Speak to Me of UPSes (Uninterruptable Power Supply)

[Drowsy Dancer]

I think the best solution would be to add a battery to your solar system so it will last through the night .... Or fix the generator so it starts automatically.

that would make it available to the rest of the house also.

Those are undoubtedly the best long-term solutions.

Apparently, when we built this house, we didn't buy quite a big enough array of batteries. I am informed by our Solar Guy that we can't just add additional capacity to an existing array. Assuming this is true, upgrading our storage capacity does not appear to be an option until we replace the current array.

Sometimes power lasts through the night. It depends a lot on our power consumption the previous evening (e.g. are we running our large television?). If the weather is really bad we sometimes don't generate enough juice during the day to last through the night (storage or no storage).

Fix the generator. Heh. Sometimes it actually will start automatically the way it is supposed to. It seems a little capricious. That's what we get for ordering something so fancy neither of us understand it.

[grayghost4]

yes adding new batteries to an old group can be a problem

[Drowsy Dancer]

Hmm. As I ponder my longer-term solutions, I notice that my Vagabond Mini has an inverter that appears to be detachable. I wonder if I could use the VM without inverter using the appropriate cabling* and get more juice out of it <checks manual>.

Like, a DC power cord and this baby

[CapnLoki]

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.

[CapnLoki]

I noticed you posted on the battery usage thread - I trying to move the discussion back to this thread where it belongs. Your situation is quite different from what others encounter.

You mentioned again losing power in your "off grid" system. If this is happening more then once a month you have a serious problem. Aside from the fact that you are killing your house batteries if you run them dry several times a week, this will be a failure in trying to keep a separate cpap battery charged.

The problem is that any charger that is plugged into the wall socket will be very inefficient. This is true even of a small BatteryTender and especially true of any larger charger. The is no incentive to make it efficient because one assumes the wall plug is an infinite source by comparison. Since you're using a humidifier, you may be up to 25 amp-hours a night on the battery, but you're using double that or more charging it during the day. So now the load on your solar system if 50 amp-hours or more - an enormous load for an appliance that should be a minor load on the system. My house bank is 480 amp-hours (4 large batteries) .

By comparison, my TOTAL load is about 100 amp-hours a day, half of that going to my small fridge, the TV and computers are the other main loads. Since I run the cpap without humidity directly from the main battery, its load is only 4 amp-hours a night - almost negligible by comparison.

Charging one battery system from another only makes sense if one battery is much larger than the other. Otherwise you'll just end up with a lot of dead batteries.

On another note, focusing on the decoration of a box tells me you're more interested in fulfilling a fantasy than committing to living off-grid.

[Goofproof]

Basically, it comes down to your ability to make and store the power you want is too small. There is only a few things that can cure it, use less power ( Prioritise Usage), Or add more power and storage.

Best would be to add to the house system as it's under powered, a worse solution would be a smaller Solar unit, to charge the deep charge battery to run the XPAP. After running me XPAP for years with the HH, I found I didn't need the HH at all, so I no longer use it, period.

By adding more storage to the house, that could be charged in the day by your Generator, would add more power, but at a cost of fuel, and more to keep it up and running, the generator problem need to be fixed, if it's supposed to come on correctly and isn't, it needs to be repaired to work correctly, if not it should be replaced with a system that will work. Generac, makes good Gen Sets, but costly, If I had one it would be Propane or Nat Gas. Petro would be my last choice for generators.

Smaller LED T.V.'S use less power, also put them on a Switch, to shut the power to them off, they draw power when off, same with any wall warts plugged it, use led lighting only.

Living Off Grid is a nice solution, but it comes with many hard ships. Jim

[CapnLoki]

Basically, it comes down to your ability to make and store the power you want is too small. There is only a few things that can cure it, use less power ( Prioritise Usage), Or add more power and storage.

Best would be to add to the house system as it's under powered, a worse solution would be a smaller Solar unit, to charge the deep charge battery to run the XPAP. After running me XPAP for years with the HH, I found I didn't need the HH at all, so I no longer use it, period.

By adding more storage to the house, that could be charged in the day by your Generator, would add more power, but at a cost of fuel, and more to keep it up and running, the generator problem need to be fixed, if it's supposed to come on correctly and isn't, it needs to be repaired to work correctly, if not it should be replaced with a system that will work. Generac, makes good Gen Sets, but costly, If I had one it would be Propane or Nat Gas. Petro would be my last choice for generators.

Smaller LED T.V.'S use less power, also put them on a Switch, to shut the power to them off, they draw power when off, same with any wall warts plugged it, use led lighting only.

Living Off Grid is a nice solution, but it comes with many hard ships. Jim

Well said - running off grid requires work and vigilance. I've gotten to the point that I hardly ever use an inverter, and only turn it on for the seconds that I need it - like the coffee grinder and the pump for the sleep number bed. I use a small inverter for the toothbrushes (teethbrush?). An early lesson was when a guest turned off the TV but left on the inverter - it costs around 20 AH for the night in idle mode. After that I started looking for 12V TVs and small computers with 12V supplies. All the lights are LED of course. 20 years ago I was using 240 amp-hours a day and running an engine 2 hours to keep charged. Now I use about 100 and with double the solar its almost no work to keep it all happy - I can even leave it unattended for a week or two without worrying about the fridge because with no one on board the load is under 40AH.