power inverter

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rclark

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Edinburg Va
Hello, I bought a little 12v inverter made by Cyber Power, it has a model no of CPS140CHI, input 10.8-15.8vdc,output120vac-60Hz and input current 12A max.. I wanted this to power a string of lights that says watts per foot 2.8w 120v,0.45A,60Hz...
My question is why are the lights so much dimmer in MH than when I plug them in, in the house?? Battery gauge says that the coach batteries are full!! I thought this inverter would have handled this!!

Thanks Randy
 

Gary RV_Wizard

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Well, with an inverter input of 12A your inverter can generate at most 1.2 amps at 120 VAC. That's 144 watts max and likely a bit less in practice, maybe 125-130W.  You didn't say how long the string of lights is, so 2.8W/foot doesn't help much.  But if the 0.45A mentioned is the max draw, you are certainly well within the capacity of the inverter. If the string is under 44 feet in length it should be fine.

Assuming it is within the capacity, if the lights seem dim my guess would be that the lights aren't happy with the modified sine wave the inverter puts out. A modified sine inverter has a lower peak voltage than regular household AC, but it holds the peak longer. Mathematically you get the same amount of power but those little bulbs don't ever get to their peak brightness.
 

rclark

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Thanks Gary, the string of lights is only 18 ft long, so your theory about the lights not liking the modified inverter must be correct!! 

Do they make the pure sine inverter in those little models??

Thanks Randy
 

John From Detroit

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When running light bulbs it should not matter if it's pure sine wave or not,  The modified sine wave is designed to light a light bulb to the same level as a PSW.  It's one of two cases where the waveform does not matter.

It is possible the inverter is not up to spec
 

Lowell

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RV Roamer said:
Yes - I have a 150 watt model I use to power my cell phone & camera battery chargers and other sensitive things.

I have a 300 watt modified sine wave inverter that I had intended to use for recharging the cell phones and laptop. Is it not OK to use a modified sine wave to recharge these batteries?
 

Lou Schneider

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Are you plugging the inverter into the cigarette lighter jack behind the TV?  These are notorious for having too long and too thin  wire between them and the motorhome battery.  When you connect a load the DC voltage coming out of the socket drops, which in turn reduces the 120 volt output from the inverter.

If you have a cigarette lighter on the dash of your motorhome, try plugging the inverter into that and see if the lights get any brighter.  You don't want to run the lights from there for long since you're drawing from the starting battery instead of the house batteries.  If the lights get brighter, you'll have to get a cigarette lighter socket that is either closer to your house batteries or wired with thicker wire to reduce the voltage drop under load.
 

rclark

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Hello Lou, thats what I was wondering about, if the 12 volt wiring was able to carry enough current to power the lights.. I guess that is another reason to quit looking at these xantrex inverters that plug into the lighter. I need to just go ahead and get one that is hardwired I guess!!

Do you all think that would be a wise thing to do??

Randy
 

Gary RV_Wizard

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Those string with embedded lights aren't  quite a normal light bulb, so I'd try the inverter with a standard table lamp before I decided that there was a problem with it.

If your 12v outlet is low on voltage, your 120 VAC output will also be low and cause a brown-out. Being under-wired (low amperage) should just blow a fuse or burn up the 12v wiring. But an inadequate outlet could cause both low voltage and low amps, so its possible that's the problem. Try it somewhere else, e.g. the car.  Better yet, if its an SUV it may have a utility outlet instead of the typical cirgarette lighter socket. Most car 12V outlets are wired for 10 amps, though some may be 15A.

As for powering battery chargers from modified sine inverters, your mileage may vary. Some chargers get upset with them and buzz loudly or just quit, some work but get rather warm and others work just fine.  I've lost one and don't care to risk another.  I also had an X10 remote control system set up in our coach to control decorative lighting on our site and all the X10 relays and controllers burned out when I ran them on our 2000 watt inverter. EVERY one of them. They weren't even in active use, but they were plugged in and I realized something was wrong when I smelled one of them cooking...  The charger for my Bosch drill/driver was one of those that buzzed loudly enough that I was afraid to continue charging it - had to wait til we had the genset on.  On the other hand, all the laptop computers we've used have been happy on modified sine. They probably have better power management circuitry.
 

