Adding a second DC/DC charger on 400ah Battle Born battery bank, does it makes sense? Victron, Supertramp Camper

[SimplyAnAdventure]

Hoping someone on here more familiar with electrons that me can shed some light onto this for me.

I have a Supertramp camper ordered with the following electrical specs:

4, 100Ah Battle Born batteries to power a 1500W inverter, a Isotherm fridge, and a Dometic RTX2000 12V air conditioner.

Supertramp includes:

330W of solar on the roof and a Victron MPPT 75/15 Charge controller.
Progressive Dynamics 45amp charger for shore power.
Victron DC/DC charger is an Orion 12v/12v - 30amp.

I saw a few videos suggesting/ recommending using TWO DC/DC chargers as they can be "stacked" sort of. I am wondering if this is a good idea for a couple reasons. 1) Redundancy seems useful, 2 is one and 1 is none right? If one failed the other would be still working. 2) More power, this is what actually had me looking in the first place as a single 30A charger seems small for a 400Ah set of batteries. If I could charge at 30A with one, I could charge at 60A with two right?

My questions really are can I do this/ is it a good idea? Will the 2, 30A chargers AND the 330W of solar be too much for the batteries to handle when running down the road? How do I wire it? I don't have the camper yet but Supertramp runs a single power cord from the engine bay to the rear bumper to a 30A trolling motor plug. Do I just run another wire from the same place to the back and create a second plug and whip? Lastly my truck is a 2023 F350 w/ 7.3L gas engine, 2 batteries and 2 alternators (410A's) so I am sure I have ample power.

Thanks in advance for any and all help and ideas!

-SAA

 

[fratermus]

I saw a few videos suggesting/ recommending using TWO DC/DC chargers as they can be "stacked" sort of. I am wondering if this is a good idea for a couple reasons

Since there will already be one Orion provided it's not a crazy idea to parallel another one. If we were starting from a blank sheet the discussion might go off in different directions.

a single 30A charger seems small for a 400Ah set of batteries.

30A into 400Ah is a 0.075C charge rate, quite mild. The max recommended charge rate for 400Ah of BB would be ~200A (0.5C) if I remember the specs correctly.

Will the 2, 30A chargers AND the 330W of solar be too much for the batteries to handle when running down the road?

The 15A MPPT charger will limit output to 15A no matter how much panel is feeding it. There could be 1000w of panel and output would max at 15A. I'd expect a practical max of ~215w. It's common to overpanel MPPT controllers this way for technical and economic reasons.

With the 15A MPPT and 2x Orions maxxed we'd have a total 75A, or
0.1875C. LFP cycle ratings are typically derived from slightly higher (0.2C) charging currents, and the longest-lived LFP bank we have solid data on was charged over 2x as fast (0.4C).

my truck is a 2023 F350 w/ 7.3L gas engine, 2 batteries and 2 alternators (410A's) so I am sure I have ample power

Heads up: the dual-alt setup might operate counterintuitively. A non-issue at 60A, but worth mentioning for those considering monster alt charging setups.

 

[SimplyAnAdventure]

was

Since there will already be one Orion provided it's not a crazy idea to parallel another one. If we were starting from a blank sheet the discussion might go off in different directions.



30A into 400Ah is a 0.075C charge rate, quite mild. The max recommended charge rate for 400Ah of BB would be ~200A (0.5C) if I remember the specs correctly.



The 15A MPPT charger will limit output to 15A no matter how much panel is feeding it. There could be 1000w of panel and output would max at 15A. I'd expect a practical max of ~215w. It's common to overpanel MPPT controllers this way for technical and economic reasons.

With the 15A MPPT and 2x Orions maxxed we'd have a total 75A, or
0.1875C. LFP cycle ratings are typically derived from slightly higher (0.2C) charging currents, and the longest-lived LFP bank we have solid data on was charged over 2x as fast (0.4C).



Heads up: the dual-alt setup might operate counterintuitively. A non-issue at 60A, but worth mentioning for those considering monster alt charging setups.

What an amazing and thoughtful response that is exactly what I was looking for!!!!! I can’t thank you enough! So my initial thought is to run a heavier cable and an 80A breaker to a bus bar in the camper than from that bus bar split into the two DC/DC chargers 75A including solar into the system seems great. I guess in a worst case scenario or if I seem to use power faster than I think I may, I have a 2200 Honda generator that’s been converted to run on propane and can always use that to feed the 45A charger when parked. But 60A while driving seems like a bare minimum.

