DC to DC Charger

[TSL]

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.

Thanks for the input. The pop up is wired as you describe, near as I can tell. I'm still working on the conversion project, so far I've installed the Lithium battery and installed a new power convertor that will charge Li properly ( A Progressive Dynamics 4100 model ). I've wired everything up but haven't buttoned it all up yet. I did hook up to the truck's 7 pin, with the motor running and what I observed was that voltage across the trailer battery terminals stepped up from ~ 13.6 to ~ 14.4 or something like that with the 7 pin connected. So I know the truck was sending power to the battery. The battery has a bluetooth app which shows me current flow ( + into the battery or - if it's draining ). I'll have to experiment with it over a few weeks and see what happens.
Adding a DC charger in the camper running off the +12V from the 7pin would certainly be simpler than running separate cable from the truck battery and putting an Anderson connector on the back of the truck, albeit that might well be the "best" way to do it.
I did also figure out that the Absorption Fridge on the camper pulls 10A when running on 12V, which I would be doing while on the road, switching over to Propane when at the campsite.
I think the "corner case" I was concerned about was let's imagine the case where the camper battery is depleted at the end of camping trip - it's a Li battery with low internal resistance, so it might put a strong current pull on the +12v pin from the truck. Meanwhile the fridge is also pulling 10A. I suppose that's where that 30A fuse in the truck comes into play right? Worst case that blows. Then I know I need a DC-DC charger. Or maybe it doesn't, and I get home and find the camper battery barely charged on the way home. In which I don't care because I'm going to plug in to shore power at home and charge it up.
Now if I was going to drive from CA to the top of Alaska like @boogielander is planning on, well then I'd need my battery to charge up during the day's drive, so that's a different story.

 

[boogielander]

Thanks for the input. The pop up is wired as you describe, near as I can tell. I'm still working on the conversion project, so far I've installed the Lithium battery and installed a new power convertor that will charge Li properly ( A Progressive Dynamics 4100 model ). I've wired everything up but haven't buttoned it all up yet. I did hook up to the truck's 7 pin, with the motor running and what I observed was that voltage across the trailer battery terminals stepped up from ~ 13.6 to ~ 14.4 or something like that with the 7 pin connected. So I know the truck was sending power to the battery. The battery has a bluetooth app which shows me current flow ( + into the battery or - if it's draining ). I'll have to experiment with it over a few weeks and see what happens.
Adding a DC charger in the camper running off the +12V from the 7pin would certainly be simpler than running separate cable from the truck battery and putting an Anderson connector on the back of the truck, albeit that might well be the "best" way to do it.
I did also figure out that the Absorption Fridge on the camper pulls 10A when running on 12V, which I would be doing while on the road, switching over to Propane when at the campsite.
I think the "corner case" I was concerned about was let's imagine the case where the camper battery is depleted at the end of camping trip - it's a Li battery with low internal resistance, so it might put a strong current pull on the +12v pin from the truck. Meanwhile the fridge is also pulling 10A. I suppose that's where that 30A fuse in the truck comes into play right? Worst case that blows. Then I know I need a DC-DC charger. Or maybe it doesn't, and I get home and find the camper battery barely charged on the way home. In which I don't care because I'm going to plug in to shore power at home and charge it up.
Now if I was going to drive from CA to the top of Alaska like @boogielander is planning on, well then I'd need my battery to charge up during the day's drive, so that's a different story.

yeah i like to build things for extreme use case so i know it can handle whatever i throw at it that is not the extreme.
i mean, with my build i can just run an extension cable to the truck and charge the EcoFlows every 4-5 days with the truck not running and the fridge on all the time without using DC-DC, but i like to have that peace of mind knowing i can lol

the alaska trip will probably have multiple nights at RV sites with hookups instead of wild camping, since it's my first time in bear country and i figured at RV sites with people it'd be less chances of bear coming to me. so... i probably overkilled it LOL

 

[rdugedug1]

