Building a CPAP battery backup

[CactusBob]

In the next week or two I am going to start the process for building a battery backup for mine and my wife's Cpap systems. This is for off grid and when power goes out.
They both draw about 150 watts a night and will run from 12v. That should go down once I move to 12v. In addition when I am off grid it will charge cell phones, and maybe run some low wattage dc lights.

I would like to be able to charge from solar, shore power or alternator if necessary

the batteries I'm looking at are 4 Costlight 150ah cells
solar panels I am going to get at SanTan Solar are 250 or 300w. I believe I need to run them in parallel so MC4's for that
BMS - unknown
Charge - controller unknown
Cabling - 10g minimum
Fuse block - unknown
Battery box - I have a plastic ammo can type that should fit everything

Inverter - I'm not looking at running any AC loads off this at this time, however I may put an inverter aside as a failsafe in case the 12v cord to my cpap dies I cant still power it, since its peak draw is 285W I figure a 500 w should work for that.

Have I missed anything that's needed?
If anyone has recommendations for specific components that are good quality and cost effective it is highly appreciated. I am not looking at spending a fortune but would like to get the most bang for the buck.
Any ideas are welcome even if it means going a different route than what I'm looking at.

Thank you in advance,
Bob

 

[snoobler]

No specifics, but food for thought:

3.2 * 4 * 150 = 1920Wh - about 6X what you need for a night.

Will loves the cheap "dumb" DALY BMS. For what is perceived to be a low current application, that may suffice. I paid about $20 for a 60A 4S DALY from Amazon about 6 months ago.

How sensitive is the CPAP to voltage? It might make sense to power the CPAPs from a DC-DC converters that takes a wider input range (maybe 8-20V) and puts out a steady 12V. These are usually about $20-30 on Amazon.

Concerning the solar panels, if you get those, you aren't limited to parallel, but you will be forced into an MPPT controller since they are going to have a 30-36Vmp or so, and that's not compatible with a cheap 12V PWM controller.

 

[Alphacarina]

I ran my wife's CPAP on a 22 AH Motorcycle AGM battery when we were cruising on our boat - Recharged it during the day from the engine alternator. Her Devilbiss Intellipap doesn't draw much when running on 12 volts, but then the Humidifier doesn't work on 12 volts - I think that's more of the AC wattage than the CPAP power. With the fresh outdoor air, she never missed not using the Humidifier

Before you buy big batteries and large solar panels, I would run both of your machines on 12 volts for a few nights and see what capacity you actually need and then select solar to recharge maybe 150% of your actual needs - You might get by with a smaller, lighter, cheaper system than you're thinking

Don

 

[sshibly]

My resmed (heated) does not consume that much, I will killawatt it tonight for ya.
I use it in my van with the RESMED 12v adapter and an AGM starting battery, 90Ah, I don't recharge for days. 7 hours a night.

 

[snoobler]

Bob's dug into this before:

How to power a cpap

I am thinking of using lifepo4 batteries to build the battery bank for the cpap. It is more expensive but it saves a whole lot of weight I don't feel like lugging around. The AGM's I have seen weigh about 24lbs for 35AH battery. Plus its much easier to find an inexpensive case to build with...

diysolarforum.com

 

[CircuitsActivated]

I am rather interested in what you find to work for you. I use a ResMed S10 autocpap every night. I too and looking for a solution for backup or emergency use.

 

[CactusBob]

Bob's dug into this before:

How to power a cpap

I am thinking of using lifepo4 batteries to build the battery bank for the cpap. It is more expensive but it saves a whole lot of weight I don't feel like lugging around. The AGM's I have seen weigh about 24lbs for 35AH battery. Plus its much easier to find an inexpensive case to build with...

diysolarforum.com

Yes, I have dug into this before, the last time I was trying to figure out if it was better to bay a unit or build one and with the help of those here I decided to try the build route. Now I am trying to find out the best components to use and what is needed to charge and best use the batteries I am looking at. Is this overkill, yes but I would rather be able to run two cpaps for over a week without charging if I ever had to rather than have to worry about charging everyday. If your thinking that I am just a troll or here to waste everyone's time then you are mistaken. I figured it was better to start a new thread than continue the other one where info could get lost easily. If you feel I've wasted your time, my apologies.

