Battery Back up for Airsense 10

[DaveY]

Nothing to report yet. Hope to try out the Medistrom this weekend. My pressures are on the high side...median at over 10 and a max at over 14 (APAP was originally set up at 10/16...now it's 10/18...sleep tech wanted it at 12/18 but it was causing me to be dizzy (vertigo) and have headaches).

Dave

[srlevine1]

I saw the specifications on the Pilot-24 Plus and questioned their accuracy. So I sent a query to the distributor ...

Hi guys,
 
There is something I do not seem to understand. 

I want to use the Pilot-24 Plus with my Airsense 10 -- w/o humidifier @ a pressure setting of 15
 
I noticed that the battery is rated ...  Capacity: 98 Wh or 19,000 mAh -- Output voltage: 24
 
But, by my calculations ...
 
98 Wh @ 24 volts = 4083.4 mAh
and
98 Wh @ 12 volts = 8166.7 mAh
 
So how did you derive the numbers because 19000 mAh @ 12 v = 228 Wh and 19000 mAh @ 24v =  456 Wh? 

They promptly replied ...

Hello Stephen,

19000mAh would be closer to the capacity when using 5V USB. Your calculations for 12V and 24V are correct.

Which I confirmed -- 98Wh @ 5 volts = 19,600 mAh.

So anyone relying on the 19,000 mAh number might be confused as to the real capacity of the battery.

Can't wait for some field reports as this looks like a good backup scheme that is lighter and more portable than my homebrew 56 aH deep cycle battery solution which weighs approximately 50 pounds with the cabling and charger.

[christian4870]

@srlevine1
good to know, it seems that all the manufactors work with this misleading definition.... and trust, that nobody make the own calculation..

[Bubba in NC]

I bought the Medistrom 24 about a month ago to use while flying to Europe this coming week. We're scheduled to arrive at 9:00 am, their time. I didn't want to spend the first day of my trip zombied out so I bit the bullet and paid for the battery with my HSA. I've used the Medistrom twice at home to test it out. At my pressure of 10 and the humidity turned all the down and on airplane mode, it lasted all night. One of the LED power indicators (of four maybe?) was out and the next one was blinking, so I guestimate I could get at least two nights out of it before recharging. It recharges using the power brick that come with the Autosense, so you still have to take that with you. It's built like a tank, heavy metal housing and a plush bag to hold it along with the cable. I tried to use it last week and was distressed to find it didn't work. After calling their support line, I discovered I'd failed to flip the tiny on switch on the end... Doh!

The problem is that the powers that be limit the size of a battery that can be taken on board a plane. This and similar units have the max power that you can carry. There's lots of cheaper solutions if you don't need to pass airport security, like camping etc.

[Ron AKA]

This is a subject of some interest to me in that we have a trailer and do occasionally camp for several days at a time with no AC power. Up until now my wife has been the only user of a CPAP and I have set the trailer up for her use only. Now I have just gotten on the CPAP train too, and I will have to determine how I will handle it. For what it is worth here is what I have learned over the past 3 years of her use. 

Our trailer uses two 6 volt golf cart batteries which have a pretty significant capacity of about 215 amp hours at 12 volts. However with a total weight of about 120 lbs they are not the kind of thing you carry on a plane! To supply my wife's ResMed S9 Auto using a basic 300 watt inverter, the batteries are fine for 2-3 nights if the humidifier is off and the standard non heated hose is used. To allow us to go longer I have also bought a 70 watt solar panel. It really only provides about 50 watts in full sun when feeding into a reasonably charged battery. Our experience has been that unless you get several cloudy days the solar panel keeps the batteries fully charged. This is in Canada where we get pretty long days in summer. 

The big learning we have had is that these basic inverters have a limit on how much current they can provide before the fan starts up. And that fan sounds like a jet aircraft taking off. I tried increased capacity units up to 750 watts and they do not help. They start the fan at even lower current levels. Providing the heating and humidity is not used so draw is about 30 watts, the 350 watt inverter gets by without starting the fan.

My son uses a CPAP too and his insurance covered the cost of AirSense 10 and a Z-1 Auto Travel unit. He claims the Z-1 unit simply makes too much noise and he has given it away (to my wife). Now my problem! I tried to convince him that the noise was coming from the inverter he uses, but he insists it is the Z-1 itself. He now does the same as my wife, and uses the ResMed with the humidity off and standard unheated line for camping along with a basic 350 watt inverter.

Now that I will have to use one, an AirSense 10, the easy solution would be to plug into my wife's inverter, but I know for sure that will start the inverter fan, and that is a definite no go. So now I am thinking that I will fork out the extra money and buy the ResMed 12 volt to 24 volt DC converter. It does not appear to have any fan cooling so should be perfectly quiet. If it works really well, I will possibly get one for my wife as well. The other option would be to get another cheap inverter, but I have found it is very hard to get one that does not run the fan. 

