SOK 12V 100Ah + Victron Charger for CPAP... UPS?

[BeerMeister]

This is my first post here, so hello to all!

Battery: SOK 12V 100Ah (New)
Charger: Victron Blue Smart 12V/15A (Also new)
CPAP: ResMed Airsense 10 Autoset + ResMed 12V adapter (90 Watts/7.5 Amps max)

I wasn't planning on making a UPS system for my CPAP, but since the charger can be left connected to battery I may have done so!
I wanted a more reliable option than grid power, and something I could also use when camping.
Seems like it will work as a UPS just fine, but also seems odd that there are no commercial UPS systems that use any type of lithium batteries.
Might be that I will get a shorter battery life connected to charger continuously vs. full discharge and charge cycles... Any thoughts on this?

I tried a new APC Back-UPS 1500, but it can only power CPAP for about 3 hours. (Now it's powering gaming router/DSL modem/switch) This thing uses 2 fat lead-acid gel batteries stuck together -same tech as older models I have from late 90's.
And also tried a cute little 300 Watt solar charger from Tenergy but it wouldn't go the distance either. (It's great for less demanding tasks though)

And do I need to make any changes to the custom charger profile below, based on my usage? (e.g. mainly at home connected to AC power and battery)

According to Current Connected, Victron chargers should be set these custom settings: (And I have done so -with phone app)

Victron’s Li-Ion profile is NOT sufficient for non-Victron LiFePO4 batteries. Enter configuration and turn on “ADVANCED” switch, then select “Custom” charge preset. Then click “Advanced Battery Settings”.

The battery preset should be set to “User Defined”. Turn on “Expert Mode” switch.

Charge Voltage Settings:
Absorption Voltage: 14.6v
Float Voltage: 13.8v
Storage Voltage: 13.6v
Recondition Voltage: Disabled
BatterySafe: Disabled

Voltage Compensation:
Temperature Compensation: Disabled

Bulk:
Bulk Time Limit: 24 Hours
Re-bulk Current: Enabled, set to full output current of charger, typically 25A

Absorption:
Absorption Duration: Fixed
Absorption Time: 1 Hr
Repeated Absorption: Every 7 days

Recondition:
Recondition Stop Mode: Fixed time
Recondition Duration: 15M (This is the minimum allowed setting. It is already disabled in charge voltage settings, but set to this as a safety precaution)

 

[sunshine_eggo]

This is my first post here, so hello to all!

Battery: SOK 12V 100Ah (New)
Charger: Victron Blue Smart 12V/15A (Also new)
CPAP: ResMed Airsense 10 Autoset + ResMed 12V adapter (90 Watts/7.5 Amps max)

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

that unit used about 0.3kWh/night, so your 1280Wh battery should be good for 4 days with no charging.

Building a CPAP battery backup

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...

diysolarforum.com

Seems like it will work as a UPS just fine, but also seems odd that there are no commercial UPS systems that use any type of lithium batteries.

They're called solar generators, and they're expensive.

Might be that I will get a shorter battery life connected to charger continuously vs. full discharge and charge cycles... Any thoughts on this?

Probably not.

And do I need to make any changes to the custom charger profile below, based on my usage? (e.g. mainly at home connected to AC power and battery)

According to Current Connected, Victron chargers should be set these custom settings: (And I have done so -with phone app)

IMHO, the Victron LFP settings are fine. Current Connected claims to have data supporting their recommendations and are working on presenting it.

 

[BeerMeister]

that unit used about 0.3kWh/night, so your 1280Wh battery should be good for 4 days with no charging.

Yes my setup is a bit overkill, but can't hurt to go big here: When I usually camp in Fall it can be cold enough to snow, and then CPAP would draw much more wattage for heated tubing and water chamber. (Vs. room temperature operation)

They're called solar generators, and they're expensive.

Indeed, but the UPS I just bought was a bit over $200... And still uses the same lead acid batteries as 20 years ago, when other battery powered implements like power tools have moved from NiCad/NiMH to lithium batteries. Why no progression here? And most solar generators aren't marketed as UPS replacements, and a good thing as many of them can't even switch to inverter operation on their own.