Bob

 

[sshibly]

Bob,
Sorry, No question is ever taken as a trolling question, trust me, I did not know LFE from my chunky azz when first came here. Ask away.
I am sorry, I have been sidelined with Spring cleanup stuff and did not get a chance to do a draw test on my ResMed
25Ah battery will be fine,

When you say, you don't want to charge regularly, I would suggest getting a set of EVE 280AH cells for a 280 AH 12V battery,
This will last you a week easily if not more.

Building is always better if you have the time, biggest hurdle for me (an engineer by degree) was to pick the right "stuff" for the project for charging, testing, cables, BMS etc.
Happy to share my list of "KISS" I short listed.

If you want to buy, get a cheapo one from Amazon like MIADY 36 ah for $109,
get 3 and connect them in parallel for mucho amps.

I can make you the cables [FOC to you, just pay it forward], happy to assist ya

 

[efmrrt]

Bob,

Do you have the 12 volt adapter plug for your S10? Also can you get by without the heated humidity or heated circuit for a night? How many nights are you looking at using this? Problem with buying a ready made unit is that the current on the 12 volt adapter maybe limited and sometimes don't always work. Its a safety feature of the lower end pre-made units. Also what is your pressure set at. The higher the pressure the higher the power consumption. Seems to be an on going question. I'm working on a build right now for PAP users , if I get time this weekend I'll put it together, test it and do a write up on it.

 

[snoobler]

Yes, I have dug into this before, the last time I was trying to figure out if it was better to bay a unit or build one and with the help of those here I decided to try the build route. Now I am trying to find out the best components to use and what is needed to charge and best use the batteries I am looking at. Is this overkill, yes but I would rather be able to run two cpaps for over a week without charging if I ever had to rather than have to worry about charging everyday. If your thinking that I am just a troll or here to waste everyone's time then you are mistaken. I figured it was better to start a new thread than continue the other one where info could get lost easily. If you feel I've wasted your time, my apologies.

Bob

I was directing the poster to that thread because there were multiple posters with kill-a-watt data in there. I could have been way more clear in my intent.

Had I believed this thread was inappropriate, I would not have responded constructively, and I would have deleted it as a moderator.

 

[Alphacarina]

When you say, you don't want to charge regularly, I would suggest getting a set of EVE 280AH cells for a 280 AH 12V battery,
This will last you a week easily if not more.

Probably more like a month, if not more

Don

 

[sshibly]

CPAP Bat solution, stuff to consider:
1. How long you sleep
2. Stationary? Mobile solution?

I hate lifting heavy batteries and bending over to check/move them, so I like a light solution like 20lbs

Miada has a 100 ah battery (399$
plus
Victron Charger (always connected, use bluetooth to turn it off/on, or set voltage ranges)

 

[Maast]

Once you get into using a DC-DC converter to keep the voltage applied to the CPAP machine stable (which I recommend) IMO the losses there + the need for a charging solution argue strongly for getting a small 500-1000w inverter/charger and then connect your panels to the battery via a MPPT solar charge controller.

That'll give you the ability to run the CPAP and charge phones + plug in any other small device like LED lights or even a coffee maker or small microwave.

I mean, it's possible to do a straight DC system on the cheap by using a meanwell-type current limiting power supply floating at 13.4v (3.35v/cell) so you dont cook your batteries, but I wouldnt recommend it.

 

[MontanaClan]

Just built one for my mother in law who still loves to get out and tent camp a couple times a year. I bought a 36 ah lithium battery off amazon (Miady) and a foldable 100w panel off ebay (Dokio - comes with a simple charge controller). My ResMed 10 uses about 330 wh with the heater and humidifier in use. That battery will give about 460 wh in capacity, and based on a 5 hour charge day and a 75% derating on the solar panel, the panel should produce at least 375 wh recharge on a decent day in sunny southern Utah where she's camping. So as long as she puts the solar pane out each day, that system should be plenty to recharge itself and allow cell phone charging without having to start her car.

All guts of the battery cords, and charge controller will be contained in a plastic ammo box so all she has to do is plug in the solar panel to the cable that will be coiled up in the ammo box. Her CPAP runs on 12v (my ResMed uses 24v), so she can plug it directly in with a standard barrel connector that I'll have pre-wired in the box as well. Weight and portability is important... with lithium battery, the box will weigh under 7 pounds, and the folded flexible solar panel is only about 5 pounds.

