DC to DC Charger

[boogielander]

Boogielander, thanks very much for the detail, and please do let me know which engine bay IGN fuse number you connected to and the description of this fuse from the owner's manual (just because our different model year trucks might have a slightly different fuse layout and fuse numbers).

I encountered the exact problem you did with insufficient voltage to charge my camper battery from the starting battery. I use portable solar panels so the Renogy DCDC with mppt allows me to both direct charge and solar charge via one device that has similar capabilities as your Victron.

And the only place I can find to mount this charger is in the very back of my camper, so I'm using 4 AWG wire, and other than this our setups are very similar.

I think that several readers of this forum would appreciate your detailed writeup and photos when you get to it.

oh yeah if I didn't have a Renogy solar controller then I'd be looking at options with MPPT.
Another method that my friend uses is way more capacity but also bank:
Same Victron setup, but instead of Ecoflow Delta 2 he uses Delta 2 Max with 2 Delta 2 Max Add-on Batteries giving him 6kw of power total. Delta 2 Max has dual input capacity, so he also has 2 Bouge RV 200w solar panels permanently mounted on the roof of his GFC. That pushes out around 600w on a sunny day while driving. No MPPT controller needed since Delta 2 Max has that built in.

But the downside is, that is a $5k setup excluding Victron lol BUT at the same time we were using air fryer to make breakfast and his +1 can use hairdryer. Oh, and we can run Starlink whole night too. In addition, he has fridge hardwired to his truck (with stock dual battery setup) from years ago, so he also has a noco charger that charges the two batteries while engine's not running.

For me i'm happy with 3kw of power because i'm not using air fryer and hair dryer when i do solo overland. I don't have an air fryer and being single with military style hair cut means no hair dryer needed. I can still run fridge and Starlink whole night on just a bit over 1kw/ night and charge it all back within a few hours of driving. All other smaller items that charge via USB can be plugged to the truck or EcoFlow if needed. For days that I establish basecamp I also have portable panels (2x160w Ecoflow portable). I also have one Renogy 170w flexible sitting at home to be installed back on (my old Renogy 100w flexible panel flew away... long story short it was attached to my soft shell wedge style RTT and it held on for half a year until I decided to do 90mph into headwind right around Memorial Day. I'm still trying to find a good solution to attach the new panel)
My setup is only $2496 before Victron.

 

[boogielander]

Boogielander, thanks very much for the detail, and please do let me know which engine bay IGN fuse number you connected to and the description of this fuse from the owner's manual (just because our different model year trucks might have a slightly different fuse layout and fuse numbers).

I encountered the exact problem you did with insufficient voltage to charge my camper battery from the starting battery. I use portable solar panels so the Renogy DCDC with mppt allows me to both direct charge and solar charge via one device that has similar capabilities as your Victron.

And the only place I can find to mount this charger is in the very back of my camper, so I'm using 4 AWG wire, and other than this our setups are very similar.

I think that several readers of this forum would appreciate your detailed writeup and photos when you get to it.

I used F54 PCM. Just note that you'll need to cut/ trim the fuse box side a bit to allow wire to come out. I'm not a fan of just forcing the lid on because it can damage the wire that you're running and potentially leave a bigger hole on top for water and other elements to get in.
I recommend using a small dremel bit to trim, but a sharp cutting tool does the job too. I was in a rush that day so I just use a small sharp pair of cutters that I use to trim zipties to make a V-shaped cut instead of breaking out the dremel and the stylus attachment.

 

[PeterB]

Super, thanks much! And I was wondering about whether to drill a small hole in the fuse box cover or put a small notch where the cover joins the base, so thanks for your recommendation; just cutting a small notch will be easy.

 

[boogielander]

Super, thanks much! And I was wondering about whether to drill a small hole in the fuse box cover or put a small notch where the cover joins the base, so thanks for your recommendation; just cutting a small notch will be easy.

yeap just cut a small notch will be fine. I believe I also trimmed inside of the cover as well to reduce the amount of notch i have to cut on the bottom side.

 

[rdugedug1]

I read this once or twice but I don't believe anyone has used the 30 amp 7 pin that is built into the truck.

