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CPAP gets 18650ed.
There is no actual communication except for overheating of the supply. It does sense for a 2.7K resistor being present to identify it is an 85W supply. Please read my previous post. This is exactly what you need to do.
I appreciate the information Norknid, but the adapter I have already does the 3.3V signal thing. It's made specifically for my cpap model. The main reason I bought it was for the compatible plug for the machine. I looked at all the parts to make a DIY unit, and buying this adapter/regulator ended up being cheaper.

I used my temporary battery and took a 2 hour nap this afternoon, with the cpap powered through the adapter. Works perfectly! I also made a diagram of all the stuff I'd like to fit in the box. No idea if it will all fit, but I'm thinking it would be great if everything I need is in the box and I just have to open it up and turn it on. Well see how that goes.

Korishan likes this post
-Mike G
I assume you are talking about the battery converter box they sell for the CPAP. I assumed you were going direct from that 24V converter into the machine. For others who might read this thread, here is a solution that would have less to carry around. Cut the Resmed cable at a convenient location and install a three pin plug that allows you to put it back together. Then make another plug that will connect to your buck or boost converter. At the connector install the two resistor divider (prior post) that will simulate a 3.3V supply with a 2.7K ohm resistor in series to simulate a 85W AC power pack. NEVER connect the center pin directly to 3.3V as it will damage the machine. I never had any need to do this because these power packs are $10 and keep a couple spare. Mine is wired permanently to my camp with the converter 50 feet away.

I have the Resmed S9 unit, with a 3pin angled plug.
Do you know if this is wired the same or where to get the info?

I think the convention is the same, just the plugs won't fit each other machine. I have no direct experience. If you connect a 2.7K resistor from center pin to common outside shell, it should measure about 1.6V. I wouldn't do this test without an insulated center connector. It would be too easy to short the 24V to the center pin possibly damaging the pack.
My BMS finally arrived from China! Still plugging away at testing cells though. So far, I've done around 70 or so, so I'm almost done. The best 66 will go in the battery.
I've realized I can't get a 4A fuse, so I'll make due with a 5A. Using the axial glass 0.5A fuses on each cell, that would allow the battery to deliver almost 11A before they start to blow. So a 5A main fuse will definitely pop before that. (I hope.)

I've been playing with an actual wiring diagram, to better imagine where all the parts will go. Here's what I've got so far:
[Image: 75be49c37ec7f697bf060706130b692c.jpg]

I definitely wanted a Voltmeter to show the battery status, but I decided to spend a couple extra bucks (I know, unusual for me.) on a Wattmeter. This will show Volts, Amps, Watts, and Whrs, to give me a better idea as to how the battery actually performs vs my math estimates. Plus, it has a low Voltage alarm that can be set. The BMS should shut it down automatically if the Voltage gets too low, but I've never really trusted BMSs.

If I can fit them in the box, I'd like to have the option of taking a battery charge controller and the AC adapter, in case I come across electrical outlets in my travels. Once I get the box, I'll be able to do a mockup of all the parts and see what will fit, and what physical shape I'll make the battery.
-Mike G
I've just realized that I used up all my copper wire on other projects! I'll have to get more before I can start building the battery.

Some good news though, I've finally finished testing all 99 cells, and they're all good! There's something very satisfying about seeing all the cells lined up together.

The range of mAh is pretty good. Nearly all are 2500mAh or higher. A few lower ones, but when I harvest random old laptop batteries, they're usually not this good.

Anyway, I've chosen the best 66 to be in the CPAP battery. They'll range from 2661-2545mAh. That should give me some nice Watt-hours.

I think it's about time to go get that box and see how much I can fit.
-Mike G
Excited following this thread. I haven't purchased a mobile source for my S9 Autoset so when camping have been bringing a 100' extension cord.

Is your machine also a bilevel machine and/or are your calculations going to be different than for my usage?

thank you
Hi Leo,
Each machine will have it's own power requirements, so the values will be different. But the basic math could be applied to any device. The really important values are Volts and Amps that the machine needs, and Volts, Amps, and Amp-hours that each cell can safely deliver. I have the ResMed A10, which is a regular CPAP (or APAP, I don't know the difference, and I've heard it called both.)

I finally went and purchased the box that all this is going in. I don't have pictures yet, but it looks like everything I want in there is going to fit! Some bad news though, is that I crashed my computer last week, and I've been working all weekend to get it back up and running. Some good news, is that I had no data loss thanks to luck and backups. Smile
-Mike G
Got my computer 95% up and running.

Now that all the cells are tested, I got them cataloged and entered into repacker. All arranged how they will be soldered up.

I ran out of the wires I normally use, so I had to scavenge some from a box of junk wires I've got laying around. Took one multi-stranded wire apart to use individual strands to connect the bottom half of the battery to each cell. Another multi-stranded wire was the right size for the bus, but insulated. I just cut a little insulation off at each solder site, and it seems to work fine.

BMS is installed. I guess it's working. At least it's not smoking, and the power out Voltage is right.

This particular BMS has the option to add a thermocouple switch. So I added one that is normally closed until 113F. Still need to add a cable for balancing and a fuse, then some outer physical protection. But it's shaping up!

Korishan likes this post
-Mike G

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