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Discussion Starter · #1 ·
Hi To All !

I have sleep apnea, I use a cpap machine at night, it runs on 110 volts AC and 12 volts DC.

I need to install a 12 volt DC outlet ( lighter type ), that way if the electric goes out I will be able to use my cpap. My question is, should I run the wiring from the converter or straight from the battery with a fuse?

Thanks.
 

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Just to understand, are you saying your CPAP runs off 110v AND 12v or did you mean 110v OR 12v?

If your 110v goes out, then so will the converter so it's better to run it from the battery with a fuse. Why don't you just skip the 12 outlet and install an "Inverter". Find out the wattage capacity for your CPAP then install the inverter which automatically converts the 12v battery to 110v for your CPAP. In other forums I belong to this is a very successful option. The reason is that the CPAP will always have power (from the batteries) and you don't have to worry about 110v not being available. When 110v is available then the converter helps keep the batteries charged anyway. Your only concern is keeping the batteries charged when not connected to shore power.

The CPAP runs plugs into the inverter just like if would from the 110v outlet. The biggest problem you'd have to consider is where to mount the inverter to get to the outlets and how to get the 12v inverter wires back to the battery. But you'd have the same problem running the wires from the 12v outlet (lighter).

Inverters are sold in many wattages. As low at 100w, to 3,000 and even higher. I had a 1000W inverter in a prior trailer and that was plenty. It was wired to the battery (with a fuse) and gave me 110v power when not connected to shore power. I used it for air compressors, and power drills when I stored the trailer elsewhere and didn't have 110v close by. The inverter should be installed by someone who is well versed in electronics. I had it done by someone since it need an isolator and I don't know how to do that. An isolator helps protect the trailer when using multiple power sources (truck supply, shore power, solar panels or whatever you happen to have).

If might cost more overall, but it will be money well spent, over the lighter solution.
 

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Discussion Starter · #3 ·
Just to understand, are you saying your CPAP runs off 110v AND 12v or did you mean 110v OR 12v?

If your 110v goes out, then so will the converter so it's better to run it from the battery with a fuse. Why don't you just skip the 12 outlet and install an "Inverter". Find out the wattage capacity for your CPAP then install the inverter which automatically converts the 12v battery to 110v for your CPAP. In other forums I belong to this is a very successful option. The reason is that the CPAP will always have power (from the batteries) and you don't have to worry about 110v not being available. When 110v is available then the converter helps keep the batteries charged anyway. Your only concern is keeping the batteries charged when not connected to shore power.

The CPAP runs plugs into the inverter just like if would from the 110v outlet. The biggest problem you'd have to consider is where to mount the inverter to get to the outlets and how to get the 12v inverter wires back to the battery. But you'd have the same problem running the wires from the 12v outlet (lighter).

Inverters are sold in many wattages. As low at 100w, to 3,000 and even higher. I had a 1000W inverter in a prior trailer and that was plenty. It was wired to the battery (with a fuse) and gave me 110v power when not connected to shore power. I used it for air compressors, and power drills when I stored the trailer elsewhere and didn't have 110v close by. The inverter should be installed by someone who is well versed in electronics. I had it done by someone since it need an isolator and I don't know how to do that. An isolator helps protect the trailer when using multiple power sources (truck supply, shore power, solar panels or whatever you happen to have).

If might cost more overall, but it will be money well spent, over the lighter solution.
The cpap will run on 110v or 12v. I have a power cable for the 12v hookup that plugs into a 12v outlet, I wonder if the inverter would draw more from the battery than it would if I ran it straight off the battery with the power cable?
 

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The CPAP directly connected to battery might use less amps than going through the inverter, because depending on the inverter it would need a small fan and maybe some LED for some power but expect these would be very very small amps.

On the power sense, going to direct to the battery would be better. But for just fractions more in amps, having more outlets of 110v available to use from the inverter for other things besides the CPAP machine might be an additional plus. I just picture you connect directly the CPAP to the battery and then you find it would be nice to have 110v for other things even though shore power is not available and the inverter would have been nice. But it will be extra cost.

For now, to meet your need and to answer your question to satisfy your concern and to keep things less expensive, go straight to the battery with a fuse.
 

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I would have to see the schematics for sure, but if it can run on 12Vdc, then what that probably means is when you plug it into 110AC, it is internally transforming and rectifying it down to the 12Vdc that it actually operates on.

Your best option is to install a 12V jack near the bed where you sit the CPAP and plug the unit into the jack.

Now if you are running 110 from an outside source (like a electric included campsite) then the power used on AC isnt a problem, but if you are trying to get the AC by using an inverter plugged into a 12v jack, you are losing a bit of energy due to the converting power twice..

It would be like melting fresh snow in order to freeze it into ice cubes to put the the cooler. Would be easier to just put the snow in the cooler.
 

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I taped on to 12v wires in my front pass thru compartment and put a receptical beside my bed for my CPAP. Prior to this I used an inverter. Without the inverter I use noticeably less power from the battery.
 
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