Camping battery Cpap set up

[Crog Welly]

Having problems with a Clore Booster Pack ES2500 battery paired with a Cyberpower CPS 400AI inverter. I use a Resmed S8 Autoset Vantage 4-12 cm.

Its an 18Ah SLA battery and should go for at least 10 hours. It ran for 5.5 hours last night camping. At 3:30am I woke to the machine trying to "boot up" over and over again but would not get up and running. Booster pack was fully charged at the beginning of the evening.

Could it be that the inverter is cutting out once the battery voltage drops or what?

Any help would be appreciatedf...

[PaulaO2]

Crog, moved this to the main forum so your question will get answered faster.

[Crog Welly]

Thx PaulaO2.

[JJJ]

Having problems with a Clore Booster Pack ES2500 battery paired with a Cyberpower CPS 400AI inverter. I use a Resmed S8 Autoset Vantage 4-12 cm.
Its an 18Ah SLA battery and should go for at least 10 hours. It ran for 5.5 hours last night camping. At 3:30am I woke to the machine trying to "boot up" over and over again but would not get up and running. Booster pack was fully charged at the beginning of the evening.
Could it be that the inverter is cutting out once the battery voltage drops or what?

I am not familiar with the S8 Vantage, but I thought that most Resmed machines would run on 12 or 24V DC, although they want you to buy their adapter to do so. If so, could you not dispense with the inverter and run the S8 directly off the battery Booster Pac?

[Crog Welly]

Yes I believe I could. Is it often the inverter that causes the kind of problems I am experiencing I wonder? I the cheapest I can find the S* DC converter is $75. Just want to make sure I am solving the right problem.

Thanks for the info though JJJ.


Crog

[PaulaO2]

Is this the first time you have used this set-up?

You have the machine with its usual wall cord plugged into an inverter, right? And the inverter is putting out 120V?

Did you have the humidifier on?

[SuperSleeper]

Its an 18Ah SLA battery and should go for at least 10 hours. It ran for 5.5 hours last night camping. At 3:30am I woke to the machine trying to "boot up" over and over again but would not get up and running. Booster pack was fully charged at the beginning of the evening.

Hi Crog, welcome to Apnea Board!

An 18 amp-hour sealed lead acid battery is woefully inadequate for CPAP usage with a heated humidifier and is close to the unacceptable level for a modern CPAP even running at 11 cmH2O of pressure without heated humidifier. With your humidifier on, there's no way that it will last for anywhere near 10 hours. Your battery is the weakest point, not the inverter.

Read my post HERE about this issue.

You need to get a battery with a much higher amp-hour rating. There are issues with the Peukert's Equation (posted in that link above) and the fact that you'll ruin your lead-acid battery if you discharge it beyond a certain percentage (again, read that post).

Look at the equation in that linked post. Assuming you're using your heated humidifier and drawing about 3 amps of 12 volt power, the formula would be:

18 AH x 90% = 16.2 AH / 3 amps draw = 5.4 hours absolute max run time x 60% (max safe discharge number) = 3.24 hours (safe level of discharge).

In your situation, you ran down your batter below the maximum safe discharge rate, and thus, got about what this equation predicts: 5.4 hours of use from an 18 amp-hour battery.

But, you've got a problem - you discharged the battery down to a level that may have done damage to the battery capacity. Do that one or two more times and you may end up with a dead brick instead of a battery.

On top of that, you used a small DC to AC inverter - and that sucked about 10-20% of your available power out before you even got the electricity to the CPAP machine, which reduces your available electricity even further.

If you can, as JJJ wrote, it's best to run on direct 12-volt DC if your CPAP will allow it. No inversion loss that way.

Also, you need to get a battery that has a minimum of around 60 AH (Amp-hours). That way, you'll get a good solid 10 hours of use before discharging the battery to a level that will not cause harm to battery capacity.

This is why if folks are going to use lead-acid batteries, many of us get the large, honkin' "marine deep cycle" batteries like you'd get from AutoZone, WalMart or K-Mart, etc. Those inexpensive deep cycle batteries are about the size and weight of an average auto battery and usually have an amp-hour rating of at least 110 AH or so. More expensive deep cycles have higher ratings. I personally have two 6 volts wired in series for a total of 12 volts. Those batteries have an 220 AH rating.

Here's some more threads that talk about these subjects:

http://www.apneaboard.com/forums/Thread-...-with-CPAP

http://www.apneaboard.com/forums/Thread-...wer-outage

http://www.apneaboard.com/forums/Thread-...or-camping

http://www.apneaboard.com/forums/Thread-...up-problem

Hope this helps!