Food for thought, I will add a renogy 1212-20 to the truck side of the 7 pin with OEM wiring which is 10 gage. I suspect roughly 10-12 feet from fuse box to the 7 pin connector. Renogy installation chart shows this to be acceptable to supply this unit. From the 7 pin to the trailer is also 10 gage wire and in my case 10-12ft, this also is acceptable to Renogy. For testing I can use the half current option on the unit and test bumping it to the full 20amps. My concern is where to mount the Renogy? Under the bed would be nice but note a clean dry environment. In the bed would be ok except for running wires back and forth. I mostly have the bed covered anyway.

If there were any issues with this then they wouldn't have spec'd a 30 amp fuse for the line?

Any takers?

I have an etorque hemi also. 200W solar 100AH lifo for fridge and furnace but would like to boost the pack while driving. I also have 3 85 AH lead acid in bed of truck for invertor for coffee and hair dryer. They charge while I drive but draw down the lifo while driving. Testing at 10amps would be because the same 10 gage wire is already delivery 3-10 amps to the lead acid. I would have to choose carefully when I could switch to 20 amps if it was even necessary.

 

[Ddubya]

Interesting discussion. I have a 2023 ETorque and have been thinking about how to charge the trailer Lithium batteries. My understanding of the Ram Etorque charging system is that the generator feeds the on board 48 volt battery and a dc to dc 12 volt charger for the 12 volt truck system.
Has anyone researched the possibilities of either a dc to dc converter fed by the 48 volt generator or a dc to dc converter fed by the 12v truck dc to dc converter. My thought is that the truck dc to dc converted will not have enough output to power another dc to dc converter to charge the trailer batteries.

 

[Bt10]

Interesting discussion. I have a 2023 ETorque and have been thinking about how to charge the trailer Lithium batteries. My understanding of the Ram Etorque charging system is that the generator feeds the on board 48 volt battery and a dc to dc 12 volt charger for the 12 volt truck system.
Has anyone researched the possibilities of either a dc to dc converter fed by the 48 volt generator or a dc to dc converter fed by the 12v truck dc to dc converter. My thought is that the truck dc to dc converted will not have enough output to power another dc to dc converter to charge the trailer batteries.

Why would you have the truck dc-dc converter power another dc-dc converter? 12 & 12?

 

[Ddubya]

To isolate the truck convertor or in case the truck convertor cannot supply enough current. Most importantly the truck convertor is set up to charge a wet cell battery and a lot of trailers are using lithium batteries. I would also like to know if a 48 volt to 12 volt convertor would work from the truck generator.
These are questions that should be answered before I would try it.

 

[boogielander]

so e-torque is achieved with 48v generator that converts to 12v for starter battery.
Theoretically plugging in a dc-dc converter at the 48v part should work. (meaning, using the 48v battery to charge the aux battery via dc-dc converter) there are products that work with 48v and step it down to 12v while boosting wattage output.

HOWEVER, because of the complexity in design and cost to replace should something goes wrong, I much rather just grab power from the 12v side and step it up to boost wattage output than mess with the 48 system.

The simplest solution, without messing with the 48v portion, is to run power from the starting battery to a dc-dc charger to step the output up to charge the aux battery. You will need a strong dc-dc charger to step up enough wattage to charge the aux battery fast though. My way of doing it pushes out around 200watt/ hr of power to charge my EcoFlow, but replacing the current charger with a more expensive one I can probably push another 100W out.

 

[hogger]

Not doing this with an e-torque, but I've set up a 200Ah LiFePO4 set of aux batteries to charge from a Victron 12-12V/30A DC-DC converter. So about 400 watts to the batteries. I'd recommend you watch your wire sizes, and maybe go for an actual charger instead of just a DC-DC converter. And at those currents, wire the GND back up to the front, as the rear GND point from my research is spec'ed for max 50A, which my set up can exceed under worst case conditions. I kinda wish I'd gone with a heaver gauge wire, and someday I may swap out, but it works well enough that it's not a top priority for me atm.

 

[Ddubya]

Ok, it appears that the charge line on the 7 pin trailer connector is fused at 30 amps. With that in mind a DC to DC charger in the trailer should be all that is needed.

 

[Rickyrocket]

Plenty of success with this project on YouTube,never heard anything about the ""battery pack" having problems.

