My back up power set up questions UPDATE

[archangle]

There may also be some pseudo-envrionmental regulations about power usage as well.

I wish more people would refuse to sell to California.

Gee archangle, that doesn't sound very neighborly...let's keep the spirit of this topic on the helpful side. Please? As the OP looking for help, that comment defeats my purpose since I've registered that I live in CA and I'm trying to find specific back up power solutions to suit my needs.

thanks,
d

I'm tired of seeing things designed badly and costing too much because of some nutjob proposition from California. I'm tired of unreliable electronic equipment because of RoHS solder that grows whiskers and shorts things out. I'm tired of big labels on harmless items telling you that "The People's Democratic Republic of California has decided that this product may cause cancer." I'm tired of harmless things having the same warning labels on it as truly dangerous things. If you cry wolf too often, nobody listens anymore.

We need to quit designing things for the whole country to keep the lowest common denominator state government happy.

[archangle]

Has anyone used a CPAP on a solar system? One unit was described at drawing like three 75Watt bulbs. That is a huge draw on a small solar system. Charging batteries on a solar system has the same problem. We spend a lot of time at our remote cabin and neither we nor our neighbors would like to listen to our backup generator all night.

There are links to ResMed's battery sizing guide in my signature line that give some indication of power usage.

My S9 AutoSet draws about 30 W AC power with the humidifier and no heated hose on 16 cmH20 pressure. It draws about 10 watts AC with no humidifier.

If you do go for a solar system, be sure to really research it well. Most people drastically overestimate how much load their system can handle. You have to handle varying sun angles, sun hours, shade, and have enough battery capacity to take you through cloudy spells.

With a battery system, you can charge the battery with a generator during the day if necessary.

[CapnLoki]

Has anyone used a CPAP on a solar system? One unit was described at drawing like three 75Watt bulbs. That is a huge draw on a small solar system. Charging batteries on a solar system has the same problem. We spend a lot of time at our remote cabin and neither we nor our neighbors would like to listen to our backup generator all night.

I spent about 30 nights on battery power this summer (less than I normally do) with most of the power coming from solar panels. However, I have a 450 Amp-hour bank (four golf cart batteries) and 3 50 Watt panels. Since I don't use humidity on the boat, my CPAP load is well under 10 Amp-Hours, a minor part of my total load. This is the type of setup you might consider for a cabin used as a weekend retreat. For full time use, I end up running a generator every few days to recharge.

I don't know where your got your power numbers; the most common current units use about 10 Watts without humidity, about triple that with the humidifier. However, you may find you don't need humidity in the woods.

A solar/battery system to run a cpap should be quite doable - if you want help designing this you should tell us what model cpap you have, and the approximate location of the cabin and the season you use it.

[raftergirl]

Has anyone used a CPAP on a solar system? One unit was described at drawing like three 75Watt bulbs. That is a huge draw on a small solar system. Charging batteries on a solar system has the same problem. We spend a lot of time at our remote cabin and neither we nor our neighbors would like to listen to our backup generator all night.

I spent about 30 nights on battery power this summer (less than I normally do) with most of the power coming from solar panels. However, I have a 450 Amp-hour bank (four golf cart batteries) and 3 50 Watt panels. Since I don't use humidity on the boat, my CPAP load is well under 10 Amp-Hours, a minor part of my total load. This is the type of setup you might consider for a cabin used as a weekend retreat. For full time use, I end up running a generator every few days to recharge.

I don't know where your got your power numbers; the most common current units use about 10 Watts without humidity, about triple that with the humidifier. However, you may find you don't need humidity in the woods.

A solar/battery system to run a cpap should be quite doable - if you want help designing this you should tell us what model cpap you have, and the approximate location of the cabin and the season you use it.

What would the smallest wattage solar panel be that you'd recommend for keeping two 12V20A batteries charged for a 10 day trip off the grid? I'm guessing 40-60 W would recharge my partially depleted battery with 8-10 hours of direct sun. Does that sound right? I'd love to cut my 4 battery set-up down to 2, if I could rely on the solar recharge.

