All in the Family featured the curmudgeonly Archie Bunker. Archie was television’s most famous grouch, blunt, blustering, straightforward and untouched by the PC crowd. He was the archetype of the conservative male. Michael desprately tried to reeducate him, but he persisted in his breviloquence.



Looking back at the last 40 years, we realize: ARCHIE WAS RIGHT!

5/27/2015

Electrical Bleg

I know we have some smart people on here.  I have a problem that I'm trying to work out and could use some help with.

I'm looking at getting a propane powered generator to supply electrical power for my up coming moose hunt of a lifetime.  I am going this route for a couple of reasons.  The first is my gas powered generator is old, heavy and very noisy.  The second is that propane is safer to transport and store in a wilderness camping situation. These are on sale thru the end of the month. 

I intend on making a purchase before the sale is over and doing a couple of "dry runs" to ensure everything is in good working order before I spend a couple of weeks hunting this fall.  My first dry run will be in June.

I have determined the appropriate size for my needs based on power generation and fuel consumption and have decided on a model.  I have also been in touch with the manufacture of the generator for their assistance and advice. 

Here is the problem: Portable power generators don't do a good job of delivering good clean AC power to run potentially sensitive electronic devices.  Because of that I'm going to have to install inline surge protection and some form of line conditioner/filter.  Does anyone have a suggestion of a good quality product that would work for this application or advice on how to go about this project?

47 comments:

  1. WaterBoy5:20 PM

    Something like this is probably what you want. It provides nominal surge protection as it regulates the line voltage to provide a steady 120V output.

    The link is to the 2400W model, but they also have it in 1800W (for a little more!), and 1200W (for a lot less).

    If you only plug your electronics into it, you can probably get by with the 1200W unit. Check the ratings on those things you want to protect and add them up.

    But if you plan to plug your other essential camping things (espresso maker, fondue pot, curling iron) into it, too, then you might want the bigger model.

    A regular surge suppressor power strip will also work for a heckuva lot less, but it won't condition the line for steady voltage as you requested.

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  2. You should research inverters. My uncle has a gasoline inverter that we use for camping in the Hills. It is very quiet, uses relatively little gas, and he said the power is safe for computers, etc.

    I don't know a lot myself, other than these are very expensive. But we can run the camper for 24 hours on about 5 gallons of gas.

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  3. WaterBoy5:46 PM

    Those are good and will also condition the line, but they are typically more expensive since they convert the power twice.

    A regular gasoline generator will generate AC power directly. An inverter generator will generate AC power, rectify it to DC, then run that through an inverter to take it back to AC again. All that extra equipment usually costs more, but it can be more efficient and quieter in doing so, as well as being generally lighter and more portable.

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  4. WaterBoy5:57 PM

    Here's a page explaining the difference, as well as charts showing the fuel consumption and noise differential between the two types of generators. If you're going to be at the high end of that usage, the smaller difference probably isn't really worth the extra cost.

    But notice with some particular Honda models, they can be used in parallel to provide more power and still remain lighter and more portable by using two smaller ones instead of one larger one.

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  5. WaterBoy6:20 PM

    Then again...can you even get an inverter generator that runs on propane?

    ReplyDelete
    Replies
    1. Depends how much you want to spend. Honda has propane and natural gas converters for their inverters and generators.

      Delete
  6. Yes Honda makes an inverter that runs on propane. In fact Honda seems to have the best quality portable invertor generators in a reasonable price range. The gas models are in the $500 range but the propane one is over $1,500.

    The propane model I'm looking at is less than $300 but its a brushless generator which means the power can be very dirty. Some of the reviews claim that the power is very clean (it could happen) BUT the manufacture isn't willing to make that claim. I've talked to them and they say that some units do produce exceptionally clean power, but the design of the unit doesn't guarantee that result. They recommend a power conditioner but do not make, sell or have a recommendation about which ones would work best.

