GE 12V refrigerator: experience thus far and power consumption testing

[Chuck_S]

Room temperature makes a difference with a compressor type refrigerator 'cuz it tries to dump the heat into the room (off those fins or wires on the back) and the heat transfer is dependent on the temperature differential: warmer room will be harder to move heat.

And the heat from the refrigerator increases room temperature is a small but vicious cycle. * Plus insulation is rarely great in campers.

-- Chuck

* This is why your junior buddy's idea of cooling a room by keeping the refrigerator door open or running a window AC completely inside a room doesn't work. Both a refrigerator and air conditioner just move the heat from one place to the other. Cold is the absence of heat.

[Larry-NC]

Originally Posted by Jimbo K.

The TABLE and related tags I was referring to use square brackets instead of angle brackets. (With a little Googling I found this description.) Curious: Does that matter in terms of functionality or vulnerability?

Right! This site actually uses BBCODE (or something close to it). BBCODE is not isomorphic to HTML.

For one thing, it's a safe, limited subset. For another, some commands are different for no apparent reason reason, e.g.,

<UL> and <OL> (Unordered List and Ordered List respectively introduce bulleted lists and numbered lists in HTML.[LIST] and[LIST=1] introduce lists in BBCODE

Some things in BBCODE seem to have been optimized for ease of entry, not regularity of syntax. For example:

HTML list items are each surrounded by <li> and </li>
BBCODE list items start with[*] and are terminated by a newline.

[Tom48]

Another factor to keep in mind, as voltage goes down amperage will go up if the load remains consistent. I'm a little rusty on ohm's law but amps times volts equals watts and if watts is consistent then when one number goes down the other number has to go up higher voltage lower amperage lower voltage higher amperage

[Chuck_S]

It's conservation of energy, not Ohms Law but you got the formula right.

Watts (Energy) = Volts x Amps. Watts is constant so if Volts decreases the Amps must increase -- that's how this rolls. Straight 4th Grade math with no exotic formula. Excessive Amps is what causes heat in wiring and is noticeable in "burned" plugs and outlets at power poles and outlets.

This is why I have an AutoFormer for my camper as campground voltage is iffy in the summer with everyone running their air conditioners. This device boosts low line voltage from the power pole to avoid excessive amperage. Earlier this month my inside power monitor beeped indicating low voltage. The AutoFormer ran the rest of the week and was boosting voltage every time I checked on it. It's just a boring device that needs no monitoring and just does its job. Camper in a neighboring site had a fancy version with a digital display.

-- Chuck

[Hclarkx]

Originally Posted by Jimbo K.

It's interesting that on two occasions voltage actually increased a tiny amount while the SOC dropped. Maybe someone more familiar with lithium battery discharge behavior can explain. Or maybe it's a reporting error with the SmartShunt.

Most likely you were seeing a bit of chemistry going on. If the battery is carrying load (the fridge) the voltage will drift down slightly (in addition to the voltage drop in the internal resistance). Then, maybe 5-10 minutes after the fridge cycles off, the chemical activity will slow and voltage will rise slightly. Likely no problem with the BMV.

[Hclarkx]

Originally Posted by Jimbo K.

. . . . .
I was struck by the 18% drop in the refrigerator's power consumption (51 vs. 41.8 Ah at the 11.5 hour mark) with just the 5-10 degree difference in outdoor temps. And the difference was only for the first few hours before the trailer's interior temperature in test #2 (without the ramp/door open) climbed into the mid-90s. Makes me wonder how much more power reduction I'll see in realistic AC-free boondocking conditions. I'll find out about that, at least during an overnight segment, next week.

Indeed, the fridge energy use will vary widely with ambient temperature. From the specs I've found, these units are designed for about 50% duty cycle at 70F and about 100% at 100F. So a 30F swing in temperature doubles the energy (or Amphour) use. It's fairly linear re the thermal energy flow through the walls, but it's not so linear when you figure the compressor/condenser isn't as efficient at higher temperatures. So a temperature change form 70 to 80F won't increase the energy use as much as a 90-100F change.

It's the same at lower temperatures; at 38F the compressor/condenser won't run at all if only the fridge temperature is controlled (and the freezer might warm up if it does not have it's own temperature control).

[Hclarkx]

Originally Posted by Jimbo K.

. . . . .The three-hour intervals through the day showed a steady but slower drop in voltage and SOC, and fewer total amp-hours, than with the lead-acid battery. I'm sure that's due to the lower ambient temperature and, therefore, lower power demands. . . . . .

The fridge will use less Ah when running on lead-acid than it will on LiFePO4. Effectively.

The huge difference in losses between LA and LiFePO4 often goes unrecognized.

