powering a bi-pap (cpap) machine

I've used a CPAP while boondocking for 7 yrs. We have an extra battery "just in case". We use solar panels now, and have a Honda gennie for back-up "just in case". We used to run the gennie every 2-3 days. My only problem is while on battery, the humidifier does not work....will not work. So I run it without -- won't hurt the CPAP, but means I don't have the moisture I need.... When I bought my CPAP, they said the warranty would NOT be valid if I used a converter other than theirs. I don't know if they're right or not.....but we paid the $65.00 and have had no problems.

moved from technology

I use a 200W inverter from the 5th wheel bat. When Dry camping I run the Gen during the day. Not had a problem in 15 years. There is no problem when using shore power.

My husband uses/needs a C-Pap nightly. We bit the bullet and got a Honda 2000 wt generator (yep... it was a $$$ chunk). I just didn't want to risk ending up somewhere and not being able to run it at night. Even if there was a power failure - I KNOW he's going to be able to use it at night.

Can't help you on finding something affordable, but I know what's working well for us.
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I hard wired a power point from the night stand directly to the battery bank for a cost of about $25. Then I purchased the 12v power cord for my CPAP, about $25 and just plug it in and run on 12v. Total cost of about $50 and it is a permanent solution. Will it run on one of those 12v powerpaks, yep, but for how long is the unknown. I run mine with the humidifier on 2 for several nights without worry.