Factory installed DC to DC charger

[Snackchaser]

I was recently asked about Oliver’s Email offering of a DC to DC charger, how long it takes to charge, and whether it’s worth it.  I can provide thoughts about the one I installed, but I don’t know anything about what Oliver is doing.  This seemed to be a good topic for the forum because it would nice to find out more details of what Oliver is installing, and what other folks think about it.

I think the DC to DC chargers are great if there is limited solar, no hook-ups, and you are frequently driving.  I don’t think they are good for regular battery charging while parked, but they are a great emergency back-up if needed.   If you use a lot of power like TV, internet, toasters, hair dryers, microwaves, cappuccino machines, etc., it’s nice to know that you will be charging on the way to the next camp.  

Charging times depend on a lot of factors.  But for a rough idea, a typical factory setup with 340 watt solar panels puts out roughly 26 amps, which theoretically can charge the 390 amp hour battery from 0% to 100% in about 15 hours, or 7.5 hours from 50% to 100%.   A 30 amp DC/DC charger would take about 13 or 6.5 hours respectively, if my math is right.  Of course I don’t know how many amps Oliver's DC to DC charger is.  

I installed a Victron 30 amp DC/DC charger because the solar was not keeping up with my old power hungry Starlink, and the battery would run down after a few days.  I originally assumed it was a lack of sun for the solar, but it later turned out that the solar charger had become disconnected somewhere in my travels.  After re-connecting it, I realized that the solar probably would have easily kept up with the Starlink, particularly with the new ones that don’t use that much power.  Please don’t ask me why I didn’t recognize this problem sooner. . . I don’t have a good answer.

My other justification for a DC/DC charger was air-conditioning.  Although the ac can run from the battery, it’s only for short periods.  We plan on doing some desert boondocking and my idea is to run the ac from the DC/DC charger while driving - so that the trailer will be cool when we get to camp.   It works, but it still uses a little battery juice also.  It’s nice to have a cool trailer for camp set-up, but a generator is still needed for long periods in hot weather.   IDK, it might be a bad idea.

FYI, I added cooling fans on my Victron DC/DC charger because it derates 3% for every degree over 104 to the point where it shuts down.  That would likely happen in the desert and I could end up draining the battery with the ac running while driving down the road.  See my “More DC to DC charger installation Tidbits” post for details on the fans.

Anyway, I’m interested to hear others thoughts on this because it's becoming a growing trend.

Cheers, Geoff

[Ronbrink]

18 hours ago, Snackchaser said:

My other justification for a DC/DC charger was air-conditioning.  Although the ac can run from the battery, it’s only for short periods.  We plan on doing some desert boondocking and my idea is to run the ac from the DC/DC charger while driving - so that the trailer will be cool when we get to camp.   It works, but it still uses a little battery juice also.  It’s nice to have a cool trailer for camp set-up, but a generator is still needed for long periods in hot weather.   IDK, it might be a bad idea.

Actually, great idea! I have a Renogy 40A DC-DC and run my a/c on LFPs via inverter while underway quite often; the total amp draw by the a/c is offset by the output of said charger. I should mention, no solar. In some instances, owners run for long duration to keep pets comfortable inside the Oliver when in transit. The only problem I’ve experienced was an aging alternator in my TV; the vehicle battery was not being properly maintained, but installation of a new high output alternator resolved that issue. 

Edited September 16 by Ronbrink

[jd1923]

20 hours ago, Snackchaser said:

Charging times depend on a lot of factors.  But for a rough idea, a typical factory setup with 340 watt solar panels puts out roughly 26 amps, which theoretically can charge the 390 amp hour battery from 0% to 100% in about 15 hours, or 7.5 hours from 50% to 100%.   A 30 amp DC/DC charger would take about 13 or 6.5 hours respectively, if my math is right.  Of course I don’t know how many amps Oliver's DC to DC charger is.  

I installed a Victron 30 amp DC/DC charger because the solar was not keeping up with my old power hungry Starlink, and the battery would run down after a few days.  I originally assumed it was a lack of sun for the solar, but it later turned out that the solar charger had become disconnected somewhere in my travels.

Your math is close enough in theory. Though roof-mounted panels, flat to the horizon, are not getting near 340W. Ours often charge at net 12A, even in the Arizona sun. Our new 400W Renogy Suitcase when aimed directly at the sun got 366W at best one time and more often was between 200 and 300W. The Victron 30A SC has showed 20+ amps charging, where theoretical max is 33A.

Starlink and other electronics, and the Oliver LED 12V lighting take so little power. Running cooking appliances, the A/C and a blow dryer is another story. I've been running A/C all week on only rooftop solar, but fall has broken up here at 5400 FT and the weather is wonderful lately. We do want to run A/C on inverter when it's hot after an efficient A/C upgrade. Running A/C when towing is a lot of drain, given sun and wind pulling the cool in your wake down the highway!

1 hour ago, Ronbrink said:

... installation of a new high output alternator resolved that issue. 

I worry about charging via the TV. I would only do so with the kind of upgrade that Ron made. OEM alternators are not designed to push out another 30-50A. Trucks today have complex ECUs and you don't want voltage-related error codes affecting fuel injectors and ignition.