The BMV-712 if set properly does a rough estimation of lead acid battery energy that goes into heat during discharge. So if you are taking out 5 amps for an hour, 5 Ah, the BMV will read something higher, typically 5.5 Ah. If the current draw is higher, say for a microwave, the BMV might add 20%. With LiFePO4 the internal losses are infinitesimal and so are neglected. The BMV712 will also account for losses during charging .. i.e., 50 Ah into the battery will register as only 45 Ah or thereabouts (depends on charge rate).

If one has, say, a 232 Ah GC battery, it's often assumed that makes 116 Ah available for discharge to a 50% level. In reality drawing not much over 100 Ah (measured at the battery terminals) will take the battery down to 50%.

[Jimbo K.]

Originally Posted by Hclarkx

Most likely you were seeing a bit of chemistry going on. If the battery is carrying load (the fridge) the voltage will drift down slightly (in addition to the voltage drop in the internal resistance). Then, maybe 5-10 minutes after the fridge cycles off, the chemical activity will slow and voltage will rise slightly. Likely no problem with the BMV.

Ahh, makes sense. Thanks for the explanation and the reassurance that the SmartShunt is likely behaving.

[Jimbo K.]

Originally Posted by Hclarkx

Indeed, the fridge energy use will vary widely with ambient temperature. From the specs I've found, these units are designed for about 50% duty cycle at 70F and about 100% at 100F. So a 30F swing in temperature doubles the energy (or Amphour) use. It's fairly linear re the thermal energy flow through the walls, but it's not so linear when you figure the compressor/condenser isn't as efficient at higher temperatures. So a temperature change form 70 to 80F won't increase the energy use as much as a 90-100F change.

It's the same at lower temperatures; at 38F the compressor/condenser won't run at all if only the fridge temperature is controlled (and the freezer might warm up if it does not have it's own temperature control).

Nothing in any of the GE documentation I found mentions duty cycle numbers. Your mention of it sent me on a Web hunt and I found this thread (relevant to this one) on another forum that reports the numbers (and the compressor brand):

https://www.irv2.com/forums/f54/12v-...ck-533517.html

In short: 32% at 70F and 57% at 90F. (I wish I had the temperament and talent to do the 12V/24V hack he describes!)

I still plan to repeat my testing when it cools off a bit more and environmental temperatures approximate internal camper temperatures during camping, maybe in a couple of weeks. We're still seeing daytime temps near 80 or above around here.

[Jimbo K.]

Originally Posted by Jimbo K.

The control knob has four settings: Off, Cool, Cold, and Coldest. My tests were done with it set on Coldest.

I might have mislead with this statement, implying that the four settings are discrete. The control actually functions like a rheostat and can be set anywhere between Off and Coldest. The four "settings" are simply marks on the dial.

[Jimbo K.]

Originally Posted by Hclarkx

The fridge will use less Ah when running on lead-acid than it will on LiFePO4. Effectively.
....

This simple mind is trying to understand all this. Wouldn't it be vice-versa? In my case, it used less on lithium. I acknowledge, again, the effect of the lower ambient temperature. But then, as others have pointed out, modestly higher voltage with the lithium results in modestly lower current for a given power level. (I do know the watts = amps x volts equation but somehow it was MIA from my brain when I was reporting this part of my test.)

Originally Posted by Hclarkx

The huge difference in losses between LA and LiFePO4 often goes unrecognized.

The BMV-712 if set properly does a rough estimation of lead acid battery energy that goes into heat during discharge. So if you are taking out 5 amps for an hour, 5 Ah, the BMV will read something higher, typically 5.5 Ah. If the current draw is higher, say for a microwave, the BMV might add 20%. With LiFePO4 the internal losses are infinitesimal and so are neglected. The BMV712 will also account for losses during charging .. i.e., 50 Ah into the battery will register as only 45 Ah or thereabouts (depends on charge rate).
....

I have a SmartShunt, not the BMV-712. But since they're both Victron products and presumably use the same app for configuration, I assume the principles and settings are the same for a given battery.

I have set mine in accordance with Victron's owner's manual's recommendations for lithium batteries. Specific to this discussion (I think), efficiency is set to 99% and Peukert exponent to 1.05.

[Hclarkx]

Originally Posted by Jimbo K.

I might have mislead with this statement, implying that the four settings are discrete. The control actually functions like a rheostat and can be set anywhere between Off and Coldest. The four "settings" are simply marks on the dial.

Got it. Mine is 0 to 7. I operate between 3.5 and 4, about a 15 degree twist. It's very sensitive. Barely moving the dial can change a degree or two. The dial moves easily, I keep masking tape on it so it doesn't get bumped. I brought this and a list of things to Nova Kool's attention.

[Hclarkx]

Originally Posted by Jimbo K.

This simple mind is trying to understand all this. Wouldn't it be vice-versa? In my case, it used less on lithium. I acknowledge, again, the effect of the lower ambient temperature. But then, as others have pointed out, modestly higher voltage with the lithium results in modestly lower current for a given power level. (I do know the watts = amps x volts equation but somehow it was MIA from my brain when I was reporting this part of my test.)

