Inverter Recommendations? - Fiberglass RV


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Old 03-08-2009, 12:24 AM   #1
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I'm trying to plan how I'm going to rewire my trailer and will need an inverter to run my laptop and perhaps a 6-700 watt sometime in the future. I just ordered some marine 12 volt receptacles for the interior and exterior of the trailer. Now I need to figure out which inverter to purchase. I understand that Xantrex makes a good product but they have so many different models that I'm quite confused. I'd like to get a reliable product that meets my needs but doesn't cost an arm and a leg. Can anyone make a recommendation? Thanks in advance!
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Old 03-08-2009, 12:56 AM   #2
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Cigarette lighter sockets aren't designed to provide lots of power, so inverters plugged into a cigarette lighter can only supply around 200 watts continuous power, which is generally enough for most laptops, small LCD TVs, etc.

Something to keep in mind when you're thinking about inverters is your battery capacity. A 200-watt inverter running at full-bore will run a battery down in less than three hours; running an 800-watt inverter will zero the battery out in an hour. The point is your battery is a very limited resource, so you might be better off limiting your 110 volt AC appliance use to charging your laptop and suchlike.

Big inverters require lots battery capacity; the larger unit you're mentioning is the kind of thing a big motorhome with four or eight big, heavy batteries might have. In eggs you have to think smaller.

I installed a 120-watt inverter setup in our trailer, enough power to charge the batteries on our laptops, cell phones, and cordless drill, but no where near what's required to run our microwave or cube heater.
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Old 03-08-2009, 03:53 AM   #3
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I have a couple of 175W models, plus a 70-75W model I keep in the truck glove box for recharging cell phone, all Vectors from Wally. I generally power a laptop, recharge drill batteries and recharge cell phone, plus the occasional light or small fan, VCR, television set, etc. I don't have anything like a hairdryer or other heat-producing appliance (I do have a heating pad, come to think of it, but never used it with inverter, and I suppose an electric blanket might be useful -- Hmm, a comparison of battery use for elec blanket on inverter vs rv furnace might be a useful thing to know)

What I usually do with my laptop is plug the inverter into the TRUCK cig outlet and then run my 120VAC extension cable back to the egg, esp if sitting on one site for a while -- That uses power from truck battery, which will be readily recharged, rather than from egg which may not be recharged until I pull it next (being careful, of course, not to actually use a whole lot of truck battery power or I will need a jump-start from the egg!).

A hidden point here is that the higher voltage can be carried much further than the lower voltage, so an inverter of any size should be located as close to the battery as possible and wired ('gator -clipped) directly to it to prevent wiring loss. When I installed a cig lighter outlet in my Egg, I used heavier gauge wire that that for the 12VDC lights.

I personally would be inclined to install 120VAC outlets and rig the inverter near the battery to power them (by plugging shore cable into inverter) than use 12VDC outlets with the inverter plugged in unless using a small inverter. This keeps the inverter's 12VDC wiring short to reduce cable loss and also means I don't have to mess with the inverter to use my laptop or whatever. Drawback is I might forget to switch the inverter off when I was finished with my task (This consideration gains importance as I gain age )

PeterH is right that a large inverter (and a large load) may drain your battery rather quickly and he's also right that factory-installed cig lighter outlets may be undersized in wiring or construction.

I don't know the relative efficiencies, in terms of inverter overhead, of medium vs small inverters (Doing some research for the generator thread, I just learned that one Honda inverter-based generator is 6500W, so I would consider that a *big* inverter!) so don't know if there is a penalty beyond size, price and wiring for having a medium vs small inverter in your system, whether in use or standby.

I'm not convinced that anything but the inexpensive inverters are called for, because while the laptop itself may be sensitive to power problems, it is the the laptop's 'brick' or power adapter that is actually going to see the inverter's output. During the course of nine years of Full Timing, I used a number of laptops, VCRs and a color tv none appeared to be damaged by use with either the Vector or Radio Shack inverters.
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Old 03-08-2009, 11:09 AM   #4
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Lisa,

I installed a 1200 watt model purchased from Canadian Tire here in Canada. It is a manufactured by Xantrex and is modified sine wave. As Pete mentioned a modified sine wave inverter will serve you well. You can find something similar in the US. The inverter was on sale for $99.00 (Can)
In retrospect, it is a bit of overkill for my small trailer. However, I needed a project to keep me busy so I did it.