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  7. Oh boy. I know more about this than I care to admit in public. Sorry I'm late to the party, I was busy (no kidding) designing a backup power system for a 90kW load. I didn't click the links, and I skimmed the comments, but here's the deal;
    Most electronic chargers do a DC conversion anyway, because modern electronics are SOOOO freaking sensitive to actual power levels, and modern buck-boost converter (look it up) circuits are so cheap, that it's just the way to go.
    So. If you're charging electronics, you absolutely need, no questions asked, NEED to do a AC to DC conversion, and then usually back to AC if it's more than a hundred watts, and then let the regular charger thing do it's job. Most consumer electronics (which is not my world, but I learn by bumping into it) will charge off a USB thing, in which case you have unlimited options.

    So, without blathering on any more. What is your actual charging need? Tablet, laptop, phone, camera? I need to know what the real power requirement is to make a suggestion. And... uh... most of my stuff is painted green, so I may only suggest general stuff. But, honestly, I do this every day. What, actually, are you trying to do?

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  8. Bill,

    The need isn't to charge equipment. I'm looking to power at least two CPAP machines for a period of 6 to 8 hours each night. The max surge draw of each unit is 300 watts, actual running draw is around 150 watts according to the manufacture.

    The generators I'm looking at all produce a surge of at least 2,000 watts and a half load ratting of over 900 watts.

    My main concern is ensuring I don't fry anyone's CPAP. Since I'll have the generator available anyway, I suspect it will get used for other things like lighting, electronic toys etc. So making sure the power is clean enough for everything is a concern.

    I'm not very knowledgeable about this subject so go ahead and educate me. I've been doing some reading and research for the last couple of weeks. I'd like to get a set up together and test it on a couple of trips this summer before I attempt a fall trip. Part of my reason for that is October can be very nice in the mountains and it can be very cold and snowy. I'm going to hope for nice but plan for snow. Also, it looks like my potential camping spots for the trip are over 8,000 feet above sea level and I want to ensure the equipment works at that altitude prior to spending 2 weeks depending on it.

    I have a hard time working in time off, so I have to schedule it around other people at work. My first window for a camping trip is week after next. It may prove to be my only shot at scouting/camping in my hunt unit so I'm trying to get the equipment together asap for a trial run.

    ReplyDelete
    Replies
    1. Res,
      What brand(s)/ model numbers are the CPAPs in question? Some work very well on 12V, even with the heater. I use two 105Ah batteries to power mine while camping, and they last a couple days before I need to charge them. Some CPAPs absolutely REQUIRE the use of a pure sine wave 120v if you use the heater-something to think about.

      Delete
  9. Res
    -- Propane doesn't always like to vaporize when it's cold out. That could lead to flow problems supplying the generator. Might want to have more than one tank tee'd into the feed line if it's brisk out. Or else keep the tank warm.
    -- The CPAP machines probably have specs around for what they tolerate in voltage swings. Match that to the generator swing window and you might be golden. CPAP's being medical equipment usually have all that tested for.
    -- Personal and consumer electronics usually aren't tested that far, and really don't expect much trouble. For this you may consider bringing a deep cycle battery along that you top up with the genny and then power the sensitive electrics from. (I'm assuming you aren't hauling everything to base camp on your back here)
    -- Lighting really depends what you're running. Incandescent's can handle about anything, florescent's and LED's can be real picky. But LED lighting is also such low power that a battery can provide plenty of light. Or the classic propane lantern since you're lugging tanks up the hill already

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  10. Just about any modern device, such as a CPAP (I also need one of those things, with my advancing years) will use a small external power supply. My CPAP draws about 30 watts, unless I use the heater/humidifier (which I do not use when camping). Using the heater thing raises it to about 90 watts (with about 120 watt surge). So, I kind of question your power requirement for the CPAP, but it sounds like you've verified it, so we'll go with those numbers. Note that my CPAP is not the kind that really controls my breathing, it's the kind that tries to keep a few PSI above atmosphere in my throat, so maybe that's the difference.

