CPAP & Inverter

A CPAP machine doesn't require a generator. Truckers and boondockers (campers with no shore power or generator) use batteries every day to power their CPAP machines. Most CPAP machines have a DC options where you can connect directly to a battery. That's the most efficient way to do it, since no battery energy is lost having to go through an inverter. But for those that are AC-only, you can use a small (175 Watt) inverter and power your CPAP machine off a Walmart deep cycle marine battery for the entire night with no problems.

They make Li-ion CPAP battery packs that will power your CPAP machine for 4-5 nights, depending on what type of machine you have and pressure setting. But I think those puppies are in the $800 range.

Most CPAP machines, depending on pressure settings, are between 30-60 Watts. That's like a light bulb. 30 Watts translates to 2.75 amps from the battery through an inverter. 60 Watts becomes a 5.5 amp draw. Using the upper end of 5.5 amps, for 8 hours of sleep that's 44 amps from the battery. 55 amps for 10 hours of sleep. In that scenario, a 110 amp hour battery is more than sufficient to run a CPAP machine all night between recharging the battery from the alternator the next day. The amp hour rating of batteries is calculated on a 5 amp draw, so a 100 amp hour battery that draws 5 amps per hour will last 20 hours (or 10 hours if you stay at 50% Depth of Discharge, which will make the battery lifetime last much longer).

An Everstart Maxx marine battery from Walmart is all that's necessary for that, whether you use it through an inverter or with direct connect DC power (if you machine is capable of that). If you want to have some extra peace of mind, or will be drawing other things from the battery, like lights or a laptop, then two Or even three or four) of those batteries is the way to go.

The manufacturer of your CPAP machine will be able to tell you the power draw (usually in Watts) of you machine at various pressure settings. Watts divided by 12 volts will give you the amp draw with a direct connection to the battery, and if going through an inverter you need to take that amp draw and then add 10% to it (if 30 Watts divided by 12 volts equals 2.5 amps, then 2.5 time 10 % is .25, and 2.5 + .25 = 2.75 amps).

If you use a heated humidifier then you will have to use a pure sine wave inverter, however. Humidifiers use a triac or thyristor to regulate the power by turning on partway through each mains cycle. The controller assumes the mains voltage is pure sine wave and 60 cycles per second, same as household current. Modified sine wave inverters do not provide a true sine wave output, thus the controllers make wrong decisions and cause the humidifier to deliver full power continuously and will inevitably burn out the heating element. If you do use a heated humidifier with a sine wave inverter, then the heating element amp draw must be taken into consideration when sizing the battery or battery bank.

 

yes you did, but it could be a cheaper option to go with 12v power cord IF your machine isnt too old. Then again, an inverter could be used for additional purposes.

Does your machine have a way of recording the data(SD card) for review to ensure compliance?

 

Mine runs on either but I had trouble with using 12v in the freightliner I used to drive, but that was probably due to the defective chassis ground that we later discovered. Kept flashing a low voltage error and shut down.