John From Detroit

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Lowell said:
I have a 300 watt modified sine wave inverter that I had intended to use for recharging the cell phones and laptop. Is it not OK to use a modified sine wave to recharge these batteries?

Generally speaking it's ok but the first time or two monitor the temp of the charger brick,  If it gets too hot, consider a true sine wave,.  If it does not get too hot, you are good to go.

What's too hot?  Well, if you can't hold it, it's too hot,  If it melts it's too hot,  Below those temps... I will have to let you use your own judgement.  I know my computer's power brick gets seriously warm on MSW  But I would not say it gets alarmingly so (that is it gets hot, but not too hot)

I use a 12vdc charger for my phone btw

The big problem with MSW inverters is when you use them for TV or Radio, they can and do cause interferencre in many cases

Even if they are NOT powering the TV or Radio
 

Lou Schneider

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On my trailer, the electrical path from the batteries to the TV cigarette lighter plug ran from the batteries at the front of the trailer, to the distribution panel under the bed in the rear, then back to the front TV location (this last was #14 wire).

I added a cigarette lighter on the opposite side of the wall seperating the batteries from the living area, wiring it directly to the battery posts.  The run was less than 4 ft. so I was able to use #10 wire and not lose too much voltage.  If you do this, be sure to include an inline fuse holder and a fuse in the lead going to the positive battery post.

In my case, the location was inside a kitchen cabinet so I was able to reach in through a door and turn the inverter on and off.

Once the voltage is up to 120 volts, you can run it wherever you want.
 

rclark

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Edinburg Va
Lou thanks for the options you mentioned!

When you experienced rv's are adding plugs or lighter outlets or running sat cable or anything, where do you run the wire??
Do you take the rv apart to get to original run wire or do you take it outside and go underneath or what??

Thanks Randy
 

Lou Schneider

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I usually take the wire whichever way is easiest.  The through the wall socket involved punching a hole through a piece of paneling to get to the main battery terminals.  I've tucked wires underneath the top edge of overhead cabinets, gone under the floor, etc.  Wherever it'll be out of harm's way and not likely to be tripped over.

Of course, any wire you add must be protected by a fuse.  If you're connecting directly to the battery you need an appropriate sized fuse as close to the positive battery post as is practical.  Even a single house battery has enough stored power to turn a shorted, unfused wire red hot - easily hot enough to catch paneling or other flammable material on fire.
 

John From Detroit

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When I added outlets I took several things into consideration

1: expected  loads (heaviest is my laptop at around 5 amps operating 10 boothing)

2: Lighting system.  I added two outlets in the bedroom one on each side of the bed, hooked to the lights  One more in the cabnet behind the bedroom tv It is hooked to the slide out power line  One more in the galley area (on the side of a cabnet) half dedicated wire back to the power distribution panel, one in an outside compartment near the galley,  The other half of said dedicitated wire and one in the front head (Bath and a half floorplan) dedicated line to the power panel about 3 feet away in the same wall
 

WA9YSD

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Wisconsin
Dimming of the light could be caused by several things.

Poorly designed regulator in your converter, Battery may be near the end of its life and not coming up to full charge, cigarette lighter plug is oxidized, oxidized lighter spade lug connectors for all the power connections.
 

rclark

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Edinburg Va
No Karl they don't blink nor are they programable.. These are just the rope lights that come out a few years ago, the lights are inside a soft plastic tube (rope) and you can connect one strand to another at the end for continuous lighting!!

Randy
 

Karl

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O.k. Some power supplies don't like modified sine wave, but guess that's not your problem. Hmmm.... puzzling. I know in Canada, hotels and motels have current limiting devices for 120VAC outlets in bathrooms (Steve, set me straight if this has changed) so the most you can run is an electric razor or other small device. Maybe there's some kind of current limiting device on your accessory outlet(s)? Not very likely, but who knows? :-\
 
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