Deep Cycle Home Backup Supply

[archangle]

Someone PMed me and asked for recommendations for a backup power supply. Rather than send it to one person, here's what I suggested.

This is for a Philips PRS1 machine.

There are quite a few options, each with its own advantages and drawbacks. For home backup use, I recommend this:

1) Deep Cycle marine battery about the size of a car battery.
2) Battery box.
3) "Float" charger
4) Adapters for your CPAP

It's sort of big, so find a place to put it next to your CPAP where you won't trip over it or kick it over, and you're safe.


Parts


1) Battery - Get a "Deep cycle" marine battery. Make sure it doesn't say anything about hybrid, starting, dual purpose, etc. It can mention trolling.

Here's one example. http://www.walmart.com/ip/EverStart-Max ... ifications

2) Battery box - Get one that your battery will fit in.

One example: http://www.walmart.com/ip/Snap-Top-Ever ... x/16781380 is one example.

3) Float charger. You need one that can stay hooked up to the battery all the time and not damage it. I've used several types and had several that are supposed to be a "float" charger, but they still ate the battery up over time. The one that's worked for me through several chargers and batteries is the Schumacher SE-1-12s. The last time I bought one, the cheapest and easiest place to get one was AutoZone. http://www.autozone.com/autozone/access ... 513702_0_0_

4) Cables. For the Philips Respironics PRS1 (Not 60 series), the adapter is https://www.cpap.com/productpage/respir ... -cord.html. For 60 series, it's https://www.cpap.com/productpage/dc-pow ... hines.html.

These plug into a cigarette lighter plug. You need a battery to cigarette plug adapter. https://www.cpap.com/productpage/respir ... cable.html You can buy this item locally, but be sure to get one with a fuse near the battery clips.



Assembly


Put the battery in the box. I set the box inside another plastic storage box, just in case I get some kind of leak from both the battery and the battery box. Be sure you won't kick it over or trip on it.

Hook the charger up to the screw terminals on the battery. Clip the cigarette lighter/clip cable to the battery. Get the polarity right. Red to plus, black to negative. Plug the Respironics cable into the cigarette plug.

Check the water level. Note that the water level should not be at the top. It should be at the bottom of the little tube you look through. http://www.wikihow.com/Check-Car-Battery-Water-Levels. Distilled water is good.

Plug the battery charger into the wall. The green light should come on. Watch it for a few days, and the red light should come on when the battery is fully charged. It make take several days if the battery is new.

Put the top of the battery box on and strap it on. The top keeps you from dropping something on the top and shorting the battery out. Strap the cover on.

When power goes out, unplug the AC power adapter from the CPAP and plug in the battery cord.

Check the water level after 1 month. Then about every 6 months or so. More often if you're using a different charger.

When the power goes out, unplug the AC adapter from the CPAP and plug in the adapter from the battery.

There are many other ways to do this with different levels of cost, portability, convenience, etc.


Notes:

[edited 11/11/2012] - This system recharges slowly. This is fine for normal standby use, but don't think you're going to run a generator for a few hours during a long outage and quickly recharge the battery. It may take a few days to recharge after you use the battery for a few nights.

[sylvie]

Someone PMed me and asked for recommendations for a backup power supply. Rather than send it to one person, here's what I suggested.

This is EXACTLY what I was looking for: step-by-step directions and links to everything one should get for a battery backup. I can't thank you enough, Archangel. And you even included stuff for 60 series machines, which is what I have. You're a blessing.

[squid13]

This is the one I built and it's a lot like the one mentioned by archangle. This is the one by John Fisher viewtopic.php?t=49115

[2Tim215]

This is certainly a good way to go. Great post. Something that some may still have time to put together in a short period of time if you can start first thing in the morning. Generators are sold out in many areas by us and as far north as Rochester, NY from a visit that we had a little while ago. Our Tractor Supply was sold out by 10:am Saturday Morning, and BJ's wholesale before Friday night. Wanted to bump this Post up!

[JohnBFisher]

I previously posted instructions in the Post "Battery Backup Design" .. It's a fairly simple approach to use a deep cycle battery to act as a backup battery. I've used this approach for about 10 years at this point. I am on my second battery. It should last another few years. I test the system about once a month. Even if you don't implement it fully, there is a lot of information that everyone contributed into that post.

Battery Backup Design
viewtopic.php?t=49115

[Sloop]

Someone PMed me and asked for recommendations for a backup power supply. Rather than send it to one person, here's what I suggested.

This is for a Philips PRS1 machine.

Just curious -- how many nights of dc power will your setup provide?

For those folks who live in the Northeast, power outages from Sandy could extend out one or two weeks. Unless you have a generator (in which case you wouldn't need the battery backup), there is no way to re-charge ANY kind of battery.

[Guest]

Unless you have a generator (in which case you wouldn't need the battery backup), there is no way to re-charge ANY kind of battery.

you can use your car to charge batteries
a neighbors if they have a generator
or at a nearby shelter as i am sure they will have power
battery power should be enuff to get you thru 2 or 3 nites
note that batteries take longer to charge then to discharge
get 2 batteries so you can charge 1 while using the other

[nanwilson]

I use the deep cycle marine battery set up and have for over 2 years. i bought a small foldable trolly at Costco for less that $20 and put my battery set up on it. Now I can wheel it around wherever I want it, since winter is almost upon us I have wheeled it in to my bedroom and put it in a safe corner of the room. I have used it for 4 nights at one time, without the humidifier, and got 8 hours each night. Hope that helps you gals out....if an old lady like me can set this up..so can you
Stay safe my frfiends
Cheers
Nan

[archangle]

Just curious -- how many nights of dc power will your setup provide?