Thanks for the input. The pop up is wired as you describe, near as I can tell. I'm still working on the conversion project, so far I've installed the Lithium battery and installed a new power convertor that will charge Li properly ( A Progressive Dynamics 4100 model ). I've wired everything up but haven't buttoned it all up yet. I did hook up to the truck's 7 pin, with the motor running and what I observed was that voltage across the trailer battery terminals stepped up from ~ 13.6 to ~ 14.4 or something like that with the 7 pin connected. So I know the truck was sending power to the battery. The battery has a bluetooth app which shows me current flow ( + into the battery or - if it's draining ). I'll have to experiment with it over a few weeks and see what happens.
Adding a DC charger in the camper running off the +12V from the 7pin would certainly be simpler than running separate cable from the truck battery and putting an Anderson connector on the back of the truck, albeit that might well be the "best" way to do it.
I did also figure out that the Absorption Fridge on the camper pulls 10A when running on 12V, which I would be doing while on the road, switching over to Propane when at the campsite.
I think the "corner case" I was concerned about was let's imagine the case where the camper battery is depleted at the end of camping trip - it's a Li battery with low internal resistance, so it might put a strong current pull on the +12v pin from the truck. Meanwhile the fridge is also pulling 10A. I suppose that's where that 30A fuse in the truck comes into play right? Worst case that blows. Then I know I need a DC-DC charger. Or maybe it doesn't, and I get home and find the camper battery barely charged on the way home. In which I don't care because I'm going to plug in to shore power at home and charge it up.
Now if I was going to drive from CA to the top of Alaska like @boogielander is planning on, well then I'd need my battery to charge up during the day's drive, so that's a different story.

Now thats an interesting one. Does a lithium battery "pull" amps like a motor or just accept was is available on the wire?

If you find that out please let us know, that could certainly change things only having 30amps available. Also, the newer 12v only fridges draw about 4.5-5 amps while running. My 200W solar panel easily keeps the fridge running 50-70 degree weather. There is a point when cabin temperature is too high and the fridge out runs the panel, found out the hard way.

In my case of discharging the lithium, I was also trying to charge 3 lead acid batteries in the bed of my truck, maybe that resistance interfered with the lithium. Sounds like another experiment.

 

[TSL]

Now thats an interesting one. Does a lithium battery "pull" amps like a motor or just accept was is available on the wire?

If you find that out please let us know, that could certainly change things only having 30amps available. Also, the newer 12v only fridges draw about 4.5-5 amps while running. My 200W solar panel easily keeps the fridge running 50-70 degree weather. There is a point when cabin temperature is too high and the fridge out runs the panel, found out the hard way.

In my case of discharging the lithium, I was also trying to charge 3 lead acid batteries in the bed of my truck, maybe that resistance interfered with the lithium. Sounds like another experiment.

Our popup camper, in addition to the 3-way absorption fridge, also has a "shoilet", which I consider of no value and would happily remove that and put an ARB or Dometic chest fridge in it's place. ( for eg this one, which claims 3.1Ah power draw ) Better yet, I'd put it on a slide with an exterior door in the wall of the camper so it could be accessed from outside and when the pop-up is closed up. Then I could look forward to pulling much less DC power for my refrigeration needs. However, the other members of the family, in particular those of the female variety, are stridently against removing the "shoilet" because "you never know, it could be useful" ! The one thing those 3-way fridges do have in their favor is when running on propane they will run "forever" on a 20lb tank, it is amazing how little propane they use.
As for the Lithium battery "pulling" amps.... I don't know either. I'll have to see what happens. Being a "data-aholic", I wish I could wire some sort of a DC current data logger in line with the battery. While there are such things of course, I can't find any at a price I'm willing to pay ( I don't need to know that badly ! )

 

[TSL]

