Battery Recomendations

I would like to hear specifics about your battery experience. For the last 8 years or so I have used a lead/acid Deep Cell Marine Battery (heavy) and I could generally get 3-4 nights out of it (without humidifier). That battery has reached the end of it's life and I would like to get a new one, ideally lighter if possible. I have seen that some people are using motorcycle batteries, which should be lighter but how much time can I get out of one? Maybe I could get two and rotate them. If I could get two nights per battery, that would give me 4 nights. I have the ResMed AirSense 10.

Resmed directed me to this link: http://www.resmed.com/us/dam/documents/ ... lo_eng.pdf but it is a dead link. I have contacted them for more info as well.

Thanks in advance

Motorcycle AGM batteries are nearly all starting batteries and would be quickly damaged by deep discharges. Maximum capacities of 32 amp-hrs are limiting in those batteries and they are much more expensive per amp than what you are using.

If you want to spend big bucks and maximize capacity, the Optima YellowTop battery produces 75 Ah in a package under 60 lbs and well under $200. In most cases you can't get around the fact AGM will cost about 2.5 times the price of a flooded acid deep discharge battery in $/Ah, but it charges much faster, can't leak and won't off-gas.

Let's not get into LiFePO4 or lithium chemistry. Lithium-iron is cost prohibitive, and you need to watch out for ratings expressed as lead-equivalent (pb-eq). Lithium ion has potentially great energy storage, but is expensive and potentially unsafe.

Capnloki is the person who's got the most info... go to Members up above and to the right, click that and type in 'Capnloki'. Finally click 'Search User's Posts'.
There's all kinds of stuff there.

I agree with the above posts. That CapnLoki guy really knows his stuff and you should read all of his posts.

A few things to remember -
Marine batteries are not necessarily "deep cycle," they must say "deep cycle." And as noted, motorcycle batteries are usually starter batteries, not deep cycle.
If you want a small cheap deep cycle, go for mobility scooter batteries, such as the U1 size.
AGM batteries are worth the extra money.
I think that LiFePO4 has possibilities, though you have to be very careful with the selection since those marketed for motorcycles have bogus ratings. Lets talk if you want to try this.
The ResMed doc has been hiding lately - search for "resmed battery guide pdf".

If you really want advice, you'll have to provide more details of your needs - for instance, is this for home backup or camping?

CapnLoki wrote:I agree with the above posts. That CapnLoki guy really knows his stuff and you should read all of his posts.

Very droll Capnloki.

Thanks all for the advice. A few more details:

I use the battery primarily in a cabin 1000ft behind my house and up a hill so i often move it with my atv but with snow on the ground i have to sled the battery. I was getting 3 nights before having to drag it back to the bousr for charging. For this use i would like a lighter battery and if light enough i can just carry it back and forth in a backpack

I also want a battery in my home that can last for 3 nights in case of power failure... sounds like i need two different batteries?

Do i have to trade amp hours for weight?

Advice?

sleepy432 wrote:Thanks all for the advice. A few more details:

I use the battery primarily in a cabin 1000ft behind my house and up a hill so i often move it with my atv but with snow on the ground i have to sled the battery. I was getting 3 nights before having to drag it back to the bousr for charging.

solar panels?

sleepy432 wrote:Thanks all for the advice. A few more details:

I use the battery primarily in a cabin 1000ft behind my house and up a hill so i often move it with my atv but with snow on the ground i have to sled the battery. I was getting 3 nights before having to drag it back to the bousr for charging. For this use i would like a lighter battery and if light enough i can just carry it back and forth in a backpack

I also want a battery in my home that can last for 3 nights in case of power failure... sounds like i need two different batteries?

Do i have to trade amp hours for weight?

Advice?

My first thought is that if I used a cpap in an (unheated ?) cabin in winter I would certainly want a humidifier, which would increase the power demand from 5-8 Amp-hours to 20-30 Amp-hours.

As for solar, that is quite possible. A 100 watt panel would provide on average about 24 amp hours a day in the winter (very location dependent) so this could keep a fair sized battery charged, even enough for humidity. Assuming you have reasonable sun you should be able to make this work for well under $200. (The panel hookup is quite easy, the real work is mounting so if you have a good southern view, its really simple.)

For your house backup, you probably want a large battery, maybe 100 AH. This would weigh about 50-65 lbs. The cheapest would be a Walmart marine deep cycle for under $100, but this would be a flooded battery that i would want to keep in the garage. A large AGM, better suited for the bedroom, would be about twice the cost. As with any lead acid battery, you want to leave the "bottom third" of the capacity unused, so a 100 AH battery actually provides 66 AH usable power.