 

[sunshine_eggo]

Yes my setup is a bit overkill, but can't hurt to go big here: When I usually camp in Fall it can be cold enough to snow, and then CPAP would draw much more wattage for heated tubing and water chamber. (Vs. room temperature operation)

Not overkill. CPAPs are kinda important.

Indeed, but the UPS I just bought was a bit over $200... And still uses the same lead acid batteries as 20 years ago, when other battery powered implements like power tools have moved from NiCad/NiMH to lithium batteries. Why no progression here?

Comparing apples to oranges. NiCd was a necessary evil. NiMH was much better. Tools have very low capacity compared to a UPS and Lithium ion in these sizes is cheaper due to the proliferation of cheap NCA 18650 cells (laptops, Tesla, etc.).


Would you pay $400 for a UPS that gives you the same run time?


Lastly, LFP and Lithium in general is a bad standby option, i.e., they actually degrade when stored at 100% SoC especially at elevated temperature.

 

[SoCalKevin]

I have the exact same CPAP and use it daily while camping.

Everyone is different of course, but i found that when i shut the heated hose and water portion off, it was MUCH more efficent and used very little power.

Oddly, i found i slept better and didnt have weird sinus issues after i shut the heating hose and water thing off.

For each is own, just sharing my experience.

 

[BeerMeister]

Would you pay $400 for a UPS that gives you the same run time?

Maybe! But my UPS also weighs 28 pounds, and even using drop in replacement lithium batteries would achieve longer run time with less weight -check it out, they even have over-charge and short circuit protection! (Must have it's own BMS):
Tenergy 12V Lithium Drop-in replacement for sealed lead-acid

Oddly, i found i slept better and didnt have weird sinus issues after i shut the heating hose and water thing off.

Yes I tried turning off humidification initially, but turned it back on to prevent dry nose and mouth.

 

[sunshine_eggo]

Maybe! But my UPS also weighs 28 pounds, and even using drop in replacement lithium batteries would achieve longer run time with less weight -check it out, they even have over-charge and short circuit protection! (Must have it's own BMS):
Tenergy 12V Lithium Drop-in replacement for sealed lead-acid

Another issue with UPS is they tend to have pretty high DC current for the battery capacity, e.g., a 1200W UPS will need to pull about 100A from the battery. That means you'll need a 100Ah LFP battery to sustain that current, and those are $350-400 for just the battery on the low end.

That battery you linked is only rated for 15A discharge, so that's 180W max. Fine for your CPAP, but not a lot else. FWIW, with a UPS or any inverter, you want to size it for the load. The APC1500 you were using was likely consuming a lot of capacity just by being powered on. It might make sense for you to get a much smaller UPS and then replace the battery.

Another thing you need to watch for with "drop in" batteries - they are sometimes rated based on the equivalent lead-acid rating, i.e., it says 10Ah, but that may mean, it will perform the same as a 10Ah SLA battery. 15A out of a 10Ah SLA will yield far less than 10Ah - probably closer to 5Ah. Doubt you want to pay $150 for a 5Ah battery.

Many pursue replacement of UPS batteries with LFP successfully. It would probably be best to rig a way to connect whatever battery you like externally.

Yes I tried turning off humidification initially, but turned it back on to prevent dry nose and mouth.

Yeah, this doesn't work for me either. Even with it on max (86°F), I sometimes wake up with the worst case of dry mouth.

 

[BeerMeister]

Yeah, this doesn't work for me either. Even with it on max (86°F), I sometimes wake up with the worst case of dry mouth.

My CPAP has a set temp for the humidification chamber's heater plate, but you can adjust the tubing temp. Got that at 75°F, and it needs at least that to prevent 'rainout'. (Excessive condensation)
86°F seems a bit low for a useful humidity, here are my machine's specs:

It also does have a humidity setting: from levels 1 to 8 and -I have it set at 4.