Finally got to test out my camper trailer / truck combination and found a couple interesting observations about power from the truck via the 7pin.
So we had the 3-way fridge running on shore power in the driveway.
Unplugged that and switched over to 12V DC for the trip to the campground.
Bluetooth app on my phone for the LiFePo battery I installed reported "-10.7A" flowing from the battery. Manual for the fridge says it will use approx 10.5A on DC, so the 10.7 the app reports seems close enough.
Then I plug in the 7pin with the truck running, and the bluetooth app shows the current flowing from the battery drops to "-6.7A"
So that's interesting : it would seem I'm only getting 4A from the truck and the other 6.7 from the house battery on the trailer. obviously one power source ( the trailer battery ) is much closer to the load than the other one.
Another observation : I turn the fridge OFF, expecting the Amps flowing from the battery to drop to 0. It doesn't : it drops to -3.1A. I unplug the 7 pin from the truck and it drops to 0. I think I had the truck switched off at this point, but not quite recalling. So it kind of seems like I was "charging" the truck battery from the Lithium battery on the trailer at that point ?
Am I right that Li batteries sit at a higher voltage than Lead Acid batteries ? If so it might make sense.
Eitherways.... I feel like I just inched a bit closer to telling myself I need that DC-DC charger !
We went ahead with our camping trip, and the battery on the trailer dropped from 100% to 96% in about one hour on the road - with the truck providing ~ 4A to the fridge and the trailer battery the other 6A.
I also see solar in my immediate future and am going to add that to the trailer soon I think.

 

[boogielander]

Finally got to test out my camper trailer / truck combination and found a couple interesting observations about power from the truck via the 7pin.
So we had the 3-way fridge running on shore power in the driveway.
Unplugged that and switched over to 12V DC for the trip to the campground.
Bluetooth app on my phone for the LiFePo battery I installed reported "-10.7A" flowing from the battery. Manual for the fridge says it will use approx 10.5A on DC, so the 10.7 the app reports seems close enough.
Then I plug in the 7pin with the truck running, and the bluetooth app shows the current flowing from the battery drops to "-6.7A"
So that's interesting : it would seem I'm only getting 4A from the truck and the other 6.7 from the house battery on the trailer. obviously one power source ( the trailer battery ) is much closer to the load than the other one.
Another observation : I turn the fridge OFF, expecting the Amps flowing from the battery to drop to 0. It doesn't : it drops to -3.1A. I unplug the 7 pin from the truck and it drops to 0. I think I had the truck switched off at this point, but not quite recalling. So it kind of seems like I was "charging" the truck battery from the Lithium battery on the trailer at that point ?
Am I right that Li batteries sit at a higher voltage than Lead Acid batteries ? If so it might make sense.
Eitherways.... I feel like I just inched a bit closer to telling myself I need that DC-DC charger !
We went ahead with our camping trip, and the battery on the trailer dropped from 100% to 96% in about one hour on the road - with the truck providing ~ 4A to the fridge and the trailer battery the other 6A.
I also see solar in my immediate future and am going to add that to the trailer soon I think.

yeap LiFEPO4 are supposed to sit at higher voltage THOUGH my LiTimes deep cycle LiFEPO4 house battery sits at 13.3v while fully charged. I'm guessing it's because it's deep cycle. I ruled out it being defective as I obtained the technical guide on setting up a monitor when I added the monitor in and I based all the values off what was provided by the techs.

And the other thing is if you don't want to do it manually every time, you'll need either a DC-DC charger or an ign triggered disconnect. I think I went over that above lol
To be fair, solar is quite optional and slower, compared to charging with DC-DC. Only exception is when you're going to leave the trailer for "base camp" mode.

 

[jrmickey62]

Just asking a question about the Ignition circuit for my Renogy DCDC30 charger. If the purpose of the Ignition wire is to detect when the vehicle is running and enable charging from the alternator why not just connect the Ignition wire to your trailer marker lights. Our backup camera is powered from this circuit, probably like most pre-wired cameras, and we always drive with our camera on. Essentially you are telling the DC-DC unit to charge from the alternator when you are on the road. We always shut off the marker lights when we stop because the truck chimes when they are left on. Seems like the simplest solution since you won't need to pass through another small wire to the fuse panel.

