INVERTER vs CONVERTER - RV-Dreams Community Forum

Doncat · RV-Dreams Family Member

INVERTER vs CONVERTER

Jack Mayer · RV-Dreams Family Member

An inverter takes 12-volt power from your batteries and changes it to 120-volt for use with residential appliances. The amount of power available is based on 1) the rating of the inverter, and 2) the number and type of batteries available. Generally measured in amphere hours. Most larger inverters really have 3 functions built in - the inverter, a battery charger, and a transfer switch.

A converter takes 120-volt shore power and turns it into 12-volt power, which is then used to charge your battery bank, and used to power the 12-volt appliances and lights in your rig.

A rig with a single 12-volt battery is not going to be able to power very much 120-volt appliances. Look at it this way: a 120-volt TV that uses 3 amps will take 30 amps DC, plus any loss from conversion to 120-volt. So really, it uses more like 33 amps. Per hour. Just multiply the 120-volt ampreage by 10 to get the DC amps. That is why people who boondock use multiple batteries. Take a look at our website for additional info....

For what kind of inverter you need, you first need to do an energy audit and determine the number of watts you will use. Then you can make some additional decisions about how many batteries, and what type of interter.

-- Edited by Jack Mayer at 20:58, 2006-08-24

blijil · RV-Dreams Family Member

Just wondering if your CPAP provided just pressure or also has a humidifier. Hopefully it does not have the humidifier with the heater or your power consumption will be way up there. Inverters quit working for two reasons, overload (to much power requirement) the inverter by 10% and it will shut down in about 10-15 minutes, low battery voltage (usually below 12.1 volts) and the inverter will shut down. With that said I have also experienced a bad connection at the plug where a voltage drop caused by heating will cause the inverter to shut down because of an apparent low voltage. All I needed to do was push the 12 volt plug in to make sure it was snug.

One 12 volt battery used for a CPAP alone will only last at most 2 nights without a recharge.

Larry

Doncat · RV-Dreams Family Member

Larry,

My CPAP does have the heated humidifier, never considered it may require more amps. It is getting old and I would like to get the new small compact model. I always have to consider where the CPAP will fit, when shopping for an RV. Our Prowler TT has a countertop next to the bed. Bringing the CPAP is a must, if I expect to sleep!

Doncat · RV-Dreams Family Member

Jack,

Sounds as though some of the solar systems could be complicated to install. I was thinking of install 2 deep cycle 12volt batteries and a solar panel to charge them. I know I would need an inverter to power the limited number of devices the 2 batteries would handle, but would I require a controller also? I am going to check out some websites, yours included, to research solar systems, however finding time to do so is another thing.

Jack Mayer · RV-Dreams Family Member

The short answer is Yes, you will need a controller.

You should refer to my website for the detailed long answer.

Basiclly, all RV solar installations need the same items. The variability is in the sizing and quality of the components, and thus the cost of them.

You need:

- Panels. At the moment I would recommend the AM Solar, high-power panels. There is an energy rebate of 30% you may be entitled to on your taxes.

- Solar controller. MPPT type is preferred. It is important to size the controller for future expansion.

- Metering: for both the batteries and the inverter, sometimes combined into a single meter depending on the components selected. And optionally, for the solar controller.

- Inverter: size, type and features depends on your needs. You will be best served by an inverter/charger that has an auto transfer function. These 3 capabilities are present in almost any inverter you will use in an RV. The battery charger is a high-powered charger that replaces you converter.

- Batteries: size, type and quantity depend on the energy audit results, and your pocketbook.

To some extent you can phase in the installation. I cover this on my website.

ehde · RV-Dreams Community Member

I also use a CPAP (no humidifier) and I was able to get through the night with the two coach batteries that came with the rig, but only if we didn't watch too much TV before turning in. Now that I've added a 3rd battery I haven't had a problem even after a few hours of TV.

See if you can lose the humidifier on the CPAP. As long as the ambient humidity is high enough, I find that I don't need a humidifier.

blijil · RV-Dreams Family Member

The do make a evaporative humidifier that pulls the air across a small high surface area water tank. Kind of a pain because it works best with distilled water in dry climates but it does work. Your plan to use solar makes a lot a sense but remember it is best to minimize the load when possible and the humidifier is an issue.

I haven't slept without a CPAP for over 10 years. Once had to leave the camper and go back home to get my CPAP. It took 4 hours but I did sleep that week.

Larry

Doncat · RV-Dreams Family Member

I know what you mean Larry, I have had to have mine for 7 years now. When I first got it I thought I would never be able to sleep with it on my face, now I cannot sleep without it. I was wondering how I will adjust to the RV lifestyle having to carry it all the time. We have been on a 5 day trip and it worked out fine, except for the part where I tried to boondock at a Love's truck stop....

blijil · RV-Dreams Family Member

Don,

Boondocking is not the only place it gets exciting. We spent 5 weeks in Namibia, Africa in 2003. Figuring out how to use local power (220v 50Hz) and bush power (small batteries in vehicles) really stressed me before we left. I now own a very efficient small inverter and a small voltage reducing transformer that works just for my CPAP. We boondocked for over 5 weeks this summer without a problem so it can be done. It just takes a little planning and a lot of conservation of energy.

Larry

bjoyce · RV-Dreams Family Member

My wife runs her CPAP with a heated humidifier off a 400 watt modified sinewave inverter when we boondock. She has a Responics REMstar Pro 2. With her settings it takes between 270 and 380 watt-hours ovenight, depending on how long she sleeps. With inverter losses and such that is about 30 to 45 amp-hours of battery. I know we saved about 30 amp-hours per night using the small inverter instead of the big 2000 watt inverter-charger we have. The CPAP runs between about 13 and 109 watts all night long. I have a Watts Up meter to do the measurements, it was a great $100 purchase five years ago.

Doncat · RV-Dreams Family Member

I bought a small 800 watt inverter, but have not had an opportunity to try it out overnight. The meter you speak of sounds interesting, Do they have a website for more info?

ehde · RV-Dreams Community Member

Take a look at Jack Mayer's 8/26/06 post. His web site has a lot of useful info.

Ed

bjoyce · RV-Dreams Family Member

I think the newest Kill-A-Watt meters can do everything the Watts Up can and are more like $30. Five years ago the Kill-A-Watts were more like $40 and needed pure sinewave, but the Watts Up used RMS readings so they could handle modified sinewave. I have been told that current Kill-A-Watt's can handle modified sinewave. Improvements happen.

On an 800 watt inverter I would expect the overhead to about about twice a 400 watt inverter so it will use more battery power to run the CPAP. Our CPAP manual wants at least a 300 watt inverter and we already had a 400 watt one. Inverters work most efficiently at 30-90% of their ratings according to Northern Arizona Wind & Sun's Inverter Information Page.

-- Edited by bjoyce at 22:28, 2007-02-13

Weaverworks · RV-Dreams Family Member

What's a CPAP?

Sorry about the stupidity. New at this blog stuff.

Paul

bjoyce · RV-Dreams Family Member

CPAP is a breathing machine for people with sleep apnea. Sleep apnea is where you quit breathing in spurts at night. Lots of people have it, many won't get tested or admit it.

jhonebhrestom · RV-Dreams Community Member

Well the difference you can say is 

A Inverter is a  device which changes direct current (DC) into alternating
current (AC). Direct current is created by photo voltaic modules or
batteries and converted to AC through the use of an inverter.

A Converter which converts an input power line voltage to a different output
power line voltage. This conversion permits the operation of electronic products
intended for the U.S. from European power sources.

-- Edited by jhonebhrestom on Tuesday 27th of April 2010 04:23:30 AM