Choosing a Battery

BigDaddy08 · Post by **BigDaddy08** » Thu Mar 15, 2018 12:03 pm

CapnLoki, I have been a lurker here for the last 2 months and have referenced your information while setting up my camping setup. I just wanted to thank you for the good material. I will be posting up my setup once it is complete but I spent $145 and got everything including a 35ah battery so I can run my Cpap for at least 3 nights. Many thanks

ducker · Post by **ducker** » Mon Apr 02, 2018 3:26 pm

Ok... CapnLoki - you've pretty much single handedly brought me to registering and posting on this forum

I've recently been using my CPAP, now a month in, and I'm trying to make some decisions on what I'll need for camping. I'll be camping with my son on Boy Scout trips, so weight/size is a little bit of a concern.
Larger, heavier batteries aren't a option. ResMed's name brand battery seems over priced for what I would suspect would be less than stellar performance.

The items I've been juggling around are the following:
Resmed official battery power station: $720 (doesn’t appear to last very long at all and is pricey)
Medistrom battery 1: $330
and then on top of that… there are countless other solutions like

giant battery 32000mAh battery: $110
Goal Zero Yeti : $200

And then I'd have to also get one of these based on pieces I've learned from this forum (ie. having an inverter is better than using AC output from a batter source in to the power adapter that is shipped with the Airsense 10)
DC Converter for Resmed : $84 - to be used with the Yeti, or with another adapter with the battery.

In a nutshell -- I want a battery that lasts 2-3 nights of approx 6-7 hrs, with out heat, preferably with humidity (I haven't tested at home if I would mind w/o the humidity yet)
The flexibility to possibly go longer than 2-3 nights either via solar charging, or plugging in to charge during the day. (ie. Scout Camp in the summer)

I personally feel, I could just go with out the CPAP machine, for a long weekend, but I would rather stick with it! Haven't missed a night since the first day I received it.

Thanks for any input you and any others may have!!

(So embarrassed, my dad's an Electrician, I just have playing around with the numbers... Amps,watts, volts...Gaaaaahh!!!

)

CapnLoki · Post by **CapnLoki** » Mon Apr 02, 2018 8:19 pm

ducker wrote: ↑
Mon Apr 02, 2018 3:26 pm
Ok... CapnLoki - you've pretty much single handedly brought me to registering and posting on this forum
...
Larger, heavier batteries aren't a option.
...
In a nutshell -- I want a battery that lasts 2-3 nights of approx 6-7 hrs, with out heat, preferably with humidity (I haven't tested at home if I would mind w/o the humidity yet)
The flexibility to possibly go longer than 2-3 nights either via solar charging, or plugging in to charge during the day. (ie. Scout Camp in the summer)

I personally feel, I could just go with out the CPAP machine, for a long weekend, but I would rather stick with it! Haven't missed a night since the first day I received it.
...

First - your need: 3 nights with average pressure of 7.5 will be only 15 Amp-hours if you can go without humidity. This could be handled by a 20 AH AGM battery - 12 pounds and $40. A bit heavier than the high priced lithium offerings, but a LOT cheaper. I would (and did) go up a size to the 35AH AGM -its a luggable 24 pounds, but another overkill solution is to just get a second 20AH.

If you really need humidity, then your need goes up a lot - perhaps to 40 AH or much more depending on settings. You might need several smaller AGMs, still fairly cheap, but to handle this with lightweight lithium would be $500 or more. However, if you're camping in a humid area you can probably go without a humidifier; I just got back from several days in DC where I was comfortable without humidifier or heated hose.

BTW, the Goal Zero 150 is just a 14 AH AGM battery with a fancy wrapping - it will be marginal for 3 nights. The 32000 is actually even less power - its about equivalent to 8 or 9 amp-hours at 12 volts. And yes, get the DC converter, it will save half the battery, both in $ and lbs. Solar power is workable if you have a good open space and you're just hanging out for a few days, but if its just for one or two camping trips a summer, you're better off just getting an extra, cheap AGM battery.

ducker · Post by **ducker** » Tue Apr 03, 2018 12:36 pm

Thank you so much for the reply CapnLoki!!