You are correct!!!!!!!!!!!!!!! My bad. Yes, it will use more energy on LA than LiFePO4. This is irrespective of the Volts times Amps equals Watts issue which is also a factor. Indeed, 100Ah from a LiFePO4 delivered at around 13.2V will give you more Watts than 100 Ah from a LA delivered at 12.4V.

But, what I was trying to get at is that taking, say, 100 Watthours from a 1300 Watthour capacity LiFePO4 battery will leave 1200 Watthours remaining.

Taking 100 Watthours from a LA battery with 1300 Watthour capacity LA will leave about 1190 Watthours remaining.

Any current you draw from a LA "wastes" some of the batteries stored energy as losses in the form of heat in the battery. In a LiFePO4 this happens but it's a very small number that is rarely paid any heed.

It's good that you have the Smart Shunt set properly, this step is often overlooked.

[Jimbo K.]

Several updates ….

I recently repeated the refrigerator power consumption test. Temps were in the low 70s during the day and dropped to the low 60s overnight. These are very close to what I and most of my traveling companions would consider comfortable, so they approximate real world camping temperatures pretty closely.

As before, I started the test at 9AM. The end point was to be 24 hours later or 20% SOC on the battery, whichever came first. After 24 hours, the battery had dropped from 13.84V to 12.96V, or 43% SOC. 57Ah were consumed, for an average hourly amperage of 2.375.

As compared to sunny days during previous testing, this test saw mostly cloudy skies. Therefore I lost most of the benefit of the 50W solar panel. I know 50W isn’t much, but it’s still a help. Via the SmartShunt, I have seen as much as 30W from the panel on a sunny August day at this mid-Atlantic latitude. So the panel can provide a few extra hours of power for the fridge.

I adjusted the temperature dial slightly from previous testing. I have found through recent camping experience in cooler weather a certain “sweet spot” on the dial between Cold and Coldest, where refrigerator temperature stays above 32F and below 40F (except, of course, after frequent or prolonged door openings).

As before, the refrigerator and freezer were empty and stayed closed throughout the test.

I mentioned in post #34 of this thread that I planned to disconnect shore power one night while camping to test actual real world consumption. This was done. From 9:30 PM when I disconnected until 10AM the next morning when I connected to my truck and broke camp, 40.3 Ah were used, or about 3.25 hourly. Besides an occasional light before bedtime and parasitic draws, the refrigerator was the only device using power. Overnight temperature was in the upper 50s; I opened windows for ventilation.

I also disconnected one night on my most recent trip last month when the temperature dropped into the low 40s. I wanted to test the combined effect of the fridge and the furnace fan. The furnace thermostat was set to approximately 60F. Over 11.5 hours, from 8PM until 7:30AM, approximately 40 Ah were used.

Another, more significant real world test is coming up next weekend. I have been invited to camp three nights with friends on a private site without hookups. I ended up buying a generator and that’s going with me, so I can top off the battery as needed. (Testing in my driveway shows the genny charging the lithium battery from 20% to 100% SOC in about two hours.) I will have a camping companion in my trailer this time (the two trips mentioned above were solo), so the fridge will get more use. The companion also will be using CPAP and I expect the furnace to be running at night. This will make a good boondocking test, but with a safety net of sorts, in that I’ll be able to run the genny if the combined overnight power consumption exceeds what the battery can deliver.

Also in post #34 I said I would spot check battery voltage periodically during travel to get a sense of how well the tow vehicle and solar panel combine to recharge the battery. The battery seems to plateau at around 13.2V, + 0.1 or so. That's only 70% charged, per Battle Born’s spec sheet. The battery will either charge to that level or, if I start out with a higher charge, discharge to that level if given a chance (which the fridge certainly provides). I think I see a DC-DC charger in my future if I can figure out where and how best to install it.

[Jimbo K.]

Originally Posted by Jimbo K.

....
Another, more significant real world test is coming up next weekend. I have been invited to camp three nights with friends on a private site without hookups. I ended up buying a generator and that’s going with me, so I can top off the battery as needed. (Testing in my driveway shows the genny charging the lithium battery from 20% to 100% SOC in about two hours.) I will have a camping companion in my trailer this time (the two trips mentioned above were solo), so the fridge will get more use. The companion also will be using CPAP and I expect the furnace to be running at night. This will make a good boondocking test, but with a safety net of sorts, in that I’ll be able to run the genny if the combined overnight power consumption exceeds what the battery can deliver.
....

