I have a 2021 nuCamp T@B 320s Boondock that I am upgrading to a LiTime 12V 100Ah Group 24 Deep Cycle LiFePO4 Lithium Battery. The trailer already has a SmartSolar charge controller MPPT 75-10. I want to properly charge the battery while connected to my 2024 Jeep Grand Cherokee via the 7-pin connector. The B+ has a 30 amp fuse, so I believe that I need a DC to DC converter that draws less than 24 amps max (80%). Grounds will be common, so non-isolated should do. The 7-pin power is always on. Smart / Blue Tooth is optional. I’m having trouble finding the correct product on your web site or internet searches. Nobody talks about connecting via the 7-pin connector. Also, I am moving the battery inside, under the seat next to the 120 volt converter and MPPT 75-10. I’m concerned about poor ventilation and overtemp protection. I would also consider replacing the MPPT 75-10 with a combination DC to DC with MTTP, but I don’t think that is necessary.
Hi Rob
You could also consider the ‘Charger’ (Smart) models, after all you are battery charging. Plenty to choose from, the XS model the flagship (it can limit Amps). Depends on the features you want, but with LFP I’d go for a Smart one (more easily adjustable).
They can all get warm, but will derate at lower than dangerous levels.
Never forget that your Jeep alternator must be capable enough. Imagine rolling around a dark city at idle revs with your lights on. The Smart ones have protection against flattening the feed battery.
Your choice, happy camping.
Thank you for your input, but I question that the XS Flagship at 50 amps is in excess of what is needed.
I’ve looked at the specs for the Orion-Tr DC to DC Converter and the maximum input current is not listed. I could only find this in a 30 amp version on www.victronenergy.com. Do I assume correctly that these do not allow limiting the input current?
I did find an 18 amp version for sale, but cannot find the specifications or the maximum input current. This is half the price of the XS and would be an acceptable charge rate as long as I could be sure it would not blow the 30 amp fuse in the Jeep. Can you verify this, or is the only choice the XS?
Ah, ok. I was somewhat overlooking your current limitations, my bad.
The /18 Converter is quoted at 87% Efficiency, that converts to ~21A on the input. That model may actually produce more than rated, but should be ok for your limit. But you’ll need to put up with tuning it with a tiny screwdriver. I added an old panel voltmeter nearby mine, but once setup to suit your batts it should stay stable. That’s for a Flat V target only, but even LFP’s can handle that if setup right.
The XS will work without these little worries. Up to you if it’s worth it.
Another alternative might be upgrading your input Amp capability and maybe another plug. Sometimes vehicle looms have unused wires that can be combined.
I’ll confirm, I have a Orion-tr smart 12/12-30 and it has no adjustment in the app for limiting the input current, only the charge voltages
In your case I would use the Orion tr smart 12/12-15 or 12/12-18, If you’re not trying to use the jeep as the main charge source either one should be just fine as you’ll likely have a couple hours driving/running with the vehicle to charge it between destinations, no?
If this is intended to be a main charging source I would suggest secondary wiring and a larger charger or you’re going to be wasting a lot of fuel for nothing idling the vehicle to charge batteries.(or get a small inverter generator to run a charger)
I was looking for that Smart /18 and couldn’t find it. I have now, would be better than the Converter model.
Dave, My intended use is to properly charge while driving and isolate the Jeep and trailer batteries. Main charging, if needed, would be A/C to the trailer. This small trailer doesn’t need much power and just want to extend life when driving between off A/C locations.
Do you think the engine shutdown detection will work given the remote location in the trailer and length of smaller gauge wire?
Do I need a remote on/off to avoid having to unplug the trailer when stopped?
John, finding all the model options has been difficult. I would go with a Smart/18 non-isolated, but I can’t find one.
Ok, I figured you weren’t looking for any kind of crazy output from the thing, thankfully!
The 15 or 18a version should work fine for you, I would almost lean towards the 15a as a lot of trailer wiring (vehicle side at least) doesn’t tend to use big enough wire that I would feel comfortable pulling 20a+ from for any length of time.
I can’t comment on how well the engine detection will work if used with the trailer plug. The unit I use is mounted in the back of my service truck to charge the body batteries back there, it’s about a 25ft run of 6ga wire and the engine detection works perfectly fine at that length of run
I’m concerned about a correctly engineered solution and using a product that is designed and tested for my application.
nuCamp tells me that the DC-DC converter/charger is optional and that they don’t use them in their new trailers with the LiFePO battery.