Do you have an suggestions for a 20 AH AGM battery? (something like THIS? )
The reason I was looking at the Yeti - was that it had the window dressing (the different connections)
So if I did go with a standard AH AGM battery what assorted accessories would I need to make this work?
I'd think I would need a few different adapters/connectors for the 20 AH AGM battery, outside of the CPAP DC converter. As I'm camping in a tent, I don't really want to have to also manage a bunch of wires on top the hose of the CPAP. I just see myself getting frustrated at the whole setup.

Your comment to get the converter to save $ and lbs. How exactly? Are your tentative numbers taking the converter into account? Because I'm not excited about the idea of carrying around another 10-15lbs in a backpack for a 20 AH AGM bettery

What would you suggest for a lithium battery that would last approx 2 days? I'm expecting that the majority of use cases will be where I am camping just Friday / Saturday night.
And/or will have the opportunity to charge via a plug typically during the day. Based on your estimation, it looks like I need ~ 5 AH a night (with out heat or humidity) that battery I linked COULD do it, but I would have to charge it every day for the next time. I'd rather have a bit more flexibility in the amount of power stored in a lithium battery.

Again, thanks for your input I greatly appreciate it!

Ron AKA · Post by **Ron AKA** » Tue Apr 03, 2018 1:04 pm

ducker wrote: ↑
Mon Apr 02, 2018 3:26 pm
In a nutshell -- I want a battery that lasts 2-3 nights of approx 6-7 hrs, with out heat, preferably with humidity (I haven't tested at home if I would mind w/o the humidity yet)
The flexibility to possibly go longer than 2-3 nights either via solar charging, or plugging in to charge during the day.

This is a long thread and I admit I have not read it all. I have found the ResMed Battery document very helpful in sorting out requirements to run on battery power. See this link:

ResMed Battery Guide

To use it you need to find your machine, what options you will use, and what you think your average pressure is. This will tell you the amps you need at 12 volts to run it. Multiply this times hours of use to get amp hours. Note that there are two sets of current estimations. One is for the ResMed standard 120 V AC to 24 Volt adapter combined with their 12 Volt DC to 120 Volt AC inverter. The other set of tables is for their optional 12 Volt DC to 24 Volt DC converter. Note that the current draw at 12 volts for this DC to DC converter is about 30% lower, at least in the comparisons I have looked up. There are big savings in current draw by not using the heated hose and turning the humidifier off.

My practical experience with my wife's ResMed S9 without the heated hose or humidifier and an inverter (non ResMed) is that we can easily get a few days off our trailer batteries. However they are two 6V golf cart batteries in series and probably weigh well over 100 lbs and probably have in the order of 200 amp hour capacity -- not good for back packing. For longer stays without power, I set up a 70 watt solar panel. Our experience has been that with reasonably sunny weather and long Canadian days, this panel can keep the batteries charged indefinitely. But again backpacking a solar panel would not be a lot of fun...

As for a battery all I can say is that I have used many standard auto batteries and so called deep cycle batteries. They generally do not have a long life. About the only difference I could see is that the deep cycle batteries have a shorter warranty period -- to protect them, not me! I have no experience with AGM batteries in deep cycle. If you are looking for a smaller size like 20 amp hours you may want to look at an aftermarket motorcycle battery at NAPA or the like. They do make them in the AGM design. They certainly would be more portable.

CapnLoki · Post by **CapnLoki** » Tue Apr 03, 2018 3:19 pm

ducker wrote: ↑
Tue Apr 03, 2018 12:36 pm
Thank you so much for the reply CapnLoki!!

Do you have an suggestions for a 20 AH AGM battery? (something like THIS? )
The reason I was looking at the Yeti - was that it had the window dressing (the different connections)
So if I did go with a standard AH AGM battery what assorted accessories would I need to make this work?
I'd think I would need a few different adapters/connectors for the 20 AH AGM battery, outside of the CPAP DC converter. As I'm camping in a tent, I don't really want to have to also manage a bunch of wires on top the hose of the CPAP. I just see myself getting frustrated at the whole setup.

