Cheap battery backup idea

[Woody3]

First off how often do you need a battery back up and for how long? If the answer is mabe once every year
or so for a day or two throw away batterys might not be a bad idea. Here is my reasoning a 12v battery pack can be made from using 2 4 D cell battery holders soldered together and 8 D cell batterys. Buying the 2 holders and batterys from Digikey would cost $17 + shipping. Now QUALITY D cells are rated at 20AH so
your 12v pack should last for at least 2 nights probably 3. If you run through a set of batterys every year
over a 10year period your cost will still be a lot less than a rechargeable battery pack.

[RipVW]

Wondering if any of you CPAP power experts know if Woody3's idea would work (?)

[LinkC]

In theory, yes.

But batteries start losing their capability immediately after their initial charge. 2Ah is what they had when manufactured. Who knows how long they've been on the shelf?

If you changed them regularly and religiously, I suppose it's better than no backup... Will insurance cover backup power?

[ww]

First off how often do you need a battery back up and for how long? If the answer is mabe once every year
or so for a day or two throw away batterys might not be a bad idea. Here is my reasoning a 12v battery pack can be made from using 2 4 D cell battery holders soldered together and 8 D cell batterys. Buying the 2 holders and batterys from Digikey would cost $17 + shipping. Now QUALITY D cells are rated at 20AH so
your 12v pack should last for at least 2 nights probably 3. If you run through a set of batterys every year
over a 10year period your cost will still be a lot less than a rechargeable battery pack.

It is not a good idea. The batteries are NOT rated at 20 AH. 4 AH is a more realistic rating. By the time you purchase non-rechargeable alkalines and use 24 batteries to be able to make it through the night, you could have purchased a marine battery for a little more and recharged it many times. That is by far the preferred low cost backup solution.

[plr66]

... Will insurance cover backup power?

I consider myself fortunate that the DME connected with the sleep lab I used, was successful in getting BCBS (and I have a really minimal policy) to pay for a Respironics battery with the accessory DC connector. I had several conversations with BCBS prior to that, and was told that these items would not be covered--which is why I decided to seek this DME's help. My copay was about $55. It took a couple of months after I got the battery to get the word on who would pay for the battery--(me or the insurance)--so I'm guessing the DME worked at it a couple of times to get it to go through. I think they told me that their sleep MD wrote a letter justifying medical necessity.

[rested gal]

Since the word "battery" in the topic title may attract people new to this message board, here's a link to additional interesting discussions about battery back up ideas:

LINKS to Battery operation, camping, power outage
viewtopic.php?t=9682

[datracer99]

First off how often do you need a battery back up and for how long? If the answer is mabe once every year
or so for a day or two throw away batterys might not be a bad idea. Here is my reasoning a 12v battery pack can be made from using 2 4 D cell battery holders soldered together and 8 D cell batterys. Buying the 2 holders and batterys from Digikey would cost $17 + shipping. Now QUALITY D cells are rated at 20AH so
your 12v pack should last for at least 2 nights probably 3. If you run through a set of batterys every year
over a 10year period your cost will still be a lot less than a rechargeable battery pack.

It is not a good idea. The batteries are NOT rated at 20 AH. 4 AH is a more realistic rating. By the time you purchase non-rechargeable alkalines and use 24 batteries to be able to make it through the night, you could have purchased a marine battery for a little more and recharged it many times. That is by far the preferred low cost backup solution.

Both Energiser and Duracell Alkaline D cells are rated at 20AH. And most quality batteries are rated to last at least a few years in storage. If if your cpap draws 2 amps or less then you should get a night out of a set.
And at $1 or less D cells each are quite good value. You only need 8x1.5v batteris to get 12v so the cost for a night should be about $8.

If it is only for occasional emergency use then I think the alkalines are a good option. For the cost af a couple of D cell holders and a bit of wire you have a backup that is always on standby.

The other option is a couple of alkaline lantern batteries, which are 6v 20AH - though they are more expensive at $8 each

The choice of battery comes down to which batteries you keep on hand for torches or other battery powered devices, and just make sure you always have sufficent stock of those used for your cpap.

One benefit is that you don't need to worry about keeping your backup charged.
I will bet that unless you are anal about topping up a rechargeable battery then the odds are it will be flat when you need it most.

[tenspeed]

I used a sealed motorcycle battery for my portable 12VDC needs. It's is currently in my Cub Cadet lawn tractor.

[billbolton]

And at $1 or less D cells each are quite good value. You only need 8x1.5v batteris to get 12v so the cost for a night should be about $8.

No.

You need to look at the discharge characteritsics to understand how much energy can usefully be delivered. For instance a Energizer E95 D cell will only deliver ~20AH of capacity if you only discharge at a 25 mA current rate and your kit can operate down to 0.8V terminal potential!

That is nothing at all like the discharge characteristic a typical xPAP application imposes.

http://www.duracell.com/oem/Pdf/new/MN1300_US_CT.pdf

http://data.energizer.com/PDFs/E95.pdf

Cheers,

Bill

[datracer99]

Thanks Bill, interesting charts. Looks like it would require 2 sets of D cells to get through the night - bu that depends on the currnet drain of the CPAP

Woody what CPAP do you have. There is a quite a difference in the requirements with the different brands.