Finally got a battery!

[nomoore]

They do mention that their batteries can take 400 charge/discharge cycles up to 80% depth of discharge though instead of the 50% that you mention.

Its your call what you do with it, but I've yet to see a AGM battery that gives what I would call a reasonable service life it is regularly discharged to 20% of capacity.

• Battery life is directly related to how deep the battery is cycled each time. If a battery is discharged to 50% every day, it will last about twice as long as if it is cycled to 80% DOD. If cycled only 10% DOD, it will last about 5 times as long as one cycled to 50%. Obviously, there are some practical limitations on this - you don't usually want to have a 5 ton pile of batteries sitting there just to reduce the DOD. The most practical number to use is 50% DOD on a regular basis. This does NOT mean you cannot go to 80% once in a while. It's just that when designing a system when you have some idea of the loads, you should figure on an average DOD of around 50% for the best storage vs cost factor (from the same web site that you linked)

Cheers,

Bill

What are you calling a reasonable service life? How many charge/discharge cycles? Even if you cut Odyssey's number in half to 200 that's still many years of camping trips. And leaving it on a battery tender would keep it topped off at all other times. I think age would kill it before the deep cycling would. For the purpose of a CPAP battery for camping trips and backup for rare power outages I see years of service.

[sam1234]

It looks like the ODYSSEY PC 680 is not a deep cycle battery. I think that is Bill's point. It is not meant to be discharged to 20%.

I have two solar battery chargers that meet the description in the links above and expect to use them to charge the battery when no other power source (other than solar) is available. I expect only a marginal gain by charging the battery in this fashion. My thought is some is better than none.

I am considering changing my battery, as I am looking to make a cross country camping trip over the course of three weeks. Electric is not available at many of the camp sites. When I do have power, I will be charging my battery with a regular charger.

Happy camping.

[nomoore]

It looks like the ODYSSEY PC 680 is not a deep cycle battery. I think that is Bill's point. It is not meant to be discharged to 20%.

I have two solar battery chargers that meet the description in the links above and expect to use them to charge the battery when no other power source (other than solar) is available. I expect only a marginal gain by charging the battery in this fashion. My thought is some is better than none.

I am considering changing my battery, as I am looking to make a cross country camping trip over the course of three weeks. Electric is not available at many of the camp sites. When I do have power, I will be charging my battery with a regular charger.

Happy camping.

But Odyssey batteries are deep cycle batteries. It talks all about the technology that makes it that way on the home page. I believe Bill has a different point though. Regular non deep cycle batteries are meant to be discharged no more than 20% DOD or 80% full. He mentioned 50% DOD which is reasonable for longevity on a deep cycle battery with heavy use.

I wish you good times with your cross country trip. It sounds like a lot of fun.

[floyd22]

I just got my Res Med 3 days ago. We travel about 6 months a year in a motorhome and use an inverter for 120V when we aren't plugged in at a campground. We "dry" camp quite often so this is some concern to me. I have a generator so I can run that for a while and recharge my batteries daily.
I was told by Res Med that I can run the unit off the inverter, but the heater won't work because it isn't a pure sine wave inverter (most all motorhomes use what they call a modified sine wave generator). Do any of you have that experience or do you not use the heater when camping etc?
The extra battery solution seems to be a possibility as I have a 12V plug on the machine, but the same question applies. Do you use your heater with the battery?
Thanks for your help.
A struggling but determined newbie.
Floyd

[nomoore]

I just got my Res Med 3 days ago. We travel about 6 months a year in a motorhome and use an inverter for 120V when we aren't plugged in at a campground. We "dry" camp quite often so this is some concern to me. I have a generator so I can run that for a while and recharge my batteries daily.
I was told by Res Med that I can run the unit off the inverter, but the heater won't work because it isn't a pure sine wave inverter (most all motorhomes use what they call a modified sine wave generator). Do any of you have that experience or do you not use the heater when camping etc?
The extra battery solution seems to be a possibility as I have a 12V plug on the machine, but the same question applies. Do you use your heater with the battery?
Thanks for your help.
A struggling but determined newbie.
Floyd

If you have enough battery power (the humidifier takes more power than just the machine without the humidifier) you can buy a pure sine wave inverter. I don't know how much power you have in that mobile home but that may very well be an option.

A lot of people will forgo using the heat and just use the humidifier in a passover configuration. That means that you still set up the humidifier with water in it and just don't turn it on. The air picks up a little bit of humidity just from passing over the water. If you hook up 12V power to your machine then the heated humidifier won't heat. It'll just be a passover humidifier.

[feeling_better]

An optimistic footnote: The actual power used by your cpap machine will depend A LOT on the normal expected leak rates of your mask plus the unwanted/unavoidable leaks. As the pressure increses the leaks increase too. A few months ago I had measured and posted here the dc current consumption of the m-series for different pressures. So the power consumed depends on the mask you use, and your pressure settings. The stated power needed for the machine is often for the higher leaks/pressure settings (although the cpap battery spec may be giving it for the average useage). So if you are running at low pressures like me, with a low leak rate mask such as swiftLT, the battery may last much longer!

My M-series has a power supply which supplies about 4.1A, but my actual useage is at about 0.6A. So even if I use a 5AH, laptop LiIo battery pack, I can almost get a good nights run. Those packs weigh less than 1 lb, and is very small. Usually LiIo laptop batteries are very expensive, but you might be surprised that the very commonly used models, mass produced in china, can be readily bought online for about $60; of course you need a proper charger...