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  #1  
Old 10-13-2011
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Unhappy 5 Watt Solar Panel & CPAP Machine

Well, I hate to admit it, but it will. Doc prescribed a CPAP machine 1.5 weeks ago in order for me to sleep more than the four hours sleep I've routinely get a night over the past four to six months. I hate it, but for now I have to use the thing. Good news is I've lost 25 pounds and have modified the diet a bit and am getting better exercise. Hopefully, I'll not have to use the darned thing my whole life. I routinely sleep on the sailboat 3-4-5 days a week. I love the relaxation. I sleep there better than at home. I need to sleep better.

My question: Any idea on what kind of mileage I'll get out of my 100 ah deep-cycle marine battery hooked up to a 5-watt solar panel? I have no shore power available. Using this thing 6-8 hours a night, will my panel be able to keep up with it? I've been off shore power for a year now and the solar panel does a great job powering my LED lights and radio (pretty much the whole load I'm demanding of the battery at this time). I usually run the radio all night and the lights are on until bedtime. Can't find any actual specs on the thing.

I don't want to trash my current setup.

Thanks for reading this and thanks for any and all replies.
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Last edited by carl762; 10-13-2011 at 10:03 PM.
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Old 10-13-2011
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It should have a sticker stating amperage used @110 volts or it wouldn't be UL approved I don't think.
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Old 10-14-2011
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Link

I'm afraid a 5 or even a 20 watt panel isn't going to handle it.

Try this search link over at Macgregor Owners dot com
SailboatOwners.com - Search Results

Quote:
Originally Posted by carl762 View Post
Well, I hate to admit it, but it will. Doc prescribed a CPAP machine 1.5 weeks ago in order for me to sleep more than the four hours sleep I've routinely get a night over the past four to six months. I hate it, but for now I have to use the thing. Good news is I've lost 25 pounds and have modified the diet a bit and am getting better exercise. Hopefully, I'll not have to use the darned thing my whole life. I routinely sleep on the sailboat 3-4-5 days a week. I love the relaxation. I sleep there better than at home. I need to sleep better.

My question: Any idea on what kind of mileage I'll get out of my 100 ah deep-cycle marine battery hooked up to a 5-watt solar panel? I have no shore power available. Using this thing 6-8 hours a night, will my panel be able to keep up with it? I've been off shore power for a year now and the solar panel does a great job powering my LED lights and radio (pretty much the whole load I'm demanding of the battery at this time). I usually run the radio all night and the lights are on until bedtime. Can't find any actual specs on the thing.

I don't want to trash my current setup.

Thanks for reading this and thanks for any and all replies.
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Old 10-14-2011
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My wife's CPAP draws about 80 watts.

(80 watts/12 volts) x 8 hours/85% efficiency factor = 63 AH. Yup, before we added larger solar panels, it would put quite a dent in the batteries (3 x group 27) after a few days (she would also sleep 11 hours). I'm thinking you need another battery and an 85W panel. Sorry for the bad news.

As stated, the power consumptions should be on the back, both in watts and amps.
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Old 10-14-2011
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Quote:
Originally Posted by carl762 View Post
My question: Any idea on what kind of mileage I'll get out of my 100 ah deep-cycle marine battery hooked up to a 5-watt solar panel?
I use a ResMed CPAP but never on the boat, yet. This isssue is also a concern of mine as I would like to liveaboard. My ResMed unit has both 110V/12V input. The 12V is listed at 2.5 amps. Interestingly, it also lists the 110V input as 2.5 amps.

If your CPAP is similar, we can calculate 2.5 amps x 8 hours = 20 amp hours. If this is the only thing that your battery is powering, you are in good shape.... but that is probably not the case.

Switching to 110V power. The documented 2.5 amps is very strange (in comparison to the 12V number) so I have connected the unit to a KiloWatt meter to record exactly what it is doing. The highest consumption number that I have seen is .5 amp. So, if we were to power this unit from an inverter, the consumption is something around 5 amps (12V) x 8 hours = 40 amp hours.

Depending on your location, hours of sun, etc... and assuming the CPAP is your only draw, your 80 watt panel is probably sufficient for the first scenario but not the second. I ran some numbers for my boat and 80 watt panel here: Electrical System | JdFinley.com

One question to be aware of; if you are going to run the CPAP from an inverter, is the CPAP happy with the output form? I've read generic statements that "medical devices" are particular and demand true sine wave power and so the more expensive inverter. I do not know if CPAP's fit into this category.
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Old 10-14-2011
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If it has a 12 volt input that will be more efficient than using AC from an inverter.
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Old 10-14-2011
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Dang!! I will look at the little label on the bottom. Didn't think of that.

Yes, I have a 12-volt cig lighter adapter, not an inverter. It's heavy duty and specifically designed for the CPAP machine, not a Radio Shack cheapie.

Last night I tried running CPAP at home on one of those emergency jump starters, with light, compressor, etc. The CPAP ran fine for about two minutes, then crapped out. I recharged it overnight and will try again tonight. Jump starter has a little meter on it, so I can track the drain, if it'll work tonight. That should allow me to guage the usage a bit.

Also, I read on the net that I might have to change the fuse that's in it to a 7 watter. I'll do that tonight and test her again.

If I actually do try it on the boat, the only thing that'll be running are two LED cabin lights. I can just not use the stereo and use the iPOD for music. When I do sleep on the boat, since having this stupid machine, I sleep pretty well without it.

Thanks for the replies.

Carl
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Last edited by carl762; 10-14-2011 at 12:45 PM.
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Old 10-14-2011
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What would be so hard about adding another battery? Is that out of the question?
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Old 10-14-2011
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Quote:
Originally Posted by LandLocked66c View Post
What would be so hard about adding another battery? Is that out of the question?
The OP stated no shore power. No matter how many batteries you have the power you generate has to be more than the power you use.
Batteries do not generate power, only store it.
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Quote:
Originally Posted by noelex77 View Post
The OP stated no shore power. No matter how many batteries you have the power you generate has to be more than the power you use.
Batteries do not generate power, only store it.
I understood it as he wasn't sure it would last through the night? I guess i'll re-read it.
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