This is EXACTLY what I was going to say.
Towing with a 200-series Toyota Land Cruiser (2 Viewers)
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FrazzledHunter
SILVER Star
My previous trailer's fridge was 120V/propane and we didn't want to run the trailer with the propane on; propane was great for off grid stationary & fairly level.
At least that's what the RV vendor (Keystone) drilled into our heads.
I just had a quick talk with an Oliver sales rep and he confirmed that the fridge is a 120VAC/12VDC unit and you can run it while towing.
As for charging the batteries from the tow vehicle, he wasn't sure if the batteries could be charged via the 7 pin, what the current draw would be or if it's even connected.
So the 12V aux pin on the LC is fused at 40A and energized via relay.
I'm assuming (uh oh
) that it must be good for something...30A give or take to the trailer while under tow would be great!Per your suggestion, Oliver sells a solar upgrade with solar panels on the roof which looks good at first glance.
The sales rep said, with that option, the solar panels would indeed charge the batteries while under tow, but of course you need sun LOL!
Anyway, the Oliver rep. said he'd get back to me with the particulars on the 7 pin.
- Thread starter
- #1,483
I can’t speak to the Oliver specifically but the 12V wire is fairly thin and while it might handle a short heavy load like running the tongue jack I’ve found it did a crappy job charging the battery. Keep in mind the alternator is putting out maybe 13.5V, which is a float charge not a bulk charge. That combined with a long wire run that’s maybe 12ga wire and your charge current is maybe a couple amps. I tried to recharge a low trailer battery like this once and it’s insufficient except unless you’re driving 12 hours. Even then you’ll only get maybe half a charge on a dead battery. It’s why I went solar, and subsequently why I built a big ass lithium battery. I can now run 10 days in the woods and then recharge in one long day of sunny drivingMy previous trailer's fridge was 120V/propane and we didn't want to run the trailer with the propane on; propane was great for off grid stationary & fairly level.
At least that's what the RV vendor (Keystone) drilled into our heads.
I just had a quick talk with an Oliver sales rep and he confirmed that the fridge is a 120VAC/12VDC unit and you can run it while towing.
As for charging the batteries from the tow vehicle, he wasn't sure if the batteries could be charged via the 7 pin, what the current draw would be or if it's even connected.
So the 12V aux pin on the LC is fused at 40A and energized via relay.
I'm assuming (uh oh
Per your suggestion, Oliver sells a solar upgrade with solar panels on the roof which looks good at first glance.
The sales rep said, with that option, the solar panels would indeed charge the batteries while under tow, but of course you need sun LOL!
Anyway, the Oliver rep. said he'd get back to me with the particulars on the 7 pin.
FrazzledHunter
SILVER Star
This is great information regarding the 7 pin. I look at the wiring diagram for the 12V but don't have any real sense of how much power you can actually get out of the darn thing, fuse size notwithstanding. Good to know and thanks!
Regarding the charging voltage trailer-side for lithiums: I understand the charging issues, there would have to be a DC-DC charging function to charge lithiums or AGM's for that matter from the 7 pin taking whatever it put out and sending it to the batteries.
Anyway, the rep said he'd get back to me regarding what they actually do and what they might consider doing custom.
As an aside, the rep seemed genuinely interested in the subject and said it was an active topic of discussion in their shop.
(Perhaps he was just being gracious LOL).
- Thread starter
- #1,485
I think LFP or AGM would charge but I can tell you that when I set my solar controller to 13.6V max i get 1-2A/hr (about 20W) in full sun but if I set it to 14.6V I get over 300W from my 350W panels. To bulk charge you have to apply more than 12V to get the battery to accept the energy. The higher the voltage the faster the charge, essentially. So a DC-DC controller might help I suppose, so long as you can get voltage in the 14V+ range
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- #1,486
Btw I highly recommend solar panels. If you don’t need to run the A/C and can forgo the 120V outlets (or don’t mind springing for an inverter) and either have good sun or a decent battery size you’ll never need a noisy generator. We did 6 days in Banff with almost zero sun and used barely half of our 271Ah LFP battery. Battery ran the fridge (along with propane), water heater igniter, lights, water pump, fan for the heat, kitchen vent fan, radio, USB chargers for 5 phones, small 12V inverter for recharging toothbrushes, etc. and then we recharged it in one day of driving.