    The small external power supplies do an excellent job of filtering power. If you look at the power supply specs, you should see the input specs, it's probably something like "110-240 VAC, 50/60 Hz". This is a nominal spec, the actual spec is a bit broader, usually about 90 volts up to about 270 volts, and there's some wiggle room on the frequency as well.

    Here is a typical datasheet; http://www.xppower.com/pdfs/SF_VEH120.pdf

    Note that actual frequency range is 47-63Hz, and the actual power range is 90-264.

    And note the isolation voltage; 3,000 volts. So, nothing under 3,000 volts is going to make it past the brick.

    These things really are designed for universal use, as in anywhere in the world. And power specs vary quite a bit by country, hence the broad input range for these power bricks. In my experience you can hit these things with hundreds of volts over spec before anything fries, and NOTHING ever gets past the power brick, even lightening strikes are usually stopped by the brick, this is because there is no direct electrical path through the brick for anything outside of it's range (the brick gets fried, but everything downstream would be OK).

    So, provided the CPAP uses an external power brick, you're not gonna fry it no matter how dirty the power is. And a brick is about $100, and they are really robust little suckers, if one fries, then it's not because of the generator, it's because the brick just had a failure. Think about how dirty power is if you just plug and un-plug the power cord (you can sometimes see sparks!), that's a worst case scenario, and it's how the bricks are designed to operate (i.e.; there is no on/off switch). And they're designed to be plugged/un-plugged, many times, into 240 volts. You are not gonna hurt the brick with dirty power. What hurts the bricks, maybe, but not usually, is if you under-power them. They can get down to about 90 volts, then they start to get hot. But all the newer ones (I have not seen one without a sensor in about 20 years) just shut off if the voltage gets too low.

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  11. Ok. About the el-cheap'o generators. I have one, and have never had problems with dirty power. Here's what the issue is; as you know, they produce power by spinning magnets, and they have (usually 4) sets of brushes to pull the power out of the spinning magnet thing. There are two problems; if the generator is not spinning at the right RPM then the power is not 60Hz, and the voltage is not 120 volts. The RPM has to be (I believe) 3600 RPM.

    So; DO NOT CONNECT ANYTHING UNTIL THE GENERATOR IS UP TO SPEED, EVER. This is a really key point.
    Any electronic thing, unless it has a decent power brick, will be fried if it's connected to the generator during startup (like cheaper TV's, radios, etc). Even electric motors can be damaged during generator startup because they will try to draw way more amps than they should (this is because the voltage is too low). If the generator starts to get bogged down because of too much load, start unplugging things in a hurry, you really don't want to use one of these unless it's spinning at speed. That's the first problem, and the biggest problem.
    The second problem is the brushes. They induce "noise" into the electricity, on a scope it looks like a square wave instead of a sine wave, and the edges are all jiggly. This can cause a problem with TV's, radios, etc but is not a problem for anything with a power brick, or an electric motor.

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    Replies
    1. Oh, I forgot to mention; unplug everything during generator shutdown as well. (when I say "unplug"; I use a power strip and just hit the switch on it).

      Delete
  12. Power conditioning. At work we only use Eaton or APC power conditioners, and we usually use big ones (they look like a refrigerator, and we usually have five or six of them). Our generators are the regular kind, not inverters, and ours are really big generators, so we need to condition the power. The only way to get good clean power is from an inverter. APC and Tripplite both make a decent small unit, they're about $250. However, for a CPAP, as noted above, it's not worth the money if they already have a power brick.

    If you want to get something, make sure it's a power conditioner, not a surge protector or voltage regulator. And the better ones have a battery backup.

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  13. On the CPAP I was just going with the manufactures data set. I assume, like you mentioned that it includes running the machine with all the features engaged and running. The main thing I was looking for with that data was having a generator that would service the load with the best fuel consumption. That's why I was going to go with a 2,000 watt generator. It's the smallest they have and will more than handle the load I need serviced. IF I'm wrong about this please tell me.

    I intended on using a standard power strip ($20 variety) as part of my circuit from the generator simply as a method of having a place to plug in more than one piece of equipment.

