Solar power for remote camp CPAP use

I need a light weight travel CPAP that can be used in week long remote camps, thus must be run from a solar rechargeable battery.

Has anybody used the Powerfilm Max (1.5 lbs, 18 Ah/66.6 Wh battery, 14 watt solar panel, $339) that is more powerful, lighter, and less expensive than the accessory (1.9 lbs, 5.2 Ah, 14 watt solar panel, $500) offered by Sometics, maker of the Transcend Auto?

tygermark wrote: ↑

Thu Jun 21, 2018 12:37 pm

I need a light weight travel CPAP that can be used in week long remote camps, thus must be run from a solar rechargeable battery.

Has anybody used the Powerfilm Max (1.5 lbs, 18 Ah/66.6 Wh battery, 14 watt solar panel, $339) that is more powerful, lighter, and less expensive than the accessory (1.9 lbs, 5.2 Ah, 14 watt solar panel, $500) offered by Sometics, maker of the Transcend Auto?

I've never used this setup, but I think you have a problem with the specs. The PowerFilm is 18 AH at 3.7 volts. The Sometics power pack is 5.2 AH but I'm pretty sure that's at 14.4 volts, the rated output of the Transcend pack. Thus the PowerFilm is 66.6 Watt-hours, while the Transcend is 75 Watt-hours.

While the PowerFilm looks like a slick gadget, I'd lean towards the Transcend because all the components should be matched for highest efficiency.

Also, the "rule of thumb" for much of the country is to assume a panel generates the equivalent of 3-4 hours of full output on average for a day. This is taking into account average weather, latitude, etc. You may expect better in the desert, or closer to the equator, but if you run into a cloudy stretch, you could have a problem.

Thank you very much for your kind reply.

I read some of your threads, and they are impressive. You know this topic up, down, and sideways.

There is this from the Powerfilm blog:

https://www.powerfilmsolar.com/about-us ... ttery-life


Since the Lightsaver Max (LSM) has a 12v output port, I thought that I would get sufficient power for the CPAP via a simple barrel-barrel cord from the LSM to the Transcend.

But that is not true?

tygermark wrote: ↑

Sat Jun 23, 2018 5:16 am

There is this from the Powerfilm blog:
https://www.powerfilmsolar.com/about-us ... ttery-life

Since the Lightsaver Max (LSM) has a 12v output port, I thought that I would get sufficient power for the CPAP via a simple barrel-barrel cord from the LSM to the Transcend.

But that is not true?

I would guess it has enough power. It was great that the blog actually confessed that the output has to be downrated 10% to match the desired output voltage - you don't see that honesty often. I wonder if there is a voltage where you get full output. The Transcend pack is configured as 4 cells in series so the output is 14.4 volts which I think matches the input of the Transcend pump, so there's no loss in conversion. I'm not sure which pump you're planning to use. If its the Transcend, I think the 12V adaptor for that has to raise the voltage up a bit, so there could be be another hit. The Transcend is a very efficient pump, so you might still have enough power for two nights. Transcend doesn't like to publish numbers, but they do bill the larger pack as being "multi-night."

The other issue is whether a 21 Watt panel will reliably generate enough power for a night. With a Respironics or Resmed pump you'll need 50-75 Watt hours a night, so you'd want to see 3 to 4 hours of good sun for every night. You also need to have the sun perpendicular to the sun - lying flat or vertical at latitude 45 downgrades the power to 70%. And no trees! This is why the rule of thumb says that a full day only gets you, on average, 3-4 hours worth of power.

This is why you want the largest possible pack. If you only can power one night, you can't handle one cloudy day; a two night pack allows you to go an night even with no sun, etc. The LSM probably can handle one night, but for an extended period with no fallback I'd be looking for the largest battery possible. A lot depends on the details -the location, the weather, how well you can place the panel, etc.

Thanks for that. Yes, the blog taught me a lot.

Sometics has discontinued their one night (P4) battery. As far as I can tell, people who use the "multinight" (P8) battery get, on average, 1.5 nights (use without deHOH, heat, etc).

At this time I plan to get the Transcend because it does have the solar option. In the future, others might offer solar solutions, but it very well could be years before a light weight solar recharge/battery package becomes any more realistic than it is today.

"Transcend doesn't like to publish numbers......"

Amen. For the life of me I cannot find what the wattage of 'their' made-by-PowerFilm panel is.

I would not be surprised if the Sometics panel was 14 watts.

Found this:

SOLAR RECHARGE TIME ( In Full, Direct Sun Conditions)
Transcend P8™ Multi-Night Battery: 12 Hrs for Full Charge from Completely Depleted Cells
Time Varies Depending On Sun Conditions

A guy could find themselves short of CPAP in a hurry.

I think I have convinced myself that lightweight solar recharge for remote CPAP use just isn't 'here' yet. And it could be years and years away.

tygermark wrote: ↑

Sat Jun 23, 2018 7:42 am

"Transcend doesn't like to publish numbers......"

Amen. For the life of me I cannot find what the wattage of 'their' made-by-PowerFilm panel is.

I thought it was 21 watts, but then I looked on the cpap.com site and it says 13-14 watts.
https://www.cpap.com/productpage/somnet ... arger.html
look on "specs" tab

<rant on>
I find it very frustrating that there are a multitude of products that ALMOST work together! I've chosen to stay in the traditional 12v world, but most of the viable solutions for light weight are lithium that all seem to have differing requirements, odd connectors, and obscure specs! (not to mention high price!) I was hopeful the LiFePO4 batteries that are compatible with 12V would become popular, but they are still niche market. Maybe in 10 years we'll see some standardization.
<rant off>

Really.

It looks like I am going to have to contact the outfitters that operates the remote camps, send them money and tell them to buy a wheelchair battery and have it in camp when I fly in. Then let them keep the battery and fly home.

Well.....I mean scooter AGM U1 battery.