Residental Fridge Revisited

[arcticfox2005]

This is to a certain extent a continuation of a previous post, but with a different question in mind. We recently bought a 2015 Tiffin Allegro Open Road that is like new, only 9300 miles on it when we picked it up in Florida. Because it was kept in covered storage for most of it's life, not hooked up, I am confident the house batteries are pretty well sulfated.

Here comes the rub - it has the factory residential fridge option with a smart inverter and the LG fridge is a monster, huge. I have not looked into the current draw, but since we boondock overnight frequently, I decided that in addition to replacing the house batteries I would add another pair (they are 6v).

The new pair would be in the storage compartment immediately behind the entry steps where the original batteries are located. Gary Brinck in the earlier thread suggested AGM's because of the lack of proper venting for the new pair.

The AGM's I have zeroed in on are 200 aH  compared to 225 for conventional flooded cells. Now I am wondering if maybe I am going too far in trying to solve a problem that maybe doesn't exist. What if I just replaced the existing batteries with flooded cell ones from Costco? Would that be sufficient for an overnight stay without drawing them down below 60% or so, or do I need to bite the bullet and add the second pair? If I do add the second pair then I would buy 4 AGM's and immediately we are at $800-$1000.

If I just replace and find out that 2 flooded cells won't do the job, then I would have to buy the AGM's and do away with the newly replaced ones. I am assuming that 2 flooded cells and 2 AGM's wired in the conventional series/parallel setup would not do. Correct?

Any thoughts?

[muskoka guy]

If you are only boondocking overnight, the two batteries you have would probably do. While travelling, they will be charging. If you are extended boondocking, run your generator in the morning for a few hours, and a few hours in the evening. Adding more batteries without solar to charge them will only extend your boondocking so long. You still need to recharge the batteries somehow. This means running the genny. Your existing batteries are probably on their way out, but give them a try first. With 9000 miles on the rv, it may have been used enough to not have ruined them. Residential fridges and boondocking really only work if you have at least four batteries, solar charging, or run the generator four or more hours a day.

[arcticfox2005]

Thanks for the response. If I had bought the rig new, I would have never gone for the residential fridge, but the way it was, I had to overlook that issue. (As well as the 4 TV's)

You pretty much reinforced what I was thinking. I will replace them as I am sure they are sulphated beyond saving. We bought it from a widow and for the last year, it probably was driven less than a hundred miles total.

[UTTransplant]

Do you have four batteries now or just two? My Tiffin with RR came with a default of 4, and we added another two during the build process. The four new batteries should work, but you will be much happier with 6 if you want to do things like watch TV or have generator hours that stop at 6 or 7 like some parks we have been in. Oh, and plan on unplugging the entire entertainment system when dry camping and you aren’t using it. It is a huge energy hog, even when turned off. We also unplugged the two TVs we never use (above driver’s seat and outside).

[arcticfox2005]

Just two. Our previous class C had just two and we were able to watch TV for four or five hours without a problem. Of course the fridge was running on propane. We never run the furnace at night, so once we hit the sack, the batteries are pretty much at rest.

Just a curiosity question - when you added the two extra ones, how did you handle the venting?

[UTTransplant]

All six batteries fit in the tray, but they are turned 90 degrees from “standard”. I am actually really surprised you only have 2 batteries. Tiffin has been putting 4 batteries in the RR units for quite a while. Did they add the RR after delivery? Basically two batteries could power the coach, but the extra power the RR needs drove them to a total of 4 standard. We dry camp about half the time, so we just wanted the extra 2 so we aren’t ever pushed. I like it warm too, so we run our heater regularly. And the Tiffin video distribution we have is a power hog. Yours might be different, but it is surprising to us how much the battery monitor showed it using.

You might check with Tiffin to see if they have wiring harness for more batteries. They had one available for our rig.

[Gary RV_Wizard]

I think 2x 6v flooded cells is probably inadequate if you expect to boondock overnight with a large residential fridge, at least if you attempt it without any genset runtime in the evening.  But that's my guesswork vs yours. If you want to make an informed decision, you need to measure the power consumption of the fridge, plus your other power uses, and compare that to the amp-hour capacity of your battery bank.  Frankly, I suspect you may want replacement 6v PLUS and a second pair.  However, if you run the genset for a couple hours in the evening and top off the two batteries, you will get through to the next morning. Probably a deeper discharge than 60%, tho.

