Operating CPAP with battery....

[trish6hundred]

When I go to battery power, I disconnect the humidifier and use the machine without it, same goes for the heated hose. I use the slimline hose at that point..

[archangle]

My husband Sam & I have always had trouble with deep cycle marine batteries. It seems like, no matter how hard we tried, even though they are supposed to be sealed, we still found that we had to put distilled watter in them to keep them from boiling dry.

That sounds like you've got the wrong charger for this kind of usage. Do you know the particular charger you had?

You need a good "float" charger if you're going to hook it up full time. A lot of chargers that are supposed to be good for full time hookup will actually ruin the battery over a time period of 6 months or so.

I've had excellent results with the Schumacher SE-1-12S charger. It's a "trickle" charger, and it shuts down or turns off when the battery is full. I and my dad have been through about 10 or so deep cycle batteries over the past 20 years with one of these chargers hooked up full time to the battery.

I usually get 5 years or so on a deep cycle battery, and don't need to add water more than once a year or so. It does take a week or so to recharge the battery if you discharge it deeply, though.

[archangle]

Even with the best battery, don't you have to turn off the heated hose and heated humidifier to get a decent life out of it between charging?

My PRS1 Auto with humidifier (no heated hose) draws about 3 amps. I'd get about 30 operating hours from my 100 Ah battery. Two nights would be a pretty safe bet.

If it's just "ordinary" storms, the power around here isn't usually off for a terribly long time period. I could easily use it with humidifier during normal outages, but switch to no humidifier if it looks like the outage will be long.

[SuperSleeper]

My husband Sam & I have always had trouble with deep cycle marine batteries. It seems like, no matter how hard we tried, even though they are supposed to be sealed, we still found that we had to put distilled watter in them to keep them from boiling dry.

I won't use a completely sealed lead-acid 12-volt battery for CPAP. Normally, most lead-acid deep cycles come with removable lids to add more distilled water when needed. It's part of the regular maintenance of lead-acid deep cycle batteries (and Marine deep cycle batteries) to add distilled water from time to time. How often depends upon how you charge them. I have my good quality Trojan deep cycle golf cart batteries hooked up to my cheap Harbor Freight solar panel system, and my MorningStar SunSaverDuo charge controller regularly goes into "desulfation mode". Some trickle chargers have this feature as well. In desulfation mode, the charging amperage is stepped up to remove build up of sulphur from the battery plates (extending battery life), and I can actually hear the bubbling of the water inside the battery if I listen carefully.

For my system, which goes into desulfation mode at least every other week, I top off the water level about once every 2-3 months, but I could get by with doing it every 4 months easily before the water level gets down to the top of the metal plates. If your trickle charger doesn't have a desulfation mode, then the charging amperage isn't going to spike like mine does, and the water will likely not evaporate as quickly. But, I like to use the desulfation mode to extend the life of my batteries, so I need to check my water levels more often.

If you only put your deep cycle battery on a charge once a month or so for a day, then you shouldn't have to check the water levels but maybe once every six months (even though you may want to do it more often for safety's sake, because if the water level goes below the metal plate fins, it will damage the battery).

Even with the best battery, don't you have to turn off the heated hose and heated humidifier to get a decent life out of it between charging?

Not on a good quality deep cycle that has a higher amp-hour rating. If the battery is rated for more than 100 amp-hours, then you should be able to at a very minimum get a couple of nights out of it before a recharge, even with a heated humidifier going at full blast and at a higher pressure. For me, I don't use a heated humidifier or heated hose and my pressure probably averages around 14 or so-- so I can probably use a fully-charged 12 volt 100 amp-hour battery for maybe 4-5 nights before I'd need to re-charge it. I usually don't wait that long to re-charge, however, but I could use it that long if I had to.

Trish sent me a few of the manuals associated with the ResMed Power Station II that we're talking about in this thread. CLICK HERE for ResMed's run times PDF, and you can clearly see that this Power Station II's Lithium-ion battery has nowhere near the capacity of a standard 100 amp-hour lead-acid 12-volt deep cycle battery. And, according to the chart in the PDF, if you run the heated humidifier and heated tube at a higher pressure, the run times are going to be unacceptable (probably between 2-5 hours, depending upon the heat and pressure settings). That's why I thought that a price tag of $700 was a bit steep for a system that won't even power such a system for even one night. Yeah, it could work for one night, but only as long as you don't use the heated tube and humidifier, and your pressure setting is on the lower end (below 13 or so, if I'm extrapolating out properly from the data on the PDF).

The only way I'd even consider buying the Power Station II is if I needed it for a trip via plane; and even then, it would only work if I wasn't using a heated humidifier or heated tube, and my pressure was less than 13-14 or so on average, and of course, you'd still have to re-charge it every single day for 4 hours if you plan on using it again the following night.

