What do you look for in a portable battery backup for medical devices (like CPAP)?

You'll need a backup that supports the DC output voltage of your CPAP. Longevity depends on your CPAP pressure, humidifier settings and hours used. Both Amazon ads have charts estimating CPAP longevity for the backup.

Maxoak CPAP backup/$298/Amazon - 297 watt-hours, cannot handle refrigerator power usage -

If you want 3 days on your CPAP you should be considering a generator to charge the battery backup.

First thing to do is determine the load you will have.

Standard Resmed CPAPs - 24V DC output Portable Resmed CPAPs - 12V DC output

Both Amazon CPAP backups support 12V/24V DC output.

On Tue, 4 Jul 2023 at 18:04:57, kelown snipped-for-privacy@privacy.invalid wrote: (my responses usually follow points raised):

The CPAP companies want to sell their own "special" DC power supplies.

While my CPAP is 24 volts, it's "more" than that as it has three wires. My "ResMed AirSense 10 Autoset" has a special "tamper proof" 24V input.

They require a special circuit before they'll work with 24VDC. Of course they did that only to sell their power supplies to you.

But it won't work with just any 24VDC - it has to have the right resistor. Luckily, the inverters being provided by the power company are all 120VAC.

So there's no need for the direct DC (although it would be nice but it won't work with the tamper-proof "ResMed AirSense 10 Autoset" CPAP box.

On Tue, 4 Jul 2023 at 01:02:03, Ed P snipped-for-privacy@snet.xxx wrote: (my responses usually follow points raised):

The portable AC power inverter battery backup from the utility is free.

And it fits in the bedroom closet and can be used in the bedroom. The generator is not.

It's a "ResMed AirSense 10 Autoset" so the load is whatever that uses. Probably something like special 24VAC at probably something like 3.75 Amps.

At least that's what it says for the 3-wire DC output for the CPAP machine.

Using an inverter is certainly convenient but you'll lose some backup longevity over using direct DC output due to efficiency loss.

On Wed, 5 Jul 2023 at 22:55:56, kelown snipped-for-privacy@privacy.invalid wrote: (my responses usually follow points raised):

Unless the 24VDC has the special tamper-proof chip output that ResMed engineered into the AirSense 10 AutoSet CPAP, that 24VDC will be useless.

It's only the free battery backup inverter's 120VAC that will be useful.

All I'm asking is what's the most important specs to look for in these.

Peter's response applies. Ignore it at your own risk.

And "free" is not what you told us: "They offer the following portable battery backup units, where I want the most bang for the buck"

Fine, argue. We're trying to help.

Ok, now for the help you need. The manual for your device shows the power requirements as:

The last two lines are the most pertinent for you.

Next, the manuals for the backup devices in the link you provided give the following capacities in ascending order:

yeti 500 505 wh yet1 1000 983 wh ecoflow 1008 wh yet1 1500 1516 wh yeti 3000 3075 wh yeti 6000 6010 wh

The yeti 6000 will last longest. They're using the symbol wh to indicate total power in watts that the device can provide over time. For example, the yeti 6000 should be able to provide

I hope that helps you understand the electrical specs. As regards the specific use of these devices with your CPAP, I can only quote the specs from the manuals. I have no personal experience with any of the devices.

Ed