Your comment to get the converter to save $ and lbs. How exactly? Are your tentative numbers taking the converter into account? Because I'm not excited about the idea of carrying around another 10-15lbs in a backpack for a 20 AH AGM bettery

What would you suggest for a lithium battery that would last approx 2 days? I'm expecting that the majority of use cases will be where I am camping just Friday / Saturday night.
And/or will have the opportunity to charge via a plug typically during the day. Based on your estimation, it looks like I need ~ 5 AH a night (with out heat or humidity) that battery I linked COULD do it, but I would have to charge it every day for the next time. I'd rather have a bit more flexibility in the amount of power stored in a lithium battery.

Again, thanks for your input I greatly appreciate it!

Yes, the battery you linked to should be fine. I also like the Universal Battery brand - they have the UB12220. The extra stuff needed is listed in the 12th post of this thread, on the first page. Basically its a BatteryTender charger which comes in three sizes. This is a high quality trickle charger, very gentle on the battery. It comes with all of the cables needed except the "cigarette lighter socket" which is under $10. The socket will accept the ResMed converter (or the Respironics 12V cable, or an inverter if you're so inclined). I like a box, but you can also use "boots" to protect the terminals which should not be left exposed. You can get by with under $80 but I think most would go a size up on the battery and charger, so for most the tab would be about $120. The charger of coarse doesn't have to be carried in, only the battery, cable and converter.

The issue with the 12/24 volt converter is that it is 90% or more efficient, while inverters tend to be 60% or worse, in spite of their advertising hype. This means that for a given load, you'll need a battery almost twice as big. My guestimate of your load is from the ResMed Battery Guide, which gives numbers for both using an inverter and using the converter, with numerous corroborations from forum members. It assumes the converter is used, but be advised that every situation is different, so every estimate should include "give or take 30%."

If you only need 2 nights with no humidity, and use the converter, you might get by with a basic Lithium pack that measures 100 watt-hours, the airline limit. The "32000" you mentioned has been claimed to run for two night so it might be worth a try. Since I've never run a cpap on lithium I have trouble doing more then passing on observations of other users, but I generally tend to go with large overkill, which is a lot easier (or at least cheaper) with AGM batteries. BTW, if you recharge during the day, you can charge 70-80% ina few hours but topping off usually takes 5 hours or more.

So I guess the issue is, how far to you have to carry in? If its 100 yards, I'd go with the AGM; if its a mile, then I'd be trying the lithium.

Cici · Post by **Cici** » Sun Apr 08, 2018 2:50 pm

CapnLoki wrote: ↑
Tue Apr 03, 2018 3:19 pm

ducker wrote: ↑
Tue Apr 03, 2018 12:36 pm
Thank you so much for the reply CapnLoki!!

Do you have an suggestions for a 20 AH AGM battery? (something like THIS? )
The reason I was looking at the Yeti - was that it had the window dressing (the different connections)
So if I did go with a standard AH AGM battery what assorted accessories would I need to make this work?
I'd think I would need a few different adapters/connectors for the 20 AH AGM battery, outside of the CPAP DC converter. As I'm camping in a tent, I don't really want to have to also manage a bunch of wires on top the hose of the CPAP. I just see myself getting frustrated at the whole setup.

Your comment to get the converter to save $ and lbs. How exactly? Are your tentative numbers taking the converter into account? Because I'm not excited about the idea of carrying around another 10-15lbs in a backpack for a 20 AH AGM bettery

What would you suggest for a lithium battery that would last approx 2 days? I'm expecting that the majority of use cases will be where I am camping just Friday / Saturday night.
And/or will have the opportunity to charge via a plug typically during the day. Based on your estimation, it looks like I need ~ 5 AH a night (with out heat or humidity) that battery I linked COULD do it, but I would have to charge it every day for the next time. I'd rather have a bit more flexibility in the amount of power stored in a lithium battery.

