CPAP and Camping Trip

[Alshain]

Marine batteries are 7.5 Ah? If that's the case I can probably take a 12 Ah regardless of machine & pressure differences and take a little 1 watt solar panel just in case.

Edit: oops I forgot, our 1W panels are 6 volt. Ah well the 10watts aren't that big either.

Now that I know the unit has a DC power connection, I'm fully capable of using the equipment in our lab to test it's current draw and formulate the exact power/solar I need.

[xenablue]

Hope you get the camping thingy all worked out and have a blast!

DH and I just bought a pop-up camper - we love camping but decided we are just too old and crabby to sleep on the ground any more (or get up from ground level). We plan to "rough-it" in more luxury these days and always use a powered site for the CPAP, lights and a fan.

Cheers,
xena

[Alshain]

Hope you get the camping thingy all worked out and have a blast!

DH and I just bought a pop-up camper - we love camping but decided we are just too old and crabby to sleep on the ground any more (or get up from ground level). We plan to "rough-it" in more luxury these days and always use a powered site for the CPAP, lights and a fan.

Cheers,
xena

Lol, I don't blame anyone for that, but I'm gonna do it the good old fashioned way while I'm young enough to enjoy it.

[archangle]

? Marine batteries are 7.5 Ah? If that's the case I can probably take a 12 Ah regardless of machine & pressure differences and take a little 1 watt solar panel just in case.

Edit: oops I forgot, our 1W panels are 6 volt. Ah well the 10watts aren't that big either.

What do you mean "Marine batteries are 7.5 Ah"? While that would be small for a "marine" battery, "marine" vs. "non marine" doesn't really have anything to do with Amp Hours. What you want is a "deep cycle" battery. Some people mistake "marine" for "deep cycle", but the terms aren't equivalent. Some deep cycle batteries aren't "marine." Some "marine" batteries aren't deep cycle.

If you buy a "marine" battery, be sure it's a "deep cycle" marine battery, not a "starting" or "dual purpose" marine battery.

A 1 watt solar panel isn't worth bothering with. A 10 watt panel would probably be inadequate, too. You need something like 10-20 watts for 8 hours to run your machine (varies by machine, settings, leaks, and pressure). That is 80-160 watt hours. With a "perfect" setup on a sunny day, your 10 watt panel might get 80 watt hours. You won't get 100% efficiency charging and discharging your battery. You'd be lucky to get 50%.

For $70 or so, you can buy a 75-100 Ah deep cycle marine battery that looks and weighs like a large car battery. It will probably run your machine for several nights. Another $40 or so for a good trickle charger and battery box, and you can keep it in your house on charge all the time in case of power outages at home. It will be a spillable like a car battery, so if you turn it over while transporting it, you'll spill acid. Non-spillable deep cycle batteries are around twice the price for the same capacity.

The Respironics DC power cable is $25. If you want to hook it to the battery you'll also need an alligator clip to cigarette lighter socket adapter. Respironics wants $25, but that's a ripoff. You can probably find them cheaper elsewhere. You could also make a bare wire to cigarette lighter plug adapter.

By the way, don't try to run long DC cables. Power loss in cables is 100 times worse at 12V vs. 120V.

[Alshain]

Oh don't worry, I'm well versed in the properties of DC/Solar power (I design these for a living). The only thing I don't know as of yet is how much amperage the unit draws at my settings. I'm going to bring it up to work when I have time and run some power simulations with our equipment to determine it's draw and then I will know exactly what I need to use. (I have access to various panels, so if I need more than 10, it's not a problem. I could get an 85 watt if I needed to, but I don't think it will fit in my little car, lol)

Remember that trickle charging a battery that under a load 24/7 takes a ~3x more to maintain then charging it while it is not under a load. Since the CPAP won't be in use while the battery is charging, you get a lot more efficiency from the charge. I just need to be sure that the battery is large enough have at least 2 days of autonomy and hope that I get enough sun to charge it for the remainder (if we get unlucky and it rains all week, we will find a hotel anyway). The batteries I will be using are non-spillable.

As for the Respironics Power cable, it's just a inverted mini-pin. I can get that for $1 or less from Mouser.