My understanding is that would not charge the LiFePO correcty, not fully, and perhaps shorten the life. However, that would only be when connected to the tow vehicle, not the A/C or Solar. If the battery is low, it would probably get a quicker charge through that strait connection … just not to a full charge. However, when the vehicle is off, the LiFePO could feed current back to the vehicle battery. I read about someone simply using a diode to prevent this. That would cause about a .7 volt drop in charge voltage to the trailer.
So, I believe using the DC-DC converter/charger is the best solution (although isolating the ground is not necessary.)
The jeep 7-pin is fused at 30 amps, a 7-pin connector is rated at 40 amps. At peak load, the wires will surely get warm and there would be a significant voltage drop on the smaller gage wires. But the design wire size should be safe for the fused amperage.
The real question is if the DC-DC converter/charger is actually designed and tested to reside in the trailer on that length of wire and voltage drop at higher currents.
I’ve searched long and hard, read the user manuals, but cannot find information on properly using one in the trailer.
Has Victron tested in this type of installation?
I’m all for doing this right, but don’t want to invest time and money into a solution that may fail or is no better than not using a DC-DC converter/charger at all.
Thank you for your input.
Like I said, any factory vehicle wiring I’ve seen I would not trust to run at the rated/fused amps for this kind of setup. The vehicles wiring wasnt exactly designed for this, big difference between dragging it down for 30sec with a trailer jack and pulling constant load with a charger. This is exactly why victron recommends 6ga wire to feed a 30a charger at that kind of distance, factory 7pin with ~12ga just isn’t going to be ideal
I have never seen a trailer that properly charges a lead acid battery from the 7pin let alone a lifepo4. That’s exactly why this product exists.
Only you will know exactly what kind of voltage drop you are going to see at the charger. Every vehicle and every trailer is different in terms of wire length and gauge. you might pull it down to 10v, maybe it’ll go to 9v. As long as it’s above 8v and the wire is whatever you would call acceptable for temperature it’s good.
If you’re dead set on using the existing wiring and 7pin, I would strongly suggest going with a smaller charger than the 30a
For some reference, this is my 12/12-30 in my truck. I drew down my batteries and bypassed the victron to turn it on. I know this is nowhere near “hot” it’s just a reference, with appx 25ft of 6ga wire I am seeing a 1.3v drop on the input and in a 20min timespan the wire temperature has increased 30° (is a cool 61° ambient in my shop right now)
Food for thought if you think you’re going to do the same thing with ~12ga wire without melting things!
I just had to try it tonight just to see for my own eyes. I had a maxi fuse holder in my truck with 8ga wire, I rigged that up at the battery post and got the charger going full pin again.
After 30min the short 8ga piece of wire was hovering around 120°, that’s ~60° above ambient. On a 100° day and with underhood temperatures that would put this wire near its melt point quite easily and definitely hotter than I would feel comfortable using even in our cooler climates!
Hi Dave,
I truly thank you for your testing efforts that have provided some very interesting results. I am quite puzzled about the engineering that goes into trailer wiring.
Any electrical circuit shoud be fused to protect against overload … and fire. There should be no wire run that cannot handle the continuous amperage allowed by the fuse. I am amazed that only a 10 or 12-ga wire would be fused at 30 amps when a sustained current draw could produce dangerous heat.
Now I am concerned that my stock Jeep and trailer could produce dangerous heat if I plugged in the trailer with a deeply discharged battery. The fuse would not protect the circuit from overheating with a 20-25 amp continuous load. Is the engineering here really that sloppy?
In no way was I considering a 30-amp charger, only the 18-amp. I cannot find a 15-amp. Do you have a link?
The way the vehicles are rigged up from the factory it’s very unlikely that anything plugged into it will ever draw that much current. Nothing is built to exceed any safety standards these days, it’s bare minimum and as cheap as they can build it!
even with a near dead trailer battery without some type of dc-dc charger like this, you really aren’t throwing a lot of current at the trailer battery due to the voltage drop.
I can’t seem to find the 15amp unit, I may have been confused with the 24/12-15. But the 12/12-18 would be the next best option. The 12/12-18 is recommended to be fused at 40a (60a for a 12/12-30) so it can pull a bit of power. It sure would be nice if there was a current limiting setting on these!
That being said, there is a setting to limit how long the charger can run in bulk mode, if you do find that the charger is causing some heat related issues in the wiring after prolonged use you can limit the bulk mode to say 30min or whatever you feel comfortable with
One other note, with the amount of voltage drop you may see over that length and size of wire it might be tricky to get the engine shutdown detection to work properly. If that does end up being an issue I would use a relay wired into the trailer marker lights to use as an on/off trigger. Anytime the trailer marker lights are on, the charger turns on!