Last, I am a bit worried that the 70 watt solar panel will not keep up to the demands of two CPAPs. I guess time will tell. Perhaps Costco will have a good price on another panel I will use two. 

If anyone has any experience with the ResMed 12 to 24 Volt DC converters I would appreciate comments. Is there any disadvantage to them, other than the cost (about $135 here in Canada).

I saw a lot of calculations on power consumption and battery size for portable use. Here is what I think it takes based on a CPAP draw of 2.5 amps at 12 volts which about 30 watts. It depends on the battery voltage.

At 12 volts over say 7 hours this is 15 amp hours of power consumption and the required battery size. In milliamp hours it is 15,000.

If you have a 24 volt battery the current is approximately reduced in half so required capacity is 7.5 amp hours or 7,500 milliamp hours.

Hope that helps some.

[jaswilliams]

I have just purchased the dc-dc converter for my Resmed S9 expensive for what it does but it will use less power than an inverter and the losses due to conversion will be less I am expecting a 30% improvement over a dc-ac inverter. I am putting together a leisure battery and solar panel an charge controller as I want it to last 7days camping with unreliable sun in the UK I may need to charge it along the way I hope not. We shall see

[Ron AKA]

I have just purchased the dc-dc converter for my Resmed S9 expensive for what it does but it will use less power than an inverter and the losses due to conversion will be less I am expecting a 30% improvement over a dc-ac inverter. I am putting together a leisure battery and solar panel an charge controller as I want it to last 7days camping with unreliable sun in the UK I may need to charge it along the way I hope not. We shall see

I am curious as to how you have calculated an efficiency improvement of the DC-DC converter over the AC to 24 volt converter combined with DC to AC inverter? I recall I paid about $200 for a 70 watt solar panel about 3 years ago at Costco, and that the panel they were selling the past season was 100 watts and still about $200. If both myself and my wife used the ResMed DC to DC converters then my current 70 watt panel may be enough to keep up. It might save me $75 or so and avoid the hassle of using two solar panels...

[srlevine1]

If you are going mobile, the inverter is a waste of energy, you need the ResMed DC-DC Converter which bumps the 12v battery output to the 24v needed to power the S10.

If you want a clean installation without the slip and fall danger of long cords, you can wire in cigarette-style sockets near your sleeping area. Be sure to get the ones that are fused and with the covers to keep dust, dirt, bugs, and foreign objects out of the sockets. You will need one converter for each machine because using one converter for both machines is an unacceptable (and unsafe) load.

As for load calculations -- you may wish to purchase a small voltmeter/ammeter combination to check current draws at different settings as well as deal with battery condition and remaining charge.

If you are thinking of powering your unit off a running vehicle using the cigarette lighter -- be sure the vehicle is running before inserting the plug. The start-up voltage/current fluctuations can kill an electronic device.

As for the solar panels, they should be run through a solar controller and used to charge the battery. So it is a time versus recharge calculation. There is an issue if the panels are mounted on top of your RV -- you need to choose between an additional internal heat load if you need to park in the sun or get a portable solar panel setup to locate the panels while you park in the shade. Remember, the longer the cord -- more resistance -- less charging power, so keep cable runs to a minimum.

If you are going to power additional devices with a motor load or starting current draw transient, you may wish to isolate the circuit and/or use a separate battery.

I have an external battery switch that kills ALL battery power and a trickle charger for when the vehicle is parked on separate leads.

Check all connections thoroughly as most RVs are susceptible to fires from electrical shorts.

[Ron AKA]

If you are going mobile, the inverter is a waste of energy, you need the ResMed DC-DC Converter which bumps the 12v battery output to the 24v needed to power the S10.

Do you have any data on the total loss of an inverter and AC to DC adapter compared to a ResMed 12 volt DC to 24 volt DC converter?

[OMyMyOHellYes]

If you are going mobile, the inverter is a waste of energy, you need the ResMed DC-DC Converter which bumps the 12v battery output to the 24v needed to power the S10.

Do you have any data on the total loss of an inverter and AC to DC adapter compared to a ResMed 12 volt DC to 24 volt DC converter?

Googleate up the Resmed battery guide.  You can compare battery requirements for various units using the DC-AC perverter or the DC-DC converter.  My advice is always to ++not++ consider using the DC-AC perverter.  It takes nice, clean 12 V DC, then burns up power to turn it into 120 V AC.  Then you take that, and put i into the bedside converter to get it all back over to DC.  On CPAPs made by more progressive manufacturers, you don't even have to do any of that - you can go straight from the 12 V DC battery to the CPAP.  Note the brand of CPAP I have standardized on, except for travel, when I use an old model S-8 which still uses straight 12 V straight off of a battery (reverse polarity plug rules apply). 

OMMOHY