 

[Bruno Sailor]

I have a 2023 ram Etorque. I was going to do Dc to dc charging for my travel trailer but decided against it. I was advised by 3 independent sources not to do it. One was a Ram service manager at a local ram dealership stating that the level of complexity of the controls on the system will probably go into an error code and possibly worse. The second was from Explorist life an expert in converting rvs and vans to LiFePo4. The 3rd was also an expert in solar rv. That was enough for me to not risk causing massive damage to my new truck.

 

[boogielander]

I have a 2023 ram Etorque. I was going to do Dc to dc charging for my travel trailer but decided against it. I was advised by 3 independent sources not to do it. One was a Ram service manager at a local ram dealership stating that the level of complexity of the controls on the system will probably go into an error code and possibly worse. The second was from Explorist life an expert in converting rvs and vans to LiFePo4. The 3rd was also an expert in solar rv. That was enough for me to not risk causing massive damage to my new truck.

ive been running not one but TWO DC-DC charger on my etorque. one is victron 12/24 that powers my ecoflows and another one is Renogy 50A DC-DC with MPPT. both are hooked to the starting battery with their own breaker and power line, and both are ign triggered.

as long as you're not running it to the 48v on the etorque you're fine. Also as long as you're using quality components (Renogy Victron etc with ign trigger) and use quality parts (Blue Sea breakers) you're going to be ok. Those smart chargers know when to kick in and when not to so they don't put too much stress on the e-torque system

 

[TSL]

I book marked this thread and have been coming back to it lately. We have a pop-up camper trailer now ( Somerset Evolution E3 - it's a sort of off-road-ish popup ). anyways, I'm working on converting it to use a Lithium battery and am questioning whether or not I need a DC-DC charger. I don't actually care about charging the trailer's 100ah LiFeP04 battery with the truck, more concerned about will I make the truck's 12V system "unhappy" without one.
I intend to have a solar setup to replenish the battery. Worst case scenario I can think of is trailer battery is quite depleted on a camping trip ( maybe not much sun and don't get recharged that way ). We would be on our way home and the 3-way fridge in the trailer is running on DC while on the road. So that is pulling power, and the battery is probably absorbing power too because it wants to be charged. Again, I don't care that the battery gets charged, I just don't want it to ask too much of the truck and cause a problem.
I suppose the right thing to do is install a DC-DC charger and stop worrying about it. Just trying to get a sense of my risk exposure if I don't bother. Maybe I just risk blowing a fuse on the 7pin connector ? I assume the 12V power line in the 7pin is fused on the truck somewhere ?
By the way, my truck is the EcoDiesel power train, so don't have any e-Torque concerns as others here have mentioned. I think my truck has a 250A alternator.
@boogielander , appreciate your input here, although you have a more sophisticated setup than I have and I know you do have eTorque.

 

[boogielander]

I book marked this thread and have been coming back to it lately. We have a pop-up camper trailer now ( Somerset Evolution E3 - it's a sort of off-road-ish popup ). anyways, I'm working on converting it to use a Lithium battery and am questioning whether or not I need a DC-DC charger. I don't actually care about charging the trailer's 100ah LiFeP04 battery with the truck, more concerned about will I make the truck's 12V system "unhappy" without one.
I intend to have a solar setup to replenish the battery. Worst case scenario I can think of is trailer battery is quite depleted on a camping trip ( maybe not much sun and don't get recharged that way ). We would be on our way home and the 3-way fridge in the trailer is running on DC while on the road. So that is pulling power, and the battery is probably absorbing power too because it wants to be charged. Again, I don't care that the battery gets charged, I just don't want it to ask too much of the truck and cause a problem.
I suppose the right thing to do is install a DC-DC charger and stop worrying about it. Just trying to get a sense of my risk exposure if I don't bother. Maybe I just risk blowing a fuse on the 7pin connector ? I assume the 12V power line in the 7pin is fused on the truck somewhere ?
By the way, my truck is the EcoDiesel power train, so don't have any e-Torque concerns as others here have mentioned. I think my truck has a 250A alternator.
@boogielander , appreciate your input here, although you have a more sophisticated setup than I have and I know you do have eTorque.

