One night tent camping success for $60 (and 10 lbs)

[rtbagwell]

I had my first camping trip this last weekend since becoming a CPAP user, and I figured I should share my success story.

I did a great deal of research into the problem of camping with a CPAP. Here were my requirements:

1) Must power my GoodKnight 420G for at least 8 hours (no humidifier)
2) Must be at least marginally portable (no big 55 pound batteries please)
3) Must be inexpensive

If I'd had an unlimited budget or a real need for an ultralight system, I'd have bought one of the lithium-ion battery kits from cpap.com. But I don't have to hike more than a mile or two, and I definitely don't camp enough to justify a $300 battery kit.

Here's what I came up with:

Parts list:
1 12V-12Ah lead acid battery (these are commonly used in mobility scooters) $35.00
1 Cig Lighter (male) to DC power cable (Radio Shack Model: 27-1594 Catalog #: 270-1594) $15.00
1 Cig Lighter (female) to Battery Clip cable (Radio Shack Catalog #: 270-1527) $10.00

I did a little math before buying this stuff and determined that this battery should run my CPAP for 8 hours while draining it down to about 25-30% (I run my 420G at 13cmH2O). I did a test run a few days before camping and everything worked great. It did, in fact run the battery down to 30%. Now, this is not exactly ideal as the battery should really only be discharged down to about 60% ( 40% used) in order to maximize the number of cycles. Still, when looking at the charts, I should still get a few dozen good uses out of this battery before it starts hurting. Since I only go camping a few times a year, this is more than adequate.

The scooter battery is heavy but small. It weighs in a 10 pounds. Now, I don't want to hike 10miles with 10 extra pounds, but a short 1-2mile hike is no problem. After putting all of this together, I found this site with my basic rig all assembled with a nice case:

http://www.batteryspace.com/index.asp?P ... rodID=3184

I can't say if the above product is any good (since I didn't buy it), but it should work just like my rig if you don't want to assemble the stuff yourself.

Cheers,
Rick

[Bearded_One]

They also have a 3.9# NiMH version:

http://www.batteryspace.com/index.asp?P ... rodID=2675

[Snoredog]

That is pretty good, but I never had much luck with NiMH batteries, like the batteries for my power tools they seem to develop a memory and before you know it they are shot. I've bought the individual cells and reloaded them but still they don't seem to last as long as a sealed lead-acid battery.

These are batteries used in UPS computer backup supplies, Alarm Systems, Emergency Light sources etc. You can get them in almost any side you want and ah rating you want. The don't appear to have any memory effect like NiMH.

For example you can buy a small 10Ah Sealed Lead Acid battery for $27 bucks or so and the battery is only 8lbs. (see specs on size), but I have several of these and I use a BatteryTender to recharge them. You have to be careful in knowing what you buy as some have a inrush current limitation, and these Xpaps like the Remstars can have a high inrush current requirement when that happens battery power is lost. But they have others that don't have that limitation.

I purchased mine at BatteryMart, got good service from them.
http://www.batterymart.com/p-12v-10ah-s ... ttery.html

The above is an example of the 10ah battery, you will see a charger at the bottom of the page for 16 bucks. Then all you need is the cigarette socket and adapter from radio shack and a camera bag.

[GuyK]

Please forgive my ignorance -- what kind of "Ah" capacity should one be looking for? A minimum of 10 maybe? (although maybe that varies from machine to machine)

So as long as a battery pack has a lighter socket (and I know my Resmed machine has some kind of reverse polarity think going on, so an adapter is needed), and has a minimum "Ah" capacity, and can be charged...what other considerations are there to look for?

Thanks,
Guy

[WNJ]

Depends upon 1) how many amps your machine draws at your pressure, and 2) how long you need the battery to power your machine before recharging.

Multiply amps of your machine times the number of hours before recharging. Amps X hours = amp-hours

Since batteries don’t last long if they are too deeply drained, it is a good idea to buy extra battery capacity. For lead-acid batteries, 50% maximum discharge is a good rule, so you should double the amp-hours arrived at in the formula above if you want maximum battery life.

My Remstar Auto seems to draw about 1 amp at my pressure. At 8 hours per night, I need 1 amp X 8 hours = 8 amp-hours.

I have a deep cycle battery of about 75-80 Ah capacity. At 50% discharge, that gives me about 40 Ah usable. At 8 Ah per night, this gives me 5 nights before recharging.

Wayne

[Guest]

I don't think this would work for an airplane but camping for $25-$30 it even already has the lighter plug attached and a 17amp battery with a charger = done.

viewtopic.php?f=1&t=28154&p=242683&hili ... er#p242683

[GuyK]

Thanks, Wayne and "Guest".

I don't recall my APAP having specs that list current draw. How does one determine that otherwise?

Guy

[rtbagwell]

I tried a "jump start" box about a year ago, but had problems since it was a "starter" battery and not a "deep cycle" battery. I basically forgot to charge it once and then it went dead on me.

I don't think this would work for an airplane but camping for $25-$30 it even already has the lighter plug attached and a 17amp battery with a charger = done.

viewtopic.php?f=1&t=28154&p=242683&hili ... er#p242683

[rested gal]

Thanks, Rick! I've added your topic to the list here:

LINKS to Battery operation, camping, power outage
viewtopic.php?t=9682

P.S. If you're an RT, that's a clever nickname you came up with.
Hope you had a wonderful vacation.

[wyhusker]

I was diagnosed with sleep apnea only four months ago, and I'm still getting used to the whole concept. My question deals with camping, or more specifically backpacking. Every year I go on a week-long backpacking trip into the mountain wilderness. Obvously there is no power available where I camp and sleep. Also obviously, weight is a HUGE issue. Does anyone have any way to power my CPAP?

Thanks for your help....Brian