For those folks who live in the Northeast, power outages from Sandy could extend out one or two weeks. Unless you have a generator (in which case you wouldn't need the battery backup), there is no way to re-charge ANY kind of battery.

It's hard to tell for sure, power usage varies between CPAPs, varies with settings, leak rates, batteries vary, batteries age, etc. My CPAP draws around 2 amps without humidifier. 2 Amps would be about 16 Amp Hours per night. That's around 5 nights. Maybe 4 nights with some safety margin.

Your results may vary widely.

It is a good point that any battery system does eventually run out of power and you have to do something. Exceed that limit and you'll need to move out, get power some other way, or figure out how to charge from your car or other source.

[sylvie]

i bought a small foldable trolly at Costco for less that $20 and put my battery set up on it. Now I can wheel it around wherever I want it, since winter is almost upon us I have wheeled it in to my bedroom and put it in a safe corner of the room.

What an extra GREAT tip!! You all are such great help

[DiverCTHunter]

Archangel:

What are your thoughts on inserting a voltage regulator between the battery and the machine's DC-DC adaptor?

I suspect both PR and ResMed are being conservative about their machine's voltage sensitivity, but since both recommend against using the DC-DC adapter while the alternator is running, I'm tempted to err on their side. My PRS1's power brick gives between 12.21 and 12.24 VDC under no load, so I'm not willing to subject it to the 13.5VDC or 14.2VDC that the float charger puts out in Float and Bulk charge modes unless others have done it with no ill effects.

Here's the setup I'm considering for home. If it works as planned, then the 60-watt PR power brick will go in the travel bag:

PSU:
300-watt AC->DC PSU from old PC @ +12VDC (could also use the -12VDC power rail for ground reference), but my DC Theory always references to earth ground & I doubt the common buss is isolated on the combination voltage regulator / charge controller)

Combo Charge Controller / Voltage Regulator:
Minibox Corp OpenUPS DC-DC voltage regulator and mixed-chemistry charge controller
The pics show 3 buck/boost transformers, so I should be OK using +12VDC in instead of +14VDC in. I can always swap out the PSU for a better one at a later date.

Battery:
28 Ah Sealed Lead-Acid bank (2x load-tested good 14Ah batteries from discarded UPSs, wired in parallel) Battery Cutoff voltage programmed for 70% max discharge gives ~20 Ah usable which should be plenty for 1 night with 8-11.5 cm/H2O APAP.

Charge controller can handle single parallel banks at up to 24V battery bank (30V bulk charge) at 3A max and can also be configured for up to 6 single cells batteries (2V or 4V cells) in a modified serial config, so I can always slip a flooded deep-cycle or AGM trolling battery in there later.

[Lizistired]

This is certainly a good way to go. Great post. Something that some may still have time to put together in a short period of time if you can start first thing in the morning. Generators are sold out in many areas by us and as far north as Rochester, NY from a visit that we had a little while ago. Our Tractor Supply was sold out by 10:am Saturday Morning, and BJ's wholesale before Friday night. Wanted to bump this Post up!

2Tim, I hope you are talking about John Fisher's setup. Arch's is for PRS1 machines. S9's need the Resmed DC adapter, unless there has been another solution I haven't read about.

[Sloop]

Just curious -- how many nights of dc power will your setup provide?

For those folks who live in the Northeast, power outages from Sandy could extend out one or two weeks. Unless you have a generator (in which case you wouldn't need the battery backup), there is no way to re-charge ANY kind of battery.

It's hard to tell for sure, power usage varies between CPAPs, varies with settings, leak rates, batteries vary, batteries age, etc. My CPAP draws around 2 amps without humidifier. 2 Amps would be about 16 Amp Hours per night. That's around 5 nights. Maybe 4 nights with some safety margin.

I only tested my rig to the equivalent of two 8-hour nights. But as I said in another post, the meter barely budged off of full charge, so I guess it is possible I too might get around 4 nights. I can say this -- I hope I never have to find out!

[archangle]

I only tested my rig to the equivalent of two 8-hour nights. But as I said in another post, the meter barely budged off of full charge, so I guess it is possible I too might get around 4 nights. I can say this -- I hope I never have to find out!

You might get more if your current draw is low. I haven't done any long term tests of my CPAP with the Kill a Watt power meter and no humidifier, so the average might be lower than I think. Maybe when it gets humid, I'll run without humidifier overnight and get better numbers.

Don't put much faith in the power meter. The way lead acid batteries discharge, the voltage drops very slowly, then sort of falls off a cliff. It's very difficult to make a cheap "remaining power" meter for rechargeable batteries.

Here's an example:



In practice, building a "remaining power" battery meter is even tougher than that diagram would indicate.

[DiverCTHunter]

In practice, building a "remaining power" battery meter is even tougher than that diagram would indicate.

Yup, that's why I was originally going to use the "true sine wave" APC UPS I pulled out of the pile at the recycling center. Unfortunately, the board and both of the 12V batteries in the 24V bank were bad.

The board I'm considering for DC-DC UPS operation has a "columb counter" feature, so theoretically I can use the management software to set the charge curve and approx Amp Hours of my batteries, then it'll give an "accurate" charge meter.

Oh well, at least the APC got separated into Lead, Ferrous and Copper/Ferrous here instead of in a fire at some slum in Africa.