DC-DC Charger
Fleet Mechanic
Joined: Dec 2016
Posts: 1,810
Likes: 539
From: Florida
Yes, you should get a DC-DC charger. I just installed one on my TT to charge my lithium batteries while driving, using the OEM 7-wire umbilical. My Victron 12-12/18 is seeing 13-14 volts from the truck on the regular. But since LiFePo batteries have a specific charging profile, it's important that you're able to charge your batteries in accordance with that profile. As long as my Victron is seeing 8v at the umbilical, it boosts to the voltage I select. Since I'm getting 13-14v at the umbilical, it's a breeze for the Victron to provide the 14.4-14.6v that my batteries need to see.
I do have the dual batteries/410 alternator setup, but i have installed NO extra wires coming off the truck batteries. Everything is OEM. But as always, YMMV.
I do have the dual batteries/410 alternator setup, but i have installed NO extra wires coming off the truck batteries. Everything is OEM. But as always, YMMV.
Fleet Mechanic
Joined: Feb 2021
Posts: 1,405
Likes: 1,171
From: East TN
Yes, you should get a DC-DC charger. I just installed one on my TT to charge my lithium batteries while driving, using the OEM 7-wire umbilical. My Victron 12-12/18 is seeing 13-14 volts from the truck on the regular. But since LiFePo batteries have a specific charging profile, it's important that you're able to charge your batteries in accordance with that profile. As long as my Victron is seeing 8v at the umbilical, it boosts to the voltage I select. Since I'm getting 13-14v at the umbilical, it's a breeze for the Victron to provide the 14.4-14.6v that my batteries need to see.
I do have the dual batteries/410 alternator setup, but i have installed NO extra wires coming off the truck batteries. Everything is OEM. But as always, YMMV.
I do have the dual batteries/410 alternator setup, but i have installed NO extra wires coming off the truck batteries. Everything is OEM. But as always, YMMV.
OP - if you are going to bother running cable at all, run all copper 2 AWG welding cable. With low voltage DC, resistance is the enemy and 2 AWG isn't crazy expensive. You also need to run 2 AWG on the RV side. Use a TrailerVision Anderson plug mount at the rear and it will be a sturdy, reliable connection.
I ran some quick calcs for you. The voltage drop V in volts (V) is equal to the wire current I in amps (A) times 2 times one way wire length L in feet (feet) times the wire resistance per 1000 feet R in ohms (Ω/kfeet) divided by 1000: = Iwire (A) × (2 × L(feet) × Rwire(Ω/kfeet) / 1000(feet/kfeet))
For 30 feet of 2 AWG copper cable, at 14.4 volts with 51 amps flowing (assuming you get the full 98.5% efficiency claimed by Victron) you will have a 3.3% loss, about .48 volts of drop.
Cross-Country
Joined: Aug 2023
Posts: 96
Likes: 74
If you're going to get the 50A Orion I'd definitely recommend wire no smaller than 2 AWG.
By the time you consider the circuit length in the truck (around 25') and the additional to get from the truck to the charger, that's a pretty long circuit.
I ran 4 AWG for our 12/12-30 and that's the smallest I'd go for a 30A charger.
By the time you consider the circuit length in the truck (around 25') and the additional to get from the truck to the charger, that's a pretty long circuit.
I ran 4 AWG for our 12/12-30 and that's the smallest I'd go for a 30A charger.
Fleet Mechanic
Joined: Dec 2016
Posts: 1,810
Likes: 539
From: Florida
IF he gets the 18 amps that 12-12/18 can output and the 540 AHs of batteries he has is at 20% capacity it will take 24 hours of driving to re-charge them. Using the 12-12/50 unit will allow the batteries to fully recharge in a little over 8 hours - if his alternator survives. Alternators are not rated to output their max amp rating 24/7 but that is a discussion for another thread.
It's an easy day for the Victron to top off the OP's batteries while traveling, which is likely all he'll ever need.
Thread Starter
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Trailering
Joined: Mar 2018
Posts: 16
Likes: 1
From: SW Missouri
But that also assumes the alternator is the only charging mechanism and that the trips starts out with batteries at 0%. Plus with the OP's 800W of solar, that situation will likely never exist. Been camping for over 20 years and I've never seen that situation. We don't boondock much as I like my A/C, but if I did, I dang sure would have a solar set-up to keep the batteries going while camping.
It's an easy day for the Victron to top off the OP's batteries while traveling, which is likely all he'll ever need.
It's an easy day for the Victron to top off the OP's batteries while traveling, which is likely all he'll ever need.
Mountain Pass
Joined: Dec 2017
Posts: 142
Likes: 23
From: Southeast Wisconsin
I also think of the DC-DC charger as handy to have in a pinch.
Let's say you show up to storage and your batteries are dead an the landing gear doesn't work. Connect the DC cable, flip the switch to high idle, and you'll be back in business in a few minutes. (I've been in this situation, and used the 7-pin connector, but it's much slower obviously).
