Drowsy Dancer wrote: ↑Thu Apr 25, 2019 9:24 am
Greetings!
I face the following challenge in off-grid living.
Our new house in the wilderness is run on solar power with a backup generator. Power systems of this sort being somewhat finicky, we sometimes run out of stored power in our battery bank before sunrise, and the generator, for reasons known only to itself, fails to kick in, thus killing the power to the house until the sun comes out or someone gets up and turns the generator on manually.
My portable backup battery is a Paul C. Bond Vagabond Mini (hereafter "VM"). I have found that it is difficult, when awakened from a sound sleep in the middle of the night, to unplug my CPAP in the dark and plug it into the VM.
I tried plugging the CPAP (PR560P with humidifier and heated hose) into the VM and the VM into the wall, with the VM switched on, but when the power goes off, the VM can't always sustain the machine with humidifier and heated hose until it is time for me to get up.
It seems to me that what I need is an old-school UPS (uninterruptable power supply) that will keep my system going for a couple of hours, and that I can leave plugged in at all times with my CPAP plugged into it. I do *not* want to use a car battery because reasons.
So: recommendations, please?
As someone who lives off grid several months of the year, I would say that the "finicky" power system is the primary problem. As a rule of thumb, you should have enough battery power to run three days (or more) without charging. You should try to never go below 50%, and never ever go below 20%. The solar panels should be oversized enough so that even on a moderately cloudy day the batteries stay charged. The genset should only be needed when it rains for 3 three days straight, something that should be anticipated, not discovered in the wee hours.
But aside from all that, a UPS is reasonable for short power outages. The 500EV and 600EV models that go for under $100 typically use 7 AH APS batteries. Running through an inverter, this is only only 4 amp-hours. This is enough to maybe run a night without humidity, but with the humidifier its only going to run for 2 hours. BTW, this is roughly the same size as the Vagabond. Thus, if you're concerned about the last hour or so in the morning, this might get you by. The larger units, 2000 EV or more will have larger batteries that could handle a night, but they are pricey, over $300 and often use expensive custom battery packs that will cost several hundred every few years to replace.
The "DYI" system uses the exact same style of battery but a size that is cheap and easy to replace. You can run your PR 560 on 12v all night with the humidifier. You can run a charger simultaneously so it will automatically roll over in a power failure. In this mode I would upsize the charger, but it will work. This isn't an "automotive" battery, its a clean sealed battery that you can easily put in a box and slide under the bed.
Frankly, you'd be better off spending the bucks upgrading the house bank. You should be able to tap 12V off the house bank and run more efficiently. Perhaps you can add several batteries to the main charger and then use them exclusively for the cpap.