you're mostly correct.
you don't HAVE to have way to charge it. 100a at 12v is around 1000Wh capacity, give or take. if you pre-ran your fridge before leaving home, it will last you one to two nights, depends on ambient temperature. If it's hot, then fridge will work harder. It's okay for over the weekend trips. BUT, if you're looking at multi-day trips, it's not going to be enough especially when there's overcast or something that makes the solar not work as good.
I don't recommend running DC-DC to the 7-pin connector. 7-pin wirings are at most 14 gauge (probably 16 gauge) and are used to run low draw items like brake, turn signals, etc. Without DC-DC charger, you're basically running it at the voltage that 16 gauge wires can handle, which is really slow (best case scenario) or you're risking pulling too much amperage and risk causing wiring to melt (due to heat) (worst case scenario).
With your 250A alternator, you're gonna be fine running a DC-DC charger. Just use proper gauged wiring (6 gauge or bigger). TO make it easier, you can use a 50A Anderson connector so you have quick disconnect when you're not towing, and put the charger inside/ on the trailer. Remember to use a circuit breaker by the battery too so you can shut it off completely when not towing.

You're welcome man! I over-engineer mine so it CAN work with other applications. To be honest, I'm not even sure if there's gonna be any problem with running that setup with etorque but my onboard voltage meter has been fine so far... no voltage drop or anything. But i know it's making etorque generator work more because before, it'd go down to as low as 12.5v when highway cruising but now it's always 13.5v-ish unless both systems (in-cab and in-bed) are fully charged.

 

[TSL]

you're mostly correct.
you don't HAVE to have way to charge it. 100a at 12v is around 1000Wh capacity, give or take. if you pre-ran your fridge before leaving home, it will last you one to two nights, depends on ambient temperature. If it's hot, then fridge will work harder. It's okay for over the weekend trips. BUT, if you're looking at multi-day trips, it's not going to be enough especially when there's overcast or something that makes the solar not work as good.
I don't recommend running DC-DC to the 7-pin connector. 7-pin wirings are at most 14 gauge (probably 16 gauge) and are used to run low draw items like brake, turn signals, etc. Without DC-DC charger, you're basically running it at the voltage that 16 gauge wires can handle, which is really slow (best case scenario) or you're risking pulling too much amperage and risk causing wiring to melt (due to heat) (worst case scenario).
With your 250A alternator, you're gonna be fine running a DC-DC charger. Just use proper gauged wiring (6 gauge or bigger). TO make it easier, you can use a 50A Anderson connector so you have quick disconnect when you're not towing, and put the charger inside/ on the trailer. Remember to use a circuit breaker by the battery too so you can shut it off completely when not towing.

You're welcome man! I over-engineer mine so it CAN work with other applications. To be honest, I'm not even sure if there's gonna be any problem with running that setup with etorque but my onboard voltage meter has been fine so far... no voltage drop or anything. But i know it's making etorque generator work more because before, it'd go down to as low as 12.5v when highway cruising but now it's always 13.5v-ish unless both systems (in-cab and in-bed) are fully charged.

Thanks ! Good input, appreciate it.
So in summary I could run wire from the battery to the back of the truck, connect up an Anderson connector, put a breaker on the connection at the truck battery for safety, then have the DC-DC charger in the trailer, with corresponding Anderson connector on the trailer.
That leaves me two questions : (1) the existing +12V supply in the truck's 7-pin : would I want to interrupt that circuit on the trailer somewhere and make sure it's not also trying to charge the battery and (2) a lot of DC-DC chargers have an ignition trigger wire. I see the need for that on an overland rig / van etc, but seems I don't really need it with the Anderson connection on the tongue, right? I just unplug and that's that. Obviously I could forget to unplug and drain my starter battery, but assuming I remember then I'm OK. But do the DC-DC chargers with an ignition trigger wire insist on having that connected up ? If the charger is in the trailer, then that's more work with running that wire all the way, plus more messing with the truck ! I'm fine with hooking things up to the battery but if I have to start tying into the ignition circuit, then I get nervous that I'll screw something up Maybe I cheat and connect it to the trailer battery and that way it always thinks the ignition is on.

