The eternal camping question

[NewsmanBG]

Hi all:

I have ResMed S8 Elite II CPAP. Going camping. Any reason I can't just plug the regular AC cord into the AC socket on this unit?

http://www.amazon.com/Duracell-DPP-300E ... sbs_auto_7

Have read for a few hours without finding this answer, so thanks in advance. Now, off to plug a hose into my head (12:18 a.m.)

Newsman

[cflame1]

I think that what the experts will want to know... is are you using the heated humidifier or not?

[NewsmanBG]

Good question, cFlame.

I just updated my equipment in my profile. So you can see that at home I use the heated humidifier. I would be willing not to use it while camping (figuring that outdoors humidity will be pretty even high without it), if that would enable me to use the portable power pack. That would also make for one less thing to bring along, also a plus.

As I understand it, the Duracell unit I posted is essentially a 12V sealed lead acid battery with an AC inverter built in. It also has a DC "cigarette lighter" socket. So I could also use it with the Resmed DC-12 DC adapter. Of course, that adds a piece of equipment to buy and bring.

Thanks in advance. This community has been so much help and support to me since I began therapy about two months ago.

Newsman

[JohnBFisher]

... I have ResMed S8 Elite II CPAP. ...Any reason I can't just plug the regular AC cord into the AC socket on this unit?

http://www.amazon.com/Duracell-DPP-300E ... sbs_auto_7

... Have read for a few hours without finding this answer, so thanks in advance. ...

Thanks for taking the time to research first. Here is Rested Gal's link on this. It might help:

LINKS to Battery operation, camping, power outage
viewtopic.php?t=9682

However, I can answer your questions directly.

First, that batter is rated as a 14 amp-hour AGM battery. From the website:

The heart of the Duracell Powerpack 300 is a sealed, non-spillable 14 amp-hour AGM battery.

A caution is that the tech specs (see the link below) are only 12 amp-hours! So, it's not quite as much as you might expect.

It is a deep cycle battery and can be used for a long time - as long as you do not drain it too far.

Second, no using the humidifier is the best way to extend the life of a battery like this.

Third, the inverter in that unit outputs a modified sine wave (see the tech specs link below). So, your humidifer will not work with that inverter.

Fourth, you will do better if you use a DC connection, rather than the inverter. Though it will work, you will get more time out of the battery with the DC connection.

Fifth, you can find the battery amp-hour requirements from the ResMed battery guide:

http://www.resmed.com/us/assets/documen ... lo_eng.pdf

See page 15. What is your current pessure for CPAP. If it is 12, then a 12 amp-hour battery should last 8 hours. With a 12 amp-hour battery you will need to recharge it most of the following day. (It often takes one to two hours for every amp-hour used to charge the battery). The battery guide actually provides you the 50% margin you need to not exceed the capacity of the battery. So, while your CPAP unit will only draw 6 amp hours for 8 hours, it means you should have a 12 amp-hour battery. That will drain 50% of the battery before you would have to recharge it.

Of course, if you pressure need is higher, the amp-hours required will also increase.

The Tech Specs on that battery are:

http://www.duracellpower.com/documents/ ... -pp300.pdf

The Charging time (if the battery is fully discharged) would be:

From AC outlet Max. ................ 24 hours*
From DC outlet Max. ................ 2.5 hours*
*Maximum charging time occurs when battery is completely discharged

So, your best bet would be to recharge your batter by connecting it to a charger for a couple hours. Or connect it to the cigarette lighter in your car (with the car engine running) or ...

In other words, if you are sleeping for one night this battery will be fine. If it is more than one night, you might need a more powerful battery or be certain you can recharge the unit during the following day.

The Duracell PowerPack 600 provides a 28 amp-hour battery, so it would last a couple nights before you had to recharge it. Here are the specs on it:

http://www.duracellpower.com/documents/ ... -pp600.pdf

And here's an Amazon link to it:

http://www.amazon.com/Duracell-DPP-600H ... sbs_auto_1

Hope that helps.

[NewsmanBG]

JohnB:

Thank you so much for all of the great information. The link to the ResMed battery guide was particularly excellent. My pressure is 8, so that looks like .94 amps. It says 11Ah battery will run it, including a 50% margin of safety. You are quite right that it will need to be recharged every day (but assuming the table's correct, only recharged halfway or so from dead. I will be at a campground, and so I think I should be able to make that happen. I think I am willing to accept that tradeoff since the 12 or 14 Ah Duracell is so much lighter and less expensive. I may even buy two of the smaller ones so that on one-day trips, I can bring one, and on two-day trips, I can bring the second. Also, in the event of pack hiking, I could have two different hikers each carry half the load.

Anybody else want to double-check our work here?