    The next question would be are the $40 to $50 WalMart type products like this good enough from my application, or do I need something else?

    Help on what specific product to buy is appreciated since I'm not sure I grasp all of the important concepts involved in making the choice.

    Thanks.

    I think the advice on unplugging the extension cord prior to starting up the generator will be part of my standard protocol.

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  14. The link to that last product might not be the right device. Am I looking for something like this?

    Either way, is their a less than $100 solution that would fit my needs and be worth while or do I need to increase the budget?

    ReplyDelete
  15. I would not trust any sub-$100 power conditioner to actually condition the power if it were my expensive electronic stuff on the line, and if I was going to be in the woods for a week or two and needed it. The cheap power conditioners just clamp the voltage at 120 (more like 150) and put in some filters. They assume that what's coming in is power company regulated 110 volts, with some noise from some kind of motor or other really noisy thing inducing ripples onto the power. And that's what they design for.

    What you want is an inverter conditioner. That means that the voltage coming in is converted to DC voltage, then put through a solid state inverter to generate a true sine wave. That's what the expensive generators do; they spin a generator (not an alternator) and they generate DC voltage and put it through a solid state inverter to get AC voltage out, that's why they make clean voltage no matter what engine speed, thus they are quiet, and very efficient, no need to run the motor at 3600 RPM. What generator are you thinking of getting? Does it have 12 VDC output? Many of them do. If it does, heck, get a separate inverter. There's some pretty nice inverters with a built-in battery for around $100, or you can get a 500 watt regular inverter for about $50. Otherwise, if it was me and I didn't have DC out, bring a battery charger, plug it in to get the usual crappy clipped DC, and put that through an inverter.

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  16. And, hey, an inverter is a really nice thing to have laying around anyway. I have two, and am thinking of a third. I use my big one (1700 watts) to power tools at remote sites, and I use my little one (800 watts) just about all the time for my laptop, to charge stuff on the road, etc etc. And I often borrow one with a battery to power LED lights when camping, works great, I get hours and hours of two 100 watt equivalent LED lights (I calculated about 20 hours, but usually only run the lights for 10 hours a weekend).

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  17. Anonymous5:26 PM

    Can you point me to some different brands?

    ReplyDelete
  18. Mine are all Xantrex, and Trace is the same company, different branding. Both are owned by Schneider Electric, which is a pretty solid company. At this point, I would hazard a guess that any brand you have heard of (Black and Decker, Coleman, etc) that sells inverters all have the same guts, and it's probably the same as Schneider Electric. (Welcome to Chinese manufacturing...)

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  19. Oh, one further thing. Almost every non-inverter generator has two generating banks, so you can't pull the full power from one outlet. You need to verify that you can pull your load from one outlet. If you only need 600 watts for your CPAP's, then you may be OK, it depends on how they're getting the 12 volts. But be aware that with a 2,000 watt generator you're probably only getting 1,000 watts per outlet set. Just something to check.

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  20. Anonymous10:22 PM

    Bill,

    Is there a way to test the power before I hook something important up to it?

    ReplyDelete
  21. Bill,

    The unit I was looking at buying, is this one.

    I was wanting to keep the cost of this part of my trip down below $300 but I can adjust that a bit if needed. The majority of my hunting, from antelope to elk is done within an hour of my house. This hunt is going to set me back some cash and I'm trying to economize.

    ReplyDelete
  22. Wow, $200 bucks?! Dang, that is a DEAL. And it has 12 volts out, so you could get an inverter. And I notice that it only has one charging bank, so... I wonder how much power you can draw from the 12 volt outlet? Note that if you measure the DC port it's probably going to be 14 volts, don't sweat that, it's normal.