[CapnLoki]

What would the smallest wattage solar panel be that you'd recommend for keeping two 12V20A batteries charged for a 10 day trip off the grid? I'm guessing 40-60 W would recharge my partially depleted battery with 8-10 hours of direct sun. Does that sound right? I'd love to cut my 4 battery set-up down to 2, if I could rely on the solar recharge.

The way to figure this is to find the Average Sun Hours for your location and season. Much of North East and Mid West is about 4, so you can figure 4 hours of full power. Arizona goes up to 7, but some locations can be as low as 2. With and ASH of 4, a 50 Watt panel will generate 200 Watt-Hours, or about 15 Amp-Hours. Of course, and overcast can cut the power in half, heavy cloud cover can kill it. And this assumes you can setup in a location free of shading. And remember that the ASH means that in a full day you're likely to gather 4 hours of power. The question on battery size comes down to how you can handle the risk of reduced charging. In my case I'm willing to run a generator if I fall behind,

[CapnLoki]

Here's a map of average sun hours:
http://www.wholesalesolar.com/Informati ... USMap.html

[archangle]

What would the smallest wattage solar panel be that you'd recommend for keeping two 12V20A batteries charged for a 10 day trip off the grid? I'm guessing 40-60 W would recharge my partially depleted battery with 8-10 hours of direct sun. Does that sound right? I'd love to cut my 4 battery set-up down to 2, if I could rely on the solar recharge.

Is that 20 Amp Hours? 20 Amps doesn't make much sense.

Will you be sitting in one place all day long or moving from place to place? Can you angle the panels to the proper angle to the south? Do you have any trees shading your panels?

Be sure and check the "sun hours" for your location and time of year. Also calculate something for cloudy days.

[CapnLoki]

What would the smallest wattage solar panel be that you'd recommend for keeping two 12V20A batteries charged for a 10 day trip off the grid? I'm guessing 40-60 W would recharge my partially depleted battery with 8-10 hours of direct sun. Does that sound right? I'd love to cut my 4 battery set-up down to 2, if I could rely on the solar recharge.

Another thought on your situation- the common wisdom for using batteries is that you'll get more from them by joining them in parallel, essentially converting 2 20AH batteries into a 40 AH bank, or 3 into 60AH, etc. This has several affects: Since you don't want to run the AGM batteries to zero (20% should be a minimum, 40% would be better if you want to get many hundreds of cycles) combining several reduces the chance of doing this, and on average means one or two extra nights from a set. The combined bank will be able to accept a larger charge, so its possible that a more powerful charge source (AC, or car, etc) could bring a bank up to 80% in an hour or so. A 50 Watt panel will put out at most 4 Amps so this won't help for the bulk charge phase, but you can top off several together because above 80% the acceptance of the batteries will drop down to around 1 Amp.

Of course the most important factor is your usage. Its hard to get a handle on this, but if your usage is 6 AH per night, 2 20AH batteries used as a 40 AH bank and run to 20% supplies 32 AH, or 5 nights. Thus the shortfall for a 10 night trip is 28 AH. A 50 Watt panel should be able to recover this in 2 days, weather permitting, and maybe even less in your location, with the caveat that the last 10-20% will take an extended time, so regardless of how it turns out you're not coming home with a fully charged battery.

I'm a bit curious about how your rafting trips work. When I did rafting (many years ago), there was never a chance to set panels for a good mid-day charging session. Do you setup a base camp that you return to, or are you assuming several "lay days" for recharging? If you're hoping to get some late afternoon or morning sun power, it will be challenging but perhaps works if you do it every day.

[sleep_quest]

Well here it is, the fruit of my labor (with your much appreciated wisdom and assistance)!

After I finally understood I could buy a battery box* that had everything I needed, I put together this plug and play back up mobile power cart to run my PRS1 560 in case of an extended power outage. I also have shorter term redundancy/overlap with a powerpack and multitasking options for other needs so the design ranges from being mobile (can be moved) to components that are also portable (easy to carry) if that makes sense.