Again, thanks for your input I greatly appreciate it!
Yes, the battery you linked to should be fine. I also like the Universal Battery brand - they have the UB12220. The extra stuff needed is listed in the 12th post of this thread, on the first page. Basically its a BatteryTender charger which comes in three sizes. This is a high quality trickle charger, very gentle on the battery. It comes with all of the cables needed except the "cigarette lighter socket" which is under $10. The socket will accept the ResMed converter (or the Respironics 12V cable, or an inverter if you're so inclined). I like a box, but you can also use "boots" to protect the terminals which should not be left exposed. You can get by with under $80 but I think most would go a size up on the battery and charger, so for most the tab would be about $120. The charger of coarse doesn't have to be carried in, only the battery, cable and converter.

The issue with the 12/24 volt converter is that it is 90% or more efficient, while inverters tend to be 60% or worse, in spite of their advertising hype. This means that for a given load, you'll need a battery almost twice as big. My guestimate of your load is from the ResMed Battery Guide, which gives numbers for both using an inverter and using the converter, with numerous corroborations from forum members. It assumes the converter is used, but be advised that every situation is different, so every estimate should include "give or take 30%."

If you only need 2 nights with no humidity, and use the converter, you might get by with a basic Lithium pack that measures 100 watt-hours, the airline limit. The "32000" you mentioned has been claimed to run for two night so it might be worth a try. Since I've never run a cpap on lithium I have trouble doing more then passing on observations of other users, but I generally tend to go with large overkill, which is a lot easier (or at least cheaper) with AGM batteries. BTW, if you recharge during the day, you can charge 70-80% ina few hours but topping off usually takes 5 hours or more.

So I guess the issue is, how far to you have to carry in? If its 100 yards, I'd go with the AGM; if its a mile, then I'd be trying the lithium.

I've been trying to follow along and think I may be okay, but wanted to double-check.

I will be taking a nine-hour flight soon and want to be able to use my ResMed AutoSense 10 without the humidifer during flight.

I purchased the NexGadget 24000mAh external power bank with and AC outlet. It says it can be used to power equipment within 95W.

My ResMed AC adapter says it is 90W.

Will this work for the occasional night without access to power? At $99, it was much cheaper than the $270-$450 for "cpap" battery packs out there but if it won't work, then I will bite the bullet and get one made specifically for cpaps...

Thoughts?

Thanks much,

RafterDenise · Post by **RafterDenise** » Tue Apr 10, 2018 6:51 pm

Check with your airline, but last I heard, this is above the legal limit to take on an airplane. That said, I agree that CPAP batteries are overpriced for what they are. You're on the right track, but may need something smaller for airplane travel.

CapnLoki · Post by **CapnLoki** » Wed Apr 11, 2018 5:14 am

Cici wrote: ↑
Sun Apr 08, 2018 2:50 pm
I've been trying to follow along and think I may be okay, but wanted to double-check.

I will be taking a nine-hour flight soon and want to be able to use my ResMed AutoSense 10 without the humidifer during flight.

I purchased the NexGadget 24000mAh external power bank with and AC outlet. It says it can be used to power equipment within 95W.

My ResMed AC adapter says it is 90W.

Will this work for the occasional night without access to power? At $99, it was much cheaper than the $270-$450 for "cpap" battery packs out there but if it won't work, then I will bite the bullet and get one made specifically for cpaps...

Thoughts?

Thanks much,

Yes, this might work - if anything its a bit small. First, the numbers: 24000mAh is the total of the 3.7volt lithium cells. This converts to about 89 Watt-hours, the new way to rate lithium packs. Most US airlines have a 100 Watt-hour limit, though in some cases they allow 140Watt-hours. 89wh is about the same as 7.4 amp-hours at 12 volts so this should be enough to run without humidity for a night. However, the inverter is probably about 60% efficient, so the net is around 5 amp-hours. Add to this that the airline cabin pressure it the same as an altitude of 6000-8000 feet, which the pump compensates for at the cost of more power. Also, if you use high pressure it takes more power.

(The 90 and 95 watt ratings are meaningless here - without the humidifier/heated hose the load is around 15 watts.)

Bottom line, this will work but probably not for 9 hours- you might only get 6-7 hours. Also, don't count on gas left in the tank- you'll need a generous 5 hours or more to recharge for the return trip.