 

[sunshine_eggo]

My CPAP has a set temp for the humidification chamber's heater plate, but you can adjust the tubing temp. Got that at 75°F, and it needs at least that to prevent 'rainout'. (Excessive condensation)
86°F seems a bit low for a useful humidity, here are my machine's specs:
View attachment 95134

I've never investigated how it works. I may be adjusting tubing temp for all I know... Yep...

https://cpap.1800cpap.com/manuals/s9-series-fact-sheet.pdf

86°F is the max "ClimateLine" temp.

 

[BeerMeister]

I've never investigated how it works. I may be adjusting tubing temp for all I know... Yep...

Oh no! ResMed still has older manuals online:
https://www.resmed.com/en-us/sleep-apnea/cpap-parts-support/cpap-product-manuals/

 

[BeerMeister]

This setup has been working peachy!
So this weekend I unplugged the Victron charger and used CPAP for 2 nights on just battery.
According to the charger's data after charging yesterday, it charged my new SOK toy just under 40Ah. And since battery was full to start with, CPAP used about 20Ah per night.
(7.5 hours, 7.12 hours sleep times -and at 71°F room temp with humidification/heated hose on as usual)
So this DiY setup (while hardly being a budget option) has the power required to run my CPAP for days!
This is better than any commercial option that I've seen. (Short of a high power solar charger)
And with charger always connected to battery, it is effectively a UPS. (Just a more efficient 12V version)

 

[Saul]

This setup has been working peachy!
So this weekend I unplugged the Victron charger and used CPAP for 2 nights on just battery.
According to the charger's data after charging yesterday, it charged my new SOK toy just under 40Ah. And since battery was full to start with, CPAP used about 20Ah per night.
(7.5 hours, 7.12 hours sleep times -and at 71°F room temp with humidification/heated hose on as usual)
So this DiY setup (while hardly being a budget option) has the power required to run my CPAP for days!
This is better than any commercial option that I've seen. (Short of a high power solar charger)
And with charger always connected to battery, it is effectively a UPS. (Just a more efficient 12V version)

FYI
I use a 12VDC adapter for my CPAP and run it for a full night on a Ryobi 4AH drill battery.

 

[sunshine_eggo]

FYI
I use a 12VDC adapter for my CPAP and run it for a full night on a Ryobi 4AH drill battery.

Ah requires voltage to be a complete description of energy capacity.

What voltage?

 

[Substrate]

The problem with using an LFP "drop-in" for UPS duty when it originally had a lead-acid charge circuit is that if the absorb OR float charge in the ups is 13.6v or higher, given enough time, it will charge to full capacity. That could take days or weeks, without giving any significant rise in terminal voltage. THIS is what fools many that think their ups application is ok, but the battery seems to die early.

Full capacity, not voltage, is the real determination of how bad it is to hold an LFP at "full charge" (aka full capacity).

Soooo .. you would have to modify the charging circuit in the UPS to not have anything higher than 13.5v. You will be sacrificing some overall capacity, but won't be holding the battery at full-capacity charge either. Practically speaking, if you are already fully charged, and have modified the UPS for nothing higher than 13.5v, run it through a discharge to get it away from the top and now be limited by the 13.5v CV.

 

[BeerMeister]

Ah requires voltage to be a complete description of energy capacity.

What voltage?

Likely 18, I have a bunch of these as well. And a Ryobi adapter that has 5 USB and a 12V port. (And as a side note: the chargers for these batteries will refuse to charge if the battery is under a certain voltage, and I've cracked one of these batteries open and used the Victron charger to charge it from 3V to 14V... Then Ryobi charger works fine)

I've also found a better option for UPS: (Get it on sale for $209!!) Using 1 of these as my gaming PC's UPS

 

[Saul]

As a follow up. This weekend I was able to get 14 hours out of a 18V 4AH Ryobi drill battery. Ran until cutoff.
Phillips Dreamstation 2, Used without Heat or humidity.

Ryobi Battery Dock Power Connector
12-24 VDC adapter for dreamstation 2
Cigarette lighter adapter
Ryobi 18V One+ 4AH battery

 

[Grimmster]

Lastly, LFP and Lithium in general is a bad standby option, i.e., they actually degrade when stored at 100% SoC especially at elevated temperature.

