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- #61
I am a poor sleeper. I have a CPAP and it has helped me a lot. I was worried about not having it on our camping trip. If I don't use it for one night, I'm irritable the next day. I don't want to think about what I'd be like after two nights. How can I solve this? Well, one way is to borrow/purchase a portable power station with AC inverter. But those are a lot of money after I've already sunk a bunch into the house battery for the truck. Plus, I don't want to owe anyone a favor for letting me borrow theirs! But how can I power my CPAP from the house battery? One option is to get an AC inverter. However, I didn't want to go this route as they can waste lots of power and with 100Ah (~1280Wh) in the house battery, I needed all I could spare. The other option is to power the CPAP from DC power directly. The CPAP requires 24V at 3.3A (79.2W, and over 8 hours of sleep that equals 633.6Wh full blast, at 80% usage, 506.8Wh). This option makes more sense as I will have very little conversion loss. So, I decided to build my own portable power box that would plug into the house power system via a long cable. The cable would run from the house fuse block, through the closed rear door, 30ish feet into the tent.
Harbor Freight trip! There are some power hurdles to get through. The longer a cable is, the greater the voltage drop will be on that cable. Having a thick gauge wire is important. I went with 10 gauge. The other way to combat voltage drop across a cable is to utilize a higher voltage. I purchased a 12v to 24V boost converter and put PowerPole connectors on it. That plugs into the fuse block, and the 30' cable has PowerPoles on it as well. The box has the matching PowerPoles and a power switch rated for the amperage it could see.
Inside the box you will see that the 24V lines goes directly to a fuse box. There is a single 7.5A fuse that goes out to the 7.4mm DC barrel jacks. These are for the CPAP. As I said, the CPAP requires 24V @ 3.3A. I added two barrel jacks in case the wife ever needed to power a CPAP too. There's another fuse that goes to a DC buck converter. This buck converter takes the 24V and drops it down to 12V. I did this so I could power two USB C chargers. This way, the wife and I could charge our phones in the tent as well.
This solution worked great! Except for one thing... My CPAP utilizes a heated tube to keep the air humid and not condense back into water. If the water condenses in the tube, it can cause a very loud, sleep interupting gurgling sound. The standard CPAP power adapter looks like a normal DC adapter, but it actually has three wires. Standard DC + and -, but also a "sense" wire. That sense wire is what allows the unit to operate the heated tubing. Check out this video for more info. Long story short, I didn't have time to get the sense wire configured. So
my CPAP worked, but the heated tube did not and caused some issues in the middle of the night. At least I was more rested than not having the CPAP at all.
The battery was at 99% charge when we went to bed. In the morning, after charging our phones and running my CPAP, the battery dropped to 55%. That's quite a lot, and if I were to use my heated tubing, it would be even greater. If my wife brought her CPAP on a future trip, we would be really low on battery power. How would we survive a second night??
Harbor Freight trip! There are some power hurdles to get through. The longer a cable is, the greater the voltage drop will be on that cable. Having a thick gauge wire is important. I went with 10 gauge. The other way to combat voltage drop across a cable is to utilize a higher voltage. I purchased a 12v to 24V boost converter and put PowerPole connectors on it. That plugs into the fuse block, and the 30' cable has PowerPoles on it as well. The box has the matching PowerPoles and a power switch rated for the amperage it could see.
Inside the box you will see that the 24V lines goes directly to a fuse box. There is a single 7.5A fuse that goes out to the 7.4mm DC barrel jacks. These are for the CPAP. As I said, the CPAP requires 24V @ 3.3A. I added two barrel jacks in case the wife ever needed to power a CPAP too. There's another fuse that goes to a DC buck converter. This buck converter takes the 24V and drops it down to 12V. I did this so I could power two USB C chargers. This way, the wife and I could charge our phones in the tent as well.
This solution worked great! Except for one thing... My CPAP utilizes a heated tube to keep the air humid and not condense back into water. If the water condenses in the tube, it can cause a very loud, sleep interupting gurgling sound. The standard CPAP power adapter looks like a normal DC adapter, but it actually has three wires. Standard DC + and -, but also a "sense" wire. That sense wire is what allows the unit to operate the heated tubing. Check out this video for more info. Long story short, I didn't have time to get the sense wire configured. So
my CPAP worked, but the heated tube did not and caused some issues in the middle of the night. At least I was more rested than not having the CPAP at all.
The battery was at 99% charge when we went to bed. In the morning, after charging our phones and running my CPAP, the battery dropped to 55%. That's quite a lot, and if I were to use my heated tubing, it would be even greater. If my wife brought her CPAP on a future trip, we would be really low on battery power. How would we survive a second night??