Another battery question

All,
I have been reading all the articles about CPAPs and batteries and have read the Resmed document regarding batteries and battery sizes, etc. Still it doesn't quite make sense to me. I have a Resmed Elite and plan on going camping for 3 nights...my question is - What size deep-cycle battery do I need that will last for 3 days. The "size" suggestions in the documents don't really help me, I guess I am just not understanding the lingo. I know that I need the special cord from ResMed for DC but at this point I am more interested in what kind of battery I will need. Any help would be appreciated.

Thanks

So you probably already have the battery document from ResMed:
http://www.resmed.com/us/assets/documen ... lo_eng.pdf

When I travel I only take the base machine. I leave the humidifier at home. Power used by the unit varies with the pressure setting, higher pressure setting, more power draw. With the pressure set at 10, the S8 Elite II base unit only draws 1.09 amps. If you add in the humidifier, it jumps to 3.66 amps. So a much larger battery if you use the humidifier. Let's assume you leave the humidifier at home (or just turn it off).

In the battery power document link above, look at the charts and reference the pressure your machine is set at. For example: If your pressure is 12 and you power your S8 Elite II base unit with an inverter, you will need 14 amp-hours for each 8 hours or a minimum 42 amp-hours battery for three days. If you power your S8 Elite II base unit with a converter, you will need 10 amp-hours for each 8 hours or a minimum 30 amp-hours battery for three days. If your pressure is different than the 12 used in the example, look up your pressure (use the next higher if not listed) and read the 8 hour amp-hours value. Multiply by 3 for three days. Please note that the amp-hour values listed in the tables are conservative, they include a 50% margin. Personally, I think this is good. Batteries inevitably degrade over time so having some reserve helps offset the aging. You will still get your three days worth even as the battery ages. Can you run your machine directly from the battery without a converter? Probably so since the S8 Elite II will operate directly from 12 vdc. However, the converter provides some isolation and low voltage cut-off protection and it's apparent that ResMed is recommending the converter (or inverter since they also have a low DC voltage cut-off as well). I'd stick with the converter or inverter per the document.

Are you going to schlep a heavy deep cycle battery on your trip out into the wilderness, or stay close enough to a vehicle to be able recharge a portable battery during the day?
I had great success with my little 2 pound litium ion (11.1V 10Ah [111 Wh, 7A] from (batteryspace dot com) on a boat that ran a generator during the day, allowing me to recharge for another 8-10 hour use. The investment was worth it in my mind, because if I lose power in my house because of a storm etc, I'll have the first night covered and can recharge each day from wherever there is AC or DC power. The light weight made it easy to take (and use) on a plane for international travel to an "iffy" location power-wise, as well.

I was running at a setting averaging about 15 (no humidifier) for 8-10 hrs per night.

snoreking makes a very good point about some availability to recharge during the day. This reduces the amp-hour requirement to a single night (8 hour). In my previous example with converter and pressure of 12 you only needed 10 amp-hours for 8 hours. This would be a much smaller battery than the 3 day scenario and would lend itself to a commercial solution. Many of the car jump products have a battery in the 14 to 18 amp hour range and most have a DC cigarette lighter outlet. The Wagan 400 Watt Power Dome has an 18 amp-hour battery plus the jump start, air compressor, and 400 watt inverter. I would not trust the inverter to run my cpap but the unit makes a good portable DC power source. During the day you would need to recharge. It takes approximately 10 hours to fully recharge from a 12 volt DC source such as boat or auto. It will also recharge from a 120 volt adapter (included with product) but it takes 24-30 hours to do a full recharge. Since you would not be using the full battery for the 8 hours of cpap, it would take about 15 hours to recharge using the 120 volt adapter and 6 hours to recharge using 12 volt . The 120 volt recharge may not workout because of the time required to recharge (and is probably not available out camping anyway), but if you have a boat or vehicle to recharge from, this might be a solution to consider. There are many products similar to the Wagan unit out there and they are competitively priced and readily available.

I find that a 35-amp hour battery used in "hoveround style" scooters will handle about 3-nights.
Hurricane Gustav (last year) came right through us.....and we were without power for a little over 3-days.
Interstate Battery has them at a reasonable price....and they have a neat little "trickle charger" that does a good job.
Add your DC power cord....and a marine style battery box....and your done.
A good solution....for not many bucks.

Gerald

I am going to be camping on Padre Island National Seashore actually, so I will be driving up to my camping site. Not sure how I am going to protect my CPAP from the sand but I will figure out something. I am leaning toward a heavier battery for less cost. Most of the smaller batteries are way too expensive...