[bearded_two]

I do not know what sort of campground you will be staying at; at some campgrounds you may be able to reserve a camping spot that has an electrical outlet.

[harry33]

needless to say do try out your system at home first

[5aces]

viewtopic/t49452/viewtopic.php?f=1&t=45 ... 37#p411015

Here is a link to an in home test I did with a ResMed S8 elite II and a 600W version of the battery pack.

[NewsmanBG]

Good stuff, bearded, harry and 5aces. Interesting, 5, that you found out there is a lot of headroom in the ResMed table (or that these units' batteries are good for more Ah than they're rated for. Maybe they build in extra so they exceed spec when they are new and then meet spec when they're a little older.

Smaller/lighter Duracell pack ordered.

Cheers,
Newsman.

[JohnBFisher]

... Interesting, 5, that you found out there is a lot of headroom in the ResMed table ...

The table builds in headroom. Intentionally. By dropping the battery to only 50%, then recharging it, you don't damage the battery as much. That will allow it to last years. If you discharge it until the low battery alert comes on, then it will cause the battery to fail more quikly (if you do it frequently). From the battery guide, you will find:

Deep-cycle batteries
The major difference between a true deep cycle battery and other types of batteries is that the plates are solid lead. They are manufactured with much thicker plates in each cell and can be discharged as much as 80% or more.

And on each table listing the required amp-hours:

Battery size for 8 hours
use (amp-hours)
(includes 50% safety margin)

So, they designed the headroom into the tables.

[nghy]

Hi, First, from an engineering point of view your approach is a very inefficient method that wastes a large portion of the battery power. Without a complete analysis of this battery pack, and judging by the price of the unit, I don't think it will have sufficient energy stored in the battery to last more than an hour or so if that much. Second, the specification for the ResMed S8 Elite II CPAP says it will run directly off a 12 volt battery. All you will need is the ResMed D. C. cable. You can use the battery in your car or any other 12V battery of sufficient size. If you go camping a lot and are away from your car, I would recommend buying the D.C cable and a deep cycle marine battery used on small boats. A trickle charger used to charge car batteries at home would be suitable to recharge this battery. Third, not all D.C. to A.C. converters produce a sine shaped output. More than likely the output looks like a square wave. The difference would not bother a light bulb or a resistance heating device but it would strain a motor. See http://www.smps.us/power-inverter.html

AaronM

[NewsmanBG]

nghy, what do you base these assertions on?

Seems like AC inverters waste about 10% of the power, which I find an acceptable tradeoff, given Resmed DC adapter costs $79 and adds another item to bring.

Resmed documentation linked above says it is fine to use a modified sine wave inverter for the flow generator without damage, just not to use the heated humidifier with one.

Also, 5aces tested a similar setup with exactly twice the capacity of the one I bought and got something like 25 hours of blower use out of it. Makes it seem reasonable I could get 12 hours of blower use out of mine easily. And I really only need eight.

[5aces]

If you only need it to last a couple nights for a cpap machine with no humidifier,it's going to work.

The blower can operate on a modified sine wave.

I have used mine for the very odd power outage wihout incident,purchasing the larger capacity model so it would have more grunt(CCA) to boost a vehicle.

Just bear in mind the info from the manufacturer:

1)-use the unit every 6-8 weeks,to achieve a discharge (up to 50%),then recharge for a longer life (plug in and turn on a radio etc.).
Use the powerpack minimum every 3 months and recharge.

2)-expect at least 200-300 'complete' discharge/recharge cyles before you have to recycle this unit,depending on your use.

You will be pleased with this solution,when you get it test it yourself,revive this thread and let people know how it works for you.

i would be curious to know if your Duracell unit has the "Low Power Alarm" which sounds off before the power supply gets too low,preventing any issues with your attatched devices.

If you need more hours out of the pack you already know that the D.C. line out will give you that,honestly for $50 how can you go wrong?

Good Luck and enjoy camping with your new powerpack,which will be most useful for many things around the campsite.

[bearded_two]

All of the common CPAP flow generators work just fine off of modified sine wave; they would probably even work with a square wave. Respironics, Fisher Paykel, and DeVilbiss humidifiers also work with modified sine wave.

[JohnBFisher]

The ResMed batter guide specifically mentions this unit as working with a modified sine wave, which the inverter in this battery pack outputs. It cautions the humidifier can not be used with the modified sine wave. But that's not a big issue for a night or two.

Though this flow generator might not damage a car battery, I do not generally recommend that. Not all units would be that nice. My ASV unit is a power hog and would probably destroy a car battery within a couple nights.

However, this battery pack actually provides the deep cycle battery in an AGM format. So, it's less likely to leak or have problems than a marine battery.