 

[boogielander]

Just asking a question about the Ignition circuit for my Renogy DCDC30 charger. If the purpose of the Ignition wire is to detect when the vehicle is running and enable charging from the alternator why not just connect the Ignition wire to your trailer marker lights. Our backup camera is powered from this circuit, probably like most pre-wired cameras, and we always drive with our camera on. Essentially you are telling the DC-DC unit to charge from the alternator when you are on the road. We always shut off the marker lights when we stop because the truck chimes when they are left on. Seems like the simplest solution since you won't need to pass through another small wire to the fuse panel.

you can do that.
it is basically a trigger wire to tell the Renogy to start passing current through. If you so choose to, you can actually use a separate switch to turn it on and off.

Actually, that is my preferred way of doing things and exactly how I wired mine, especially with a switch-pro installed.
The switch-pro is the only thing that is tapped into the fuse box under the hood, and I have a switch set for the amber back lights on my Baja Designs LP9 to use as running lights. I set that switch to be turned on automatically when ignition is on, so I don't have to tap into another ign powered cable. Then, I spliced that output to include the Renogy to trigger it.

Personally (and professionally), I don't like to tap into the OE wiring harnesses unless absolutely necessary (ie: the ign trigger wire for Switch-Pro and the brake lights on my camper). If you want to run trailer marker lights or reverse camera, unless you're using a trailer plug adapter or something and plug it into the trailer plug to get power, I don't recommend getting your power from the harness. Reason being, if something goes wrong, you will not damage your OE harness, which can be a pain to replace and troubleshoot.

Or, if you want to tap into the OE harnesses, be sure to include a fuse for safety.

 

[TSL]

With the Victron charger, is it possible to get it to work _without_ the trigger wire ? I've managed to get mine installed on my camper trailer ( Aside : running wires under the length of the truck WITHOUT access to a lift for the truck is something I never ever want to have to do again ! What a royal pain in every possible part of my body ! I'm reasonable confident I succeeded in routing the wires away from hot things, things that rotate, and suspension parts that might pinch it. )
I've done a test run and it worked, just using Engine ShutDown Detection and Input Voltage Lockout options, and it seemed to work fine. I pulled out of the driveway with the battery at ~ 98% SOC and the 3-way fridge on the camper running on DC ( pulls 10.5A !!!! ) I drove around my area for a while and when I got home the battery was at 100% ( I use a Victron smart shunt to monitor ) and it showed 0A flowing. So the truck was providing all the power to the fridge. As soon as I plugged out the Anderson connector on the back of the truck, the shunt showed -10.5A flowing from the battery.
So that was all great. But my worry is whether the Smart alternator will always cooperate with me, or whether it will maybe sometimes drop the voltage enough that the Victron will cut out.
Does the trigger wire force the Victron to always run when it sees a voltage on that pin, or will the Engine Shutdown detection still over-ride that?
Victron's manual is well written but very detailed, and not sure I've grasped everything in it yet.

 

[boogielander]

With the Victron charger, is it possible to get it to work _without_ the trigger wire ? I've managed to get mine installed on my camper trailer ( Aside : running wires under the length of the truck WITHOUT access to a lift for the truck is something I never ever want to have to do again ! What a royal pain in every possible part of my body ! I'm reasonable confident I succeeded in routing the wires away from hot things, things that rotate, and suspension parts that might pinch it. )
I've done a test run and it worked, just using Engine ShutDown Detection and Input Voltage Lockout options, and it seemed to work fine. I pulled out of the driveway with the battery at ~ 98% SOC and the 3-way fridge on the camper running on DC ( pulls 10.5A !!!! ) I drove around my area for a while and when I got home the battery was at 100% ( I use a Victron smart shunt to monitor ) and it showed 0A flowing. So the truck was providing all the power to the fridge. As soon as I plugged out the Anderson connector on the back of the truck, the shunt showed -10.5A flowing from the battery.
So that was all great. But my worry is whether the Smart alternator will always cooperate with me, or whether it will maybe sometimes drop the voltage enough that the Victron will cut out.
Does the trigger wire force the Victron to always run when it sees a voltage on that pin, or will the Engine Shutdown detection still over-ride that?
Victron's manual is well written but very detailed, and not sure I've grasped everything in it yet.

