What size inverter and how did you decide? - Fiberglass RV


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Old 10-16-2018, 08:47 PM   #1
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What size inverter and how did you decide?

I am contemplating adding an inverter to my 1994 Bigfoot trailer. I do not have an AC unit or a microwave but might want to run a 100-w lamp, charge a laptop computer, charge a cordless drill battery, etc.

I would be interested to know what sizes others have installed and how they decided on the right size for their needs.
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Old 10-16-2018, 09:08 PM   #2
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For small loads like charging a phone or laptop, I use a cigarette lighter plug-in inverter. They are cheap and found all over the place. About 100-150 watts is fine. They will also run a DVD player. IF you want to go a bit bigger, get a 400 watt one with alligator clips for the battery, as they can be too much power for a cigarette lighter. These will charge re-chargeable batteries for power tools. Or, they will run small power tools and fans directly. Or go to a 2000 watt, built in one for running the microwave, coffee makers, hair dryers and other things.

I have a 3000 watt unit that runs a 120 volt air compressor for pumping up tires.

If you want to run the AC, you'll need an even larger capacity one or an easy start controller to go along with it.
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Old 10-16-2018, 09:18 PM   #3
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Have you any idea what it might take to run a small (maybe) 32" TV? I suspect it might be a bit as so many folks in RV's seem to run the generator when they want to watch TV.
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Old 10-16-2018, 09:33 PM   #4
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Quote:
Originally Posted by bobblangley View Post
Have you any idea what it might take to run a small (maybe) 32" TV? I suspect it might be a bit as so many folks in RV's seem to run the generator when they want to watch TV.
Mine is a 12 volt TV. I would never run a generator to run a TV. But it's not just the TV. If you are out away from the signal and shore ties, you might want a blue-ray or DVD player too. Just look at how many watts the TV you are interested in draws and match it with an inverter. Leave yourself some headroom to run a player and charge the phone at the same time, etc.

Don't forget to match the load with enough battery.

If you need a TV and a generator to run it, are you really camping? What about the neighbors or the required quiet hours? Might be best to go to RV parks with hookups and avoid the whole problem.
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Old 10-16-2018, 09:35 PM   #5
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100W light bulb?!? get a LED that uses less than 10 watts and puts out just as much light, and runs on 12VDC.

I looked up a typical cheap 2 year old 32" HDTV, Vizio D32h-D1, MAX power consumption is less than 28 watts, standby power is less than 0.5 watts. but phew, 32" would be HUGE in a small fiberglass trailer. the aisle in my Casita is only like 28" wide.
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Old 10-16-2018, 10:10 PM   #6
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We have a 400 portable inverter in our Casita and a factory 1500 watt inverter in our SOB trailer . We have never used either one , in fact the 400 watt is still in its’ original carton . Everything I can do with an inverter I can do equally well without an inverter .
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Old 10-16-2018, 10:56 PM   #7
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An inverter is of no use without a battery bank to power the microwave and A/C.
Everything else can be done with propane and 12V.
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Old 10-17-2018, 08:56 AM   #8
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Robert,
Here's an article that might help you decide:
https://www.donrowe.com/power-invert...8.htm#how_long


I have an 800W inverter that is only there if I need to recharge my laptop or camera batteries. Those batteries never charge to 100% on their 12V chargers. I recall that my Bosch 12V batteries did charge up OK on the inverter, but some cordless tool batteries won't, or so I've read. I do road repairs with hand tools. I've got lots of time. I haven't used a plug-in style inverter for those batteries, but that could be a cheap alternative. Wish I had tried that first.

Most smaller TV's operate on 12V DC and are easily modified for this (if needed), just check the specs and do some homework.



Good Luck!
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Old 10-17-2018, 09:46 AM   #9
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how?

your needs/wants sound a lot like mine.....I looked up how much a 20 inch tv consumes....about a hundred watts....and bought a 150W inverter....it's a portable one and is mounted "semi-permanently" in the trailer (has a mounting clip on the back)....that way I can use it somewhere else if/when need arises



"out of the box" this little inverter came with a cigarette plug...I shortened the the cord to just what I needed to reach the outlet on the bulkhead



I don't watch/have a tv....I use the inverter to run/recharge the laptop (watch movies on that)...recharge other devices/battery powered tools....and occasionally my e-bike... in full insolation after the batteries are topped up
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Old 10-17-2018, 09:58 AM   #10
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I have a 400W Tru-sine inverter in my Scamp hard wired to a group27 lead acid battery. It works great to run stuff like my TV and DVD player, etc.


Truth is, times have changed... You can buy a TV with a built in DVD, USB ports and powered antenna which runs on 12V for $135.
You can charge most devices on 12V power points.
Anything which you still need 110VAC for will likely draw more power than you can reasonably supply with your onboard battery.


I say put your money into more power points, USBs, and modern low voltage toys and lights and just forgo the inverter.


You could get a cheapo modified sine inverter and run it off your TV for the few times that you might need 110V which is probably not often.
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Old 10-17-2018, 01:10 PM   #11
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I have a KRIĖGER 2000 Watt 12V Power Inverter with Dual 110V AC Outlets. I have a 2013 Casita 17' Spirit Delux. My TV is a 2011 Tundra with 5.7L engine. I also havre a 3000k generator attached to the trailer.