If you could identify the LG fridge model or its actual power consumption, we could help you figure it out on paper, but even that has to allow a substantial variance for ambient temperatures, how often the fridge door gets opened, etc.

[arcticfox2005]

Kevin, my Tiffin is an Open Road, Ford chassis, gas not diesel. Your rig is diesel and that would be the difference probably. No, the fridge was an option installed when built. I have the invoice when it was originally sold to La Mesa RV by Tiffin. The main problem with adding 2 batteries is space - what we have now is under one of the entry steps but there is a storage compartment immediately behind the entry door. If I use AGM' s as Gary suggested then that setup would probably work.

Gary, thanks for the input. I will go over to the storage lot and copy info on the LG fridge relative to model # and power consumption. Also, the factory inverter is a modified sine wave rather than pure sine wave so the efficiency of it will also come into play.

Bill

[Gary RV_Wizard]

If the fridge still has its Energy Star label, it will show a standardized energy consumption figure in kWH/year. You have to make some assumptions to prorate that for your actual RV usage (usually only part-time use), but it gives you a place to start.  It's fairly common for even a largish residential fridge to get by on 1.5-2.0 kWH per day of use..

[arcticfox2005]

Kevin and Gary, I owe you a big apology. As I had posted earlier, we flew to Florida, picked up the Tiffin and when we got home, immediately put it in covered storage. I went out there just now to check out the fridge and for the first time removed the bolts holding the top entry step in place to look at the batteries. You guessed it, there are 4. I assumed it had only 2 because I thought there was no way to fit 4 under that step. But they did it. On the way there I stopped at Auto Zone and got a spec sheet for their GC2's (Duralast)  and after I do some more investigating, will probably get them. The l,w, and h check out, but getting the old ones out and the new ones in is going to be a major major pain - there is just no wiggle room.

Gary, it is probably a moot point now, but the LG model is LCTS20220S /01 and the current draw is 2.7 amps.

Bill

[arcticfox2005]

For future reference, GC2 prices:

Sam's Club $90
Costco $99
Auto Zone $112

[Gary RV_Wizard]

GC2 6v batteries commonly come in two different AH (amp-hour) ratings, 210 and 225, so make sure you compare apples to apples.  Flooded cell GC2 are a commodity, so buy based on price and AH rating.


Just a reminder: GC2 are 6v batteries so each pair is wired in series to make 12v; the two pairs are wired in parallel.

You may find more interesting facts in this 2015 Open Road brochure:
https://library.rvusa.com/brochure/2015_Tiffin_Allegro.pdf

[solarman]

Gary, it is probably a moot point now, but the LG model is LCTS20220S /01 and the current draw is 2.7 amps.

Bill

gotta get you guys thinking in Watts not Amps.. LOL

ok here is a rough estimate.

that fridge has an energy star rating of 471 kW/h per year, if we rough estimate it to 471 / 365 days then that's 1.29 kW/h per day
or 1290 W/hrs. a typical GC2 has a 20 hr rate of 220 A/h and an ideal storage of 6 V * 220 A = 1.32 Kw
a pair of GC2 in series for 12 V has a theoretical capacity of  = 2640 Watts @ 12 V
and two strings will give approx 2640 * 2 = 5280 W

in theory we could run the fridge for ( 5280 / 1290 ) = 4 days.. but we can't due to the battery chemistry, Mr Peukert and inverter efficiency..

your figure of 2.7 A at 120 V = 324 W so 324 * 24 = 7776 W/h so the energy star rating suggests an approx ( 1290 / 7776 ) = 17 % duty cycle..
i'll wager it's more like 20% in hotter weather.. however..

your fridge will consume 1290 W/h and at 12 V with 90% inverter efficiency that's now approx ( 1290 * 1.1 )  = 1419 W/h
in theory we now get ( 5280 / 1419  ) = 3.7 days or 1.85 to 50% DOD

in practice, Mr Peukert will steal our capacity from us and that run time will now be closer to 30 hours for 50% capacity loss..

now if only we could have a lead acid battery without the Peukert effect.. hmm.. oh wait ! it's called Lithium.. LOL