[bryank1]

I agree with Super as far as the problem more than likely being a bad battery . I work with this type of equipment and the battery is usually always the problem. Any battery has so many life cycles. The battery usually will charge up ok initially, but as you draw a load on it, it fails prematurely. On UPSThis type of problem is typical with inverter related equipment, ups's, ect...
type of equipment it goes into a loop just like your describing.

My S9 autoset with heated tube and humidifier's power supply is rated at 1.0-1.5amps ac. I believe Supersleeper is going by the Dc rating not the
AC input current rating. So; 18AH x .9 (or efficiency rating) =16.2/ 1.5 (worst case) is 10.8 hours (assuming you have a good battery and are using a heated tube & humidifier). If your not using a heated tube & humidifier your hours are even higher. Incidentally, 10 hours seems like a long time to be sleeping.
Try a new battery, or if you have an external power supply to test the inverter with would be a plan of action. Good luck.

[SuperSleeper]

Problem is that the original poster (Crog) has an S8 AutoSet Vantage.

From this ResMed Battery Guide [PDF], that unit uses .98 amps for the unit itself, but this does not include the amperage draw from the H3i humidifier that attaches to that unit...

If you consider the CPAP machine PLUS the H3i humidifier, if you scroll down further in the document, where it lists the requirements for the S8 AutoSet Vantage +
HumidAire 3i, the listed amperage draw is 4.12 amps at 10 cmH20 of pressure, which is even higher that my estimated amperage draw of 3.0 in the above example. But keep in mind, the 3.0 may be closer (depending upon how high you set the heat setting). ResMed is probably using the heat on maximum level to get that 4.12 amp draw listing. If it's half that, who knows, it could be closer to 3.0 as my original post estimated.

So, this solution of an 18 amp-hour battery is even worse than I thought. I'm surprised that he got over 5 hours of use before it went ka-put. Must not have had the heated humidifier turned all the way up, or the 95% pressure is pretty low.

Also, please keep in mind that you cannot discharge a 12 volt lead acid battery below 60% of capacity, unless you want to destroy the battery. So the so-called "amp-hour rating" is not a complete picture. You must use the formula I listed in the above post to get the accurate number of hours you can use the battery without doing permanent damage to it.

So, getting a new 18 amp-hour battery will do nothing but waste money and (although it will run the CPAP and humidifier for up to 4-5 hours max before a complete discharge causes the malfunction Crog described) if you use it past 3 or so hours (the safe level), you'll destroy the battery. You may get lucky and doing this once or twice will not permanently destroy it, but overall capacity will definitely be negatively affected and do this more than 1-2 times and you'll definitely destroy the battery.

You need a higher amp-hour rating (minimum of 60 amp-hours), not a new low 18 amp-hour battery.

bryank1, not sure where you are getting your numbers. On your S9 Machine, according to the official Resmed Battery Guide, the "S9 AutoSet + H5i (EPR Setting 0, H5i setting 3)" has a total amp draw of anywhere between 2.57 - 4.10 amps, depending upon the pressure.

Here's the numbers for the S9 AutoSet with H5i Humidifier:

8 cmH2O of pressure = 2.76 amp draw
10 cmH2O of pressure = 3.01 amp draw
12 cmH2O of pressure = 3.32 amp draw
16 cmH2O of pressure = 3.77 amp draw
20 cmH2O of pressure = 4.10 amp draw

And, since this doesn't include the amperage draw from the heated tubing, I'm sure that with that, you'll have an even greater amperage draw.

And yes, I'm talking about 12 volt DC amperage draw here. That's the best-case scenario with 12-volt. If you run it through an inverter that changes it from 12 DC to 110 volts AC, you'll have an even greater amperage draw (on the battery) than the above numbers, since the inverter itself uses power in the inversion process.

[archangle]

If that's a modified sine wave (MSW) inverter, ResMed says it will damage your humidifier heater. Given the price and the fact that the manufacturer doesn't say it's a pure sine wave inverter, I'll bet it's a MSW inverter.

[edit - Only S8 and earlier humidifiers will be damaged by MSW. S9 humidifiers are fine. In this case, the member is using an S8 machine.]

Even though it claims 85% efficiency, I'll bet that's at full power, 400W.

How new is your battery pack, and have you done any kind of testing to see how much charge it holds? Lead acid batteries are notorious for not holding their full rated charge if they're old, or if you haven't charged them right.