Battery backup for S9 AutoSet

How much time would you approximately get out of an 80 AmpHour battery,with and without humidifier, does anyone know?

The problem with battery ratings is that the manufacturers tend to be "optimistic" with their ratings.

With that caution, your S9 draws about 1 amp without the humidifier and about 3 amps with the humidifier.

If we take 80 amp hours and divide it by 1 amp we come up with 80 hours.

If we take 80 amp hours and divide that by 3 amps we come up with a little over 26 hours.

To get the most life from a lead acid battery it is best not to completely discharge it. This means that you should reduce the number of hours by 30 - 50%.

squid13 wrote:How much time would you approximately get out of an 80 AmpHour battery,with and without humidifier, does anyone know?

Based on my experience I think you would get two nights, or about 14+ hours, with a humidifier, probably six or more without. That's using an inverter and the standard power brick. Might be a little more using the Resmed DC converter brick.

HoseCrusher wrote:The problem with battery ratings is that the manufacturers tend to be "optimistic" with their ratings.

With that caution, your S9 draws about 1 amp without the humidifier and about 3 amps with the humidifier.

If we take 80 amp hours and divide it by 1 amp we come up with 80 hours.

If we take 80 amp hours and divide that by 3 amps we come up with a little over 26 hours.

To get the most life from a lead acid battery it is best not to completely discharge it. This means that you should reduce the number of hours by 30 - 50%.

My experience is the S9 with humidifier draws close to 5 amps, thus you would get upwards of 16 hours from an 80 ah battery. A deep cycle can be drawn down more than a regular auto lead acid battery, but probably still best not to discharge all the way. That won't happen anyway with an inverter, or with the Resmed DC converter I think, because they will turn off on low voltage.

I haven't measured the actual current draw.

I choose 3 amps from this document from ResMed.

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

HoseCrusher wrote:I haven't measured the actual current draw.

I choose 3 amps from this document from ResMed.

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

As one can see from that doc the current draw varies a lot depending on the humidifier settings. That's why anyone wanting to use a battery and needs to know with some certainty how long it'll last needs to test their own individual setup.

In my case I use climate control on set at 78°.

Thanks to everyone for your input it's greatly appreciated. I think I'll go with a 80 AH battery. I can get a deep cycle for $129, the 100AH is $179. If and when a hurricane hits again I can charge it off of my portable generator when it gets low. I've been without power for 2 weeks at a time from 2 different hurricanes since I've lived here. Short power outages from others, so definitely need a backup.

squid13 wrote:Thanks to everyone for your input it's greatly appreciated. I think I'll go with a 80 AH battery. I can get a deep cycle for $129, the 100AH is $179. If and when a hurricane hits again I can charge it off of my portable generator when it gets low. I've been without power for 2 weeks at a time from 2 different hurricanes since I've lived here. Short power outages from others, so definitely need a backup.

Check Costco. I bought my 125 ah deep cycle for less than $100, including core charge.

Be sure it's a "Deep Cycle" battery. There are Marine staring batteries, Marine Dual Purpose batteries, Marine Deep Cycle/Starting batteries, and Marine Deep Cycle batteries.

The only one to buy for this usage is Marine Deep Cycle. If it says Starting/deep cycle or dual purpose, it's much less desirable for CPAP.

Also watch out that it's 12V. You may see deep cycle batteries that look like they give you a lot of amp hours for the buck, but they're only 6V. If they only have 3 filler caps, they're 6V.