Operating on DC while camping

[pullin]

Hi everyone... newbie here.

Forgive me if I've used the search feature wrong, but I can't find my particular question addressed. I'm looking for some rough estimates of usable time on a vehicle battery. I have a Respironics M series and will be powering it via a 200 Watt inverter on my boat. (I know I said 'camping' in the subject line, but I figured that was more relevant to most users)

My boat has a dual battery setup, with the ability to isolate either battery (ie. I can reserve one battery solely for the CPAP machine, and use the other for starting, lights, etc.) Both batteries are 600 amp/hour deep cycle marine.

I'm curious if anyone has used a similar arrangement for camping (vehicle battery + inverter to run CPAP), and how long their setup lasts between charging. Will it run all night? I frequently overnight in my boat, but it's usually for just 1 night. It would be back to shore and recharging each day. My main goal is simply enough DC power to get thru one night, and I don't really have a good idea if a vehicle battery can supply that much juice. Obviously I wouldn't be using the humidifier heater (the manual claims 1 amp w/o heater running).

Thanks to any and all for your help.

[Sir NoddinOff]

Here's a recent thread on that topic: viewtopic.php?f=1&t=81876&p=743758&hili ... ry#p743758

[tmiker]

You shouldn't even make a dent in a 600 AH battery. I measured energy consumption of PR 1 using a DC Inline Power Analyzer on a Deep Cycle AGM 100 AH battery. Average was 1.4 Amp Hours consumed per hour with Humidifier on. Details:

Humidifier was ON and set to System 1 Level 2.
Machine:
System One 750P
RemStar BiPAP Auto with Bi-Flex
Mode: Bi-Level
EPAP: 5.0 IPAP: 10.0 cmH2O

Results:
Hours Run: 9.4
Total Amp Hrs consumed: 13.308 (Humidifier ON Level 2)
Avg Amp Hrs per Hr: 1.416
Peak Amps: 5.29

I also did a quick check with humidifier set to 0 (passive) for 6 minutes and it consumed 0.054 AH, so under 0.6 AH per hour.

Regards

[tmiker]

Probably want to double those numbers using an inverter but still no problem with capacity.

[Guest]

surprised no one told you it is advisable to run on DC rather than an inverter. search for just battery backup or battery power then spend some time reading thru those. you should have no problem going 1 nite if the battery used is healthy

[archangle]

Warning: UNPLUG your M series humidifier if you're operating on an inverter. You're probably OK using just the blower and unplugging your humidifier.

Be sure to not have any water in the humidifier tank at any time the boat may be rocking. Getting water into the blower could ruin it, and the M series doesn't have the best arrangement to prevent water flowing back into the blower.

If you do decide to forgo the humidifier and leave it at home, be careful. The blower unit comes off of the humidifier, but there's a little connecting piece that's needed to couple the hose to the blower without the humidifier. Be sure to try your setup at home first. And be sure the connecting piece doesn't fall off.

Running on DC without the humidifier is simpler and will probably give you better battery life. You need the DC adapter here: https://www.cpap.com/productpage/respir ... -cord.html. If you don't already have a cigarette lighter plug, you need a cigarette lighter to alligator clip adapter. https://www.cpap.com/productpage/respir ... cable.html or equivalent.

There should be no problem getting one night's usage on a car battery sized marine battery. Are your batteries actually 600 AmpHour? Those would be about 6 times larger than a car battery. Are they really that big? One of those would probably run your CPAP for well over a week, even with the humidifier.

Unfortunately, this gets complicated, but you could damage your humidifier if you don't do it right.

First, Respironics has never published any information on running their humidifiers or CPAP on inverters. They only discuss running directly on DC.

Some inverters and generators produce an abnormal voltage waveform called "Modified Sine Wave" or MSW. Also sometimes labeled "stepped approximation to sine" in order to fool the unwary customer. This can damage some heating devices like humidifiers. ResMed, for instance, warns their S8 humidifiers will be damaged by MSW. As I said, Respironics doesn't discuss inverters at all. I THINK the M series blower itself would be OK on an inverter.

In theory, you'll be OK if you get a "pure sine wave" inverter.

There are also two different versions of humidifier for M series CPAP. One powers the humidifier off of AC power. This version has a cord that goes from the humidifier to the power brick and another cord that runs from the blower to the power brick. Later models power the humidifier off of DC power. The DC version has one cord coming from the power brick, and the humidifier has a cord that goes over to the blower unit. I believe the DC powered humidifier also has the number "5" underlined next to the temperature adjustment knob.

If you have the DC powered M series humidifier, you're probably safe using an MSW inverter. (Although Respironics doesn't say so, as I said.) You would also be fine running the humidifier off of DC.

Confused yet?

[Sir NoddinOff]

That was a pretty impressive writeup Archangle. You certainly answered some of my questions too. I just happen to have a PR M-series hanging in my closet as a back-up unit. Serendipity. I might even go camping!

[Guest]

Be sure to not have any water in the humidifier tank at any time the boat may be rocking. Getting water into the blower could ruin it, and the M series doesn't have the best arrangement to prevent water flowing back into the blower.

actually there are 3 versions of the water chamber and the later two are both designed to keep water from entering the machine.
if you use DC and the humidifier is not a DC model it just wont work no bad things will happen like this (insert adj & noun here) wants people to believe. but you can believe every village has one VI
if yours is a DC model it is prob has the latest model water chamber

[pullin]

Thanks everyone for your responses (esp. archangel for the detail, and tmiker for the specs).

