Converting to residential fridge

[Bob86ZZ4]

My original batteries were in vented boxes. White ones. Guessing the builder thought they should be vented out. The storage bay they're in has a pretty well sealing door. But there is a large vent right there behind that red switch I put in to cut the power to the 2k inverter. So, I wouldn't think the batteries would need to be vented either. But since they were I decided to vent the new boxes too. Wasn't a huge job cutting up the old boxes and cutting the holes into the new boxes. I have a very large band saw in my shop, worked great. The Iota charger/converter is mounted in the same box so I guess that might be why they figured the more venting the better. I did have to cut notches into the covers of the boxes to allow the wires to clear when putting the covers on. So it's not like the covers are real sealed up or anything.

[Bob86ZZ4]

I took the 12 volt batteries to my guy for the cores. He checked the batteries and said the one battery was real bad and the other was "marginal." They were a little over 4 years old.

[Bob86ZZ4]

Here's the batteries I put in: U.S. Battery | Leader in Deep Cycle Batteries | US 2200 XC2 - U.S. Battery | Leader in Deep Cycle Batteries

[38Chevy454]

Glad to hear you got to the root of the problem - bad batteries. Seems the old batteries had a surface charge to indicate voltage was seemingly OK, but no real amps capacity.

[Bob86ZZ4]

38Chevy454, what are you doing to power yours? I only get about 6-8 hrs. run time on my two golf cart 6 volt batteries. Then it doesn't seem to have enough juice to start the compressor. If I switch the battery switch to add in my 3 truck batteries it will kick on the compressor and run the fridge. I don't know how long since I don't want to run down my truck batteries and not be able to get it started. I have a good area between the frame rails at the back where I think I can mount 4 more 6 volt batteries. I've bought two and will fabricate the rack to mount those two first. Should be pretty easy to add two batteries first and wire into the system. Then I might add two more. I want to fabricate the mounting system for 2 batteries at a time. I'll try running the system with the 4 batteries and see how that goes. If it'll run for a couple days maybe I won't bother with another pair. We'll see. Curious what 38Chevy is using for batteries since your fridge is bigger than mine (theoretically it should need more battery power to run?).

[bushpilot]

bob

whats the amp hour rating on of those 6D (6v) golf kart batteries? the problem is you have to wire the 6v in series to get 12v out of 'em and then you don't get the benefit of doubling the Amp Hour rating (like you would if they were 12v wired in parallel).

why not 2, 12v batteries wired in parallel - surely you'll get more Amp Hours.

[Bob86ZZ4]

Don, here's the battery I'm using: http://usbattery.com/wp-content/uplo...a_2015_WEB.pdf

I don't know all about amp hours and such. I trust my battery guy. He's told me that using two golf cart batteries wired in series (to end up with 12 volts) is going to give me the most longest power (my wording, not his, hahahah) for my household needs. There is another guy that knows the most there is to know about batteries. Duff. Hopefully he can comment for us here?

[bushpilot]

Originally Posted by Bob86ZZ4

Don, here's the battery I'm using: http://usbattery.com/wp-content/uplo...a_2015_WEB.pdf

I don't know all about amp hours and such. I trust my battery guy. He's told me that using two golf cart batteries wired in series (to end up with 12 volts) is going to give me the most longest power (my wording, not his, hahahah) for my household needs. There is another guy that knows the most there is to know about batteries. Duff. Hopefully he can comment for us here?

so it LOOKS like (and i could be wrong) that those batteries are rated at 232 Ah,
wiring them in series (necessary to supply 12v) only maintains the amp hour rating.

only when batteries are wired in parallel do you increase the Ah.

I suppose if you had another pair you could wire them in series and parallel and double the amp hour rating to 464 and so on.

[Duff]

The typical 6-volt "golf cart" battery is rated for around 200Ah at a 10-hour rate. That puts you at a little over 1kWh, but you only generally want to discharge a FLA battery to about 50%, so call it 0.5kWh. You've got 2, so you're back to 1kWh total (usable).

I don't remember which 2kW inverter you have, but with it turned on, it's probably drawing about 30-50W. If your refrigerator is drawing on average about 50W, we can say you're drawing about 100W, which means you've got about 10 hours of runtime (not counting startup needs). It would be worth knowing what the refrigerator (and anything else on the inverter) is drawing--if it's around 150W total, that would put you right about 7 hours to 50% DoD.

But you're dealing with a slightly different problem, namely that the inverter isn't able to supply enough power to start the compressor. On mine, that spike is in excess of 1000W, only very briefly--if you're 50% discharged, that large draw may be momentarily dropping the supply voltage below the inverter's low voltage cutoff. A digital voltmeter likely won't be quick enough to pick it up, but a test light might.

[Bob86ZZ4]

Yes, that agrees with what I'm seeing on the inverter digital display. When the fridge is humming along it's showing about 40 watts going out. Once I spotted it showing 9xx (can't remember exactly but somewhere in the 9's) for a moment. I figure that was when the compressor was starting up. I'm using a Xantrex pure sine wave. The digital display switches back and forth between the input voltage and the output wattage. So I have to try to catch the display when the compressor is starting and hope it's on the wattage part. Only been able to catch that once so far. I haven't been able to work on it lately. I have been working over plans in my head for the battery tray I'm going to construct to hang the next two golf cart batteries between the frame rails back there. I think I've got a pretty good plan for that now. Just have to go to the steel supply yard and get some stock to work with. And some more 1 gauge cable to hook them up. If it works the way I think it will then I should be able to get another pair in there too. That will give me a total of 6 golf cart batteries. I'll take pictures, and hopefully post them (but we all know how much trouble I have with that).

