Q. Hi David,
I use a CPAP machine at home which runs via 240V into a transformer to bring the power down to 24V DC. The ‘boss’ and I do a bit of overnight free camping, so I enquired with the CPAP manufacturer if they have a battery set up that could run the unit overnight. The answer was yes, but the cost was over $600.
I began thinking the house battery in the van is 110Ah, so is there is a way to utilise that when we do free camp?
Below is the tech info on the CPAP machine and hopefully you can advise a way to utilise the house battery and what I would have to buy. The manufacturer does supply some equipment I am sure could be adapted just by having a cigarette type connection installed in the van by a sparky.
RESMED DC/DC CONVERTER (FOR AIRSENSE™ 10)
Operate AirSense/AirCurve 10™series of devices and Lumis™ ventilator using 12V or 24V DC power sources. The ideal solution if you need to connect your therapy device, heated humidifier and heated tube on a car, truck, caravan, boat or other vehicle equipped with a suitable power source.
The AirSense 10™ DC Converter makes it possible to operate your AirSense/AirCurve 10 device or Lumis™ ventilator from 12V or 24V DC power sources. It’s the ideal solution if you need to connect your therapy device on a car, truck, caravan or boat, and can also be used to power if connected, the HumidAir and ClimateLine Air™ heated tube. Enjoy the benefits of effective therapy alongside the pleasure of an active lifestyle.
• Practical: use your therapy device in a car, boat or other vehicle equipped with a 12V or 24V DC power source or a suitable battery. Supplied with a Cigarette Plug Lighter End and Croc Clip Adaptor.
• Functional: can be used to operate any AirSense/AirCurve 10 device or Lumis ventilator, including HumidAir and ClimateLine Air heated tube.
• Liberating: your therapy device is no barrier to enjoying travel or vacations off the beaten track. Are there any obvious pitfalls to watch out for? What I know about 12V systems can be written on the back of a stamp!
Regards, Barry Jones
A. Hi Barry,
Glad to hear that you’re getting a good sleep out there with your CPAP machine. Whilst you sent your question in earlier this year, with all the recent lockdowns you may not have yet had a chance to get out and explore and complete your setup. Hope the details below will help.
Many travellers out there are enjoying the benefits for getting a great night’s sleep and keeping a gentle hush over the caravan parks after hours with less snoring! There are essentially two ways in which to set up your system for peace of mind overnight. You can either utilise a power transformer to reduce the voltage or you could invest in an inverter to simply plug your CPAP machine directly in.
If you decide to utilise the plug pack option — 12V DC power source, you are correct that you could connect this directly to your power management system (PMS) in your caravan which would utilise the house battery when free camping and have no direct access to 240V. Simply determine what types of connectors you have available at the fused outputs and get your local ‘sparky’ to create the appropriate terminal connections. Depending upon your setup, it might be appropriate to create a permanent cable setup with a simple connector or a convenient DC inline switch to make it easier when heading off to bed.
The alternative setup, which is what many use as it provides additional convenience, is the use of a small inverter. The inverter is connected directly to the house battery and converts 12V DC power into normal everyday 240V power, enabling you to simply plug in the normal wall plug pack adaptor you would use at home. As the inverter is likely to be tucked away near the battery or PMS, set-up a short extension lead so again, it is ready for instant use. Also, ensure you get a setup with a remote switch for the inverter so that when the machine is not in use the inverter is not running idle on standby, consuming power from your battery. Some inverters are well known to being ‘power hungry’ when left on, as they power lights and displays and can inadvertently drain a battery just before you really need it.
The main area to pay attention to is the actual consumption of the CPAP machine. If the humidity is turned up high, then some CPAP units can consume 6–7Ah. Depending upon what setting you utilise though, it could be down as low at 1.5A. It would be wise to ensure your battery is in good condition and certainly advisable to trial running the machine overnight a couple of times to understand how much energy your setup is consuming from the battery, before you head away free camping.
Another pitfall to be aware of is if you are planning to connect something directly to the house battery for power, that you utilise an appropriate shunt to measure the energy in and out of the battery. Most monitors inside your caravan, which display the State of Charge (SOC) are only measuring the power that goes through that system — not what may be taken directly from a battery. If your power management system cannot ‘see’ this information, it will give you an incorrect measurement of the SOC, meaning that the battery will likely be flatter than you expect. The popular BMPRO Power Management Systems have a product call BC300 Commlink which transmits this information from the battery terminals up to the PMS to ensure the battery status is accurate. Otherwise, ensure you have a system which includes a shunt to provide this critical information.
Safe, well rested travels, 12V Guru