I've ordered the DC plug that archangel recommended from cpap.com. It should be here by next weekend and of course, I'll need to test this by spending part of the weekend on the boat at anchor ("Honest honey, I have to go fishing for medical research."). I spent yesterday with a friend welding a custom rail-mount for my propane stove/cooker. I've fashioned it so that it hangs out over the water on the starboard side. I'm still trying to talk someone** into sewing a small propane "locker" to keep the bottles on the outside of the hull (below the rub-rail). My goal is to be able to cook a steak, enjoy a few inspirational beverages, fish after sundown, and then get a good night's sleep (and of course a pot of coffee the next morning).

After making my post yesterday, I started wondering about the amp-hours too. I recently bought the boat and have been going on the specs the previous owner told me*. I think he (and I) have been confusing amp-hours with CCA. I pulled up the battery compartment hatch and stuck my head in with a flashlight, and my batteries are actually 875 CCA, and 90 Amphours. That sounds a little more believable. Sorry about the goof.

Thanks also for the warning about waves and the humidifier. Looking at mine, it appears it would be relatively safe rolling in one axis (longitudinal, for lack of a better term), but the hose could take on water if rotated along the other axis. Since the boat tends to roll at anchor rather than pitch, I'll align the unit accordingly. I'll also minimize the water in the chamber itself to be sure.

As far as disconnecting the humidifier, my unit appears to be permanently affixed to the power brick. I'm not sure I can completely disable it. But using tmiker's numbers, I should be OK with the current battery setup. (right?)

I'm contemplating carrying one of those emergency car-start packs (like the booster pack here: http://www.pepboys.com/tools/booster_pa ... ter_packs/. Just to be sure I can turn over the engine in the morning in a worst-case scenario.

*Before buying, I went over almost everything with a fine-toothed comb. But I didn't stick my head in the hatch and actually verify the battery size. Just made sure they were in good shape and relatively new.

**Apparently, there are a variety of waiting chores at the house, which can be used in trade.

[pullin]

Oops. Forgot to mention. I checked the inverter and it is a modified sine wave. That's why I decided to go with the 12V DC adapter suggested. I have two generators here at the house, one is MSW, and a smaller that's a true sine-wave. I do occasionally find electronics that aren't happy on the MSW. I don't want to risk frying my CPAP machine over a 30 dollar adapter. Thanks again for the advice.

[Guest]

I'm contemplating carrying one of those emergency car-start packs (like the booster pack here: <link removed> Just to be sure I can turn over the engine in the morning in a worst-case scenario.

what you should do is use the jump start for the cpap then
search the forum there are people here who use one every nite to power their cpaps

[tmiker]

The 90 AH battery is fine for a night, especially without humidifier. Since you already have a dual battery the car start piece is probably overkill. If its a deep cell, the battery that powered the CPAP should still turn the engine.

[archangle]

Thanks also for the warning about waves and the humidifier. Looking at mine, it appears it would be relatively safe rolling in one axis (longitudinal, for lack of a better term), but the hose could take on water if rotated along the other axis. Since the boat tends to roll at anchor rather than pitch, I'll align the unit accordingly. I'll also minimize the water in the chamber itself to be sure.

First, the worry is not about getting water in the hose. The worry is about getting water into the blower unit and ruining it.

I wouldn't put any faith in which axis it's rolling around. Once it starts rocking, even a little, the waves in the tank might start building up until they splash out in the wrong place.

As far as disconnecting the humidifier, my unit appears to be permanently affixed to the power brick. I'm not sure I can completely disable it. But using tmiker's numbers, I should be OK with the current battery setup. (right?)

Does your power brick have three cables (one to the wall outlet, 1 to the blower, and one to the humidifier)? If so, then you have the AC humidifier version. The end of the power brick with the AC plug comes off and leaves you with a much smaller rectangular brick that only powers the blower. The brick sort of splits in half.

[archangle]

Be sure to not have any water in the humidifier tank at any time the boat may be rocking. Getting water into the blower could ruin it, and the M series doesn't have the best arrangement to prevent water flowing back into the blower.

actually there are 3 versions of the water chamber and the later two are both designed to keep water from entering the machine.
if you use DC and the humidifier is not a DC model it just wont work no bad things will happen like this (insert adj & noun here) wants people to believe. but you can believe every village has one VI
if yours is a DC model it is prob has the latest model water chamber

Pay no attention to the troll with no userid.

Even with the improved water tank, you don't want to have water in the tank in any boat or other vehicle that's moving or rocking. That's true for pretty much all CPAP machines, even later models with better water tank designs.

You probably ARE OK running directly from the DC adapter, even if you have the AC humidifier. I would expect it would simply run with no heat to the humidifier. Since the blower is electrically connected to the humdifier, it might not work, so try it on dry land before your trip.

[pullin]

Pay no attention to the troll with no userid.

I'm not. When someone starts ragging on another's post, no useful information follows (and I skip on to the next).

Yet again, I owe you guys. I've looked at my brick and it's as described. Two wires going to the unit; One (12V I assume) seems to run the machine/blower, and the other (110V?) going apparently to the humidifier. I didn't know the brick disassembled.

I didn't realize the problem was water backflow into the blower unit. I see what you're talking about now. I'll use it dry when on the boat. There always seems to be more humidity when directly on the water, so it'll probably be OK for a night. I camp a lot too, and can use the water when on dry land.

If you'll tolerate one more question, do these units handle fluctuating power very well? I've noticed some fairly large voltage swings when I'm in RV parks, and have even had to repair my fridge once when the power "sagged" too much. I suspect a lot of RV parks don't really have the wiring to handle the new 50 amp crowd when they're full. My RV provides a 12V outlet (powered by the house batteries, which are automatically charged in the park). I suspect it might be wise to power my unit via 12V in the parks as well. Any opinions? In my experience, the state parks have reliable power. It's the private ones that'll fry your appliances.

Thanks again for all your help on this stuff.