    For the AC outlet; what you really want to check is the regular RMS voltage, and peak-to-peak if you have a meter that will do that. (RMS means Root Means Squared, it's a kind of complicated mathematical formula to calculate the area within a sine wave). Whenever anyone talks about AC power, unless they're an engineer discussing technical aspects, they refer to the RMS number. 110, 120, 240, are all RMS numbers. Just about any volt meter will give an RMS reading, but the cheaper ones just measure the peak voltage and multiply it by (I think) 0.7, because they just assume it's 60 cycle. But if the meter reads about 110-125 RMS voltage, even on a cheap meter, it's 99% certain to be OK. Two things you do not want to see; lower voltage, like in the 100 volt range, and wildly fluctuating voltage. It's OK if it bounces around in the 110 to 120 range, maybe even up to 140, but if you keep seeing 150, 180 or higher numbers flashing on the display then you're getting really bad noise spikes.

    If you don't have any kind of meter, the next best thing would be an older television, one that uses a tube. They tend to have pretty robust power supplies, and are sensitive to noise on the power line only as static on the picture - no actual damage. Don't use a newer LCD kind of TV, those can take a hit from really dirty power.

    Or, you can spend $50 on a volt-meter. One problem with the cheaper volt meters; they tend to have a hard time with noisy power, the display is so slow to change that it makes it really difficult to get a reading. My Fluke meter ($300) can do sampling, so it gets a good stable series of numbers to review. But some meters I've used just have a constant flashing random pattern on the display because it just won't lock onto anything (this tends to be a real problem with the $20-$30 price range meters). Do you have a meter, or do you know someone that has a meter? You may hear that an oscilloscope is the best tool for this, we have a few portable o-scopes at work, but a meter is just so much easier to use that I hardly ever use the o'scope.

    As far as digital vs analog meters; I personally prefer digital meters, some folks prefer analog because, obviously, there's no problem with them locking onto a number if the power is noisy, but they're not fast enough to see high-voltage transients.

    Oh, one other thing; you need to have something plugged in when measuring the voltage. Open circuit is going to look really ugly. So, plug in a toaster, hairdryer, any kind of thing that has a heating element (because you won't fry those no matter how dirty the power is), and measure the voltage on the plug (pull the plug out just enough to get the probes in).

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  23. I looked at the link to the generator again, it puts out 10 amps on the 12 volt circuit. So, you only have 120 watts off that, barely enough to be useful, and not enough for what you need. Bummer. You need about 400 to 500 watts to get 300 watts of useful power out of an inverter, they're usually only about 80% efficient.

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  24. Bill
    What if he just put a load that was consistent (100 watt incandescent) on first? I would think some of the electrical noise is dependent on the engine going from full idle to load and back again as opposed to lightly loaded to medium load.

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  25. KJ; an incandescent light would work as a load, and on a small generator a 100 watt would be about 10% loading so that would work. The loading does not depend on being idle to full load, the noise problem depends on SOME load being on the generator. It has to see a load, otherwise you can't trust the measurement. The noise problem should be the same for a light load vs a full load, but no-load is going to give bogus readings.

    ReplyDelete
    Replies
    1. Thanks for that info. Explains the wild readings I was getting on the one I use to run power tools.

      Delete
  26. So do I need to go to the next bigger size?

    If I go that route what inverter should I pair it with?

    Thanks for the help I'm not knowledgeable about this stuff.

    ReplyDelete
  27. The bigger one also says the 12 volts is only 10 amps. I guess it's there to charge a battery in case the generator has an electric start, which is a pretty common feature (so the 12 volt tap is probably just built into the head unit that they used).

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  28. Taking what I've learned into consideration:

    Should my system include a generator going to a DC converter and then running to a AC converter then running to the items I want to run?

    If I go that route it seems that based on your 80% efficiency rule that a generator producing a steady 1200 watts would lose 20% at the first DC stage so 1200*.8=960 then would lose an additional 20% at the next stage so 960*.8=768. Does that mean I would have a total of 786 to use at that point? If so, that should work for a total expected load of 600 watts, correct?

    Assuming the above, which boards should I buy to make this system work?

    ReplyDelete
  29. Another possible solution I see is running the generator to a trip lite LC1200 line conditioner.

    Your thoughts on the best way to proceed?

    ReplyDelete
  30. I think the line conditioner is the most cost effective way, but there are a few things that need to be checked first.