CapnLoki · Post by **CapnLoki** » Wed Apr 11, 2018 5:18 am

RafterDenise wrote: ↑
Tue Apr 10, 2018 6:51 pm
Check with your airline, but last I heard, this is above the legal limit to take on an airplane. That said, I agree that CPAP batteries are overpriced for what they are. You're on the right track, but may need something smaller for airplane travel.

Sorry, this is wrong- this pack is well under the airline limit. They should have included the watt-hour rating, but it works out to 89 wh,which is under the 100 wh limit.

ducker · Post by **ducker** » Thu May 03, 2018 9:30 am

I believe I'm missing a key piece in my puzzle

what is the additional adapter I'd need to connect:
DC Converter for Resmed
to
something like: giant battery 32000mAh battery

It's something that changes the output from the battery to a female DC plug for the resmed-dc-converter to then plug in to it.

Goofproof · Post by **Goofproof** » Thu May 03, 2018 10:04 am

CapnLoki wrote: ↑
Wed Apr 11, 2018 5:14 am

Cici wrote: ↑
Sun Apr 08, 2018 2:50 pm
I've been trying to follow along and think I may be okay, but wanted to double-check.

I will be taking a nine-hour flight soon and want to be able to use my ResMed AutoSense 10 without the humidifer during flight.

I purchased the NexGadget 24000mAh external power bank with and AC outlet. It says it can be used to power equipment within 95W.

My ResMed AC adapter says it is 90W.

Will this work for the occasional night without access to power? At $99, it was much cheaper than the $270-$450 for "cpap" battery packs out there but if it won't work, then I will bite the bullet and get one made specifically for cpaps...

Thoughts?

Thanks much,
Yes, this might work - if anything its a bit small. First, the numbers: 24000mAh is the total of the 3.7volt lithium cells. This converts to about 89 Watt-hours, the new way to rate lithium packs. Most US airlines have a 100 Watt-hour limit, though in some cases they allow 140Watt-hours. 89wh is about the same as 7.4 amp-hours at 12 volts so this should be enough to run without humidity for a night. However, the inverter is probably about 60% efficient, so the net is around 5 amp-hours. Add to this that the airline cabin pressure it the same as an altitude of 6000-8000 feet, which the pump compensates for at the cost of more power. Also, if you use high pressure it takes more power.

(The 90 and 95 watt ratings are meaningless here - without the humidifier/heated hose the load is around 15 watts.)

Bottom line, this will work but probably not for 9 hours- you might only get 6-7 hours. Also, don't count on gas left in the tank- you'll need a generous 5 hours or more to recharge for the return trip.

Question to CapnLoki: The Alt of the plane at 6000ft is less than sea level. However XPAP works by using the difference between outside air pressure, in this case @ 6000 ft (lower). Would not in this case make the needed treatment lower too? I would think the pressure should be a ratio that's also lower, all the XPAP pressure is there for is to keep the pipe open.

Also @ 6000 ft, I would then think the fan may run faster, but the work done would be the same, I don't think it should cause the amps to be much higher. If it does require less pressure to keep your airway open at 6000 ft, lowering the pressure could cause less power to be drawn. Does this make sense.... Jim

It also possible the XPAP does this on it's own, as it supports auto alt adjustment. Just thinking!

chunkyfrog · Post by **chunkyfrog** » Thu May 03, 2018 11:03 am

Just a little question: this thread (and Loki) is so brilliant that . . .
Why is it not stickied?

Goofproof · Post by **Goofproof** » Thu May 03, 2018 11:13 am

chunkyfrog wrote: ↑
Thu May 03, 2018 11:03 am
Just a little question: this thread (and Loki) is so brilliant that . . .
Why is it not stickied?

So true! Or maybe create a Sticky Page, but I'm sure the problem would be getting others to use it.

The Front Page is like a Waste Can, only the top is seen, but it's used. Jim

chunkyfrog · Post by **chunkyfrog** » Thu May 03, 2018 11:19 am

Then let us just recognize Loki for his amazing contribution.
Looking ahead to the disaster season (all year long, any more),
any of us could ultimately need to use battery power.
Everyone should know that AFFORDABLE alternatives are available (and seen here).
Of course, Resmed is probably "not amused", but that thought makes me happy.

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