[archangle]

My MorningStar SunSaverDuo charge controller regularly goes into "desulfation mode". Some trickle chargers have this feature as well. In desulfation mode, the charging amperage is stepped up to remove build up of sulphur from the battery plates (extending battery life), and I can actually hear the bubbling of the water inside the battery if I listen carefully.

It's been pointed out before, but bears repeating.

If you have a charger that does desulfation mode, it's critical that you don't have the CPAP machine hooked to the battery while charging. Desulfation involves high frequency voltages at fairly high currents and voltages that might harm the machine or confuse the computer that runs the machine.

Sulfation is most common if the battery sits for long periods of time without a charger attached.

It's not a good idea to hook the charger and CPAP to the battery at the same time with any charger unless you know how it charges. I would do it myself with my SE-1-12S, just because I am fairly confident it won't do anything weird.

[SuperSleeper]

Good advice, Arch. And I meant to say "voltage" in that quote, not "amperage".... (0r maybe both?) elexcticty be cornfusing to me.

[Sleepster]

You don't get the same charge (technically that's the name of the quantity that's measured in units of amp-hours) out of a lithium ion as you do from a lead acid battery. I'm not sure why that's the case. Maybe it's because the lithium ion technology is so much more expensive it's marketed for applications where a light weight battery is desired.

The other thing that's going to affect battery performance is air temperature. They don't do well in really hot climates, and they really don't do well in cold climates. Of course, that's gonna be more of an issue for outdoor applications.

[archangle]

You don't get the same charge (technically that's the name of the quantity that's measured in units of amp-hours) out of a lithium ion as you do from a lead acid battery. I'm not sure why that's the case. Maybe it's because the lithium ion technology is so much more expensive it's marketed for applications where a light weight battery is desired.

Lithium ion batteries tend to give you more Amp hours per pound of battery. I think that's because each lithium atom weighs a lot less than a lead atom. Each lithium atom gives up one electron in the discharge process. More electrons per pound means more amp hours per pound.

Also, since the voltage of the cell is higher, you get even more watt hours per cell with the same amp hours. Two lithium ion cells will give you as much voltage as 3 lead acid cells. That also gives you a weight advantage.

Lithium ion batteries are superior to lead acid in several ways. Unfortunately, they are not as tolerant of "bad" treatment, so you have to be more careful charging them, and they tend to have protective circuits that will cause them to fail unexpectedly. Then there's the risk of fire if not done right. All the Boeing 787 planes sat idle for several months because of problems with fire in their lithium batteries.

[SuperSleeper]

Lithium ion batteries are superior to lead acid in several ways. Unfortunately, they are not as tolerant of "bad" treatment, so you have to be more careful charging them, and they tend to have protective circuits that will cause them to fail unexpectedly. Then there's the risk of fire if not done right. All the Boeing 787 planes sat idle for several months because of problems with fire in their lithium batteries.

I had a lithium-ion battery overheat and melt half my cell phone while charging. Thankfully it was a cheap Tracfone that cost me about $30. That might have been part of the problem - cheap China parts controlling the charging rate. Had I not been there, it might have started my house on fire. Now I never leave the house with my laptop or cell phone actively charging. I always unplug them when I leave.

In the news a couple of years ago or so that there was a rash of Lithium-ion laptop batteries starting fires. That's why I suggested that they might not be as safe as lead-acid, (assuming one takes precautions).

[JJJ]

In the news a couple of years ago or so that there was a rash of Lithium-ion laptop batteries starting fires. That's why I suggested that they might not be as safe as lead-acid, (assuming one takes precautions).

Those were Lenovo Thinkpads (made in China now). They never set anything on fire, but they did melt the plastic of the laptop and destroy it. In this case the problem was in the "battery" because the charging controller circuitry was inside the battery, rather than in the laptop. It was the components of the charging circuitry that failed, similar to your story.

The problem with lithium batteries (including the cost) is the shortage of lithium supply. The largest known deposits are in Chile, but their law requires earth resources to be developed only with Chilean capital. They don't have the capital, so the deposits sit there unused. China has the second largest deposits, but they haven't been able to exploit them fully either. Industrialized countries have the capital, but mostly lack the deposits. The result is that almost all lithium batteries today are manufactured / recycled in China, and they are not famous for quality control.

Lead acid batteries have problems that are just as bad. For example, it is against US federal law to take a lead acid battery on any public transportation vehicle. Why? Because the acid is not very friendly to human life. But we have been using lead acid batteries for a century and everyone understands the dangers. If the public was as familiar with the electronics in lithium batteries they might be just as safe.

Personally, if the power goes out I will power my CPAP with the generator out in my garage. That is, if I can keep from burning the house down with the gasoline.