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Old 04-17-2014, 01:05 PM   #1
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Brand: Thor Motor Coach
Model: Challenger
State: Connecticut
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THOR #773
Any experience with how long you can go on battery power?

We just bought a new Thor Challenger. It has an electric only residential refrigerator. The coach has two 6 volt house batteries. Has anyone dry camped and run off batteries to a point where the batteries dropped too low. Am curious how much power this fridge draws. We have the autogen start system but, am concerned that the generator may start during quiet hours if the batteries get too low.
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Old 04-17-2014, 02:29 PM   #2
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If your owners manual doesn't tell you how many watts the fridge draws, why not call Thor and ask them, or your dealer? Another option would to Google it.
Then it should be a simple matter to figure out how long it would take to draw your batteries down.
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Old 04-18-2014, 12:20 PM   #3
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Most rv frig's have a propane option.
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Old 04-18-2014, 12:25 PM   #4
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Unfortunately, they seem to be putting residential refrigerators in the new coaches now. Some are going all electric with residential fridge, electric stove etc. Ours has a residential Whirlpool that runs only on 110. We would have preferred the conventional RV fridge we were familiar with but, it wasn't an option.
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Old 04-18-2014, 01:34 PM   #5
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OK, if the frige is 110 then its' not running off the DC.
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Old 04-18-2014, 01:46 PM   #6
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OK, if the frige is 110 then its' not running off the DC.

Well in a sense it is-----They have an inverter to run the fridge, and that draws from the battery bank and changes it to AC.
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Old 04-21-2014, 11:03 AM   #7
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Unfortunately, the specs of the appliances will only provide the maximum power consumed, not the average. For instance, a residential refrigerator with a compressor will consume much more power when the compressor kicks on.

To get an accurate idea of your energy requirements, you need to determine the long term load. Consider a load tester, such as a "Kill A Watt" brand tester. You can buy one of those for about $20.

A tester for that price will only handle up to 20A @ 120VAC, but it has a standard outlet, so you can plug it into your RV (with adapter) or individual appliance - and test one appliance at a time (to stay under the limits of the meter). The Kill A Watt will tell your average power consumption over time - which is more accurate than reading the specs.

You will then need to figure out the AH draw (Amp-Hour, or Amps x Hours) at 12VDC. This gets complicated as you have to determine power factor and losses at the inverter. But a good rule of thumb is to subtract say 10~20% for these losses.

For example, say your device you are testing takes maybe 100Watts at 120VAC.

Then simply use OHMs Law (ignoring things like the Power Factor of AC for now), and by dividing the 100Watt figure by 120V, you get an answer of about 1Amp. Then multiply that by 10 - to get to 12V of your batteries.

The answer then is the device drawing 100W at 120V is equivalent to around 10Amps at 12V.

Now, add 10 or 20% to that figure as a fudge factor to account for the AC power factor and any inefficiencies of the inverter.

So you will end up with say 12Amps. This is the approximate current demand of the item at 12V.

So, if you have a battery rated at 80AH, that means it will supply 80A for 1Hour or 1A for 80Hours (but we need to do something with Peukert's Law).

Therefore, if you put a 12A load on the batteries, you should get almost 7 hours of run time.

But... Peukert's Law states that you cannot get full capacity out of the battery at high discharge rates, so you may need to subtract another 10% or so from the run time. Peukert's Law is specific battery brand and model dependent, and Trojan batteries are generally the most favorable in that regard.

OK, so now we are at 6hours run time for an 80AH battery supplying 100W @ 120VAC through an inverter.

But we are not done yet.

You will severely shorten the life of your deep-cycle house batteries if you drain them completely. The rule of thumb for longest life is to never discharge them more than 50% capacity.

Uh oh... that now means you have to reduce the time by 50%.

Final answer - 3 hours run time.

Of course this is hypothetical, but you can see the complexity of the issue.

Also, consider some power reduction items, such as replacing all of your 12V incandescent lighting with LEDs. LEDs consume about 1/10th of the energy that incandescent bulbs do.

And a couple of solar panels will help to recharge your batteries. You won't be able to keep the charge up on your batteries if you run the A/C, but RV refrigerators (the kind without a compressor) are pretty efficient, and three or four 150Watt solar panels just might supply enough power to keep the batteries above the 50% discharge point.

Needless to say, it gets complicated.
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Old 04-21-2014, 11:33 AM   #8
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Complicated is right. We voiced concern about being able to go through the night without the generator turning on. The dealers all said it isn't a problem but, I read an article where the testers said that they had to turn the fridge off at night because the batteries would drain down to a point where the "auto generator start system" would turn on the generator. Because of quiet time at the park where they were staying, you couldn't have generators on at night.

