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Old 03-15-2022, 07:29 AM   #1
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Brand: Still Looking
State: Arizona
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THOR #26238
High power draw in Cahaba with nothing running except fridge

Hi - I'm new to the RV world and I was looking at a Tiffin Cahaba over the weekend but am confused by the idle power draw shown by the Volta system.

I was trying to estimate a best-case time until recharge is necessary if I only ran the fridge, so I had everything turned off except the fridge, including the inverter. The van was outside under a clear blue sky in the middle of the day so the solar panels should be providing something over 200 W (I think that's conservative - they're rated for 300 W). A fridge the size of the one in the Cahaba shouldn't draw more than 100 W, probably more like 80 W.

However, the Volta system showed a net power draw of 250 - 350 W.

Given that the solar panels were probably producing at least 200 W that means total power draw in the van was something like 500 W.

Assuming the fridge is pulling 100W, what the heck is pulling the other 400 W? And can I turn it off?

One other possibility is that the solar panels aren't working, but still, what the heck is pulling the other 100+ W?

Another possibility is that the fridge is *extremely* inefficient and is, in fact, pulling 400 W. But I seriously doubt that.

Anyone have any ideas of what's going on?

Thanks,

rgames

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Old 03-15-2022, 12:54 PM   #2
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My understanding is that the solar panels charge the batteries and does not run any component directly. Therefore the draw you are seeing is directly from the items within the RV.
The refrigerator and lights would be drawing ... any electronics or monitoring systems would be drawing (aka Volta) ... not sure if the Tiffin has an onboard wifi extender or hotspot but those usually draw anytime the RV is on. 250-300 watts could be accurate.
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Old 03-15-2022, 01:56 PM   #3
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Hi - thanks for the info.

Yes the fridge is drawing power but as I said there was nothing else on that I (or the sales rep) could find - no lights, no inverter, nothing. There is no wifi extender or hotspot as far as I know.

Therein lies the mystery: what is drawing all that power?

And yes, the solar system is not directly powering anything but the Volta system would still monitor the solar power generation. Since there is no separate way to view power generated by the panels it must be included in the overall power draw. Otherwise the "Time Remaining" estimate would be mostly meaningless. I have experience with several solar systems (residential and portable) and they always have some way to show the status of the panels and figure out net power consumption.

Cheers,

rgames
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Old 03-15-2022, 02:05 PM   #4
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It could be when you checked the power draw that the fridge was on a defrost cycle which uses lots of extra wattage for a shot while.

But the easiest way to track down a phantom power draw is with a clamp on DC ammeter. You can check solar, etc directly with one. A decent one is about $75 on Amazon. Klein tools is a decent brand but there are others. Make sure that the description explicitly says DC clamp on current measurement to avoid useless AC only ones..

David
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Old 03-15-2022, 02:09 PM   #5
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Originally Posted by rgames View Post

.....cut.....

Anyone have any ideas of what's going on?

Thanks,

rgames

I do not, but think that 250~300 Watts in the background, if actually correct, is way too high. That represents 6~7 kWh of electricity in a 24-hour period, which would come close to draining the Volta batteries.

If RVs required that much power when pretty much everything was turned off, they would not be able to operate with standard batteries, or even with a couple of 100 Ah X 12.8 Volt lithium batteries, for very long.

You are correct in wanting to know where that much energy is going.



P.S. ó Any chance ambient temperature was cold enough that battery required heat? If so, maybe monitor accounts for that.
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Old 03-15-2022, 02:48 PM   #6
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I do not, but think that 250~300 Watts in the background, if actually correct, is way too high. That represents 6~7 kWh of electricity in a 24-hour period, which would come close to draining the Volta batteries.

If RVs required that much power when pretty much everything was turned off, they would not be able to operate with standard batteries, or even with a couple of 100 Ah X 12.8 Volt lithium batteries, for very long.
Yeah it doesn't make any sense...!

FYI the sales rep called the Volta rep with me on the phone and the Volta guy said that's the way it goes. I pointed out that means I'd have to drive the van for 1.5 hr every day to make use of the battery (it does not charge at engine idle). And he said yeah, that's what you have to do.

That makes no sense to me. A 4x4 van designed for off-grid use shouldn't require you to drive it 1.5 hr a day just to keep the fridge cold. If I'm running the AC and inverter and a bunch of other stuff, sure. But not just an 80W fridge. With the 12,100 Wh battery supposedly in there I should be able to run an 80 W fridge for ~150 hr. A bit less in reality, of course, because there's some power draw in the Volta system itself, but not 300W.

There's no way Volta designed a power management system that draws 300W at idle. Unless they're wildly incompetent...!

Something is not right - either there's a bunch of stuff turned on that I can't find or the fridge is defective or the Volta monitoring system is defective.

Thanks,

rgames

EDIT: regarding temps, good thought but that's not it. It was in Tucson and temps were ~75 F. No way the heaters were on.
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Old 03-15-2022, 02:56 PM   #7
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Agree it makes no sense at all.

I have seen video report from reputable source of other motorhomes with Volta system where this issue did not come up. It was a Winnebago and without air conditioning running, solar kept battery fully charged.


By the way, doesn’t engine have fast idle option so that you don’t have to actually drive the van?
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Old 03-15-2022, 04:19 PM   #8
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By the way, doesnít engine have fast idle option so that you donít have to actually drive the van?
Not as far as I or the sales rep can tell. You have to use the old "brick on the accelerator" method.

Cheers,

rgames
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Old 03-15-2022, 05:09 PM   #9
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Not as far as I or the sales rep can tell. You have to use the old "brick on the accelerator" method.

Cheers,

rgames
Try using the cruise control acc and dec buttons to control idle speed. That’s how it’s done on my rig. Acc to increase idle speed and dec to decrease idle speed. Cruise control on but not set.
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Old 03-15-2022, 05:25 PM   #10
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Try using the cruise control acc and dec buttons to control idle speed. Thatís how itís done on my rig. Acc to increase idle speed and dec to decrease idle speed. Cruise control on but not set.
Sounds good - I'll give that a shot.

Thanks for the tip!
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Old 03-19-2022, 09:21 PM   #11
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As they say just my 2 cents, start unplugging things and monitor the draw as you do. Start with the refrigerator then sensors etc.
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Old 03-21-2022, 10:10 PM   #12
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Monitoring this thread. My rig is much older and doesn't have a Volta system, but I've had perpetual headaches off/on with my home-grown solar system. Made lots of tweaks over the past year and currently running a multi-day test but it still doesn't behave the way I think it should. Similar issue.
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