    The big issue is the sine wave power (your generator should provide plenty of power, your conversion efficiency is correct). Did you verify that there is no power brick for the CPAPs? And since we're talking about a hundred bucks, I'd call the CPAP manufacturer to verify that it needs sine wave power, and that they don't have a DC solution (many do, since this is a really common problem). Drawing that much power they may be using a simple resistance heater, which won't care about sine wave power. My CPAP draws 90 watts when the humidifier is running, but it's very sensitive to power conditioning. So, maybe if yours draw 150 watts then they don't have the fancy electronics, in which case the power conditioner is the best option.

    If it's bad news on the CPAP front; and the manufacturer says they are very sensitive, then that's worst case and I'd recommend going from AC, to DC, and back to AC.

    The entire problem is how much power you need, 600 watts at 12 volts means 50 amps, which is a lot. So. The actual running load is really only 150 watts each, which is about 13 amps (we still need to account for the surge). A decently sized battery charger can do this. Here's one; ($80 times 2)
    http://www.amazon.com/Schumacher-SE-1510MA-Automatic-Charger-Engine/dp/B000NCI854/ref=sr_1_2?s=automotive&ie=UTF8&qid=1433192278&sr=

    Now you need a pure sine wave inverter that can handle the anticipated 300 watt load. Xantrex is a good brand name for inverters. ($170)
    http://www.amazon.com/Xantrex-806-1206-PROwatt-600-Inverter/dp/B002O5P8BA/ref=sr_1_4?s=automotive&ie=UTF8&qid=1433192874&sr

    So, we're over $300, even if we hook both battery chargers up to the same inverter (which should work, I've thought about it, and asked another engineer I work with, we can't think why it wouldn't work, but it definitly needs to be tried at home first)

    Just to be thorough;
    The APC J25B power conditioner is $227.
    http://www.amazon.com/APC-J25B-8-Outlet-Conditioner-Battery/dp/B003GSLL2E/ref=sr_1_1?s=electronics&ie=UTF8&qid=1433194787&sr=

    Note that the APC units all put out a "stepped approximation to a sine wave". Here's the details on that;
    http://www.schneider-electric.us/support/index?page=content&country=ITB&lang=en&id=FA158851&locale=en_US

    Not recommended for things with motors, so it may not work well with the CPAP. But I think it's going to be similar to what you'll get with the Tripplite unit.

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  31. This is of interest;
    http://www.rpc.com.au/pdf/battery-powering-products-usa.pdf

    Note that one of the units notes "Do not use with an inverter". And, apparently, just about any CPAP made after the year 2000 draws less than 60 watts (without the humidifier). And there's even some humidifier units with really low power draw. Those S8 units look pretty attractive as a camping unit - only about 14 watts, I could power that for days on a regular battery.

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  32. I just checked Craigs List, found a CPAP that only uses 10 watts for $50. I have no idea if it's the same kind of machine you need, it looks like it's the kind I use (just constant pressure, no other features).

    https://washingtondc.craigslist.org/nva/for/5050584416.html

    ReplyDelete
  33. Bill,

    Thanks for your hard work and help.

    I rechecked that 300 watt figure. It was a misprint its supposed to be 30 watts. So the two units are 90 watts and 30 watts. Both units have bricks. It looks like I can run an extension cord to a conditioner to a power strip to the machines with no problem. It also looks like I won't ever need more than half load on the generator so my fuel consumption will be lower than I thought.

    Thanks for the other links I'll check them out too.

    ReplyDelete
  34. Whew! That's a relief! So you have one 90 watt unit and one 30 watt unit? Those are much more reasonable numbers to deal with. So 120 watts total, plus a little extra. And since they have power bricks that's even easier. I would not get a conditioner, I would get two small inverters, you can get a 500 watt inverter for about 50 bucks, smaller ones are in the $30 range. You could run at least the 30 watt CPAP off a car battery for two nights at a time (16 hours of 2.5 amp draw is 40 amp/hours).