Costco:
Interstate 27DC RC160 Deep Cycle Marine Battery $102 (would have been $15 cheaper if I had a battery to exchange)
Magna Cart Personal Hand Truck $21 (folds down for storage/travel, adjustable handle, light weight, holds up to 150 lbs)
Duracell LED Flashlight $5 (comes in a set of 3 for $15)

CPAP.com
Respironics, 12volt DC Battery Adapter Cable with Battery Clips $25 (not pictured)

Amazon:
*MinnKota Power Motor Trolling Center $64 (very easy to set up; no tools needed! just insert battery and attach cables to corresponding posts with nuts (included) )
Stanley BC1509 15 Amp Automatic Battery Charger $46 (provides a quick charge and will live in garage since it is noisy when charging. it also has a float charge which can be used to keep a battery topped off - will be used with second battery when I get it)
MinnKota Digital Battery Meter $12
Stanley STST16410 16-Inch Toolbox $11 (holds all miscellaneous items: cords, meter, extra batteries for flashlight, manuals, etc. (not pictured))
Master Lock 3029DAT Snap-Lok Bungee Cord x2 $10 (attaches battery tender and toolbox to cart)
Master Lock 3039DAT CamLok Adjustable Steel Cord Bungee Cord $6 (attaches battery box to cart)

Redundancy/Overlap:
Duracell Powerpack Pro 600 (new model as of Sep 2014) $120 (standalone power and can power multiple devices plus it was used to jump my daughter's dead car battery on a busy street last night! That lesson alone was priceless; she didn't think so but it really was .)
Battery Tender Plus $43 (this will reside indoors with mobile power cart to keep battery topped off)
Duracell 175W Power Inverter with USB ports $27 (provides additional AC and USB ports to power other devices- can also be used in car)
Shielded DC Cord for PR System One 60 Series Machines $30 (can be used with battery box, powerpack or in car if necessary)

Please keep in mind that my requirements were: "I don't want to solder, weld, wire, or otherwise construct my back up power solution. My ultimate set up would last more than a few days (I live in earthquake country), be easy to set up (keep those "caution! make sure you have your positive/negative cables in the right place lest you blow up your CPAP machine and who knows what else" warnings to a minimum), be safe indoors, and be cost efficient. Think plug and play...not a lot to ask, right? " and I believe that is what I have. Can it be done differently and/or cheaper? No doubt, but for my piece of mind this design is worth it.

I feel much better prepared for an emergency or a power outage now but if you can see any deficiencies please chime in.

Many thanks!
d

[Guest]

And I was trying to get you off cheap. I am impressed, very impressed. What was the total cost?

Be sure to charge em all up before you need them. Then I would try em out before you need them also. I would plug my machine right into the Duracell with the charger on it and sleep like that too.

[archangle]

If you're leaving the charger connected 24/7, the particular charger will make a lot of difference in whether your battery lasts 6 months or 6 years. Unfortunately, it's not easy to tell which one will eat batteries and which ones won't.

One suggestion, get a one week mechanical timer and set it up to run the charger just a few hours each week. That way, there's less time on charge to eat the battery. I've also seen "smart" charger go nuts and not go into float mode. Turning off the power will sometimes reboot them and make them work again.

[raftergirl]

What would the smallest wattage solar panel be that you'd recommend for keeping two 12V20A batteries charged for a 10 day trip off the grid? I'm guessing 40-60 W would recharge my partially depleted battery with 8-10 hours of direct sun. Does that sound right? I'd love to cut my 4 battery set-up down to 2, if I could rely on the solar recharge.

I'm a bit curious about how your rafting trips work. When I did rafting (many years ago), there was never a chance to set panels for a good mid-day charging session. Do you setup a base camp that you return to, or are you assuming several "lay days" for recharging? If you're hoping to get some late afternoon or morning sun power, it will be challenging but perhaps works if you do it every day.

