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

[Jimbo K.]

Originally Posted by Rolland

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

In case s/he doesn't reply right away, this appears to be the latch:

https://www.recpro.com/rv-refrigerator-door-latch/

My fridge came with it already installed, hence my stating "appears to be" rather than a definitive "is." But it looks identical to what I have.

It works well, simple in design but effective. It also can be swung into position when the door is open, keeping the door slightly ajar for air circulation when the fridge is off and empty.

[Hclarkx]

Originally Posted by Jimbo K.

. . . . . . . . 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. . . . . . .

Jim, if you find satisfactory small small inverter, please let us know. I looked for one and didn't find one that was sine (my Resmed 10 runs about 10 seconds before shutting down with non-sine) and had low overhead. Most had the same or higher idle current as my 900W Xantrex. It takes about 0.6 amps when idle. Efficiency numbers are few and far between but I assume a small unit would be equally or less efficient than a name brand larger unit even at low load. Though this is a best guess.

I am about to replace my 900W Xantrex ProWatt SW1000 with the 1800W version. I've bench tested the new one and found it takes only 0.4 amps at 13V input when idle. I'm going to re-test to be sure, but if it really only takes 0.4 amps at idle it will be hard to beat. I'll also try to compare input and output (efficiency) with a load equivalent to the Resmed 10.

[Larry-NC]

Originally Posted by Hclarkx

Jim, if you find satisfactory small small inverter, please let us know. I looked for one and didn't find one that was sine (my Resmed 10 runs about 10 seconds before shutting down with non-sine) and had low overhead. Most had the same or higher idle current as my 900W Xantrex. It takes about 0.6 amps when idle. Efficiency numbers are few and far between but I assume a small unit would be equally or less efficient than a name brand larger unit even at low load. Though this is a best guess.

I am about to replace my 900W Xantrex ProWatt SW1000 with the 1800W version. I've bench tested the new one and found it takes only 0.4 amps at 13V input when idle. I'm going to re-test to be sure, but if it really only takes 0.4 amps at idle it will be hard to beat. I'll also try to compare input and output (efficiency) with a load equivalent to the Resmed 10.

Not sure why idle current is a factor if it's only going to be used for the CPAP. Just put a switch on the 12v input and only turn it on when using the CPAP.

[Mikec557]

Originally Posted by Larry-NC

Not sure why idle current is a factor if it's only going to be used for the CPAP. Just put a switch on the 12v input and only turn it on when using the CPAP.

I have a Xantrex Freedom 1000 watt pure sine wave (with bypass). It has a simple on/off button. No need to add a switch...

[Hclarkx]

Originally Posted by Larry-NC

Not sure why idle current is a factor if it's only going to be used for the CPAP. Just put a switch on the 12v input and only turn it on when using the CPAP.

It's a factor because it's "overhead" that adds to any load current. I.e., if you have an inverter that draws around an amp when idle, then add an amp of load, you are drawing two amps overnight instead of one amp. Or, for an 8 hour night, 16 Ah instead of 8 Ah. Cut the idle current in half and you are using 12 Ah instead of 16 Ah.

If the CPAP machine draws about 2.3 amps like mine (hose heater off), then it's 3.3 amps instead of 2.3 amps with a 1 amp idle current. So, idle current looms large.

My son's fairly large Renogy inverter draws 1.5 amps at idle (and on top of any other load current).

Efficiency is a different issue. Higher efficiency is better, but a few percent higher efficiency is splitting hairs compared to the idle current.

[Mikec557]

I guess I'm confused about the concern for idle current. Maybe we just use our inverters differently. I leave mine off unless I want or need to invert. If I don't need 120vac for the night or a project, then I turn it off. My concern is for efficiency when it's on and being used. I think that's the combined overhead it costs me in Ah to invert.

What sort of circumstances would you leave it on, in idle, and not being using it? Is it a unique circumstance or simply a way of camping?

[Hclarkx]

Originally Posted by Mikec557

I guess I'm confused about the concern for idle current. Maybe we just use our inverters differently. I leave mine off unless I want or need to invert. If I don't need 120vac for the night or a project, then I turn it off. My concern is for efficiency when it's on and being used. I think that's the combined overhead it costs me in Ah to invert.

What sort of circumstances would you leave it on, in idle, and not being using it? Is it a unique circumstance or simply a way of camping?

I'm not sure where you got the idea it was to be on and not in use. The subject at hand and that I was addressing when I replied to Jimbo (he mentioned a smaller inverter for a CPAP) was getting the most nights of CPAP use from a modest battery by powering it with a small inverter.

The CPAP requires power through the night. Not much, just an amp or two but the inverter (large or small) idle current adds to that and is not insignificant in most inverters.

A DC-DC converter is surely the most efficient solution for non-12V CPAP machines like my Resmed 10. But, the approved converter is about $100. One can get cheapies on ebay and Amazon, but I don't know that I want to trust one of those with my $1000 CPAP machine. Hence the idea of an inverter powering the CPAP machine is plausible, especially if one is already in place and its idle current is tolerable.

