WELCOME! to the forum.!
Hang in there for more responses to your post and much success to you with your CPAP therapy.
08-09-2015, 02:02 PM
(This post was last modified: 08-09-2015, 02:04 PM by foss.)
I use a 55 amp hour, absorbed gas mat battery hooked up to the Resmed DC-DC converter for all use at home. I keep the battery topped off with the 1.25 amp Battery Tender. I no longer use the Resmed AC power supply. The local AC supply drops out once in a week or so. Before going to the constant battery supply I would wake up and have to restart my machine. Now with the battery supply in place I don't have that problem. This system is easy, trouble and maintenance free. The power went off for 30 minutes in the middle of the night several days ago. I didn't know it until the next morning when my wife told me that it had gone off. (And all of the clocks were flashing 12:00.)
For me it works well.
Sleep is worth the effort.
My backup system is still working very well. A five amp Battery Tender would be an improvement for a small increase in initial investment. After a full nights use off the grid, it takes the small 1.25 amp Battery Tender 17 or 18 hours to fully recharge the battery. The 5 amp version would recharge the battery in a third the time making it much more convenient. I will probably purchase the 5 amp version eventually.
Also, powering the ResMed A10 from this system protects the machine from possible electrical spikes. The DC-DC power supply from ResMed has a built in protection circuit. Added to that, the BatteryTender and 12 volt AGM battery further isolates the power supply. The Battery Tender has protection and the large 12 volt battery acts as a large capacitor smoothing out spikes and power surges.
Sleep is worth the effort.
My power is good enough that I normally run off the AC power brick. I think a 35 amp-hour AGM battery on Amazon is your best bang for the buck and best size for a transportable solution for a boat or car camping. Sub-$65 with free shipping. They weigh 25 pounds so they're pretty easy to move around. I use it on the boat with the humidifier and heated hose turned off and get 3 nights out of the battery.
If I had truly lousy power, I'd run two 35 amp-hour batteries in parallel with a battery tender and use the DC power brick all the time like others are recommending. That would run the humidifier and heated hose for 8+ hours. That would still give me a transportable solution.
Some day, I need to do better than the alligator clips on the ResMed A10 DC-DC converter power brick since they can slip off if you bump into them. I should buy another female cigarette lighter/power port and permanently attach it to the battery terminals.
12-19-2015, 07:24 AM
(This post was last modified: 12-19-2015, 07:40 AM by OMyMyOHellYes.)
For those momentary outages, I switched over to a dedicated homebrew UPS that includes a 35 AH 12 V AGM battery, a 12 V power supply (actually an Astron 13.8 V power supply for radios tuned up to put out 14.5 V) and a power gate (West Mountain Radio) to automatically switch power from the 12 V radio power supply to the battery in the event of a falloff in the line power. The powergate includes a smart charge function like the BatteryTender to keep the battery charged and in shape.
Oh, and that setup gave me a lot of opportunity to play with Powerpoles (Anderson Powerpoles) which are really handy for 12 V wiring for things like radios and in this case, CPAP machines. WARNING: playing with Powerpoles can be addictive and you may find yourself doing things like wiring up lamps for 12 V application in power out scenarios (requires 12 V light bubs too).
If you do go the LiFePO4 battery route, I would be interested in any observations and after action reports. They are still pricey but they *are* light weight. I think for in home use, the SLA/AGM batteries are probably still the most cost effective route for most folks unless they have an unlimited supply of cash (oh, to have that kind of problem).
Consumer electronics store UPS systems designed for allowing graceful computer shutdown are not generally robust enough to get a CPAP user through an outage lasting past an hour or two, if even that much. I suppose it may be ok if the longest reasonable anticipated outage was less than 15-20 minutes. Before building my CPAP capable UPS, I would just wake up (instantly) when power dropped, get up, retrieve a battery, ditch the humidifier, hook the battery up and go back to sleep.
Be cautious with LiFePO4 as most are rated in lead-equivalent (Pb-eq). Lithium iron batteries have very low resistance, and can discharge a lot of power quickly, compared to lead acid or AGM. That means a 6-amp battery can do the work of an 18 amp battery, but it won't last as long in continuous draw. Just watch for pb-eq if you're buying. Large capacity LiFePO4 batteries are crazy expensive.