Battery Backup solution for Resmed S9 with H5i

Howdy all. Just found these forums.

I did a quick ancillary search and didn't find much. Don't hate if you know of a well known thread somewhere, maybe my search skills aren't the best.

Last night, for the first time in years, my power went out unexpectedly, and did so a couple of times. I can't sleep without my cpap, so you can imagine how difficult this was for me.

I'm choosing to live by a "better to have it and not need it than to need it and not have it" mentality with my CPAP machine, which leads me to ask.

What's a good solution for a battery backup for this machine? I've done some ancillary research, and I see a lot of comments on forums that say if you have a humidifier you can't use certain types of battery backup solutions because of how the inverter creates a certain sine wave or whatever....I know there's tons of UPS solutions all over amazon but I don't want to buy something without doing the proper research.

So what say the collective minds here? I realize there's some solutions that are (in my belief) sponsored solutions, that are well within the $300+ range. Is that really the only answer to needing my cpap machine to keep running should the power go out again, or are there more cost effective solutions that, I can plug my machine into, and should the power go out, it'll just keep trucking?

drummerdude152002 wrote: ↑

Sun Feb 18, 2024 9:18 pm

I'm choosing to live by a "better to have it and not need it than to need it and not have it" mentality with my CPAP machine, which leads me to ask.

IMO anyone who uses cpap should have the DC cord that fits their cpap and a battery setup to plug in to. If you are handy you can build something.

IF not then search and read some more.
Not sure where you read about the humidifier but most often it is recommended to not use heated hose or heat for the humidifier when on battery power. Put water in the chamber just use it in Passover Mode.

To extend battery life You will want to use DC power and not AC even if your setup has AC.

I have a battery Jump Starter I use.

https://www.cpap.com/search?query=DC%20Power%20Cord

Guessing your machine takes 24 volts like my Resmed AS10. That's basically two car batteries in series, 12v each. You'll need to have those batteries charged up... you can parallel them to charge them if they're decently matched (e.g. brand new). Amazon sells 7ah batteries that will give you 1 amp for seven hours... they're about 30$ each. Any more money you put in will give you more hours use... get crazy enough and the humidifier won't matter. You'll need a battery charger etc, these are good things to have around anyway. We're talking hillbilly sub-70$ solution.

I live in the great state of Texas, where we freeze without power every other year for days at a time. I have *two* generators, one capable of running most of my house. I have 100gal propane outside that I have filled before each candidate freeze... my big generator uses propane and will run for weeks on that much. I also have a smaller gasoline generator that got me through the First Great Freeze, I owe that little guy a lot... had to scrounge gasoline, hence the bigger solution, came in very handy for the Second Great Freeze.

I also cannot sleep without cpap... so it's worth it to have multiple backups, multiple machines, multiple generators, multiple fuel types/sources. I have an upstairs desktop computer near my bed, I use a UPS capable of 1300w, so I plug my AS10 into that and sleep through most power glitches... turn off the beep warning of course.

drummerdude152002 wrote: ↑

Sun Feb 18, 2024 9:18 pm

I'm choosing to live by a "better to have it and not need it than to need it and not have it" mentality with my CPAP machine

In that same vein, do you have a backup CPAP machine?

The best thing is to get one of these, specifically made for the S9:

https://www.directhomemedical.com/cart/ ... d_source=1

That will let you run off 12- or 24-volt batteries. You can pick up a deep cycle scooter battery like this one on Amazon that will power you for 3-5 days, depending on your settings:

https://www.amazon.com/Weize-Rechargeab ... 101&sr=8-2

Make sure it's a deep cycle battery. Regular car/motorcycle batteries aren't designed to be discharged too far. The deep cycle will let you discharge it almost completely and recharge with a battery tender or charger and still be OK.

loggerhead12 wrote: ↑

Mon Feb 19, 2024 4:43 pm

Make sure it's a deep cycle battery. Regular car/motorcycle batteries aren't designed to be discharged too far. The deep cycle will let you discharge it almost completely and recharge with a battery tender or charger and still be OK.

If by "Regular car/motorcycle batteries" you mean a flooded lead acid battery, yes it's true they are not intended to be used like this. AGM lead acid batteries like the one you linked to are more tolerant of deeper disacharges, but by no means would I expect to discharge one "almost completely" and expect it to recover fully. 50% depth of discharge is about as far as I would take it if possible. Negligible impact to the battery performance & lifespan. Beyond that and you're going to shorten its useful life. Go no lower than 80% depth of discharge (where you're still doing some shortening of its lifespan). Rule of thumb is probably to figure out how many watt hours you might need between charges and double it - that's the capacity to have on hand.

amenite wrote: ↑

Mon Feb 19, 2024 5:36 pm

Beyond that and you're going to shorten its useful life.

