Cpap, 12 volt frig and furnace- run all overnight on trailer batteries?

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Pedro Dog

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Jul 9, 2022
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887
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South Shores, CA
Yes Mark, you make very points on measuring. You and I have what I consider good understanding of batteries and plenty of experience. Much of what we discuss here is more educational in nature. Things are not always the way the book says, the assumptions being made here is that the OP's batteries are not degraded. Down the road when the batteries are not tip top shape, worst case situation happen not due to the load but by lack of margin in the initial calculations, assumptions and measurements.
 

Mark_K5LXP

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Nov 17, 2018
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3,314
Location
Albuquerque, NM
the assumptions being made here is that the OP's batteries are not degraded.
Of course, the other side of the equation. Indeed, there's a lot of moving parts so getting a high degree of accuracy can become complicated. That degree is different for someone running an oxygen generator vs coffee brewing. One can create highly accurate models for both sources and loads if one has the need or interest. Advanced battery monitors take a lot of the guesswork out. Giving the impression here it's OCD on my part to dive into the minutia but the takeaway for the non nerds is that none of this is guesswork or mystery, and actually not all that hard to do once a few key principles are understood. In a perfect world RV's would be as simple as cell phones to charge and operate. It's technically possible but RV marketing and accounting departments aren't on board. So for now the customer is the systems engineer. Most folks think they're just going camping... :unsure:

Mark B.
Albuquerque, NM
 

ronthet

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Joined
Mar 26, 2021
Posts
8
Location
Flower Mound Tx 75028
Just because the power supply is spec'd for a given input/output value doesn't mean that's what the device is drawing, so knowing what the CPAP itself is spec'd for (or you actually measure) is where the rubber meets the road. A few nights with the units plugged into a power measuring device (kill-a-watt, et al) will give you an excellent idea what the "wall to wheels" power draw is, and from there you can more accurately gauge run time on battery. Using the power supply *rating* I would offer is worst case and very well may be true but if it's not, you may falsely rate your storage as insufficient when it might be OK.

Mark B.
Albuquerque, NM
Thank you for you information.
 
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