I made this trip but it wasn't the real world overnight battery test of the fridge, etc., that I had expected. My companion had a new CPAP with a 12V adapter, which we tested in the RV in advance to check current flow (1-3 amps or so, cycling with breathing) and estimate its potential added effect on overnight battery discharge. However, she realized before the trip that she wasn't able to tolerate it, so she had to revert to her old device -- without a 12V adapter. Therefore we had to run off the generator each night.

[jaudet71]

I have the same GE fridge. Been using for about year. I am on a 1 year trip.
I have an extra monitor/shunt just for the fridge that also shows accumulated over time. In a 24hr period in the 70s. It uses about 70ah.
I have 510ah lithium with 960w solar and my fridge stays cool just fine.
I have temp monitors in both chambers to make sure.
Food will freeze against the back on the top two shelves only. We put adjustable barrier against the back and only lose about 2 inches of space.
I bought a locking latch from recpro that was a direct bolt on.
I like it.

[Mikec557]

Originally Posted by Jimbo K.

I made this trip but it wasn't the real world overnight battery test of the fridge, etc., that I had expected. My companion had a new CPAP with a 12V adapter, which we tested in the RV in advance to check current flow (1-3 amps or so, cycling with breathing) and estimate its potential added effect on overnight battery discharge. However, she realized before the trip that she wasn't able to tolerate it, so she had to revert to her old device -- without a 12V adapter. Therefore we had to run off the generator each night.

For what it's worth. I've used my CPAP for almost 3 years. When camping I always plugged into an inverted outlet with enough lithium Ah I didn't care about the inefficiency of going from 12vdc up to 120vac, then into my CPAP power supply that took 120vac down to 24vdc (ResMed AirSense 10).

But I recently experimented with a EcoFlow River Pro 600 (with supposed 720Wh of battery power). During my experiments I bought a new power supply for my CPAP. It's 12vdc to 24vdc. It plugs into a cigarette lighter.

The CPAP consumed literally half the battery power using this DC power supply and NOT using the inverter to make 120vac for the stock power supply. I also left the heated humidifier set on 5.

By the way, I too saw the "large" power draw on inhale, and very little power draw on exhale.

If you're close on amp hours, you might look into the DC power supply. Mine was $35 on Amazon.

[Mikec557]

Originally Posted by jaudet71

... I have an extra monitor/shunt just for the fridge that also shows accumulated over time. In a 24hr period in the 70s. It uses about 70ah.

I have 510ah lithium with 960w solar and my fridge stays cool just fine...

I like the idea of a dedicated shunt on the fridge. That would easily isolate the info you want to know. What monitor did you install?

510/960... I'm envious! We have 200a/320w, it's been very adequate. But we don't have a 12v fridge. Yet.

[Jimbo K.]

Originally Posted by Mikec557

For what it's worth. I've used my CPAP for almost 3 years. When camping I always plugged into an inverted outlet with enough lithium Ah I didn't care about the inefficiency of going from 12vdc up to 120vac, then into my CPAP power supply that took 120vac down to 24vdc (ResMed AirSense 10).

But I recently experimented with a EcoFlow River Pro 600 (with supposed 720Wh of battery power). During my experiments I bought a new power supply for my CPAP. It's 12vdc to 24vdc. It plugs into a cigarette lighter.

The CPAP consumed literally half the battery power using this DC power supply and NOT using the inverter to make 120vac for the stock power supply. I also left the heated humidifier set on 5.

By the way, I too saw the "large" power draw on inhale, and very little power draw on exhale.

If you're close on amp hours, you might look into the DC power supply. Mine was $35 on Amazon.

I think my friend's new CPAP was the same ResMed model you have, with the 12V cigarette lighter-style adapter. It caused some rather uncomfortable GI side effects, so she decided just prior to our trip to go back to the old one until she could visit her doctor again. (We had already confirmed with other campers that it was acceptable to run the genny all night at our site.) Regardless of what model she ends up with, I've encouraged her to assure it has, or she can get, a 12V adapter.

Meanwhile, plan B is likely a small inverter. (That could come in handy for other things.) It could be one that plugs into the 12V receptacle or one that clips to a battery. I still have the lead-acid battery that the Battle Born replaced. I could clip an inverter to that as a stand-alone power supply for the CPAP for 2-3 nights. I would need to figure out how best to recharge it for longer trips.

Regardless, she won't need the humidifier so that reduces the power needs.

[Rolland]

Originally Posted by jaudet71

I have the same GE fridge. Been using for about year. I am on a 1 year trip.
I have an extra monitor/shunt just for the fridge that also shows accumulated over time. In a 24hr period in the 70s. It uses about 70ah.
I have 510ah lithium with 960w solar and my fridge stays cool just fine.
I have temp monitors in both chambers to make sure.
Food will freeze against the back on the top two shelves only. We put adjustable barrier against the back and only lose about 2 inches of space.
I bought a locking latch from recpro that was a direct bolt on.
I like it.

Would you post the info on your Recpro fridge latch or send me a PM about it?