A while back I was looking into getting a UPS for my CPAP, and what I read suggested that it was impractical because they draw a lot of power. (The power draw is even worse if you have a humidifier).

Apparently I can't post photos right now...

My charger that I use as battery backup for my cpap is similar to this one:

https://www.amazon.com/Schumacher-SC1281-Automatic-Battery-Charger/dp/B07BLLRM8R/ref=sxin_18_pa_sp_search_thematic_sspa?content-id=amzn1.sym.6fd80408-71b6-44da-b059-082bba9089d3%3Aamzn1.sym.6fd80408-71b6-44da-b059-082bba9089d3&crid=17UPJXCDPKTSB&cv_ct_cx=schumacher+battery+charger&keywords=schumacher+battery+charger&pd_rd_i=B07BLLRM8R&pd_rd_r=183a6a90-4841-4633-af2b-8a6aff35f87d&pd_rd_w=KNImJ&pd_rd_wg=AGU57&pf_rd_p=6fd80408-71b6-44da-b059-082bba9089d3&pf_rd_r=1FC3M7PKK4BHBXB7PNB7&qid=1687885194&sbo=RZvfv%2F%2FHxDF%2BO5021pAnSA%3D%3D&sprefix=schuacher+%2Caps%2C186&sr=1-1-364cf978-ce2a-480a-9bb0-bdb96faa0f61-spons&ufe=app_do%3Aamzn1.fos.006c50ae-5d4c-4777-9bc0-4513d670b6bc&sp_csd=d2lkZ2V0TmFtZT1zcF9zZWFyY2hfdGhlbWF0aWM&psc=1

Make sure the one you get has a 12v cigarette lighter-type adapter socket, because your cpap manufacturer will likely have an adapter for your unit to plug into your car.

Did you try this at all yet? Makes me wonder how much juice does the machine use? I've never looked before. It's it too much for one of those portable battery packs you can use for cellphones?

It honestly depends what "reasonably priced" means to you. EcoFlow has some great battery options. I find my ResMed AirSense 11 used about 40% of the capacity of an EcoFlow Delta 2 (1024 kWh capacity) using 110V AC. That was with humidification and a heated tube over an 8 hour night.

You could probably get one of their high-end River models and a 110W panel to recharge through the day.

Using a DC power cable for the CPAP machine may save on some conversion. So it would go DC from the battery to DC for the CPAP instead of DC from the battery to AC 110V back down to DC for the CPAP.

This was my idea, You just need to find a plug, right?

The last time I looked into it, it's only practical if you're camping in an RV or trailer which already has the panels and battery capacity. Otherwise the size and weight makes it impractical for just a car.

I have a portable battery jump thingy that has emergency power for USB etc. It also has a 12v out. I've got an adapter from the cpap company that plugs right into it. It's basically a portable car battery. A full charge will give me about 5 nights of use. I paid about a hundred dollars for it.