No doubt. Fortunately these batteries are pretty cheap. Maximizing its lifespan isn't my goal. I test mine 3-4 times per year all the way to empty to validate the whole system. Three years in and it's still kicking so far!

drummerdude152002 wrote: ↑

Sun Feb 18, 2024 9:18 pm

Howdy all. Just found these forums.

I did a quick ancillary search and didn't find much.

If you are open to more reading...
viewtopic.php?f=1&t=183027&p=1402793&hi ... i#p1402806

Instead of a flooded lead acid I am using a LiFePO4 (LFP) chemistry is a better deal. Much higher capacity in a lighter and smaller.

Attached is the diagram of what I am using. The whole pack weighs about 30lbs, less than half the weight of a single deep cycle battery. Mine is more flexible than you actually need. You could just bolt together the battery, 12v sockets (or direct wire the PSU), the 12v MRBF fuse,, switch, and the charger.

Currently the
litime mini is $299,
charger is $109,
MBF holder $30,
fuse $10 ,
wires made to order are $10 each you need 1,
switch $15,
two 12v sockets $16
------------
$489

For an enclosure I picked up a used plastic box at the thrift shop - it is a sewing box without the tray - $3.
NOTE - Don't cheap out on the fuses and components - the fake stuff looks real but is a fire hazard - I list the quality brands on the diagram - everything from amazon.

LFP batteries have a DOD (depth of discharge) of 100% (well, don't go below 80% unless you want to shorten battery life.
Flooded Lead acid batteries (FLA) only have a DOD of 50% which means if you go below that you damage the plates. Deep cycles increase thast some, but not so much.
LFP batteries are 1/2 the weight of FLA batteries or less. The mini I use weight 19lbs.
LFP do not vent or off-gas when charging
LFP batteries can be charged at MUCH higher rates than FLA
LFP are less flamable than their Lithium ion cousins. Meaning you pretty much have to drive a nail through the LFP battery to make it vent then provide a spark to make it burn. When it vents from this the gas is hydrogen.

What this all means is the 12v mini I list has the capacity of 4 deep cycle lead acid batteries for 1/2 the weight of one.



The 100Ah LFP battery I list has enough juice in it to run my ASV with heater and heated tube on for 3.5 nights. I stuck wth 12v because I also need to run an oxygen concentrator as well. When I do that the battery only has enough juice for 1 full night.

The way I run things is I always run my cpap off the battery at night and I have the charger on a wall timer set for noon to 4pm to recharge it. Typically it takes just over an hour to recharge from 75% to full.

Note - you MUST use a LFP charger with the LFP battery - other charge profiles/voltages are not the same and either won't fully charge them or will damage them as they charge.

Self discharge on these is pretty minimal which I like very much. I've not had to try but I understand they are not good in cold temperatures. Since I live indoors for our northeast winters should be OK They all seem to be rated for many times the number of cycles than other chemistries which I guess offsets the higher cost. Maybe one day these will be much closer in cost to their lead acid counterparts.

Well, when you consider the extra usable DOD on them they are pretty close to parity or just a bit more expensive. 12v 100ah AGM runs about $180ish, but you can't go below 50%.

And you are right, they are typically rated for 10k charge cycles with less than 10% loss of capacity typically. So 10 years verse 3 years on an AGM or deep cycle.

And if you are just using it for a resmed CPAP you can just get a single 24v 50ah LFP battery and the adapter cord off amazon for your model. Plus the charger and you can run like. I chose not to do this because I didn't know what the cpap would do with the 29.2v charge voltage. Ordinarily the PSU evens out the voltage to exactly what the cpap wants.

What you don't want to do is string them in series to get 24v without an active balancer. Otherwise the SOC will get unbalanced and cause issues. Active balancer aren't very expensive so it can be done easy enough. Just an added layer of complexity.

I got the resmed 12/24v PSU for my aircurve 10 on a black friday sale for $80. So if I ever do something different it is no problem.

And you can get cheaper batteries but you have to research and watch teardown videos to see which ones are crap and which are not. There are a lot of them on amazon for cheap but in the tear down they use B grade cells, smaller cells than specd so the capacity is half what the rating says, the cheapest BMS or none,and poor assembly quality.

For cold weather they have self heating models or ones with just a cold temp protection. Cold protections automatically shuts down charging at 32f and discharge at 0f on the good ones.

Some have bluetooth built in if you want fancy monitoring.

In my case I was just looking for simple and safe and not to heavy. So the LiTime mini fit the bill. If I turn off the tub and tube heater I can get 10 days out of the battery.