 

[MrNatural22]

One idea on Cpap or Bpap operation dawned on me so I was curious To see how much use I would get from one of the used but tested at 100% capacity Valence 40ah 500wh U1 12rt batteries for my Bpap machine out camping on my Respronics 12v operation Bpap with a lighter plug on the battery and 12v cord adapter from the machine.

I have been using it for two 8.5 hour nights with the pre heated wet section operating on level 1 out of 5 with no problems. (Using it without moisture is quite uncomfortable as it drys out your nasal passage) very compact and light LiFePo (only 14lbs) Tonight will be the 3rd night with out charging.

I do unplug from the battery when I’m not sleeping and there is no issues doing that.
Don’t know about other machines but the respronics is fine unplugged.

I don’t know the specifics on how much power it uses at this time. I’ll post tomorrow on how it’s doing.

 

[jpcjtrtj]

I just built this smal box for my cpap: 4 x 25 Ah LIFPO4 Fortune cells ($29 each plus delivery) with a Daly 12v 4S 40 amp BMS ($15.60); in a box ($25) with Anderson connector for solar or AC charging ($12 for 4) and cigarette lighter port ($7) for CPAP 12 V adapter. I added a 25 amp fuse ($19 for 4) on the charge line for the 20 amp solar charge controller ($18). I can do a spreadsheet and link the items and prices if anyone wants.

My 35 Agm battery lasted 4 nights without charging last week for eight hour nights; I’m guessing I will get 5-6 nights out of this; but one 100 watt solar panel, a sunny day and the charge controller should recharge to 100%. Unit weighs in at 7.5 pounds and fits under the CPAP.

No more lifting the lead acid battery over my head to set up and take down. I like this build. It tested at almost 27 AH on its first cycle and you can plug in a small (100-300 Watt) inverter for small electronics/iPhone/iPad charging.

 

[roadrunner]

there's your answer their Bob, i would build that last one, i just bought these from batteryhookup, 4 lifepo4 for $60 plus shipping, which not much for ship. i bought 8 of them and with shipping came out to around $140.00

 

[CactusBob]

there's your answer their Bob, i would build that last one, i just bought these from batteryhookup, 4 lifepo4 for $60 plus shipping, which not much for ship. i bought 8 of them and with shipping came out to around $140.00

Thanks for posting, i've been off for awhile due to planning for two memorials this summer back east and had to put a loved family dog down this weekend so I have shelved this idea for awhile. Also since Arizona is on fire again camping has been postponed for the summer

I just built this smal box for my cpap: 4 x 25 Ah LIFPO4 Fortune cells ($29 each plus delivery) with a Daly 12v 4S 40 amp BMS ($15.60); in a box ($25) with Anderson connector for solar or AC charging ($12 for 4) and cigarette lighter port ($7) for CPAP 12 V adapter. I added a 25 amp fuse ($19 for 4) on the charge line for the 20 amp solar charge controller ($18). I can do a spreadsheet and link the items and prices if anyone wants.

My 35 Agm battery lasted 4 nights without charging last week for eight hour nights; I’m guessing I will get 5-6 nights out of this; but one 100 watt solar panel, a sunny day and the charge controller should recharge to 100%. Unit weighs in at 7.5 pounds and fits under the CPAP.

No more lifting the lead acid battery over my head to set up and take down. I like this build. It tested at almost 27 AH on its first cycle and you can plug in a small (100-300 Watt) inverter for small electronics/iPhone/iPad charging.

This looks super promising, when I get time I hope you dont mind a PM for some questions. If you could post the links that would be awesome. Thank you for this

Thanks guys
Bob

 

[efficientPV]

I have simple circuit to power 24V Resmed from 12V and provide correct signal for center pin. My use without humidity is just a little over 100WH, 27W peak and 10AH a night @12V. My coverter automatically turns on and off with the sun. Kind of a rude alarm clock just so I forget to turn it off in the morning. It consumes 3.5W when hot in use, only a hair difference between off and standby.