@Snackchaser I read your DC-DC upgrade post (very nice work). I believe at the start of 2024 only the Victron 30A was available. The newer 50A is much more efficient, producing less heat, half the size, no large heat sink attached and likely no need for adding a fan. See video @rideadeuce added to my question post: Choosing a DC-DC Charger - Ollie Modifications - Oliver Owner Forums (olivertraveltrailers.com)

Lastly when traveling, we I go out of our way to drive only 2-3 hours between stops and generally not more. We like to maximize time at the campsite vs. time on the highway. Some of you drive a lot of hours in a day where this is more useful. I will likely add a DC-DC charger but went the suitcase route first because of this. When adding this capability, you should consider the cost of the charger, another $150+ for 4 AWG cables and connectors, plus the cost of an aftermarket high-output alternator, to do it right.

Victron Energy ORI121217040 Orion XS 12/12-50A DC-DC battery charger | Powerwerx 

[Cameron]

I'm definitely interested, especially since I think I might have the trailer serviced at OTT in January. I checked and they can't hold this month's special until then, but there might be another special. I'm thinking that OTT service would be a good place to get the trailer system installed. I don't use lots of power when boondocking, and usually am in a sunny place. But for times when there's not a lot of sun, and I'll either be running the AC or furnace, I'm wondering if the DC-DC charger option could take the place of me hauling a generator with me. 

[jd1923]

2 hours ago, Cameron said:

I'm thinking that OTT service would be a good place to get the trailer system installed.

This is the advertised special: "Charge your lithium batters from your tow vehicle.
*Camper system only. Truck must be outfitted by automotive shop for system to fully operate. Limited Supply. Sale Price: $1,350.00"

I zoomed in on the picture and can just see the '30' for the 30A on the charger. These go for $204 on Amazon: Amazon.com: Victron Energy Orion-Tr Smart DC to DC Charger (Bluetooth) - 12/12-Volt 30 amp 360-Watt - Battery Charger for Dual Battery Systems - Non-Isolated : Automotive

On 9/15/2024 at 1:06 PM, Snackchaser said:

I was recently asked about Oliver’s Email offering of a DC to DC charger, how long it takes to charge, and whether it’s worth it.

OTT will likely add a Bussman breaker (about $40, not shown in the picture). Say $100 for 4 AWG cable and parts (trailer side only), so they are charging about $1000 for labor! You would still have to wire the TV to connect at the hitch.

You really want this charger instead, for greater charge rate and less heat (watch the video in the link supplied above): Amazon.com: Victron Energy Orion XS Smart DC to DC Charger 12/12 50A (700W) - Advanced Battery Protection : Electronics There are a couple authorized sellers on eBay that accept $300 offers on this same charger for greater savings.

If I could not do this myself for <$500 in parts, I would purchase the components and get a trusted local installer or truck service company to install both sides at the same time. There are so many great examples here in mod postings from @Snackchaser, @Ronbrink, @MAX Burner, @rideadeuce, demonstrating this installation.

Don't forget an alternator upgrade! (also not included)

Edited September 19 by jd1923
Added last sentence

[Ronbrink]

3 hours ago, Cameron said:

I'll either be running the AC or furnace, I'm wondering if the DC-DC charger option could take the place of me hauling a generator with me. 

Furnace is not a problem, but running the a/c off battery for more than a few hours will be too tasking for the average battery bank. I carry a small dual fuel genny and use propane for overnight stays when a/c is needed off-grid. That said, lengthy travel stops for rest, lunch, shopping, etc. are prime times to use the a/c on battery since when back underway the DC-DC will likely recharge as you reach the day’s destination. 

[Snackchaser]

There are some good comments so far.  It was interesting to learn that some solar panels were not meeting their rated capacity, and the sun doesn’t always cooperate either.  This is a positive for the DC to DC charger because they have a more reliable output.  It was also good to hear that others run their ac off the DC to DC charger, this is a strong selling point IMO.

Yes I was disappointed when the 50 amp Victron charger came out after I installed the 30 amp, it’s way improved in efficiency, thus reduced heat.  I'm surprised that  OTT is not using it.  On the bright side, the 30 amp uses smaller gauge wire, but I think a cooling fan is still needed because it starts derating at 104 degrees.   This could be  less than ambient air temperature when you'd want to run the ac, and you could run down the battery faster if the charger output is not 100%.  From what I've seen with the 50 amp specs, this should't be an issue.

This raises another important point that trailer folks should be aware of.  Most of the DC to DC chargers are used in camper-vans and boats with short wire runs to the alternator, and the multitude of videos and wire specifications reflect that.  However, trailer installations have much longer wire runs, typically around 50 feet one way, so they will require larger wire to minimize voltage drop.  Even the Victron 50 amp is sized for maximum #4 wire, which would be too small for most trailer applications.

Alternator capacity was not something I've given much thought to,  because mine was something over 200 amps.  It’s good idea to check your'e alternator rating by looking up the alternator code or use an on-line VIN decoder.  I believe most newer trucks are at least a 100 amps or more.  TV voltage errors should’t be a concern because Victron has safeguards to shut down in low voltage conditions, and they are designed to work with smart alternators that are constantly adjusting output for better fuel economy.

Cheers!  Geoff