We recognize that some PSG attendees use CPAP machines, and that powering those devices is an important part of getting good rest. Our current PSG site has very limited electric availability, so this guide will help you navigate your options.
Disclaimer: If in doubt, check with your CPAP manufacturer or your medical equipment supplier. Don't do anything stupid with your expensive equipment! And test everything before you leave home.
Whether you're camping in a larger unit like an RV or you just don't want to be tied down to the Disability Camp area, a battery-powered solution may be right for you.
The typical CPAP unit without a humidifier draws around 25 watts, and a humidifier & heated tube increases that to around 80 watts. So, the first thing to consider when camping with a CPAP is to jettison the humidifier. Missouri in June tends to be hot and humid, so this may not pose a problem for you.
Solutions from the CPAP manufacturers may be prohibitively expensive, such as this $670 option for a ResMed S9. However, it may be more convenient to use a 12-volt converter -- either one from your CPAP vendor (example), or an inexpensive inverter.
How Much Battery Do I Need?
Batteries are rated in amp-hours (Ah): for example, a 10Ah battery will supply 10 amps for one hour, or one amp for ten hours. So let's do some rough math:
- A CPAP machine which needs 25 watts will, if powered by a 12-volt supply, need just over 2 amps. Let's round that up to 2.5 amps to account for power loss in the converter.
- Let's assume you get 8 hours of sleep every night, so 8 x 2.5 = 20Ah needed to get you through the night. If you're running a humidifier, bump that up to 55Ah.
What Kind of Battery Should I Get?
Depends on how much you want to spend and how much hassle you're willing to deal with. One convenient option would be a better-quality car jump starter unit, such as this one for around $150 which comes with a built-in charger. Note that I have not found a jump starter for less than $150 which has a large enough battery -- do the research and don't buy something inadequate!
If you want to spend a little less, and have something that is safely sealed and won't leak, you could consider a sealed lead-acid battery for closer to $75.
If you want to spend less yet, or if you're running a humidifier -- and you don't mind lugging around a big battery which may spill acid if tipped -- then something like a group 24 deep-cycle / marine battery for around $60 will work. One extra advantage of a big battery is that you'll get 2 or 3 nights out of a full charge. Motorcycle or tractor batteries can work as well -- but keep in mind that if it weighs less than 20 pounds, it's probably not enough battery.
How Do I Charge My Battery?
There will be power available at most pavilions, and you can carry your battery there daily for charging. If you do that, make sure to bring a battery charger! A 10-amp charger like this one will top off one night's worth of use in about three hours.
Solar charging is also an option, though you do need to take care to buy a large enough one. A 100-watt panel and a controller will, for about $150 and a little wiring, get you through both sunny and cloudy days. The little 10-watt panels sold for charging cellphones and the like will never keep up, even under optimal conditions.
If you'd like to discuss this further or talk over a specific setup, please feel free to contact Bob Paxton at firstname.lastname@example.org.