 

[jpcjtrtj]

Here's the part list, links to amazon, and prices for my build. I bought the tools for other builds, so, I don't count them in my overall cost. Also, you'll have leftovers on connecters, fuses, wire, etc. I've also priced out a cheap power supply you can use to charge it; or you can hook it up to a 100 watt solar panel with the solar charge controller i listed (should charge in less than a day). I also included a link to a small 300 watt inverter you can plug in for other things like charging cell batteries, ipads, computers . . . Electric car parts charges $75 for the delivery, so you might want to source the batteries somewhere else; but I liked their customer service and can do attitude, plus they are in the USA. You need some zip ties to hold the cells together and a roll of electrical tape and something to cover the terminals (I cut up a clear thin plastic sheet cutting board from dollar tree)

Item	Link	Price
4 x 25Ah Lithium LiFePO4 LFP Aluminum Shell Battery	Affordable Electric Vehicle Batteries & Components from Electric Car Parts Company Electric Car Parts Company is your one-stop-shop for affordable electric vehicle parts and components including batteries. Shop our selection and order now! www.electriccarpartscompany.com	$117.60​
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ALLPOWERS 20A Solar Charger Controller Solar Panel Battery Intelligent Regulator with USB Port Display 12V/24V	Amazon.com : ALLPOWERS 20A Solar Charger Controller Solar Panel Battery Intelligent Regulator with USB Port Display 12V/24V : Garden & Outdoor Amazon.com : ALLPOWERS 20A Solar Charger Controller Solar Panel Battery Intelligent Regulator with USB Port Display 12V/24V : Garden & Outdoor www.amazon.com	$17.99​
GG Grand General 55260 Black 10-Gauge Primary Wire, 25 Ft	Amazon.com: GG Grand General 55260 Black 10-Gauge Primary Wire, 25 Ft: Automotive Buy GG Grand General 55260 Black 10-Gauge Primary Wire, 25 Ft: Single Lead - Amazon.com ✓ FREE DELIVERY possible on eligible purchases www.amazon.com	$12.99​
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Wirefy 120 PCS Heat Shrink Wire Connectors - Electrical Connectors Kit - Marine Automotive Crimp Terminals	Amazon.com: Wirefy 120 PCS Heat Shrink Wire Connectors - Electrical Connectors Kit - Marine Automotive Crimp Terminals: Home Improvement Buy Wirefy 120 PCS Heat Shrink Wire Connectors - Electrical Connectors Kit - Marine Automotive Crimp Terminals: Butt - Amazon.com ✓ FREE DELIVERY possible on eligible purchases www.amazon.com	$16.99​
total		$243.44​
Tools		Price
IWISS Ratcheting Crimping Tool Set 8 PCS - Quick Exchange Jaw for Heat Shrink, Non-Insulated, Open Barrel, Insulated and Non-Insulated Ferrules AWG 20-2	IWISS Ratcheting Crimping Tool Set 8 PCS - Quick Exchange Jaw for Heat Shrink, Non-Insulated, Open Barrel, Insulated and Non-Insulated Ferrules AWG 20-2 - - Amazon.com IWISS Ratcheting Crimping Tool Set 8 PCS - Quick Exchange Jaw for Heat Shrink, Non-Insulated, Open Barrel, Insulated and Non-Insulated Ferrules AWG 20-2 - - Amazon.com www.amazon.com	$48.99​
TEMCo Hammer Lug Crimper Tool 5 Year Warranty	TEMCo Hammer Lug Crimper Tool 5 Year Warranty - Battery Terminal Crimper - Amazon.com TEMCo Hammer Lug Crimper Tool 5 Year Warranty - Battery Terminal Crimper - Amazon.com www.amazon.com	$23.94​
1500 Watt 11 Amp Dual Temperature Heat Gun	1500 Watt 11 Amp Dual Temperature Heat Gun 1500 Watt Dual Temperature Heat Gun www.harborfreight.com	$16.99​
		$89.92​
	Extra
300Watt Pure Sine Wave Power Inverter DC 12volt to AC 120volt Car Converter Adapter with Dual USB Ports for Smartphones Laptops Tablets	Amazon.com: 300Watt Pure Sine Wave Power Inverter DC 12volt to AC 120volt Car Converter Adapter with Dual USB Ports for Smartphones Laptops Tablets: Car Electronics Amazon.com: 300Watt Pure Sine Wave Power Inverter DC 12volt to AC 120volt Car Converter Adapter with Dual USB Ports for Smartphones Laptops Tablets: Car Electronics www.amazon.com	$55.96​
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