The new lightweight batteries are frequently LI-Ion and the heavier and larger batteries are lead-acid. LI-Ion is great if you have to carry the battery because you can get a lot of power in a comparatively small and lightweight unit -- they also don't spill, are non-corrosive, and can be used in any position. Laptop computer batteries and the new "CPAP batteries" are usually Li-ion. Nickle cadmium (NiCad) batteries were at one time commonly used as rechargable batteries, but they have largely been repalced by non-spillable lead acid and Li-ion batteries.

There are two types of lead-acid battery construction; flooded cell, gelled electrolyte, and AGM (Absorption Glass Mat).

Common lead-acid batteries such as are normally used in cars are flooded cell type. The acid is a liquid that covers the plates.
Lead-acid batterie are corrosive and can easily spill. These are either starting batteries or deep cell types.

Gelled electrolyte batteries have the acid suspended in a gel. These are commonly used in electric wheel chairs,
kid's electric cars, UPS's, and small car battery jump packs. One brand name is Gel-Cell, which were even available as "D" cells.
Gelled electrolyte batteries don't spill, are non-corrosive, and can be used in any position. These are usually deep cell types.

AGM batteries have the acid suspended in a fiberglass mat. These are commonly available in car battery sizes and are frequently
used as car and RV batteries. AGM batteries don't spill, are non-corrosive, and can be used in any position. These are available as
starting batteries, deep cell, and combination types. These are typically larger batteries and are usually 12 volt types, which can be
charged using automobile charging circuits.

I have two AGM batteries in my car; one replaced the regular starting battery (a starting type that can tolerate deep discharge) and
the other is mounted in the trunk (a deep discharge type that can be used to start the car). Both of them are charged/kept charged
as the car is driven. I can remove the batteries, bring them in the house, and use them to power my CPAP. I also have a 20Ah
Li-ion CPAP battery that I use for normal backup and travel. With the Li-ion battery and the two AGM batteries, I can power my CPAP
for nearly two weeks. As they are car batteries, I could conceivably power my CPAP as long as I have gasoline to charge the batteries.


Just be glad that we don't have to use these any more.

Ok, lets take this a bit further. I am planning a wilderness hunt, so unless the horses come with batteries?????? Anyway my thought was a Li battery and maybe solar panels, but I think the charge time might be an issue. any thoughts?

What is the longest period you will be away from an ac or dc charging source? Will the wilderness be deep woods, where solar might not help, or sunny? A fixed location as in camp site, or constant moving? The place I got my LI has a solar charger option, but that would be useless in deep woods, I would assume. (batterysource dotcom)

Even with bright sunlight, it would take a rather large solar panel to keep a CPAP battery charged. Depending upon some variables, you will need about 10Ah@12V / 120Wh per day -- and that is just for a CPAP machine; it is impractical to operate a heated humidifier off of batteries. I am fortunate that heated humidifiers weren't foisted onto patients when I started using CPAP and because of that, I don't have to power (or schlep) a humidifier.

It will be a deep wilderness area, out 6 to 8 days. Although I use a humidifier, I can do without, so that wouldn't be an issue. Doesn't sound very promising though and I won't give up the hunting. I can't believe no-one else has come up against this.

MadSwede wrote:It will be a deep wilderness area, out 6 to 8 days. Although I use a humidifier, I can do without, so that wouldn't be an issue. Doesn't sound very promising though and I won't give up the hunting. I can't believe no-one else has come up against this.

Well, have a look to see...
Rested Gal's amazing list of "LINKS to Battery operation, camping, power outage."
viewtopic.php?t=9682
When you finish exploring that list by at least Christmas, come on back and tell us what you decided on!
I do remember reading a thread during the past year (but cannot find it with the Search box) about a guy who bought an Everest 2 with about 3 of the integrated battery packs, to last through a week of wilderness camping (maybe backpacking?) with no chance for recharging.

plr66 wrote:When you finish exploring that list by at least Christmas

ROTFL!!!

That IS more links than the law should allow!

And guess what! I've just added another one. Yep, this one.

Nothing that about four two-pound LI batteries wouldn't take care of, if you want to shell out about $700.00! Actually, there probably are LI's with a lot more "horsepower" than the one I use (110wh) that would get the job done. If I went six to 8 days without my machine I would be a zombie after day three, so if you are like me, even if you find a solution that you could use every other day with a 3-4 day capacity you might get by. I would call the 800 number at batterysource and see what they tell you.