03 April, 2021

Powering a CPAP for camping, off grid living, or emergencies.

 If you are like me, on CPAP therapy, and have had experiences where you couldn't do therapy either because you were off grid by choice say on a camping trip, or you were without power because your electrical grid operator decided to pull the plug on you due to, whatever reason, you know the terrible burden this leaves on you. For me, one night of no CPAP means a night worse than if I had just not slept, and an almost guaranteed migraine level headache. 

Medical grade CPAP battery packs typically run as much as the CPAP itself or more,  They are little more than a battery pack, a charging circuit, and a 12V output for most CPAPs. And even with efficient travel CPAPs these battery packs rarely last a user for 2 nights sleep, so for extended outages you absolutely MUST have a way to recharge off of 110V AC power. So i your budget is tight, and your CPAP can run off of 12v DC keep reading. I have a solution that will save you a mess of money, and provide you with much longer run time between needing to be recharged. 

I have multiple reasons to run it, but I do have a small, and I mean tiny small generator, a Harbor Freight Tailgator, which is a little 900w peak 2 stroke generator that will easily handle my battery charger for this rig, or a small 5K BTU window AC etc... So I have a way to recharge, but honestly nobody wants to try to sleep while a generator that sounds like a chainsaw is running. I needed a better, more efficient solution to the problem. 

In my last blog post, I described the materials that would be used for a build like what I was doing. Today I present my finished product. 

The project didn't come off perfectly, and I will explain below, but overall I am VERY happy with the results.

So if you see my first photo with the box closed, you will notice that on the group on the left, the 12V outlet is positioned a bit too far left, apparantly I didn't have things measured out was well as I could have liked. Oops.

The charging circuit, I.E. bench top battery charger seen in the second pic leaves a bit to be desired, but it is sized so that I have no issues running it off of my Harbor Freight Tailgator generator, and topping the charge off quickly at 25 amps @ 14v output. (peak I believe). 

I want an onboard charger but they are EXPENSIVE, and typically max out at around 10 amps. I may upgrade my workshop battery charger at home and figure out a way to mount this thing to the box, and add ring terminals to it... Yeah that's probably not going to happen.

Anyway Upon testing, I find the Deyooxi 3 in 1 works, but the voltometers are innaccurate, and they don't even match each other, but rather they both read high and are .1v apart from each other. At best they are a good guess. Good enough, but not perfect.

I found the face plates the 3 in 1 sets came with don't fit accross the raised sections of this battery box. No shock there, So I left them out. This really doesn't need them, and with the oops hole, well...

Now during my hurried testing after the Great Texas Ice Storm and power outage of February 2021, I found that this battery, and a 12V power outlet can and will EASILY power my Z2 Travel CPAP for 4 nights in a row without recharging. Upon setting up to recharge I measured the standing charge in my battery with my multimeter and it measured 12.4V DC, which was still at a very high level. Mind you the Z2 is freakishly efficient. I would have had no issues or concerns running my Airsense 10 with the humidifier turned off during that time on the battery either.

If you want a great off grid power box for items like a CPAP, or USB charging, or even running a 12v compressor fridge, look at my last post as well. I go into the nitty gritty of what I did. It's all bound up nicely, and built in honestly as professional a manner as possible for a hand crafted item. And on the plus side, the skills needed to build this thing are minimal at most.

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