For lightweight the cheap option is a lithium pack designed for airplane travel which limits capacity to 8 AH, enough for one night. This only weighs a pound or two, so you can carry it back and forth easily, but it does need daily charging, which can take 5 hours or more. Or the compromise is a U1 scooter battery that provides 35 AH (24 usable) and weighs in at 24 lbs.

So you have a lot of options. If I were worried about long term outages, I would consider solar because then I could recharge the house battery if need be. (Actually I use 350 watts of panels on my boat and that's enough to run fridge, TV, computers, and a cpap as long as there's some sun.)

One more thing, because you have a ResMed cpap, you need a 12-24 volt converter to run off of most setups; otherwise you end up using an inefficient inverter.

sleepy432 wrote:Thanks all for the advice. A few more details:

I use the battery primarily in a cabin 1000ft behind my house and up a hill so i often move it with my atv but with snow on the ground i have to sled the battery. I was getting 3 nights before having to drag it back to the bousr for charging. For this use i would like a lighter battery and if light enough i can just carry it back and forth in a backpack

I also want a battery in my home that can last for 3 nights in case of power failure... sounds like i need two different batteries?

Do i have to trade amp hours for weight?

Advice?

I think a move to two batteries is a no-brainer, one for house and one for the cabin.

Another poster has suggested solar charging for your battery. But have you considered getting a small, 1 kw genset to charge the battery? These are quite affordable and the better ones are quiet, too. If you had such a genset for your cabin the only thing you would have to carry up there is some fuel for it. And when the power goes out in your house, it's probably worth it to you to move the genset from cabin to house for the duration of the outage.

I searched and found the battery document that you couldn't find on the Resmed website and you can get it from here: http://www.resmed.com/assets/documents/ ... lo_eng.pdf

You say you did something similar before? Did you use the official Resmed DC converter? https://www.cpap.com/productpage/resmed ... hines.html Or was that perhaps with a Respironics machine that's 12 volts instead of Resmed's 24?

One wonders why Resmed went with 24 volts when every other brand of cpap on the market works fine on 12 volts and can be used without voltage converters. I guess it's the same reason why the cpap won't power on even if you already have a 24 volt source, unless you have their special cable which has the correct signal voltages on the correct pins of their special cable connector.

I do appreciate all the information I'm getting here including the recommendation to get a solar panel or a 1Kw genset. Just for some background I sleep in my cabin about 1-10 times a month (depending on the weather). My lead/acid battery is about 8 years old and is not holding a charge like it used to.

I like the idea of leaving the battery on site instead of having to move it back and forth all the time. Also I have very good wind at my location so a wind generator could be a good option. I am just trying to keep the expense manageable and my ground is VERY ledgy so I am not sure how i could set up a stable mount a wind generator ... perhaps on a tree or some type of base?

So here is some more information and some more questions (assume I know little about batteries/power hookups/solar/wind etc)

I have a small coleman solar panel that I used with my lead/acid battery this past summer.
* How can I tell when the battery is full vs needs charging (beside having it die)? Or in other words, I've not been able to tell how well the solar panel is keeping the battery going.
* How can I figure out if I need a bigger or additional solar panels?
* How can I tell how much charge is in my battery (besides lugging it home and hooking it up to my charger or waking in the middle of night when it dies)?

I have the Resmed AirSense 10 with the Resmed battery converter (whatever that does). Can someone recommend a good battery solution for that? I don't mind buying one for the cabin and one for the house but if I do I would want the cabin one to be as light as possible to give me at least one solid night sleep and the heavy one can be in the house.

I see that the Resmed airsense 10 uses 24 volts instead of 12. Should I go back to my cpap provider and request a 12 volt machine because of my 'battery' situation or will my equipment work just fine with a 12V battery?

Right now I am leaning towards an AGM Battery and it sounds like I should focus on a min of 100 amp hours to get 3 full nights. That looks like it would be a heavy unit so if that's the case then I really need to figure out how to charge it without moving it all the time.

More advice/thoughts - all input appreciated!

sleepy432 wrote:I do appreciate all the information I'm getting here including the recommendation to get a solar panel or a 1Kw genset. Just for some background I sleep in my cabin about 1-10 times a month (depending on the weather). My lead/acid battery is about 8 years old and is not holding a charge like it used to.

8 year old means probably dying, if not dead

sleepy432 wrote:I like the idea of leaving the battery on site instead of having to move it back and forth all the time. Also I have very good wind at my location so a wind generator could be a good option. I am just trying to keep the expense manageable and my ground is VERY ledgy so I am not sure how i could set up a stable mount a wind generator ... perhaps on a tree or some type of base?

