We both use CPAP units that draw 13A at 12 volts, the quoted Power Consumption is 70W typical.

I figure this to be 13A times a typical 8 hour night is 104 Ah, therefore 208 for the 2 units.

The battery that is provided is a Group 27 providing 92 amp hours with 195 minutes reserve.

Assuming I understand what I have read this battery, even 2 will not run the CPAPs.

2-6 volt golf cart batteries appear to be able to do the job but at a cost of almost 800 CDN (including a battery box) plus putting my tongue weight up to about 350 lbs, even using a WDH this causes me concern.

Seems I would be better to invest in the quietest 2000 watt inverter generator I can find rather than spend the $$ on the batteries plus I get the benefit of running other electrics (although not the a/c).

I would really appreciate some expert advice from knowledgeable folks who are using CPAP units, especially in dry camp situations, before we close our deal.

Thanks, Norm

Hope I put this in the right place.

Then simplify your calculations by using watts for everything.

70 watts * 2 * 8 hours = 1120 watt-hours.

The battery you mentioned (group 27, 92 AH (is it 12 volts?)) will provide 1104 watt-hours to complete discharge. You can't use that value, as discharge below 50%. It's only going to provide ~~ 550 watt-hours before it will start to be damaged.

So you're going to need more than twice that power, and that is only going to accommodate the CPAP, and nothing else.

I'm thinking there must be more efficient CPAP machines. That power consumption seems excessive.

 

Anyway, you confirmed my gut feel that batteries, even golf cart are not going to safely run these units.

The units are a few years old and I am sure new ones are more efficient but new are not in the budget.

It is good to know there are now restrictions on generator use as we have experienced the noise and fumes in our tent trailer days.  

However, I do need to pursue that option.  Seems like a small 1200 amp unit would run the CPAPs and be the quietest, but I need to understand the noise issue better.  The CPAPs would be more important than the A/C or microwave.

We are planning a few long trips and I am sure we will run into sites and locations without power where we need another source.  I expect our usual stopping places will be camp grounds with power available.

I will look further at generators and that will probably generate more questions but for now I will accept the single 12 volt battery the dealer provides.

Cheers

Thank you for the advice, I did not realize that we could turn off the CPAP heaters, in fact we do not even need to use the tank and being that I have read humidity can be a problem in the Pod perhaps that might meet our needs.

I will go with the single 12 volt or get the dealer to not provide a battery at all and then get golf cart batteries and case in the US.

Assuming your calculations are better than mine, I believe it is worth going the battery route, that is my first choice and if we find the need we could consider a generator at a later date.

Cheers

Thanks

We are in Canada and hope to close this week, we plan to store at the dealer until April.

I will p/u Duracells at Batteries plus Bulbs from their outlet on Glenwood Ave in Raleigh as it is only a couple miles from our daughters home.

I did some digging into our ResMed units and there is a humidifier off setting, in addition we can use the main unit without the humidifier attached which should really help the draw.  From what we read with night time humidity in the R-Pod with 2 people sleeping we should not need the extra moisture.

Experience will tell but I feel much better about the dual golf cart batteries than any other option.

Cheers

It got me to wondering, and it appears that this is a new market segment for people that need to travel with a CPAP. In the little bit that I looked around this morning, I found several different makers of mini-CPAP machines; and many of them operate on DC power from a cigarette lighter plug and/or a small (separate) battery pack. In addition, many of them operate at less than 30 dbA (meaning really quiet).

Several of the ones that I looked at consume less than 20 watts; which would be ~~ 1.7 amps at 12 volts. It seems one of these would be an ideal solution for someone looking to boondock with their CPAP. These are some that I've found:

My estimate for the wet batteries would be ~~ 1380/65 = 21 hours (what you figured)

My estimate for AGM batteries would be ~~ 2070/65 = 31 hours

Of course, that's assuming that nothing else is drawing from your batteries (unlikely).

If you were using a mini-CPAP that was running at ~~ 20 watts would get 69 hours or 103 hours respectively.

When It is time for new ones we will definitely consider them.

Until then the dual GC batteries should do us fine.