get a lot more charging with the dedicated wiring. In the Victron XS literature they mention something about developing it for European vehicles, so maybe they are talking to me.

[JeffKim]

Originally Posted by shannonc

You'll be fine. I towed my previous trailer for 3 years with Lithium's and no 7-pin changes and never had any tow vehicle issues.

I think this video is helpful.

Thanks, I thought the video was interesting and I haven't seen anyone test the charging wire like this guy did. However, he didn't address that simply attaching the charging wire does not charge with a lithium profile and that if you have rooftop solar charging as well, it can confuse the charge controller so it does not provide any charge (anecdotally I've seen this).

What really confuses me and he's just wrong is that he uses a straw analogy that the battery can't pull more from the alternator because of the resistance in the wire. If the load/demand is large enough, it could fry the charging wire, but then in the trailer it's fused to 30A. In the comments he makes some argument that it's a difference in the voltages of the vehicle and trailer batteries that's driving the current from the alternator (???). Anyways, I'm going to dust off my EE background (it's been 40 years) and do an analysis.

[pboomerx]

Originally Posted by tunnelboy

Ok, quick follow up. If I disconnect the + from the TV coming into the trailer, won’t that also kill my brakes and running lights on the trailer? Or is there a separate positive for that? And what would be the correct configuration for a DC-DC if I went that route? If I got the 20A amp Renogy, I don’t believe it’s configurable. It simply pulls 20a max, no?

The lights on my 2021 Classic won't work without the 12V pin on the 7 pin connected. IMHO, running 4-6 gauge wire from the battery of the TV to the rear bumper is the way to go. You could then use either 20A or 40A dc to dc converter. If you have one battery, 20A should be OK...40A if you have two. I use Redarc for my dc to dc converter as the quality is excellent, tech support is awesome and it is a waterproof unit. If running the wire isn't viable, I agree with another poster that just use the internal 110 to DC converter to charge or hook up solar. Without the dc to dc converter, you should unplug the TV so your lithium battery does not attempt to charge your TV battery. Hope this helps

Good luck

[DCPAS]

Originally Posted by JeffKim

If the load/demand is large enough, it could fry the charging wire, but then in the trailer it's fused to 30A. In the comments he makes some argument that it's a difference in the voltages of the vehicle and trailer batteries that's driving the current from the alternator (???). Anyways, I'm going to dust off my EE background (it's been 40 years) and do an analysis.

There is a fuse in the tow vehicle too for the charging wire. Mine is 25A.

I just installed LiFePo4 batteries, decided that I did not need to disconnect the seven pin charge wire, and have worried about whether that was a good idea or not ever since.

Much of what I have been able to find about the batteries killing the alternator, I do not understand, but there is a Battleborn video saying that if you are just using the OEM small charge seven pin wire, you do not need to worry about harming your alternator.

That makes me feel confident unless I see yet another post where someone has disconnected the charge wire. Oh well.

https://www.youtube.com/watch?v=Gxypk8J-0Mg

[Carmen214]

Originally Posted by JeffKim

I'm currently running wild and free with the charging wire disconnected. Otherwise, I haven't quite decided. The Victron Orion XS is very sexy. I can tune the input amps to 15 or less and is compact, runs cool, Bluetooth, and plays with all our other Victron equipment, but it's a lot more money ($328) than the charger that doesn't work. I can get a Renogy 20A charger and dummy it down to 10A which is much cheaper ($100), but then it won't show up on my phone in my Victron collection. There's also a Redarc 12A they put in the Tradewind but it's $300, so I'll probably end up with the Victron.

Thanks for the heads up. I have a Cayenne diesel and I'm glad I found this thread as I have a Victorian Orion TR 18a charger on order which I will send back and order the XS unit. A bit pricey but good to integrate with the Victron inverter and solar controller.

Can you tell me which fuse was blowing? There are 3 which indicated for trailer but not sure what feeds what so just curious.

[JeffKim]

Originally Posted by Carmen214

Thanks for the heads up. I have a Cayenne diesel and I'm glad I found this thread as I have a Victorian Orion TR 18a charger on order which I will send back and order the XS unit. A bit pricey but good to integrate with the Victron inverter and solar controller.

Can you tell me which fuse was blowing? There are 3 which indicated for trailer but not sure what feeds what so just curious.

In the Q7 it's the circled one in the driver's side rear fuse box. I don't know if the Cayenne is fused the same or if it's the same location. The XS is in short supply so you might have to get on a waiting list, but I'd be interested in how it works out.

[Carmen214]

Originally Posted by JeffKim

In the Q7 it's the circled one in the driver's side rear fuse box. I don't know if the Cayenne is fused the same or if it's the same location. The XS is in short supply so you might have to get on a waiting list, but I'd be interested in how it works out.

Thanks for the fuse location. The Cayenne has 3 fuses related to the trailer hitch but on the passenger side and not sure which feeds the 12v circuit easy to figure out. I was able to order the XS from Bay Marine Supply. I'll let you know how it works out.

[JeffKim]

Originally Posted by Carmen214

I was able to order the XS from Bay Marine Supply. I'll let you know how it works out.

Thanks, I ordered one also from them (and they didn't charge sales tax - don't tell the State of Minnesota).