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Four nights on battery
#1
I'm heading off soon for a five or six night stay in a remote cabin and have prepared for that trip along with the occasional power outages that we have here in my home.

Here's what I've purchased:

ExpertPower 12 Volt 50 ah Deep Cycle Sealed Lead Acid Wheelchair Medical Mobility Rechargeable Battery. I really like this battery as it has bolt style terminals and a handle. It is an AGM battery. While I wanted something that would last longer, the 50ah batteries were about as heavy as I wanted to move around. In my test at home the battery lasted a solid four nights with the humidifier turned off. I'm using someone's trick here of using Ocean nasal spray just before bedtime and in the morning (I didn't miss the heated humidifier).
At a pressure of 10cmH2O, I think my machine needs 12 ah for an eight hour night, so a 50ah battery should last for four nights which it did. I believe it would require a 60ah battery to make it the full five nights but that was just heavier than I wanted.

BatteryMINDer Charger/Maintainer/Desulfater - 12V, Model# 2012
If I had it to do over I would buy the AGM version of this charger but this one seems fine, it charges normal AGM batteries like mine but not the specialty or higher end batteries like an Optima. It recharged my battery after four nights use in 3 hours. It's easy to use and a quality product.

ResMed's converter for the S10. The converter worked well other than the connection between the cigarette power adapter pieces was a bit fussy. I found to check that connection first if my machine wouldn't power on.

Anyway, that's my experience so far with a battery backup. Hopefully it will help someone. By the way, I didn't push the battery to go five nights as the batteryMinder, when I attached it to the battery after the 4th night, told me it was running low.

David
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#2
There have been many threads on battery backup. They occur about once per month it seems.

All good with the possible exception of your A-hr estimates.
Even a deep cycle SLA battery should not be drained near 100% of rated capacity.
Even though it appears you have done it once, I would not count on pulling 48 A-Hr from a 50 A-Hr rated battery.

You state 12A-Hr @ 10 cm-H2O pressure for 8 hours. That implies 1.5 Ampere battery drain rate.
That's reasonable. (Would be nice to put an Ammeter in series with the battery to verify that.)

I do not know if ResMed has published a battery guide for the 10 series. They have for the S9 and S8 series.

If you have the bucks, perhaps an investment in a 100 Watt solar panel and charge regulator should be considered.
Might even come in handy at home when the world economy collapses!
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#3
Below is state of charge chart that shows voltage versus percent of charge.
To get the longest battery life it should not be discharged below 50%.
[Image: battery%20voltage%20chart_zpswejn74rf.jpg]
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#4
Your numbers are spot on the ResMed Battery Guide specs. And keep in mind that those figures include a 50% sandbag so you may get lucky and be able to get 5 or even 6 nights from a relatively new battery in top condition and full charge. Just don't rely on it doing it all the time. Try to keep the 50% safety cushion there. (personally, I would probably count on it in a 4 vs 5 night camping expedition.)

And I don't worry about the 50% discharge restriction on these deep cycle batteries. I think that is more, um - conservative (notice how nicely I phrased that) - than necessary using them as you intend to use them. It is more germane if you were discussing using them daily (like in a golf cart at a busy club or in a powered wheelchair). If that were the case, then regularly running them to 80% discharge vs. 50% discharge would make a difference. To us occasional users, not so much so in the practical application sense.

And realistically, how many discharge/charge cycles are you expecting to burn through over the life of a backup battery? A few times a year? If the battery is designed to handle many hundreds of those cycles, its never ever going to show up before you replace the batteries ten years down the road anyway. So what if you cut the life down from 750 charge cycles down to 250 charge cycles? At maybe five discharge cycles a year that's still 50 years worth. The battery will die a natural death long before reaching that.

Northern Arizona Wind and Sun (where I got my solar panel and charge controller from) has a good presentation on storage (and other) batteries. Keep in mind that they are talking batteries that get discharged EVERY DAY. Included in their discussion is:

"Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The most practical number to use is 50% DOD on a regular basis. This does NOT mean you cannot go to 80% once in a while. It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor. Also, there is an upper limit - a battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. This happens because at very shallow cycles, the Lead Dioxide tends to build up in clumps on the the positive plates rather in an even film."

I would include a link to that discussion (and I think it would be fair use given this discussion), but if you want to read the full scoop, googleleate them and then find the "Deep Cycle Battery FAQ" section under the "Product Resources" button on their home page.

OMMOHY

P.S. -
The Resmed Battery Guide is at:
http://www.resmed.com/us/dam/documents/a...lo_eng.pdf
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#5
Thank you both for the information. I know batteries get a lot of threads here, I think its because they are confusing to many of us. I was pretty sure that I was reading the ResMed page correctly that the 12ah per eight hour night provided for a 50% cushion. I think on my trip I will try to go the full five nights knowing that my Resmed converter will shut power off if the battery does get low. I think there is a good chance the battery could last but if it doesn't the idea of waking up gasping for air does not sound very appealing.

My next question is, I know I can leave the battery connected to the BatteryMinder 24/7 but if I had a power failure at my house can I just attach the CPAP machine to the battery while leaving the battery tender connected? I don't think I need to have the battery connected all the time because I don't have many power failures. And, when I do our security system beeps and wakes me up anyway. At that point, I would just connect the CPAP machine to the battery using the converter.

David
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#6
(08-23-2015, 07:58 PM)Dagmar Wrote: Thank you both for the information. I know batteries get a lot of threads here, I think its because they are confusing to many of us. I was pretty sure that I was reading the ResMed page correctly that the 12ah per eight hour night provided for a 50% cushion. I think on my trip I will try to go the full five nights knowing that my Resmed converter will shut power off if the battery does get low. I think there is a good chance the battery could last but if it doesn't the idea of waking up gasping for air does not sound very appealing.

My next question is, I know I can leave the battery connected to the BatteryMinder 24/7 but if I had a power failure at my house can I just attach the CPAP machine to the battery while leaving the battery tender connected? I don't think I need to have the battery connected all the time because I don't have many power failures. And, when I do our security system beeps and wakes me up anyway. At that point, I would just connect the CPAP machine to the battery using the converter.

David

Yes.
INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#7
Another tidbit, my resmed converter did not shut off at 10.5 volts to protect my battery. Quite possible mine is faulty, but it works. I will have to keep an eye on my voltage.
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#8
There is an external device that will shut down the power at the selected cut off voltage to save your battery but it's around $100
"With ordinary talent and extraordinary perseverance, all things are attainable." - Thomas Foxwell Buxton

Cool
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#9
Thanks for the heads up ... but for that price i'll watch it and learn how long it will run on various batteries. Thanks
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