inverter help

Randy_K · 06-28-2015, 07:01 AM

I just bought a 3000 watt inverter. Its way more then I need but it was the one on sale. I really only need it on the rare time that we are at a motorcycle event camping with no hookups. The only think I need to run is my CPAP to sleep.

I have two 6 volt batteries on my trailer. It looks like I can set the inverter in the basement of my trailer. I think I can fish some wires under the trailer to the batteries, then plug the trailer plug into it. I would think that would power all my plugs inside . Unfortunately , I would have to leave the basement door open to run the trailer plug there.

Any problems doing it like this ? Im not much of a electrical person and this looks like the easiest way. I just want to be able to sleep the few times a year we have no hookups.

Thanks for any help.

Festus2 · 06-28-2015, 07:33 AM

Depending upon the length of the run between your batteries and the inverter, you should use the recommended gauge of wire to reduce power loss. Go online and Google this or perhaps this information came with the inverter.

hankaye · 06-28-2015, 07:34 AM

Randy_K, Howdy;

You haven't mentioned what flavor of RV you have, but ...
if your bedroom is near the batteries why not just run some
wires from the inverter to an outlet near where you place the
CPAP? You could install a separate outlet dedicated solely for it.

hankaye

**hankpage** · 06-28-2015, 07:37 AM

Mount the inverter as close to the batteries as possible. (See instructions for the inverter) The size wire needed for DC is much larger and costly than for AC. If you try to plug the main power cord into the inverter you will need to turn off your converter or it will drain the batteries as it tries to charge them. It is easier to run an AC extension cord to your CPAP or wire one outlet to the inverter with surface mount components. ( WireMold ) JM2¢, Hank

pnwham · 06-28-2015, 07:39 AM

It's pretty much the way I'm doing it on my 5th wheel. Just a couple of things to think about. 1) Make the run to the batteries as short as possible with as heavy a wiring as possible. 2) Make sure you turn off the appropriate breakers at the breaker panel...most importantly the one for the converter, but I also turn off the ones for the AC, Microwave and Fireplace. 3) Make sure your refrigerator is set to propane. You should be fine otherwise.

Rich - Montana HC 293RK

Randy_K · 06-28-2015, 08:51 AM

Our trailer has the bed right at the front. The basement is right behind the batteries. I kind of like the idea of running a dedicated plug . The inverter has three plugs and usb ports on it. I am wondering if the inverter should somehow be mounted inside the trailer. It does make it further from the batteries though.

Some good stuff to think about.

**hankpage** · 06-28-2015, 08:57 AM

With the remote switch there is no need to mount the inverter inside the trailer. If you do you will not like the noise it makes.

**JRTJH** · 06-28-2015, 11:42 AM

Something to consider with using a 3000 watt inverter to power a 100 watt CPAP is the wasted battery energy to run the LED's, fans, remote control mechanism that are a part of such a large inverter. Just getting enough amperage through the primary winding of the inverter's transformer to get an output on the secondary side will use more power than the CPAP would consume.

There are many CPAP's that have a simple 12 volt adapter to provide power and there are many 12 volt CPAP's that don't require any modification to use in an RV, just plug them into a cigarette lighter socket. Those types use a 120 to 12 VDC power supply to power the CPAP at home.

In a sense, using that much "inverter power" to provide an energy source for a "small draw" item is much like buying a F450 to tow a teardrop trailer. Just the battery bank required to power such a large inverter would make it impractical (both in weight and installation costs) to install the system unless you're planning to use the inverter for much more than just to run your CPAP.

I'd do a bit more research before spending any more money on that large of a power supply installation just to operate a "light draw" CPAP.

ADDED: Look at the 4th post in this thread (on another forum) concerning inverter efficiency and you'll see that a "very large" inverter does not use battery power efficiently when providing "light loads". In other words, a large inverter being used to power a light load wastes more energy than a large inverter being used to power a larger load. http://www.anotherpower.com/board/index.php?topic=125.0

arturob · 07-02-2015, 06:59 PM

The no load current drain from an inverter varies from model to model. I run a WINS 3600 watt inverter and the no load current is 0.5 amp. It will run my microwave but the power output is reduced - about half of what I get with shore power. I think this is due to the inverter being a modified sine wave type. I have the unit mounted next to my batteries and Walmart battery cables to power it though a 300amp fuse.The long cable run needs to be on the 110volt side not the 12v side.

**JRTJH** · 07-02-2015, 07:10 PM

arturob,

You're right, the "NO LOAD" current draw is low, but the "SMALL LOAD" current draw is significantly more than the load. In other words. with no load the inverter (almost every model 2000 and 3000 watt inverter) will draw about 0.5Amp. however, to produce 200 watts (small load) it will consume 350 to 500 watts. To produce 2000 watts it will consume 2200-2500 watts.

So, even though it "coasts" when there is no load, it will use 2 times the energy to produce 300 watts that a 400 watt inverter will use.

Large inverters are not "energy efficient" at low output.

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