FrazzledHunter
SILVER Star
Not sure I follow with setting the solar controller voltages - my solar panels talk to MPPT controllers and I don't do that.
Regarding charging voltages: higher charging voltages = higher charging rate.
Just look at a Tesla at 400V!
.I'm going by my experience with my 2nd AGM battery under the hood which is charged by a REDARC BCDC1225. There's 3 settings for its output: lead acid, AGM and lithium.I seem to recall that when it comes to AGM batteries some brands prefer a slightly higher voltage over others. It's a a real minefield.
RV fridges are changing. Most until now used absorption fridges powered in 2-ways (sometimes 3) but usually12V/propane or 120V. They generally work well but can be finicky in high summer temps or unlevel situations. These fridges can generally be powered by propane while underway but there's a legacy of fear from earlier generations where they would catch fire.
Last few years has seen a movement towards compressor fridges that can be powered by 12V or 120V. These are actually very similar in technology to the cooler style powered fridges we often. Made possible by compact and energy efficient Danfoss compressors. These are efficient enough that they can be powered completely by enough solar.
I'm about to switch my absorption fridge because of bad summer performance. Also I visit more BLM and odd places where the trailer is not always level...parked my trailer for a couple hours at probably 20° nose high and it locked up the ammonia cycle losing all cooling.
I have 400W solar and 500Ah battery so I'm already prepared on the power side to switch over to a compressor fridge.
Yes, the tow vehicle can charge the trailer. Need a DC-DC for anything other than lead acid. Probably can only get 15A at most through the 7-pin. Honestly with 400W solar on the roof, I really rarely need any other charge source to keep things topped off and powered perpetually.
- Thread starter
- #1,489
I have a Victron MPPT controller as well. You can set the max battery voltage in the Victron. When I want to recharge my LFP battery I have a profile which has 14.5V max. Most of the time the trailer sits and I have a separate profile I run which sets the max charge voltage to 13.6V, with a goal of not charging the LFP battery more than 90% in order to significantly extend its lifecycle. The panels themselves are ~21V open current, and my MPPT controller like yours will step down the voltage (and boost the amperage) so I don't cook the battery. My point was just that if I have my controller on the "float" profile with 13.6V max even though it went into bulk charge mode it didn't push many amps into the battery. In my case the limited charge is in part because LiFePO4 chemistry has a very small voltage differential between full and empty (you can see below that 13.2V to 13.7V covers from about 10% to 95%) - So at 13.6V there's a lot of resistance in the battery, but cranking up the voltage allows for the battery to accept all the amperage that the solar panels can send. Note that SLA batteries have a broader voltage range from empty to full.
Anyway my point was if your battery isn't significantly discharged that the 13.5V the alternator puts out is really a float charge, and will only trickle charge your battery unless it's really dead. You really need a way to bulk charge at higher voltages, which is what a DC-DC converter will do. Otherwise the charge rate will be slow. Trust me, I've tried - I ran my truck for 2 hours once with the 7 pin connected to the trailer as my old 100Ah lead acid battery was at about 10% and at the end it was barely at 15%.
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- Thread starter
- #1,490
If I had the space I wished for a residential fridge with an inverter. I didn't realize the 12V/120V propane-less options (which I'd only seen in vehicles) had made it into trailers. The absorption fridge I have can work well but it can also be highly variable depending on the temps, direct sun, etc.
FrazzledHunter
SILVER Star
Yes fridges are changin'! And for the better IMHO. It took anywhere from 8-12 hours for our ammonia fridge to get cool, even on shore power. That's due to the ammonia cycle, I get that. Running the fridge while towing with propane on was not for us. Some might disagree. We're currently using a Dometic CFX3 75L which is awesome - cools in 1-2 hours on battery. Wish our trailer had that. Another thing about not having a propane fridge is you don't need a vent; ours vented out the roof. The vent took up room that could have been used for a bigger fridge and there is no hole in the roof to caulk.
Hearing your experience with solar is a huge help - I have no real-world experience with that on a trailer. I've used a Merlin XP-170 to charge my Yeti 1500X and have been net-zero quite often. It's good to know the real-world capacity on the 12V on the 7 pin and it's intended purpose isn't to charge batteries.