I carry this will me as a back up, and would connect to the truck battery or possibly to the trailer battery if needed. I have yet to use it even one time.
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Old 10-17-2018, 02:08 PM   #12
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Originally Posted by Rzrbrn View Post
I have a KRIĖGER 2000 Watt 12V Power Inverter with Dual 110V AC Outlets. I have a 2013 Casita 17' Spirit Delux. My TV is a 2011 Tundra with 5.7L engine. I also havre a 3000k generator attached to the trailer.

I carry this will me as a back up, and would connect to the truck battery or possibly to the trailer battery if needed. I have yet to use it even one time.
Since OP asked about size (rating).. let me say that the KRIĖGER KR2000 is maybe over-sized. Its rated at max 2000 watts continuous. Assuming you run it at 2000 watts and at its max efficiency of 90% (per specs), you will be drawing 2,222 watts from the battery, or roughly 180 amps. With a single battery of the type common in these campers you get about 50 amp hours of usable power, or about 17 minutes of use. And you have to wire it for your max use. Plus it draws up to 8/10ths amp from the battery ever with no load.

My 400 max, 200 watt continuous inverter draws about 222 watts from the battery at its max continuous load. Thats about four hours from my group 31, 125 AH battery until it is at 50% discharge. Of course with 200 watts I am limited to appliances that use not much more than 1.8 amps at 120 volts.

So (IMHO) unless you plan on substantially more battery power than most of the small campers usually have, and also do much wiring upgrading, then there is not much need for a larger inverter. Sure, you can still use it at 1-2 amps for a few hours but then you dont need the larger inverter to to that. If you have 1000, 2000 or more watts of solar power and a large battery bank, then that is different. Also, using it on the truck battery with the engine running might work OK, but you still need to have some pretty beefy cables to get the higher power out of it.

But I will go even further. I agree with Floyd. In these small campers its best to use 12 volts unless you have shore power (or a generator). I never use my inverter.
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Old 10-17-2018, 02:10 PM   #13
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Quote:
Originally Posted by bobblangley View Post
I am contemplating adding an inverter to my 1994 Bigfoot trailer. I do not have an AC unit or a microwave but might want to run a 100-w lamp, charge a laptop computer, charge a cordless drill battery, etc.

I would be interested to know what sizes others have installed and how they decided on the right size for their needs.



You go by the current feeling that bigger is better and get the biggest you can afford. You'll need an electrician to wire it in.
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Old 10-17-2018, 02:18 PM   #14
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I have heavy cables to connect to the truck battery. I would only use it in a dire emergency to run power tools. I bought it before I bought the generator. Also while I have heavy cables, it will run small appliances/tools as needed, as well as the larger tools.

But I would not buy a large inverter, had I to do it over again.
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Old 10-17-2018, 02:24 PM   #15
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I too carry a cheap 400W max 200W continuous inverter, I've used this to power my wife's laptop charger, and a couple other chargers I have that are AC only but need less than 100 watts, I try and do this mid day when the sun is shining so the solar provides most of the required juice.
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Old 10-17-2018, 02:43 PM   #16
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When you graduate from the simple cigarette lighter style inverters and go with something large enough to run a microwave, you not only need larger batteries and larger wiring, but you also need a transfer switch if you plan on sending power to the existing interior plugs.

I have a 3000 watt inverter, but I carry it in the truck and connect it with jumper cables to the truck battery when I use it. it's only there to run a 120 volt air compressor or other power tools. The rest of the time we use the cigarette style ones and have several of them. I'd like to be able to use the microwave sometimes, bu it doesn't seem like it's worth the effort to make it happen. And, of course, if we are using the generator, we can run it.

One of the things that may be hard to grasp is just how much power inverters take from the battery. Take the amps of the 120 volt appliance and multiply that by eleven to get close to the battery amp draw. Then remember that only 50% of the battery rating is available. Then remember that the faster you draw the power from the battery, the less you get overall. When looking at a battery monitor, you should not let it get below about 12.2 volts (rested). Gordon explained this very well.

It sort of boils down to this: Air Conditioning is out of the question. Microwave for only very short periods. Charging laptops, phones and running a television can go on for hours with a cigarette lighter inverter. So why go to all the trouble to get larger batteries, wire them in and install a transfer switch, to support the larger inverter that has such limited use? Only if you have a specific need and a way to charge the batteries.
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Old 10-17-2018, 03:06 PM   #17
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Quote:
Originally Posted by Rzrbrn View Post
..

But I would not buy a large inverter, had I to do it over again.
Thanks for the clarification. The largest inverters do have their place, perhaps a Class A motor-home owner or someone with a large residential solar array might buy it?
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Old 10-24-2018, 01:31 PM   #18
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Inverters waste power

Hi All,


Not sure it was mentioned yet in this thread, but as the subject says - inverters waste power.


I've seen some mention of "you can do that with 12V" which I completely agree with - just hadn't seen the fact that you waste battery power if you invert and don't need to

Cheers


-Bryan
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Old 10-24-2018, 02:28 PM   #19
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With a modern inverter, the waste is fairly small. maybe 2% of the inverter's maximum output plus 2-5% of hte actual output.... so a 1000W inverter might waste 20W just being turned on, and if it has a 100W load, another 2-5W

those are strictly ballpark numbers pulled out of thin air. I've been meaning to characterize the input vs output of my '400W' portable inverter but don't have enough known 120V loads to do it very accurately... in particular we don't seem to have any 100W incandescent lamps left around here, they make a good 'standard load'..
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Old 10-24-2018, 03:00 PM   #20
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Yep....waste is waste when there is nowhere to charge your battery.


Of course the biggie here in my books is that so much can be done with 12V meaning no need for the inverter at all!
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