Is it just me, or are others also reading, on rare occasion, about charge controllers catching fire? These China made items have me a little bit concerned now. Can anyone confirm this issue is out there, or am I overreacting to a few isolated incidents?

 

I'm on the DIYSolarForum. If this was a common problem we would hear about it. We have an entire subforum called "Up In Smoke" where catastrophic failures are posted and discussed.

 

I used to a have a 12vdc refrigerator and worked well because it uses Freon, where as the LP/12v refrigerators use ammonia coolant. Your 12vdc refrig probably also runs on 120vac shore power. The Freon (non LP) work much better that the ammonia coolant ones. They use much less power and don't need to be as level as the ammonia coolant ones. I wish I still had mine.

You should measure the current it uses when cycling and assume probably a 50% duty cycle (depending on the external temp). That will let you approximate how may amp hours it uses for camping overnight. When you are driving, the truck will provide plenty of current to keep your battery charged and running the refrigerator. (If you just use the trailer hitch connection)

Charging your battery up is a compete different issue. Your battery life will be shortened significantly by letting your trailer hitch connection charge your battery. This is why you should have a DC/to DC charger in between your camper battery and you truck. Victron make high quality stuff. I have the Renogy, and I have abused the crap out of it and it still runs great. I'm an EE. Let me know if you have questions.

 

You can only charge the battery to 100%. Whether the truck or the solar is doing it is immaterial really, but while you are driving it is getting charged. 15 amps is more than enough to run your fridge (are we sure the truck pushes 15 amps? I've heard several different #s). Regardless, so given you don't boondock and you'll be on shore power overnight, I don't see a problem.

We have a similar setup but our RV has two 110v refrigerators and driving all day, both run fine and my twin 53ah lead acid batteries charge just fine on truck/solar power. We have 380w of solar on the roof and an 1800W inverter to turn the 12v into 110. I'm surprised at how well it works actually.

I'm not so sure that the solar goes into float mode however, as I monitor the system while driving and I believe the solar is producing power while we are hooked up and driving. At least that's what the BMPro is telling me. I'll verify next time by unhooking the umbilical and seeing if I get a solar voltage change.

 

I'm no expert but from the RV forums; 12V compressor fridges burn a significant amount of power - around 50 AH's/day.....which is why I'm very happy with my propane/absorption fridge as it will run for weeks on a single bottle of propane (one propane tank has the same energy as 100, 100AH batteries!)

The amount of charge you get from most trucks through the trailer wiring is very small......a DC to DC charger would be needed IMO and also the charge voltage/profile from the truck isn't ideal for LiFePO4 batteries from what I've learned.

2 cents,
Dave

 

I agree basically. I think 50 is a bit high but OK. In this case with a 100ah battery and no other power source he can get about 40 hrs...but he is drawing power from solar and the truck so I'm not seeing any problems with his travel schedule given he starts the 400 mile travel period with a full charge. Even without the 12v feed from the truck or solar he still shouldn't have a problem with his travel cadence unless I'm missing something.

 

I wouldn't loose any sleep over your concern. Throw in that the refrigerators are pretty efficient and the OP should be fine as long as he plugs into shore power at the camp ground, I've read that RV fridges will stay cold anywhere from 6-12 hours without being powered by anything, whether that's true is anyone's guess. My TT has a solar panel on top as well and have never ran into an issue while traveling where the fridge didn't stay cold enough to keep things cold and frozen. When we arrive at the final destination the battery has just as much charge as when we left according to the battery indicator in the TT. Most of our trips are closer so it's not an issue, but we've taken it on a longer trip or two and not had an issue.

 

I'm guessing he'll get very little from the truck and solar is dependant on weather and the time of day/night he's travelling. That said, it'll probably be fine IF he's going to a place with full services......if he's boondocking, then arriving with partially depleted batteries may be far from ideal. ....like all things RV, it depends what your usage is.

Based on this: my travel pattern can be long day, evening with no solar, not sure how it works in rain, can the truck keep up with fridge demands by keeping battery charged. I'm not convinced the answer is "yes".


Dave

 

https://askthervengineer.com/youre-n...r-tow-vehicle/

 

I agree with you, it was 20+ years ago and I "tried out" running my 5th wheels fridge on 12 volts on an 8Hr drive... By the time I got set up for the evening my 2 lead acid deep cycle batterie's were basically dead for the night, maybe todays fridges are much "better"... but I think not, not really. JMO I am convinced the answer is "no" if you boondock, and a "maybe", if you have shore power every night and a LiefPo4 batterie... JMO

 

Just keep in mind that running an absorption fridge on 12V (12V electric element or 120V through an inverter) does take far more energy than powering a 12V compressor fridge though all take more than I'm comfortable with.

Dave

 

I have the typical propane/AC absorption refrigerator. I have excess solar production, so I turn the refrigerator to AC during the day. I've probably saved $5 worth of propane over the past couple of years.

 

Yes, my friend has a new compressor type 12 v fridge and his ran for 2 days with 2 lead acid batteries and the help of a solar panel...

 

When my absorption refrigerator dies, I'll be replacing it with a 12 volt compressor model. They tend to cost a bit less and have more interior space for the same exterior dimensions.

 

Manufacturers stopped putting the absorption reefers in a few years ago. They are all either 12v compressor reefers or counter depth home reefers that use an inverter for travel. The OP has the 12v compressor one, like mine, which is an everchill and it works great. Cools faster, and recovers faster than the absorption ones. It will stay running off the 12v battery with the truck hooked up and not kill the battery during a 10 hour drive. Mine has the 50 watt juice pack to help keep the battery up. When I got to camp the battery was 12.6 volts.