I have a feeling I am not going to like this set up.
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Old 04-22-2014, 11:24 AM   #9
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Probably the easiest short term fix is to install larger capacity house batteries.
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Old 04-22-2014, 06:54 PM   #10
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Will likely do that. Will be bringing the coach to an authorized dealer anyway. Went out to retract the slides and the front living room slide is making a wicked rubbing/grinding sound and the long slide on the same passenger side won't retract. Getting very disappointed with this coach. Doesn't look like they have any Q.C. at Thor. When we went to pick it up there were water leaks under each sink. The hot water heater didn't work. Various cabinet doors didn't shut. The latch on the sliding door to the bedroom doesn't hold when you are travelling. The control unit for the TV's and audio wasn't connected. Two of the chairs for the dinette were missing. Because there was no hot water we couldn't use the shower. On our trip home we stopped on the first night and took a long awaited shower. When we went to the front of the coach we had a flood. The faucet control on the shower was leaking. There was no seal around the panel screwed into the wall that the faucet was attached to. The shower floor is so soft that if you step near the drain in the middle, the floor sinks to where it pushes the trap into the floor underneath. That ended up putting pressure on the connections and causing a joint to break. Now I can't get the slide in. It is a cable system. The Thor advertisement and promotional video says that they upgraded to only electric slides on the 2014.5 models. That is the model we were told we were purchasing. I called Thor. Their service tech/advisor was very nice and treated me well. He had me try a couple of things to see if we could get the slide to work. They didn't work and now he wants me to disassemble the trim around the slide to get at some kind of control to see if it could be adjusted to make it work. I really don't want to start tearing the coach apart. If I do and it still doesn't fix anything, I just have a bigger mess. Going to see if they can arrange to have a mobile service come out to get the slide in. I didn't spend $125k on a coach to have to rebuild it to make it serviceable.
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Old 04-23-2014, 11:22 PM   #11
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Wow, that sounds terrible.

I have found dozens of minor defects in my rig, but nothing major (at least not yet). These were all the result of poor workmanship - vinyl flooring cut too short, screw heads stripped, mis-aligned stuff, that kind of thing. Annoying, but fixable.

Hope you can get some remedy. Since it is a new coach, have you considered legal action to get your money back. This sounds like an example of pretty shoddy work.

While I am not a lawyer, I think the general principle is that there is an inherent assumption of useability when you buy anything - especially something that is new. You bought the coach on the assumption you could actually use it, and it seems to already have failed that.

If you are having so many problems up front, what is going to happen 5yrs from now?
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Old 04-23-2014, 11:59 PM   #12
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THOR #773
Hopefully, everything that is going to go wrong is happening now and once fixed, will be good to go. Thor customer service has been excellent which has been a pleasant surprise and relief. They are working on getting a mobile service person out to get the slide retracted. Once that is done they said to call an authorized dealer to get necessary repairs done.
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Old 07-28-2014, 01:25 AM   #13
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Originally Posted by BruceFitz View Post
Will likely do that. Will be bringing the coach to an authorized dealer anyway. Went out to retract the slides and the front living room slide is making a wicked rubbing/grinding sound and the long slide on the same passenger side won't retract. Getting very disappointed with this coach. Doesn't look like they have any Q.C. at Thor. When we went to pick it up there were water leaks under each sink. The hot water heater didn't work. Various cabinet doors didn't shut. The latch on the sliding door to the bedroom doesn't hold when you are travelling. The control unit for the TV's and audio wasn't connected. Two of the chairs for the dinette were missing. Because there was no hot water we couldn't use the shower. On our trip home we stopped on the first night and took a long awaited shower. When we went to the front of the coach we had a flood. The faucet control on the shower was leaking. There was no seal around the panel screwed into the wall that the faucet was attached to. The shower floor is so soft that if you step near the drain in the middle, the floor sinks to where it pushes the trap into the floor underneath. That ended up putting pressure on the connections and causing a joint to break. Now I can't get the slide in. It is a cable system. The Thor advertisement and promotional video says that they upgraded to only electric slides on the 2014.5 models. That is the model we were told we were purchasing. I called Thor. Their service tech/advisor was very nice and treated me well. He had me try a couple of things to see if we could get the slide to work. They didn't work and now he wants me to disassemble the trim around the slide to get at some kind of control to see if it could be adjusted to make it work. I really don't want to start tearing the coach apart. If I do and it still doesn't fix anything, I just have a bigger mess. Going to see if they can arrange to have a mobile service come out to get the slide in. I didn't spend $125k on a coach to have to rebuild it to make it serviceable.

welcome to the club! I only spent 80k but must spend $$$$ more to make the coach livable and drivable. We basically bought a shell..
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Old 07-28-2014, 01:39 PM   #14
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My 35SK has the same refrigerator and batteries that yours does. On full batteries, the refrigerator will run 6-7 hours before the low battery alarm on the inverter goes off.
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Old 08-04-2014, 04:59 PM   #15
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I have the same coach but with the gas fridge. The batteries are awful. They lasted only 1 day while dry camping and I changed the lights over to LED. With a residential fridge forget about it..! I'm headed to the factory service next month to see if they can replace them with 2 12V deep cycle. I read in MH magazine that the 6v take forever to charge and its true. I run an external generator 12-14 hrs every other day to keep them charged.
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