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Old 11-20-2014, 03:36 PM   #11
Commercial Member
Join Date: Nov 2014
Posts: 13
Hey Wwalker,

Sleep apnea machines can be configured in different ways. Some machines have a humidifier that can be turned off and different pressure settings. Using a lower pressure setting or turning off the humidifier can cut your power consumption in half - this is huge when you have two.

With that said I'd like to know if you know how many watts your particular machine uses. If you can get me that I can calculate an average usage per night and then can calculate how the solar will do.

Typically if someone cannot get me the wattage I use an average of 45 watts per machine per hour - this is a high estimate for most high quality CPAPS. I have seen watts as low as 30 and 35 per hour.

For a cpap that uses an average of 45 watt over an 8 hour period the amperes would be 30 Amps - again I think this is high. But sometimes in very dry areas and long night sleepers this can be an average.

This 30 amp figure is the amount of power your battery needs to deliver per 8 hour period. This is just for the CPAP and doesn't include any other devices. For two CPAPs we can calculate 60 amps a night, then we would want to calculate your normal electrical usage from your RV for lights, fans and other - I use an average of 40 to 50 amps for a 30 to 35 foot trailer.

Total amps in this calculation is between 100 and 110 amps per 24 hours. This is the figure we have to match using solar.

Your 200 watts should be kicking out a little over 11 amperes (per hour) and for a full 7 hour day that should be around 75 amps. In this estimate you would be putting in the majority charge back into your battery but still be short by 25 amps. If you were to add another 100 watts you would be at over 16 amperes and near 115 amperes for the day. A better situation for this estimation.

I would recommend 300 watt or better for the majority of the US. If you lived in frequently cloudy or shaded areas I would suggest 450 watts of solar.

Now lets assume the average is 30 watts instead of 40. In an 8 hour time, amperes consumption 20.

20 x 2 = 40 (2 CPAPs)
40 plus your regular usage and it's between 80 and 90. Could be the difference of over 20 amps per 24 hour period.

A small change can make a larger difference.

Let me know if this makes sense or not. If you want a personalized average I can calculate it for you with the wattage your machine draws and what you use normally per day.

Zamp Solar

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Old 11-20-2014, 03:49 PM   #12
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Join Date: Nov 2014
Location: Concord CA.
Posts: 89
Yes that helps a lot I live in Northern California and we do a lot of beach camping sometimes not a lot of sun. my wife's CPAP has a humidifier so it would be on the higher amperage side .so I have room for two more panels at 100 W each that's what I think I'm going to do Dan I should have a total of 400 W of solar panel thank you for your help Jeff

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