As Peter mentioned, if a large AC load is applied your battery can quickly become depleted . If I remember correctly I ran a test wherein I plugged a small vacuum into the inverter and watched my 240 amp/hour battery go from 100% to 80% in about 10 minutes.
In most cases the smaller cigarette plug inverters will be sufficient. In 12 volt battery applications you want to stay away from appliances that have a large power draw. Vacuums, hair dryers, electric heater, electric coffee pot, curling irons etc.

Here are links to my inverter installation to give you some ideas if you want to install a larger inverter.


Just remember to keep your cable runs as short as possible to the battery and use the correct size inline fuse and cables for your inverter. The remote switch option is nice as it allows you to turn the inverter off without having to go into the
electrical compartment.
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Old 03-08-2009, 11:47 AM   #5
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Lisa:

Be aware that the modified sine-wave or square wave from cheap inverters may or may not be appropriate for the load. Apparently most laptops do fine , but others do not. When my wife's little quilter's sewing machine was fed the modified wave form it simply refused to run. Sensitive electronics may also need true sine wave units. (Google Samlex). That same sewing machine purred like a kitten with true sine-wave power.
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Old 03-08-2009, 12:04 PM   #6
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Lisa, the absolute best way to run your laptop without out putting a dent in your trailer battery is to charge the laptop OFF and run it off it's own battery.

If you plug the laptop in to charge while it's off, I can absolutely guarantee you it will take less than an hour to come up to full charge again and then you will be off and running with it for a couple hours or more. If you invert it and use it while running the invertor, most of the power is going to RUN the laptop, and a trickle goes to battery charging.

Personally, I use a small 100 watt inverter and plug the comp into my car ciggy lighter to charge, leaving the trailer battery alone.
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Old 03-08-2009, 02:41 PM   #7
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. . . I personally would be inclined to install 120VAC outlets and rig the inverter near the battery to power them (by plugging shore cable into inverter) than use 12VDC outlets with the inverter plugged in unless using a small inverter. This keeps the inverter's 12VDC wiring short to reduce cable loss and also means I don't have to mess with the inverter to use my laptop or whatever. Drawback is I might forget to switch the inverter off when I was finished with my task (This consideration gains importance as I gain age )

. . .
Pete, I worry about that, too. Initially the wiring for our little 120w hard-wired inverter had a standard on-off control switch for the 12v power supply, but I soon replaced it with a mechanical rotary switch like you might use in a house to turn the bathroom fan on for a few minutes. I still need to snap a picture of that . . . I'll post the pic in the thread where I talk about that installation later.

I wired our inverter into the wire center where the house wiring from the battery and solar panels meet and where our wiring center with the solar charge controller, converter and fuses are. Generally speaking we do most of our laptop, cell phone, etc. battery charging during the day when the solar panel is most productive, so placing the inverter where the solar panel hooks in is fairly optimal, but what happens when the inverter runs on battery power alone?

The 120 watt inverter at max draws 11-12 amps. Since our wire center is connected to the battery using 12 feet of 10 gauge wire a worst-case scenario for our inverter results in a fairly minimal 3% voltage loss, 0.36 volts. That is, of course, energy I would like to save and use elsewhere, but given this is a worst-case scenario and most of our inverter use is comfortably under 60 watts I'm not worried.
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Old 03-08-2009, 04:01 PM   #8
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I have AIMS 1500 sine-wave inverter on my 21 Bigfoot and am very happy with it. The_Inverter_Store has AIMS 300 Watt Sine Wave Inverter on sale for $134. The current drain would be around 26A which would require 10-12 gauge See_ampacity_chart wire connection to your battery. Aims has good explanation of advantages of sine-wave versus modified sine wave. My personal experience using modified sine wave converter was fried $75 Nikon battery charger and radio RF interference. I had discussion with Aims engineers about a year ago and was told that TI was coming out with Digital Sine Wave chip set and perhaps this new 300 W unit is using this set.

George.

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