Do your panels on the roof have any negative effects? I'm wondering about access to the roof, gas mileage etc... I was up on the roof at least once per trip if for no other reason than to look for tears in the rubber pre/post trip. It was the roof failing that ultimately caused us to sell our trailer.
FrazzledHunter
SILVER Star
Ah. I get you. Fantastic post. Victron & MPPT made the light bulb go on. Pun intended.
Background:
I'm using a Victron 12/24-15 DC-DC charger running in power supply mode to charge a Goal Zero 1500X battery. There is only one way that battery charges and that's via it's solar port that's connected to an internal MPPT controller. This port can charge at the rate of 600W, btw. All their AC wall chargers masquerade as a solar panel - even their 600W AC charger. The Victron is connected to the starter battery and looks like a solar panel to the Goal Zero battery. I can get 360-380W to the goal zero via the Victron while driving; it works absolutely beautifully.
Segue...
So what if RV manufacturers did the same thing. I.e. had an option to add a high wattage 600+W DC port feeding a MPPT controller at the tongue area*. RV builder would advertise as a method to connect an array of unregulated solar panels. You could then have panels on the roof and/or on the ground. Why, due to the location, you could easily have them on either side of the trailer!!! Those that didn't want panels on the roof or already had them could still be super green. Yay!
So what would I then do ? I'd pull the same trick as above and get a DC-DC charger to masquerade as solar panels that ran off the truck and treat the RV like my Goal Zero.
It just seems like it ought to be so easy.
*Black series has a SB-50 connector for high wattage solar at the tongue area for this - the only one I've seen like this. Intech has a zamp connector for this but it's locted in the rear on the driver's side. I do not know the charging rates for these.
FrazzledHunter
SILVER Star
We actually looked into this. We were advised that a residential fridge and it's compressor aren't built to take the bumps while towing if that's the goal. Also residential fridges don't lock shut on their own. That's easy to fix though.
We also looked into running the fridge we had (a 2-way 120V/propane) to run off a dedicated battery/charger/inverter while under tow. We would have needed to manually switch the fridge power to the dedicated battery/inverter when we broke camp. I didn't want to attempt installing it myself and we didn't do it due to cost to have it installed. But it's do-able.
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- #1,494
I have two 175W glass panels on my roof, mounted on L-shaped feet. The feet mount to the roof using rubber well nuts, then are covered in Dicor, then in Eternabond, then the Eternabond edges are covered in Dicor. Excessive but I don't want any leaks. There's only ~2" underneath the panels so it's hard to clean and inspect the roof, so The feet I have are actually bolted together on one side (bolt and wing nut) and hinged on the other. I can tilt them ~30 degrees if I want to clean them or to capture the sun. I really never do the latter but it's an option. FWIW my old trailer used the flexible panels and I just taped them down with Eternabond. That worked well enough, but they're not as efficient because the hot roof reduces their peak power.
Along with the 2 panels on my roof I wired a 2-pin solar port on the side of my camper. I carry a 100W flexible panel and a solar extension cable. If I'm parked in the shade and I need to recharge I can plug that in and set it on the ground somewhere in the sun. Again I really rarely ever use it, but it's an option and only a couple extra pounds to carry so not a big deal.
My Victron MPPT is good up to 100V input/30A output, IIRC. 12V limits me to 440W, but I could run it in 24V or 48V mode if I wired things differently. I was trying to keep it simple and 450W max input is plenty for me, but they have higher power versions. You have to decide your input voltage up front, but there are options up to 100A output and essentially you can pretty easily do what you're thinking. I think my only comment is that MPPT is really designed around higher input voltages, so I don't think feeding it with a high amperage 13.5V source (like an alternator) would trigger the MPPT controller to start charging... there's definitely a point in which the MPPT controller shuts off when solar panel voltages drop, so I think in your case you'd still need a DC-DC controller. The Victron 12-12/30 would do what you want, but it has a 30A continuous power limit... which is probably OK because if you try to run your alternator at full load continuously you'll likely fry it (I've seen this with LFP batteries being charged off an alternator as they have no internal resistance so the alternator just runs at 100% until it overheats)
FYI solar-related... this was my original setup in this trailer. I've since replaced the solar controller, added hinges to the panels to allow me to angle them, and added a side port for solar. One of these days I'll update the post, but it's still generally accurate for anyone looking to do this.