 

[jonyjoe101]

I would get a larger mppt controller. I have a makeskyblue 60a mppt controller on my 365 watt solar panel, when the sun is overhead it can get up to 27 amps from the panel. Your 330 watts can at least produce up to about 22 amps. On a large battery bank you want max amps during daylight hours.
The victron 75/15 max wattage panels is about 220 watts on a 12 volt system according to the specs. Too much wattage will eventually damage it from too much heat.

 

[fratermus]

I would get a larger mppt controller.

Agreed, if the controller is maxxed at 15A for a nontrivial amount of the time. If they aren't hitting 15A regularly then >15A is makes no difference.

The website for the camper shows shrouded fans on both ends of the solar array. My guess is the mfg predicts the raised shrouds will shade the panels in summer when harvest could reasonably be expected to be >15A.

 

[DaveInDenver]

You might want to check with Victron or at least look in a manual to see if their devices are OK to parallel.

DC-DC chargers and solar controllers aren't dumb devices just blindly feeding voltage and current. They are running control loops that measure the battery condition to determine various parameters. So putting two actively in parallel can result in erratic behavior where you don't end up with what you want.

It's usually (not 100% always but usually) OK to have various devices wired in parallel as long as only one of them is active at a time. So having a DC-DC charger that's on with the engine and a solar MPPT when it's not shouldn't be a problem.

It's certainly possible that you can parallel two similar controllers but it might require making one master and the other a slave to it, for example. In this way only one of them is doing the actual control and the other just follows its commands. Could be a jumper setting or in firmware and might not be a published feature in the manual.

 

[carterd]

If you want to go "beast mode", you could install a single Sterling Power 120 amp DC DC charger (https://www.sterling-power-usa.com/SterlingPower12volt-to-12volt-120ampbatterytobatterycharger.aspx). This can be manually set to operate at 85% (102 amp) or 65% (78 amps). If your batteries got low and it was a cloudy day, this could get you recharged faster. The Victron website does say with the Orion "unlimited multiple units can be connected in parallel to increase output power". So you could in theory pair 4 Orions together for 120 amps and probably still be within an acceptable continuous charge rate of the alternators.

 

[SimplyAnAdventure]

Some fantastic ideas on here! I actually took a minute this morning to reach out to Supertramp and make the suggestion that they offer a larger charger with the larger battery banks. As a company I can't speak highly enough about their customer service so perhaps they will consider it. I also understand if they have a preset configuration that can't be altered so I might have to go at this on my own, which from the posts above seems easy enough. Run a heavier cable from the front to a 100A plug and either to two Victrons or maybe that big sterling. I can certainly see the appeal of minimizing charging time while driving as much as possible. Thank you all for your thoughtful responses. I'll post here with whatever I hear back from ST and if they are unable to do it once it arrives I've got the whole winter to tackle this project.

 

[SimplyAnAdventure]

As promised I will update this thread with the information I got back from Kelsey at Supertramp regarding adding a larger/ additional DC/DC charging.

Her response was as follows:

"My apologies for the delay on this email. I was running it up and around the chain to see what feedback/ questions. (sic) We do think this is a great idea but at the current moment we can't take it on. We hope you can understand that right now as a team we are full force focused on production of the campers and once we get ahead we can take on these types of projects."

Well..... I do understand and I think that is a very reasonable response! Supertramp seems to be known for not settling and always improving and bettering a product so I am confident in the future they will offer this as an upgrade. I've said it before but ST is a complete joy to work with, all their staff is excellent and they are willing to listen to ideas. I may pursue this on my own or perhaps wait and see what they do as a solution. I have a Honda 2200i that runs on propane so it's likely on trips in the real hot weather I will bring that along to feed through the 45A shore power charger to keep things topped up.

Again, I can't more highly recommend ST as a company. My camper is 30 days out now and than I can give back more real world feedback.

~SAA

 

[DRP]

I love my Victron gear but will say the Orion BtoB's run hot! I wired my 12/12-30 sense wire to a switch on the dash. I switch on/off at 30 minute intervals when on long drives so I don't get 30A continuous. I just moved it's mount location and added a pancake fan. Haven't been on the road yet to see if conditions have improved.

I think Victron says you can parallel up to six of them.

I also agree that you should get a bigger SCC for your panel array size