Wind generators can be handy but they tend to start at $600 or more. That would pay for a lot of solar. A genset would be a better fallback.

sleepy432 wrote:So here is some more information and some more questions (assume I know little about batteries/power hookups/solar/wind etc)

I have a small coleman solar panel that I used with my lead/acid battery this past summer.
* How can I tell when the battery is full vs needs charging (beside having it die)? Or in other words, I've not been able to tell how well the solar panel is keeping the battery going.

This is the big question and it deserves more time than I have now. I like to use an "Amp Hour Meter" but they are pricey at $250 for a proper one. (small one start at about $65.) The old standard is a hydrometer which measures the specific gravity of the acid, but this requires a flooded battery that can be opened, i.e. not AGM or cheap zero maintenance batteries. This leaves reading the voltage, but the range of low to full is only about 0.6 volts, with an error/uncertainty of about 0,3 volts. The cheapest solution is to have an oversized panel and battery, with perhaps a cheap amp-meter, so you know that when the sun is shining and the current drops down, then the battery is full. By reading the voltage often you can get a feel for how your system works. Beware of advice like "12.6 volts means the battery is full" as there are a variety of ways to have a false reading.

sleepy432 wrote: * How can I figure out if I need a bigger or additional solar panels?

Tell us how big your panel is. Nowadays, the panel is the cheap part of the system.

sleepy432 wrote:* How can I tell how much charge is in my battery (besides lugging it home and hooking it up to my charger or waking in the middle of night when it dies)?

see above

sleepy432 wrote:I have the Resmed AirSense 10 with the Resmed battery converter (whatever that does). Can someone recommend a good battery solution for that? I don't mind buying one for the cabin and one for the house but if I do I would want the cabin one to be as light as possible to give me at least one solid night sleep and the heavy one can be in the house.

Weight equals power. There is no short cut with lead/acid technology.

BTW, most flooded batteries are made by a small number of manufacturers, with a few more that specialize in high quality, such as Trojan, my favorite. There a few more players in the AGM world, I go with Optima, but also like Universal.

sleepy432 wrote:I see that the Resmed airsense 10 uses 24 volts instead of 12. Should I go back to my cpap provider and request a 12 volt machine because of my 'battery' situation or will my equipment work just fine with a 12V battery?

Give it a try, but I wouldn't expect it to work. The converter is probably only a 10% hit.

sleepy432 wrote:Right now I am leaning towards an AGM Battery and it sounds like I should focus on a min of 100 amp hours to get 3 full nights. That looks like it would be a heavy unit so if that's the case then I really need to figure out how to charge it without moving it all the time.

solar is sounding right for this

sleepy432 wrote:More advice/thoughts - all input appreciated!

Have you considered a 1000 foot extension cord? (I'm serious - the numbers work on this.)

sleepy432 wrote:Shoukd I go back to my cpap provider and request a 12 volt machine because of my 'battery' situation or will my equipment work just fine with a 12V battery?

Your present kit is fine.

The Resmed A10 battery adapter has an efficiency of about 97% (from my personal measurements of it), so that will not materially change the duration of xPAP operation from your battery

Again, thanks all ... right now I am thinking that I will get a 100+ aH AGM 12v battery and upgrade my solar setup for 100 watts. My current solar panel is just a 10w unit. I don't get full sun because of tree coverage.
Still learning how to get this all setup. Perhaps I'll get a small portable generator too at some time.

I looked at the 1000' extension cord option but there would be isolation issues - it would have to be even longer or cross several trails and be an eyesore.

Again thanks for all the advice, much appreciated.

sleepy432 wrote:Again, thanks all ... right now I am thinking that I will get a 100+ aH AGM 12v battery and upgrade my solar setup for 100 watts. My current solar panel is just a 10w unit. I don't get full sun because of tree coverage.
Still learning how to get this all setup. Perhaps I'll get a small portable generator too at some time....

Sounds like the beginning of a plan. The 100 watt panels I got from Amazon were from Renology at $140 each, brackets extra. You'll need a small regulator and some cable. If you use the cabin much in the winter you'll want to find a site that favors the winter sun angle. Estimate of available power are based on the "average sun hours" for your location and season, around 3-4 hours per day for much of the country.
http://www.solardirect.com/pv/systems/g ... hours.html
This works out to 20-25 Amp-hours a day from a 100 watt panel, less if you're shaded some. For the 10 watt panel this would only be 2 AH, which is barely enough to offset the self-discharge of a larger battery. (Actually its low enough that you don't need a regulator with a 100 AH battery because it can't over charge.) If you don't use humidity, the 100 watt panel should be plenty of power and the battery should carry you though the cloudy periods. With humidity, it depends on how things work out, but given that the house is 5 minutes away it shouldn't be a problem.
So do some research and feel free to ask more questions as your plan gets fleshed out.