Well the OP is talking about using the battery, not keeping it in standby. And you can always just charge to 80 or 90%, though again if the battery is being used then charging to higher SOC is fine.

 

[sunshine_eggo]

Well the OP is talking about using the battery, not keeping it in standby.

He literally described a standby application and asked if it affected battery life:

I wasn't planning on making a UPS system for my CPAP, but since the charger can be left connected to battery I may have done so!
I wanted a more reliable option than grid power, and something I could also use when camping.
Seems like it will work as a UPS just fine, but also seems odd that there are no commercial UPS systems that use any type of lithium batteries.
Might be that I will get a shorter battery life connected to charger continuously vs. full discharge and charge cycles... Any thoughts on this?

And you can always just charge to 80 or 90%, though again if the battery is being used then charging to higher SOC is fine.

Please describe how you would do this easily, reliably and consistently.

 

[Rabbit]

Likely 18, I have a bunch of these as well. And a Ryobi adapter that has 5 USB and a 12V port. (And as a side note: the chargers for these batteries will refuse to charge if the battery is under a certain voltage, and I've cracked one of these batteries open and used the Victron charger to charge it from 3V to 14V... Then Ryobi charger works fine)

I've also found a better option for UPS: (Get it on sale for $209!!) Using 1 of these as my gaming PC's UPS

The EB3A's are notoriously unreliable in actual use as UPS's. There are whole threads about this (I started two of them) on both this website and Bluetti's own. The short version is, this has failed both me and many others when used as a backup, and make me personally headachy for days.

 

[Rabbit]

This is my first post here, so hello to all!

Battery: SOK 12V 100Ah (New)
Charger: Victron Blue Smart 12V/15A (Also new)
CPAP: ResMed Airsense 10 Autoset + ResMed 12V adapter (90 Watts/7.5 Amps max)

I wasn't planning on making a UPS system for my CPAP, but since the charger can be left connected to battery I may have done so!
I wanted a more reliable option than grid power, and something I could also use when camping.
Seems like it will work as a UPS just fine, but also seems odd that there are no commercial UPS systems that use any type of lithium batteries.
Might be that I will get a shorter battery life connected to charger continuously vs. full discharge and charge cycles... Any thoughts on this?

I tried a new APC Back-UPS 1500, but it can only power CPAP for about 3 hours. (Now it's powering gaming router/DSL modem/switch) This thing uses 2 fat lead-acid gel batteries stuck together -same tech as older models I have from late 90's.
And also tried a cute little 300 Watt solar charger from Tenergy but it wouldn't go the distance either. (It's great for less demanding tasks though)

And do I need to make any changes to the custom charger profile below, based on my usage? (e.g. mainly at home connected to AC power and battery)

According to Current Connected, Victron chargers should be set these custom settings: (And I have done so -with phone app)

I made my own version of this about six weeks ago, after an EB3A let me down badly. I also have a Resmed 10, and am using exactly the same Victron charger. However, I bought a 50ah Li Time as my battery and added a small Victron inverter. (I think it's 350 watts.) I added this inverter for two reasons. Firstly, I have sleep apnea to such a level that my doc tells me there's a significant chance of death in the event that my machine fails. The AC adapter that the Resmed uses is known to generally be good for many, many years of continuous service, but I do not know this to be the case for the 12VDC adapter I also own and use for napping in my vehicle. So, even though it wastes a tiny amount of power, I consider it much safer to use the (super-reliable as well, and not too expensive) Victron inverter and AC power. The second reason is that 110 AC power-failure alarms are cheap and easy to get, where this isn't the case for 12VDC. I keep such an alarm plugged into the inverter on the same circuit at all times to wake me immediately in the case of some sort of breakdown. My setup is ugly and a bit inefficient but, I suspect, reliable as hell. And, for obvious reasons, reliable is absolutely what I'm after. Mine is working great, and I hope yours does too. I think there may be a commercial market out there for ultra-reliable medical-grade battery backups that is currently totally unaddressed.