At 170 watts/12V DC, your fridge is putting a 14.5 AMP load on the electrical system in your trailer. That's frigging HUGE. Adding a 14 AMP load to your RL electrical system is completely unnecessary and taxes the alternator with a continuous load. Converting DC to AC only exacerbates the demand on your system(s) - inverters are notoriously inefficient. For the most part, IMO: the only thing an inverter is needed for is to temporarily power something that can't be connected to a 12-14 VDC source like a microwave or coffee maker. And when an inverter is used, it's only for very short durations - even an unloaded inverter is an current EATER on a DC system.
To Dnick's point, the overall health of your DC power system is critical. IMO: placing a constant 14+ amp load on any DC system is huge, especially when that load causes the battery(ies) to go "dead" more than once or twice. It doesn't surprise me the OP author is having trouble with powering his fridge via DC only.I agree with OhSix that there is NO reason to be looking at 110V power for your RV fridge. My initial thought is:
- Your RV battery must be either very old/bad, or very small. No way should it drain that fast just running the fridge.
Beyond that, I will tell you that I towed travel trailer for years & did not have anything fancy in the way of battery on the trailer (brand-X, average sized deep cycle). I ALWAYS ran fridge on 12V when on the road (switched to propane when we arrived at camp, except for the rare occasions when we had hook-ups). First off, you should be able to do that just fine (run on battery) all day long! Secondly, you should NOT be running down the road towing your trailer with propane on (shut OFF the tanks before departing). You're asking for trouble otherwise. (that's not to say it isn't done a lot.... but it's just not proper practice, or safe)
You might consider stopping by an RV shop to get a quick electrical diagnosis, because I believe your rig is suffering some kind of voltage-drain (or connectivity) fault. Have it checked out, and I'll bet your problems will be solved either with a new battery or by locating/repairing your voltage leak (or bad connection).
It's also entirely possible that you have poor connections somewhere between your trailer hitch plug and your battery.... not uncommon at all on towed vehicles to have bad connections or grounds. You might not be getting any charge to the trailer battery at all..... although with a good battery, that shouldn't really matter.
In any case, I believe you're definitely barking up the wrong tree (for lots of reasons) by chasing an "inverter" solution.
Interested to know how this gets resolved. Good Luck!
Actually, even the cheapest inverters are over 90% efficient. The rest is dissipated as heat. "Idle" power is typically only a few watts, if that. If you've got a 100-watt load, no more than about 10 watts is "wasted".
Speaking from personal experience, ammonia solution based refrigeration works perfectly fine while in motion. While I'm not positive, I *think* the sensitivity to being level has to do with long term settling of the fluid in areas where heat can't be evenly distributed across the storage tank. While the liquid moves around with vehicle motion, the average seems to work out OK. What I have noticed is fridge temps are a bit higher when the vehicle is initially parked after a trip, with the temp dropping as fluid settles into the optimum location.
Oh hell, now you went and did it. The hatch covering the abyss of inverter efficiency and sine wave purity has been opened.
That discussion has been beaten to death on RV and solar living forums all over the internets. Same goes with the "choppy" nature of inverter sine waves & their effect on resistive and inductive loads. ...... another thing not mentioned here is that while traveling, the propane flame 'can' blow out, depending on trailer / fridge design & winds encountered (cross-winds, etc.), which of course ends the propane cooling. No wind-worries on 12V, and I don't know of any reason to to use 12V on the road if your systems are functioning properly.Oh hell, now you went and did it. The hatch covering the abyss of inverter efficiency and sine wave purity has been opened.
Still... 90% efficiency sounds great but only under ideal circumstances is 10% waste "OK". By ideal conditions, I mean the entire electrical system both DC and AC being in peak condition. Other than brand new, ideal conditions are somewhat unusual in the real world. After a few mechanics and/or do it yourselfers have stuck their hands in the mix, and time & weather take their toll on a new system, things degrade to less than ideal pretty quickly.
On the topic of AC inversion for running a 3 way fridge, IF the fridge in question is an absorption design (which is by far the most common) the principle behind the system is heat causing ammonia to convert to a gaseous state. That heat can originate from a small flame fueled by propane, or heating coils powered by either AC or DC. When the fridge is running on either electric source, there is no "start up" current spike caused by a compressor motor - therefore 175 Watts (DC) is pretty much a flat current demand whether starting up or running steady state. Setting aside start up energy, the most efficient heat source for the common 3 way fridge is propane. With little more than a pilot light flame, it generates sufficient heat for ammonia conversion to gas, at an average rate of about 1/2oz/hr. Since DC power is a precious commodity when camping, my preference is propane first, AC second (when connected to shore power) and DC as a last resort but only when batteries can be replenished by solar or generator.
In my rig, a Trace Legend II manages both battery and inversion tasks. As a battery manager, it's nearly perfect. As an occasional AC inverter, it's been super handy - but based on experience, I stay away from AC inversion tasks unless they are momentary or early in the day - which gives the solar system time to replenish batteries. If I need AC power for anything more than a few minutes, I'll run the little Honda generator, but that's just me being anal about keeping the house batteries about 11.5 V at all times.
Whoops! Having never visited an RV or solar forum, I was speaking purely from personal experience and observations.
SIX, I started busting up in the first 2 sentences of this write up by you. I always feel like I learn something by the time I'm finished reading your posts..Oh hell, now you went and did it. The hatch covering the abyss of inverter efficiency and sine wave purity has been opened.
Dnick, yes no wind no worries, and I would go as far as to say that if the 3-way refrigerator MFG, has instructions for operating while in motion, vs campground (shore power) vs off the grid camping, that's where I'd start.
By the time you finish reading? Are you suggesting bloviation on my part? Like I'm verbose? Long winded? A blow hard? HAHAHA. Glad someone gets something out of these posts. I tell you what, this forum taught me enough about the RL to be confident with a buying decision and to be a well informed RL owner. If it wasn't for the forum members here, I might have missed the opportunity to be a happy RL driver, and that would be a tragedy. THIS is what social media should be. :act010: The 06 is the first used daily driver purchased since the early 90's. And it has been the best damned buying decision ever. This vehicle is an absolute joy to drive and work on. I actually get excited when there is time available to tinker with her. She just turned over 103K so it's time to bust out the checkbook for the timing belt and related preventative maintenance. In a younger day I'd tackle that work myself but I learned to leave major stuff like this to the guys who do it for a living. Besides, waste fluids are a hassle to deal with.
After re-reading the OP, I think there is a larger issue. If the concept is to use the factory (or an aftermarket) inverter, the idea is unworkable in the sense that running AC from the RL to the trailer is not practical, for both travel or camping. IF the goal is to use an inverter to power the fridge, the only practical location for the inverter is inside the trailer - not inside the RL. And that comes with issues of supply from the RL to the trailer.