[Bob86ZZ4]

The batteries that the builder put in were 12 volt group 24's. I looked at a few of those and they have about 75-100 amp hour rating. So, putting two of them in will give me 150-200 amp hours. And the 6 volt batteries I put in are rated at 232 amp hours. And I know I can't add them together since I'm wired in series to get the 12 volts out. Still looks like a slight advantage over the 2 12 volt batteries I had?

[bushpilot]

i think clearly you need more than the Ah that you have today...in order to increase your dry camping run-time.

sounds like you have 2 problems: too small an inverter (can't sustain the start up) and not enough runtime / amps hours.

[Duff]

Bob,

The main thing you're getting with the 6V batteries is longer life in deep-cycle use. You might also think about a minimal solar setup to help the batteries out--it wouldn't take much to keep up with what the refrigerator needs, at least in the summer time.

It also matters (quite a bit with lead acid) how fast you're drawing power as to what the battery can deliver. In your link, note the different rate columns--you were actually down more in the 6-hour column (187Ah), not the 20-hour rate. Good luck finding a similar chart for those group 24 12V batteries--probably doesn't really exist because the numbers likely fall off a lot faster.

[bushpilot]

Duff - if all he's getting in the 6v's is the benefit of Deep Cycle, why not go w/ 12v and be able to increase the amperage over the 6v?

[38Chevy454]

Originally Posted by Bob86ZZ4

38Chevy454, what are you doing to power yours? I only get about 6-8 hrs. run time on my two golf cart 6 volt batteries. Then it doesn't seem to have enough juice to start the compressor. If I switch the battery switch to add in my 3 truck batteries it will kick on the compressor and run the fridge. I don't know how long since I don't want to run down my truck batteries and not be able to get it started. I have a good area between the frame rails at the back where I think I can mount 4 more 6 volt batteries. I've bought two and will fabricate the rack to mount those two first. Should be pretty easy to add two batteries first and wire into the system. Then I might add two more. I want to fabricate the mounting system for 2 batteries at a time. I'll try running the system with the 4 batteries and see how that goes. If it'll run for a couple days maybe I won't bother with another pair. We'll see. Curious what 38Chevy is using for batteries since your fridge is bigger than mine (theoretically it should need more battery power to run?).

Sorry for delay, been off the computer for a little. I have three 12v batteries, hooked to a 1000w inverter. My batteries are 2 large (group 27??) and one regular group 24 size. I added the 24 size with the inverter install. I don't actually know the amp-hour ratings of them off top of my head and I am at work now. While I did test the inverter for about 1 hour and the frig works, I have not actually boondocked yet to actually give it a test. I have not even gone on a trip yet this year. My understanding is the Samsung works different than the others. It has what they call digital compressor and it does not cycle. Instead the compressor ramps up and down as cooling needs change. So it does not have the high start-up current, and also has a lower avg amp usage; of course a std compressor has higher avg when on and then zero when off. So a direct avg is not really valid. I have read the Samsung uses between 0.5-3.0 amps. It even has LED lighting inside to minimize power when door is open.

Back to the battery discussion, several others have offered input since your question to me, and I tend to agree that the 6v are better. I think you just need more capacity. Although I have no plans to go this route, you could make considerable battery improvement by adding some solar to recharge. I figure when boondocking, there is good chance I will want some A/C, so I plan to just let the generator recharge my batteries.

[bushpilot]

Im running an EdgeStar (compressor base) cooler, on 3 house batteries (12v, deep cycle) and i get a good 8 hours of run time (give or take based on the outside temp).

I can be away from the coach all day long and come back to 12vdc indicated on the meters, but then my cooler is duel voltage too.

[Bob86ZZ4]

Don, I'm using a 2000 watt Xantrex pure sine wave inverter. The specs say it's 2kw continuous, and 3kw surge. I would think that should be enough for this 12 cubic foot refrigerator?

[hot rod]

All this makes me appreciate my two way rv fridge. It will run on my propane tanks pretty much indefinitely by comparison. I only have a single group 24 deep cycle, but I normally run the generator at some point for the microwave or ac at some point anyway. But I know I can park it in the driveway for almost two days when I get home before I have to worry about plugging it in for the refrigerator to stay cold.

[bushpilot]

Originally Posted by Bob86ZZ4

Don, I'm using a 2000 watt Xantrex pure sine wave inverter. The specs say it's 2kw continuous, and 3kw surge. I would think that should be enough for this 12 cubic foot refrigerator?

i would THINK so too Bob - but it doesn't seem to be the case.

[bushpilot]

Originally Posted by hot rod

All this makes me appreciate my two way rv fridge. It will run on my propane tanks pretty much indefinitely by comparison. I only have a single group 24 deep cycle, but I normally run the generator at some point for the microwave or ac at some point anyway. But I know I can park it in the driveway for almost two days when I get home before I have to worry about plugging it in for the refrigerator to stay cold.

same here, i love our RV (propane / ac volt) fridge...

might be a different story if we were full time, but it keeps plenty of food cold for us even on a trip that lasts several weeks.

I installed an ARP emergency (over temp) shut off - the ARP measures the temperature of the (ammonia boiler) and kills the power to the fridge if it gets over 420* (f). This is the #1 source of Fridge fires and probably RV fires.

I also installed Fridge Fix RV fan system (blows air across the cooling fins) to prevent icing....ive left the fridge running for more than 8 weeks (in humid temperatures) and not had any ice build up.

I tried a competitive solution from RV cooling unit warehouse....it didn't work nearly as well as the Smart RV Products unit.