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Power in the wilderness [Jun. 24th, 2008|12:55 pm]
Doug Ayen
How do you provide power to a required medical device (not mine, fwiw) in the wilderness?

Well, this is what I've put together:

1 deep-cycle marine battery
1 400-watt inverter
2 connectors
1 battery box
(charger in case it goes flat)

Put the battery in the box, along with the inverter. Strip off the cigarette lighter plug on the inverter, wire to the battery connectors. Plug CPAP machine into inverter.

I've already confirmed that the CPAP uses 1.5 amps (according to the power requirements on the device), so if we're good about unplugging the inverter (remove a lug -- if this works out well I'll add a cut-off switch) it should last for Baitcon. If not, well, I have the charger, and in an emergency can always use the small generator, though I'd prefer not to have the noisy thing near where people (including myself) are sleeping.

(The guy at Sears, when he heard what the battery was for, was simply amazed and enthralled by the concept of building a power supply like this. Is it really that unusual?)

I should have a small multimeter somewhere, if I can find it before heading out I'll add it to the box so I can check voltage levels.

Now let the chorus of why this won't work and how I'm going to kill everyone with my infernal device begin.

Assuming it does work and doesn't result in a China Syndrome meltdown, I wonder if Make would be interested in a writeup, or if this is too simple a project?


[User Picture]From: rmd
2008-06-24 05:14 pm (UTC)
speaking as a cpap-user, that sounds ideal.

i had a similar thing that was a commercial bundled unit that i used - it was only good for about 1 night, but i figured i could recharge it from my car if the power was out for days at a time.

for make to use it you might have to stick a NES controller to it somehow or put it in an altoids tin. :-)

at the very least, you could write it up as an instructable.
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[User Picture]From: frobzwiththingz
2008-06-24 10:24 pm (UTC)
open the CPAP box. See what is in it. Maybe the stuff inside it uses 12V internally, and you can delete the inverter and get longer life out of your battery as well.
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[User Picture]From: jennifoot
2008-06-25 01:06 am (UTC)
Um, you think the guy would be more surprised at that or the fact that I put something like that together so I could slow cook a pot roast in the back of my truck on a 6 hour road trip?
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[User Picture]From: garnet_rattler
2008-07-08 12:43 am (UTC)
Sounds perfectly reasonable to me but the Sears guy was surprised when I did something similar four or five years ago as well. With a bit of testing and tweaking, your home-made unit is likely to be Better than most commercial ones, as they are built as close to the edge as possible to extract more profits. You've included a ~2.2 times reserve in the inverter and can always run a long jumper cable from your (or anyone else's at real need) car/truck for a quick charge if you don't have a generator handy. Good hacking!

PS: And it will run a pair of small reading lamps essentially forever as well, a definite win.
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