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Camping with a CPAP or surviving a power outage
[If you are using a deep cycle or marine battery so long (9 days) that it actually discharges enough to "slow down" your CPAP [with a 1 amp draw], you are discharging the battery way too much. Allowing a deep cycle lead-acid battery to get that low will damage the battery's capacity and if you do this too many times, you'll end up with a dead brick instead of a battery.

For best battery life, you generally don't want to allow your 12-volt lead-acid battery to get below a 70% charge... and keeping it above 80% will extend the battery life further.

Thanks for the battery information. This was the first time that I have ever tried using one until it stops. I usually stop at 5 or 6 days and switch batteries. Still learning.

Wish I had found this website when I first got my CPAP. I had to learn the hard way.

Many Klatch
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You might want to get a solar charger. They're light weight and will allow you to recharge that smaller battery, getting more use out of it.

I actually do have one of those folding soft solar chargers. It charges at about one amp per hour so I can almost keep up with the night time usage. However on rainy days it doesn't do as well and windy days tend to flip it over and I miss getting a full charge unless I am in camp all day. This camping/battery/CPAP thing is an ongoing learning opportunity.

Many Klatch
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Battery technology is in the midst of a major upheaval. There are very few if any cellphones or gadgets that come with NiCd, NiMh, or other lesser batteries such as rechargeable alkalines. The reason is quite simple. Lithium batteries (and there are several kinds of Lithium batteries) offer greater capacity for less weight. They are a different breed of battery though and the one BIG thing you want to avoid with any kind of Lithium battery is a full discharge or a gross overcharge. It will kill it dead immediately and they are a beggar to try to revive - it generally does not work and you face a fire/explosion/fumes hazard. However, if you look hard enough you may just find some Lithium Polymer batteries that fit the bill at a price you can afford. I have been using, personally, deep cycle sealed gelcells, plus a trickle charger that 'maintains' them to full charge and shuts down so as not to overcharge (also a no-no). The better ones have a button that will discharge to 5 or 10% battery capacity and then do a full recharge..... a good thing to do to ensure the lead that coats the plates of the battery cells is evenly distributed for maximum efficiency. I use a big BIG honkin inverter that has a fan that only comes on when I am drawing big current from it... like running a small bar fridge or such...... otherwise the heat sink keeps it cool enough on its own. I would be cautious about snipping any wires as the fan itself may have a thermistor in it to tell it when it needs to be running to keep things from catching fire.

The other thing that I use is a marine carrying case with handle to haul my battery around. The inverter might just fit right inside when transporting but I would run the inverter in the open air protected from the elements.

This also happens to be part of my 'bug-out' kit in the event of disaster (like we had in Toronto a quarter century ago when 1/4 of the city had to be evacuated..... I assisted as a ham radio operator and received a commendation from the Red Cross for same). I also use same for operating low power ham radio when we are travelling and have no access to AC power or I wish to operate my gear from a distance away from power.

The other thing I use, at home, is a couple of HUGE surplus computer server backup power supplies. We actually have several in the house along with some very low power fluorescent lighting, etc., that is left connected to them all the time and which comes on when mains power fails. We are the only house on the street with lights on and a wee TV and radio working to find out what is going on around us. More importantly, they will run my XPAP overnight so I lose little sleep when the sun comes up and I have to head to work.

It is good to be aware of the pro's and con's of all of these technologies. And how they work. (Oh, one other thing, not talked about a whole lot... some of these inverters have lousy efficiency. What you feel coming away as heat is ENERGY that is being sucked from the batteries and wasted (unless you are cold).

Should our power grid get much more flakey I think we will buy a small Honda generator and switch and power the whole house that way as some of our friends are doing.

In the end, whatever works for you is good. Just remember the basics and make sure you have the batteries in a marine or similar carrying case so should they spring a leak you do not cause damage to yourself or your surroundings.

Murray L
Educate, Advocate, Contemplate.
Herein lies personal opinion, no professional advice, which ALL are well advised to seek.

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1) Get a true deep cycle battery.

Be careful about buying a "marine" battery. "Marine" used to mean a true deep cycle battery. Marketers got involved and started selling "Marine" staring batteries, "Starting/deep cycle" batteries, and "Deep cycle" batteries.

The only type of Marine/Lead Acid/Car style battery to get for CPAP is "Deep cycle."

By the way, high CCA (Cold Cranking Amps) usually indicates a "starting" battery. Deep cycle batteries will usually produce fewer peak amps, but will last longer if you discharge them deeply.

2) Get the right charger.

This is really important if you keep the battery on the charger all the time.

If you're keeping a lead acid battery on a charger all the time, you need a REAL "float charger". Otherwise, the charger will eventually damage the battery slowly over time. If you buy an expensive deep cycle battery for backup use, you'd like it to last for years. Even with a GOOD charger, you'll be lucky if your deep cycle battery lasts 5 years. It will be much less with a less good charger.

I emphasize "REAL" float charger because there are lots of imitators. "Trickle" chargers are less damaging than "non-trickle" chargers, but can still kill a battery in less than a year. A 1 or 2 amp charger can kill a battery in much less than a year. Chargers that give a heavy charge then cut back to a "maintenance" charge are good for charging a battery if you only leave it connected for a few days, but many of these will eat batteries if you leave them connected full time.

Even a lot of the "float" chargers are iffy. They may deliver the correct charge most of the time, but occasionally, they lose their mind and don't drop back into true "float" mode. It's fine for 18 months and then it cooks all the water out of your battery on the 19th month. You don't know it's no good until it eats a battery on you without warning.

I speak both from knowledge about the subject and physics involved, and as someone who's killed quite a few batteries over the years, and also has kept quite a few batteries running for years with the right setup.