- Thread starter
- #1,495
I don't really buy that, but maybe it's possible especially with cheaper fridges. The high end RVs have residential fridges and they work fine. I have a buddy who had a Tiffen Allegro which came with one and it was awesome for long trips. Agreed with the locking door issue though.
My Norcold fridge has an auto switchover option. Settings are either "Gas", "Off", or "Auto". The latter uses 120V if available and propane if not, but if I was running 120V via an inverter yeah you'd have the same switchover issue - need to flip something to go propane-only. This is ~2014 technology of course.
In my case a 12V option would be ideal IMO as I agree with @TeCKis300 that it takes too long to cool down the fridge, and there's lots of wasted space, plus I have plenty of battery available to run it. If mine ever dies maybe I'll consider one for the trailer.
I've explored several of the things you're proposing and have many of the components in place. Interestingly, with my current load, without a compressor fridge, 400W (4x100W glass panels) solar handles everything. I have a 20A DC-DC on the 7-pin that I've stepped down to 10A to preserve the plug as it didn't like the heat from 20A. I have a second 40A DC-DC in my trailer ready to go with an Anderson. It's been in place for 2 years. I have yet to wire an Anderson receptacle on the car side to use it, cause frankly I haven't had a need with solar doing so well.
That may change with the conversion to a compressor fridge. I hear they consume about 30-80Ah a day depending on use and ambient temps. That'll mean 1-2 panel (of 4x100W) will be dedicated to that consumption. That maybe when I hook up the Anderson. Though adding another panel or two might be better value. And I'm now sensitive to how much load I'm pulling from the alternator as I've worn one out at 159k miles.
My trailer setup has an inverter and I can run my current fridge on the road with it. My 7cu ft absorption fridge draws about 330W. Between solar and the umbilical, I can keep up with that power draw and it works well.
There's a way to hack the 7-pin to allow a portable solar array to feed the 12V bus from there. Would need the solar controller on the panel side. Which is what I prefer anyhow as that allows flexibility to use the panel with the trailer, car, or whatever.
My solar install is probably not applicable to most trailers as it has an aluminum roof. I use standard mounting brackets with VHB tape and sikaflex around the foot as additional support and waterproofing of the sikaflex. No penetrations and has held strong for 6 yrs now. I have room for 2x more panels. What I would recommend is to wire them all in parallel as that provide the best compensation for varying solar and shade across multiple panels. I'm sure it's impacted MPG efficiency incrementally, but so has the 3" trailer lift.
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- #1,497
Do those compressor fridges pull that much power? I feel like most of my reading of people using the ARB fridge indicate it's 20-25Ah/day. I had assumed these would be similar.
My absorption fridge needs about half an amp to run. I'd have to check the actual load but I'd bet it's <10Ah/day, which is quite a bit less than yours.
Good point and it's probably dependent on size. The ones I'm looking at are 7-9 cu ft. Compared to the ARB fridge that's probably less than 3 cu ft. So that scales about right.
I've seen ARBs coolers in the heat of summer consume way more so there's probably a lot of variability to draw depending on context. I could see loading a larger RV fridge with fresh groceries and room temperature water would really tax the battery system so perhaps would be good to size power resources not just for nominal but potential worse case?
- Thread starter
- #1,499
/off to build a second LFP battery…
FrazzledHunter
SILVER Star
We're not alone.
I have been looking at this website to get ideas as to what components might be involved in my idea of a dream system.
I love that he uses Victron (
) components. Note the path from the tow vehicle's alternator!!!
Here's one of the installs:
Camper Wiring Diagram w/ 3000w Inverter & 600-1200w Solar - https://explorist.life/3000w-inverter-400-600ah-400-to-1200w-solar-camper-solar-kit/
I have been looking at this website to get ideas as to what components might be involved in my idea of a dream system.
I love that he uses Victron (
) components. Note the path from the tow vehicle's alternator!!!Here's one of the installs:
Camper Wiring Diagram w/ 3000w Inverter & 600-1200w Solar - https://explorist.life/3000w-inverter-400-600ah-400-to-1200w-solar-camper-solar-kit/