 

[boogielander]

Thanks ! Good input, appreciate it.
So in summary I could run wire from the battery to the back of the truck, connect up an Anderson connector, put a breaker on the connection at the truck battery for safety, then have the DC-DC charger in the trailer, with corresponding Anderson connector on the trailer.
That leaves me two questions : (1) the existing +12V supply in the truck's 7-pin : would I want to interrupt that circuit on the trailer somewhere and make sure it's not also trying to charge the battery and (2) a lot of DC-DC chargers have an ignition trigger wire. I see the need for that on an overland rig / van etc, but seems I don't really need it with the Anderson connection on the tongue, right? I just unplug and that's that. Obviously I could forget to unplug and drain my starter battery, but assuming I remember then I'm OK. But do the DC-DC chargers with an ignition trigger wire insist on having that connected up ? If the charger is in the trailer, then that's more work with running that wire all the way, plus more messing with the truck ! I'm fine with hooking things up to the battery but if I have to start tying into the ignition circuit, then I get nervous that I'll screw something up Maybe I cheat and connect it to the trailer battery and that way it always thinks the ignition is on.

1. you don't need to mess with it at all because your house battery is not connected to it. unless you did something to the 7-pin already there's nothing to worry about.
2. for ign trigger wire, simply run a 14gauge and complete it with this: https://a.co/d/2gyuiEN. the purpose of the IGN trigger is to trigger the DC-DC to start charging when the engine's running or when the ignition is on. You simply use an add-a-fuse to tap into the igntion triggered fuse slot and that's all you need. Or, if that's really complicated for you then just skip that part, nothing needed to be done other than to remember to unplug and turn off the circuit breaker.
I think 60A should be plenty enough: https://a.co/d/2YGmMrA
buy that Blue Sea one and not the cheap chinese knockoffs.

 

[rdugedug1]

1. you don't need to mess with it at all because your house battery is not connected to it. unless you did something to the 7-pin already there's nothing to worry about.
2. for ign trigger wire, simply run a 14gauge and complete it with this: https://a.co/d/2gyuiEN. the purpose of the IGN trigger is to trigger the DC-DC to start charging when the engine's running or when the ignition is on. You simply use an add-a-fuse to tap into the igntion triggered fuse slot and that's all you need. Or, if that's really complicated for you then just skip that part, nothing needed to be done other than to remember to unplug and turn off the circuit breaker.
I think 60A should be plenty enough: https://a.co/d/2YGmMrA
buy that Blue Sea one and not the cheap chinese knockoffs.

boogielander,

I respectfully disagree. I have had 2 separate stock travel trailers (maybe pop ups are wired differently) and both of them use the +12V 7 pin to charge the house battery. Easy enough to verify, disconnect your house battery, plug in the 7 pin and see if you have 12v in camper.

Also, my 7 pin +12v has a 30A stock fuse. The OEM would not use that on smaller gage wire. I recently made my own 7 pin pigtail to OEM and it used 10 gage for +/- 12V, 12 gage for brakes and 14-16 gage for blinkers and brake lights.

TSL,

To keep it simple, you could add 12/12 20A charger to your popup and just remember to unplug so you don't drain vehicle battery. I switched to lithium house battery and the vehicle battery actually starts draining the house battery when not running because the lithium is at a higher voltage.

 

[boogielander]

boogielander,

I respectfully disagree. I have had 2 separate stock travel trailers (maybe pop ups are wired differently) and both of them use the +12V 7 pin to charge the house battery. Easy enough to verify, disconnect your house battery, plug in the 7 pin and see if you have 12v in camper.

Also, my 7 pin +12v has a 30A stock fuse. The OEM would not use that on smaller gage wire. I recently made my own 7 pin pigtail to OEM and it used 10 gage for +/- 12V, 12 gage for brakes and 14-16 gage for blinkers and brake lights.

TSL,

To keep it simple, you could add 12/12 20A charger to your popup and just remember to unplug so you don't drain vehicle battery. I switched to lithium house battery and the vehicle battery actually starts draining the house battery when not running because the lithium is at a higher voltage.

ah. if it works like that then it's perfect.
im not as familiar with the 7-pin on our trucks because every time i install something, I just do a standalone system.

my methodology is always not to mess with stock wiring and do my separate systems. that way, if something does go wrong, i know my stock wiring is protected and i can fix/ diagnose the separate system installed. not that it ever happens, but just like that peace of mind. (i've had enough of chasing wiring issues on various platforms, both stock and non-stock, and when things are integrated into stock system it's always more complicated and makes me put more money in the swear jar lol)