yes you can rely on the engine shut down detection BUT in my experience the shutdown detection don't work well with e-torque. when the e-troque not kicking in and the voltage sits lower than normal alternator-equipped trucks, Victron will think the engine's off and therefore, cut power supply.
If set the Victron engine shutoff dection to lower voltage, then it will continue to draw power after engine shuts off until it reaches the threshold.
If set the engine off detection to higher voltage to combat that post-shutdown draw, you will experience intermittent power supply when driving, as the e-torque itself determines the starting battery charge status and cuts power when it thinks the battery is full (which drops the output and makes Victron think engine's off).
It's an infinite loop of chicken and egg lol one thing affects the other and can't seem to find the perfect sweet spot that works. That's why I run ign trigger to bypass all that. Alternatively, I can also put it in power supply mode, turn off engine off detection, and manually turn it on and off every time. But that defeats the purpose.

I see you have eco diesel, which should come with a traditional alternator (i mean, it should still be a smart alternator but compared to e-torque i just call it a traditional one). You should be able to function just fine without trigger wire. If a trigger is present, it will override Engine Shutdown Detection instead of the other way around.

 

[Ramelot]

yes you can rely on the engine shut down detection BUT in my experience the shutdown detection don't work well with e-torque. when the e-troque not kicking in and the voltage sits lower than normal alternator-equipped trucks, Victron will think the engine's off and therefore, cut power supply.
If set the Victron engine shutoff dection to lower voltage, then it will continue to draw power after engine shuts off until it reaches the threshold.
If set the engine off detection to higher voltage to combat that post-shutdown draw, you will experience intermittent power supply when driving, as the e-torque itself determines the starting battery charge status and cuts power when it thinks the battery is full (which drops the output and makes Victron think engine's off).
It's an infinite loop of chicken and egg lol one thing affects the other and can't seem to find the perfect sweet spot that works. That's why I run ign trigger to bypass all that. Alternatively, I can also put it in power supply mode, turn off engine off detection, and manually turn it on and off every time. But that defeats the purpose.

I see you have eco diesel, which should come with a traditional alternator (i mean, it should still be a smart alternator but compared to e-torque i just call it a traditional one). You should be able to function just fine without trigger wire. If a trigger is present, it will override Engine Shutdown Detection instead of the other way around.

Hi, thanks for all the good information on this topic. It seems hard to come by. I have the Victron 12-12/30 charger in my slide in camper and want to take your advice on running the IGN trigger. It looks in the Victron manual like I just run one wire from a fuse tap that is hot when the ignition is on (you used F54?) and connect it to the L terminal on the Victron with the normal jumper still in place. Is that correct?
Also, never having installed or heard of a fuse tap until now (sheltered life, I guess..) , it allows you to add a fused connection while still keeping the original circuit fused? Thanks for the help!

 

[boogielander]

Hi, thanks for all the good information on this topic. It seems hard to come by. I have the Victron 12-12/30 charger in my slide in camper and want to take your advice on running the IGN trigger. It looks in the Victron manual like I just run one wire from a fuse tap that is hot when the ignition is on (you used F54?) and connect it to the L terminal on the Victron with the normal jumper still in place. Is that correct?
Also, never having installed or heard of a fuse tap until now (sheltered life, I guess..) , it allows you to add a fused connection while still keeping the original circuit fused? Thanks for the help!

yeap. the IGN trigger is just a trigger to tell Victron to start allowing currents to pass through to the battery. anything that is hot when ign is on can be used, though keep it low amperage (10A fuse would be good)
for fuse box in engine bay i think i used F59 or 54, something like that lol.

if you have a switch panel, like a switch pro that i've been using since 2017, you can also use one of the switch slot as a trigger and set it to be on with ignition, while being able to also run the charger when the engine's off as an option (ie, when you have shore power and you are charging the starting battery for some reason)
I have my camper charger hooked up that way, so it can be ign on or manually turned on via physical switch or bluetooth when i need to test something. not recommended with chinese panels like auxbeam though. those low quality stuff better just be used as an on/off switch due to inferior chinese spec and quality.