    90 watts is going to kill a battery just short of a nights sleep. That's a 7.5 amp draw, for 8 hours, or 60 amp/hours. Most car batteries are about 45 to 55 amp/hours. A decent sized deep-cell battery could easily do it, but that's another $150.

    Note that your draw is now equal to the DC output of the inverter; 10 amps. And if you have more than two vehicles you can charge the batteries with a vehicle, always keeping one battery as a jump-starter, this would give you a backup power source in the event the generator dies. Just about all the inverters have a pretty annoying alarm and an auto-shutoff when the battery voltage gets below about 11.5 volts, so you shouldn't really kill the battery anyway (but I'd hate to get really stuck out there), but the battery won't last all night for the 90 watt unit.

    ReplyDelete
  35. farmer Tom10:50 PM

    Res, I would like to talk to you personally, and I can't find your phone number, so I'm hoping to reach you this way.

    Call me if you still have my phone number. If you don't have it, send me an email at tjn1964@gmail.com.

    ReplyDelete
  36. FT,

    I'm just getting around to checking the blog. I sent you an email.

    ReplyDelete
  37. Bill,

    Yes one unit is a 90 watt and the other is a 30. I think the 90 watt figure is based on running all the extra's but I don't know. I suspect that it might be a max surge figure.

    I looked at going the battery route. That happens to be the manufacture's solution to portable CPAP. Its a good idea, but it assumes no more than 3 days without a power outlet. Probably for most of the folks going camping for the weekend its a great solution.

    I'm going up the mountain and taking two weeks. I have no intention of going to town unless I have a moose in the truck. I might get lucky the first day or the last but I'm not going to be by electricity until I run out of time or fill my tag.

    I checked out the marine battery method. It looks very promising but I have no idea how cold it will be and I have to keep a series of them available to power 2 units. So assuming 3 batteries @ $250 =$750 plus a charger plus inverters etc I figured a min of $900. FWIW I also was checking out getting a solar charger for the set up and being totally self sufficient but that was even more $$.

    I already have 2 large propane tanks plus two grill sized tanks. at less than 50% fuel consumption that gets me over 1 week. I can borrow another 80 lb tank and that would get me 8 more days of generator. Filling all of those will set me back about $125 or there abouts. $208 for generator plus $125 for fuel = $333.

    Now I just need to score a good deal on a four season tent or a camper, otherwise I need to borrow my buddies cabin tent and that thing is a pain to set up.

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  38. Well, for two weeks a generator is clearly the way to go. My concern is what happens if the generator dies? How many vehicles will you have? If two, then get a spare largish battery, and use one vehicle battery and the larger battery to run the CPAPs, You'd have to run the car for about two hours or so to charge the batteries (cars put out about 100 amps if they're running above idle speed). The problem is that the batteries can't take that much current without overheating, so you kind of have to keep an eye on them early in the charging cycle, once they get to about 60%-70% charged, the temp should stabilize and you can just leave them alone to finish charging. If you can charge both batteries at once (just use jumper cables to hook both up at the same time to the host car's battery) then you should be OK, then you'll only be putting about 50 amps into each battery, most "fast" battery chargers put out between 25 and 40 amps, so you're a little over those, with a little checking and disconnecting if they're hot it will work. You really don't want the battery to get too hot, the electrolyte will boil off, which may split the case, but in any event the battery will be ruined.

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  39. My concern is what happens if the generator dies?

    I shoot the first legal moose I see the next morning and go home.

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  40. Sounds like a plan! (isn't that the plan if things work or not?)

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    1. I'll be slightly more picky than that, depending on the preseason scouting.

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  41. Res,
    I have a brick like the one used here: http://www.rpc.com.au/pdf/battery-powering-products-usa.pdf
    If you're using an S8, I'd be happy to loan it to you.
    I'm using this machine now: http://www.healthcare.philips.com/main/homehealth/sleep/systemone/
    It uses 12V for pump and heater.

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    1. Thanks I'll let you know after I get a chance to see how the setup works.

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