I'm figuring 2 layover days into the 8-10 day trips. Those would be the "recharge" days. Depending on where I'm rafting (Idaho, Utah mostly) there may be canyon walls and trees involved. Angle on the sun all depends on the orientation of the layover camps. Planning those camps in advance is pretty much impossible. My rafting buddy who's been using cpap for about 3-4 years now tried a solar panel on a 21 day Grand Canyon trip in August. It didn't work out very well. He was expecting blazing heat & sun, and got 18 out of 21 days of rain. That uncertainty is what is holding me back from the solar idea. I know I can get a waterproof, rollable solar panel from Power Film that I could rig on top of a dry box or cooler during the day, plus layover days. It's the weather, cloud cover, and geography of the areas I raft in that makes me nervous to rely on the solar panel, and leave a couple batteries at home. I know I can get 2 nights and probably 3 off each battery, so 52 lb. of batteries in my dry box is the price to pay for peace of mind. And speaking of price.....the 40-60W Power Film panels aren't cheap.

My quest for a smaller & lighter battery that will power my cpap on 2-3 night kayak touring trips does continue however.

[sleep_quest]

And I was trying to get you off cheap. I am impressed, very impressed.

Why thank you! I'm rather pleased myself

What was the total cost?

$300 for the 'mobile' battery box, cart and charger and $220 for the 'portable redundancy/overlap'. I had already purchased the powerpack before I started this project but I threw that in since it is integral to the portability of the other components.

Be sure to charge em all up before you need them. Then I would try em out before you need them also. I would plug my machine right into the Duracell with the charger on it and sleep like that too.

After the photo shoot, everything is all charged and ready to go. First test of the Duracell happens tonight!

[sleep_quest]

If you're leaving the charger connected 24/7, the particular charger will make a lot of difference in whether your battery lasts 6 months or 6 years. Unfortunately, it's not easy to tell which one will eat batteries and which ones won't.

The reason I went with the Battery Tender specifically was due to CapnLoki's recommendation and other reviews/comments I read online. I sure hope it will allow for a long lasting battery life...I guess time will tell. I do have a new handy dandy battery tester now too so I will be putting that to good use.

One suggestion, get a one week mechanical timer and set it up to run the charger just a few hours each week. That way, there's less time on charge to eat the battery. I've also seen "smart" charger go nuts and not go into float mode. Turning off the power will sometimes reboot them and make them work again.

Thanks for the tip I do have one of those timers around here somewhere...

[sleep_quest]

PlinkerCraig

Has anyone done a serious measurement of the amp-hour draw of the original poster's Respironics 560 machine yet? I'm tempted to rig a fixture to measure this since I have one of the 560 machines. I'm an electrical engineer working in the test&measurement field for 30 years now so I think I know what I'm doing, but somebody here may contradict me if I get results that don't meet layman's intuition. Is it worth me taking the time to do this measurement? Let me know.

For my own selfish reasons I'd appreciate knowing what the 560 draws and thus know the limitations I am working with. If this information isn't readily available and you're offering I'm gonna say YES PLEASE...

thanks,
d

Wow there is great stuff here. Thanks for feedback Archangle and Capnloki.
I got up early this morning and used my PC instead of my iPad to cruise the forum and thought it would be wise to search a bit for things. I found an excellent topic that John posted 18 months ago that was a very thorough battery pack design. It is long and thorough and worth reading. Here it is: viewtopic.php?f=1&t=89123

Reading Raftergirl's first-hand experience and other postings I'll predict that I will measure an average of 650mA drawn by the PRS1 Auto machine. From John's work it seems that a good thumbrule would be 10Ah per night skipping the humidifier (which leaves a generous margin for any oops and mileage variation).

I'm going to attempt to use a very nifty Agilent handheld multimeter that can record hours of readings at least once per second. If it appears that I'm undersampling the current waveform (Thanks Caploki) then I'll borrow a Keysight(was Agilent) product that can source the 12V and store current readings many times per second. This should be fun and interesting. My kit for building the cable for charging the new Ford Focus EV did not ship when I expected it to ship so I won't be building that thing this weekend . That is good news for me finishing this CPAP current draw measurement this weekend.

Hello PlinkerCraig...are you still out there or are you enjoying your new electric car?