After many other chargers, including reputed "smart" chargers, have failed me, I have settled on Schumacher SE-1-12S. It's the only thing I'll leave connected to a battery full time. There may be others that will work as well, but I've used at least 4 of these and have had less battery damage with them than any others.

The disadvantage to this and similar chargers is they take a long time to top up the battery if you discharge the battery deeply. If you need to use it for a few days and then charge it back up during one day, either get a really smart and reliable more powerful charger, or do quick recharge with a different charger and hook the float charger back up for long term maintenance.

3) The battery will die on you eventually.

It will probably find the worst possible time to do so. Luckily, lead acid/deep cycle batteries usually give you a warning if you check.

You'll be real lucky if you get 5 years on a deep cycle battery even if you treat it right. Plan on replacing it eventually. Check it occasionally to be sure it's still good.

Use it for a while every 6 months or so and check the voltage. Unplug the charger, test the voltage, then run it long enough to get maybe 10% of it's intended life and see if the voltage has dropped much. Sometimes a bad battery will have a good voltage until you use it. You might want to get a 12V fan or some other "dumb" gadget to use to run your periodic "load test."

By the way, Paula is right at least in part. Lead acid batteries, especially big ones, do have some sort of problem that may develop if you leave them fully charged or on a charger for a LONG time and never discharge them. It's not as bad as some of the other things that will hurt a battery, but it's a real effect.

I'm not quite sure why they eventually die, but maybe it's just that metal plates soaking in acid eventually fall apart no matter what you do.

4) Lithium batteries die on you suddenly without warning.

Lithium batteries are great in several ways. The biggest problem to me is that you often find they've just up and died on you. This is particularly bad if you've let it sit for a long time unused, whether on a charger or not.

Part of the problem is that lithium batteries want to burn violently if they aren't charged properly. Manufacturers build circuitry into the battery packs that detect if the voltage has gotten too high, too low, or other danger signs appear. If the circuit sees something it doesn't like, it blows a fuse or something and will refuse to charge the batter again. While this sounds bad, it beats having a fire. Google "lithium battery fire".

If you have a lithium battery for CPAP use, be sure and check it often to be sure you don't end up out of luck when you need it.
Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
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(06-25-2012, 10:56 AM)SuperSleeper Wrote: These types are really not true deep cycles, but they are hybrids - a cross between an automotive battery and true deep cycle battery. It's all about how much lead is inside the battery itself - generally, the more lead, the heavier the battery and the more robust it's going to be for current draws over long periods of time (like CPAP machines).

I believe the "hybrids" are usually labelled "Starting/trolling, Starting/deep cycle, or dual purpose." The "deep cycle or trolling" batteries are more likely to be the real thing. Of course, marketers are involved so lies abound.

I think the main difference in deep cycle vs. starting is the construction of the plates, not the quantity of lead. Starting batteries may have mesh plates, multiple thin plates, or some sort of foam structure so that you get more surface area. Deep cycle has more solid plates. The mesh or foam structures are more likely to crumble when cycled.

More lead gives you more total storage, whether it's deep cycle or starting.

(06-25-2012, 10:56 AM)SuperSleeper Wrote: Good quality true deep cycle batteries will have this amp-hour rating printed on the battery label somewhere.

I think there were so many misleading or outright fraudulent "amp hour" ratings on batteries that the government started cracking down and many companies stopped using that rating. It's somewhat meaningless unless you specify the conditions and discharge rate.

(06-25-2012, 10:56 AM)SuperSleeper Wrote: For best battery life, you generally don't want to allow your 12-volt lead-acid battery to get below a 70% charge... and keeping it above 80% will extend the battery life further.

I believe you're talking about 70% of the amp hours remaining, not 70% of voltage remaining. If you discharge a 12V battery down to 10V, it's probably been discharged way too deep.
Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
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(06-25-2012, 06:13 PM)archangle Wrote:
(06-25-2012, 10:56 AM)SuperSleeper Wrote: For best battery life, you generally don't want to allow your 12-volt lead-acid battery to get below a 70% charge... and keeping it above 80% will extend the battery life further.

I believe you're talking about 70% of the amp hours remaining, not 70% of voltage remaining. If you discharge a 12V battery down to 10V, it's probably been discharged way too deep.

Yes, that's correct. The amp-hour is a unit of charge (equal to 3600 coulombs). The volt is a unit of energy per unit charge (equal to one joule per coulomb).

As a simple but practical example look at a typical "D" flashlight battery compared to a "AA" battery. They both have the same voltage, but the "D" has a larger charge.
Apnea Board Moderator

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(06-25-2012, 12:39 PM)PaulaO2 Wrote: Yes, they are sealed AGM, Group 34. HUGE heavy monsters.

No, I'd never completely kill a battery. I let it go until the red light on the indicator is on (it goes from a green to an orange to a red) once a month or so. Three times I've let it go (accidentally) to where the last red light is blinking and I practically had to be pushed to the truck.

I'm due to get another chair so when I go talk to the folks, I'll ask them about the battery charging suggestions.

I'm disappointed I was wrong. I so wanted to correct you. Dangit.

Hey Paula, just as a suggestion there is a pretty good Wikipedia article about the type of batteries that your chair uses if you search that site for VRLA Battery. It seems to be pretty good based on my scanning of it. I had to learn about batteries as I was having issues awhile back and I have a really good charger with the ability to do stuff I totally did not understand, such as decalcification of the battery. I had to look that up! You could go by what the folks tell you that are selling you stuff, but I've always found independent verification of facts to be a real life saver with the misinformation that is out there.
As always, YMMV! You do not have to agree or disagree, I am not a professional so my mental meanderings are simply recollections of things from my own life.

PRS1 - Auto - A-Flex x2 - 12.50 - 20 - Humid x2 - Swift FX
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