Or, let's say you're boondocking and haven't been able to get enough out of the solar. Better to have a generator, but a few hours of high idle on the truck isn't going to cause any harm.
Let's say you show up to storage and your batteries are dead an the landing gear doesn't work. Connect the DC cable, flip the switch to high idle, and you'll be back in business in a few minutes. (I've been in this situation, and used the 7-pin connector, but it's much slower obviously).
Or, let's say you're boondocking and haven't been able to get enough out of the solar. Better to have a generator, but a few hours of high idle on the truck isn't going to cause any harm.
Fleet Mechanic
Joined: Dec 2016
Posts: 1,810
Likes: 539
From: Florida
I’m currently camping in sw Arizona. By morning, the batteries are at 85% and then back to 100% by 2pm. My main concern is driving during cloudy days when the solar is at low efficiency. Last fall, I camped in the rain for a day and then had to hit the road early, again in dense clouds and rain - I only had one 270ahr battery then. By the time I got to my campsite, I didn’t have enough juice left for the trailer jack to lift the hitch off the truck. I had to go to Northern Tools and buy a hi lift jack to do it. I don’t want that to happen again.
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Hotshot
Joined: Oct 2015
Posts: 19,694
Likes: 12,819
From: Wyoming
Thank you to @Avoozl for the link to the new Orion XS charger. That is going to be a hugely popular charger. I run a Victron system and their products are top tier.
However (you knew that was coming, right?) the largest cable the Orion XS can accept is 4awg. That specification is in the "Other" section of the datasheet linked below. There are ways around that like running 0awg (or whatever) to a bus bar right next to the charger, then 4awg to the charger. That would not be my choice. I would prefer to throttle back the output amps to match the wire size on the input side. Keep in mind that 50 amps of output requires more than 50 amps on the input side. So the input wire size needs to take that into account.
https://www.victronenergy.com/upload...charger-EN.pdf
However (you knew that was coming, right?) the largest cable the Orion XS can accept is 4awg. That specification is in the "Other" section of the datasheet linked below. There are ways around that like running 0awg (or whatever) to a bus bar right next to the charger, then 4awg to the charger. That would not be my choice. I would prefer to throttle back the output amps to match the wire size on the input side. Keep in mind that 50 amps of output requires more than 50 amps on the input side. So the input wire size needs to take that into account.
https://www.victronenergy.com/upload...charger-EN.pdf
Cross-Country
Joined: Aug 2023
Posts: 96
Likes: 74
Hotshot
Joined: Oct 2015
Posts: 19,694
Likes: 12,819
From: Wyoming
Oh, and don't forget the over current protection. Both sides. Fuses protect the wires, not the device. Well, they do protect the device, but their main purpose is to keep the wire from burning up. A 50 amp load would call for a 62.5 amp fuse or breaker. Round up the next available breaker size.
One fuse on the truck battery/alternator end of the input wire. The second fuse on the DC-DC charger end of the output wire. The general rule is 1.25 times the expected load. The fudge factor is there to avoid nuisance trips. Don't go cheap on the fuses/breakers.
One fuse on the truck battery/alternator end of the input wire. The second fuse on the DC-DC charger end of the output wire. The general rule is 1.25 times the expected load. The fudge factor is there to avoid nuisance trips. Don't go cheap on the fuses/breakers.
Tuned
Joined: Mar 2011
Posts: 265
Likes: 54
Fleet Mechanic
Joined: Feb 2021
Posts: 1,405
Likes: 1,171
From: East TN
But that also assumes the alternator is the only charging mechanism and that the trips starts out with batteries at 0%. Plus with the OP's 800W of solar, that situation will likely never exist. Been camping for over 20 years and I've never seen that situation. We don't boondock much as I like my A/C, but if I did, I dang sure would have a solar set-up to keep the batteries going while camping.
It's an easy day for the Victron to top off the OP's batteries while traveling, which is likely all he'll ever need.
It's an easy day for the Victron to top off the OP's batteries while traveling, which is likely all he'll ever need.
.
.
However (you knew that was coming, right?) the largest cable the Orion XS can accept is 4awg. That specification is in the "Other" section of the datasheet linked below. There are ways around that like running 0awg (or whatever) to a bus bar right next to the charger, then 4awg to the charger. That would not be my choice. I would prefer to throttle back the output amps to match the wire size on the input side. Keep in mind that 50 amps of output requires more than 50 amps on the input side. So the input wire size needs to take that into account.
Put 2 layers of heat shrink over the entire splice, make sure it is mechanically supported and call it a day. As far as the amperage required, if the Victron is 98.5% efficient as claimed then it will draw roughly 51 amps from the truck. 2 AWG will deliver the amperage with minimum voltage drop, which should keep the Victron unit happy.
Cross-Country
Joined: Aug 2023
Posts: 96
Likes: 74
I've been using the engine detect option to trigger ours, it's worked flawlessly with my past 2500HD and Titan XD and also with my current 350.