As I noted previously my Xantrex ProWatt SW1000 idles at about 600 ma. That's tolerable for me since I have a lot of solar, but maybe not for folks that want to get several nights out of a modest battery presumably without solar. As I also mentioned, my Xantrex ProWatt SW2000 (waiting to be installed) seems to require only 400 ma. That's good news since the smaller 100W-200W sine inverters that I found idle at more than that.

As for actual idle use, having the inverter on continuously is a significant convenience. With ample solar our SW1000 rarely gets turned off. The SW2000 will surely only be turned off when we leave the RV for the day.

[Mikec557]

<< The subject at hand... was getting the most nights of CPAP use from a modest battery by powering it with a small inverter. >>

I guess that sums up my point. Getting the most nights of CPAP use from a modest battery bank.

To me that means giving up the luxury of leaving a parasite on 24hrs a day "for convenience." For the ability to turn on a 120vac device without the "inconvenience" of turning the inverter on first.

The power consumed during this "idle time" is contrary to the stated goal of getting the most nights of CPAP use from a modest battery bank.

But, to each his own.

[Jimbo K.]

Originally Posted by Hclarkx

Jim, if you find satisfactory small small inverter, please let us know. I looked for one and didn't find one that was sine (my Resmed 10 runs about 10 seconds before shutting down with non-sine) and had low overhead. Most had the same or higher idle current as my 900W Xantrex. It takes about 0.6 amps when idle. Efficiency numbers are few and far between but I assume a small unit would be equally or less efficient than a name brand larger unit even at low load. Though this is a best guess.

I am about to replace my 900W Xantrex ProWatt SW1000 with the 1800W version. I've bench tested the new one and found it takes only 0.4 amps at 13V input when idle. I'm going to re-test to be sure, but if it really only takes 0.4 amps at idle it will be hard to beat. I'll also try to compare input and output (efficiency) with a load equivalent to the Resmed 10.

Thanks, good information.

At this point, I'm hopeful that whatever CPAP my friend ends up with will have a 12V plug, and that I won't have to hunt for a CPAP-friendly inverter. Nor lug the old battery around just for the one task.

[Rolland]

Originally Posted by Jimbo K.

Thanks, good information.

At this point, I'm hopeful that whatever CPAP my friend ends up with will have a 12V plug, and that I won't have to hunt for a CPAP-friendly inverter. Nor lug the old battery around just for the one task.

Just in case a 12v one doesn’t happen (btw, the last three I’ve had are 12v with the adapter to plug into 110v), there are lithium battery packs available which usually last 3-4 days before needed recharged. They are targeted for those who backpack, etc., so not huge in size. Your friend should check with the DME supplier or check online when the new CPAP brand is know.

Good luck

[Larry-NC]

Originally Posted by Jimbo K.

Results:

Time Voltage SOC Temp(F)
9AM 12.76 100% 36
10AM 12.70 96% 34
11AM 12.67 93% 34
12PM 12.64 90% 35
1PM 12.61 87% 36
2PM 12.54 83% 38
3PM 12.52 80% 39
4PM 12.43 76% 40
5PM 12.39 71% 40
6PM 12.31 66% 41
7PM 12.21 60% 41
8PM 12.11 54% 40
8:30PM 12.06 50% 40

[Sorry for the table formatting. I spent two hours monkeying with the *&$!@# table, first trying to embed an image from my Excel file using the Insert Image button and three different URLs (DropBox, Google Drive, and this forum's gallery). Then trying to paste the table itself. Then typing the values in manually here, with spaces added to create aligned columns. For the latter, the app thought it was smarter than I am and kept deleting extra spaces. ]

Not the app, Jimbo. The HTML standard states that all instances of "white space" (=spaces, tabs, newline characters) shall be condensed to 1 character. You can get around that restriction by using the HTML CODE command or its variants. In the web browser version, you can use the CODE option ("#" icon), HTML Option ("<>" icon), or PHP Option ("[php]" icon). Use Courier font because it's monospaced. How does this look?

Time    Voltage   SOC Temp(°F)
 9:00AM   12.76  100%       36
10:00AM   12.70   96%       34
11:00AM   12.67   93%       34
12:00PM   12.64   90%       35
 1:00PM   12.61   87%       36 
 2:00PM   12.54   83%       38 
 3:00PM   12.52   80%       39 
 4:00PM   12.43   76%       40
 5:00PM   12.39   71%       40
 6:00PM   12.31   66%       41
 7:00PM   12.21   60%       41
 8:00PM   12.11   54%       40
 8:30PM   12.06   50%       40

Just to show you that it can be done.

Originally Posted by Jimbo K.

Sorry for the length of this post, but nerdiness and verbosity aren’t always a good mix.

Doesn't bother me a bit.