Where should I mount my Inverter? - Fiberglass RV


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Old 06-03-2007, 01:33 PM   #1
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Just picked up this inverter:

and was curious as to where you all mount yours in you Boler/FG trailers?

Its about 15" long, 8" thick and 4" deep. 1500 watts, probably more than what I need but might as well go big. I got it used and for a good price!

Also I have not even bought a deep cycle battery yet. I am in Canada and recall Costco had some cheap....any suggestions ??

thanks!! - Kurt
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Old 06-03-2007, 02:35 PM   #2
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Kurt,

Mount it someplace where you can draw 125 amps from the battery (1500 watts/12 volts). I'd recommend a BIG cable.

Note that if you run a full load and have a 125 AH battery, you'll be able to run for about one hour.

Good luck.

On edit: Most modern inverters are rated for an efficiency of 85% to 90%, so 10% or so of that power will be going up in heat. Also note that an inverter draws power from the battery even when there is no load; the bigger the inverter, the more quiescent current it draws.
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Old 06-03-2007, 04:48 PM   #3
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I would mount it in my car and only use it with the engine running..or, perhaps, attach it to a hydro dam.

Don't put that in your trailer. Morgans facts are just that.. facts. Inversion is a most in efficient way to get power.

Quote:
probably more than what I need but might as well go big


If you HAVE to use an invertor, size it to as SMALL as you can, and never have it on if it isn't doing a direct task. It'll suck the life out of your battery faster than you can say "What happened???"

For running your comp, 100 watts is probably overkill. 1500 watts is suitable for microwaves, space heaters and placing landing lights in your campsite, and not much else.

In the case of the 'wave and the heater.. you'll not get much use of either until your battery is in need of refueling.

I have several small "Pocket" invertors, all have a different "thing" they are sized specifically for, and no bigger.

Inversion = power loss at a high price. You just have to figure what price you are willing to pay for whatever you are using.. is it worth it?
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Old 06-03-2007, 06:17 PM   #4
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I have a 1250 watt inverter mounted to the side of plywood in the porti potty compartment . I used welding cable about 3 ft. long going to the deep cycle battery on the hitch. I also have a wire running direct from the battery in my tow vechicle to wiring connector so that the battery is being charged while I'am driving. I use a 550 watt 4 cup coffee maker and a little 13 inch TV that draws very little wattage.So far so good.The inverter has a digital read out of the remaining charge and a warning buzzer if the battery is getting low and it suppose to shut down and never completly drain the battery.So good luck and enjoy.
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Old 06-04-2007, 02:00 PM   #5
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I think Morgan and Gina have made the argument for more appropriately sized inverters well. If the mega-inverter is going into the trailer anyway, I think the key points are
  • as close to the battery (by cable length) as possible - much less power will be lost in any length of low-current AC wiring than in the high-current DC wiring
  • ventilation - the inverter dissipates heat, so it can't be safely buried in a small closed cabinet (yet it presumably needs weather protection)
  • control - access is required to the on-off switch, unless a remote switch is included
I am thinking of putting my slightly more modest 1000 W inverter (for only occasional use) in one of two places:
  • under the dinette seat beside the electrical panel and converter, with the switch and fan end exposed but the rest in the cabinet; or,
  • in is a weather-resistant enclosure beside the battery, out on the tongue.
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Old 06-04-2007, 02:11 PM   #6
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Mount it someplace where you can draw 125 amps from the battery (1500 watts/12 volts). I'd recommend a [b]BIG cable.

Note that if you run a full load and have a 125 AH battery, you'll be able to run for about one hour.
I don't think it will even make that. Battery capacity is rated at a specific current, which is not likely this high. Discharging at higher rates is less efficient, so 125 A will exhaust a "125 A-h" battery in significantly less than one hour.

I assume that Kurt is planning to use this for only brief bursts at this level, if at all. For instance, a microwave can be useful in a 30-second operation...
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Old 06-04-2007, 02:39 PM   #7
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If you HAVE to use an invertor, size it to as SMALL as you can, and never have it on if it isn't doing a direct task. It'll suck the life out of your battery faster than you can say "What happened???"
How exactly do you figure that? The amount of power an inverter draws is directly related to the amount of power drawn out of it by a linear function. I put a 700W inverter in my 1700. I accidentally left it turned on all week with nothing plugged into its AC outlets. This weekend my group 24 battery was still fully charged and I'm pretty sure my 55W solar panel isn't enough to compete with a 700W+ draw were your assertion true.
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Old 06-04-2007, 04:09 PM   #8
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How exactly do you figure that? The amount of power an inverter draws is directly related to the amount of power drawn out of it by a linear function. I put a 700W inverter in my 1700. I accidentally left it turned on all week with nothing plugged into its AC outlets. This weekend my group 24 battery was still fully charged and I'm pretty sure my 55W solar panel isn't enough to compete with a 700W+ draw were your assertion true.

I don't think that's the issue. More like there's an assumption that larger the inverter, the less efficiencent it is the farther away you get for the rated power. In other words, if you use a 1500 Watt inverter to chrage your cell phone you're burning up a lot of power in the inverter. I'm not sure this is true. I tried to find something about that. One web site did elulde to the loss of efficiency, but a manufacturer's site indicated 90% efficient at rated power and 95% efficient at 1/3 power.

This would indicate that there's several reasons to not buy larger than your need, but current consumption isn't one of them.

I would like find a manufacturer's chart on efficiency vs power consumption to verify one way or the other.
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Old 06-04-2007, 06:15 PM   #9
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I believe Brian is right. As far as I know deep cycle batteries are rated at constant 20Amp draw. If your draw is less, the total amount will be slightly more, if you draw at a greater rate the total available will be somewhat less.

Each battery has (if you can find it) what they call a Peukert's Exponent which will help to accurately calculate the total available at various draws (based on an equation I totally do not understand).

I discovered this when installing a battery meter, and that is how the unit stays accurate even though the instantaneous draw varies widely.
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Old 06-04-2007, 09:54 PM   #10
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Byron is assuming I am assuming.. and you know what happens when you assume... (Go to your room, Byron)

No, it has nothing to do with an unload inverter drawing it's full current or power capacity. Thats kind of.. dumb. Thats like saying all your hours will fall out of your battery if it is just sitting on the ground unconnected. (I hate when that happens)

Most invertors in our application DO have fans, and leaving them running will draw some in an un attended to battery tho.

I know that my larger 400w invertor does get warm just idoling.. and with the fan running, it IS using juice. Your 55 watt panel is plenty to keep up with that small draw.

I also know that if I try to run my comp off the 400 watt unit I kill it WAY quicker than if I am using my 100 watt one by the same manufacturer at the same charge state. The same applies to simply charging the comp battery with no other draw. My comp walwart is 85w/1.6a.

I have noted the same anomaly when running portables such as radios or lamps. The same applies, I invert with the smallest invertor I have, and I get much more use out of the battery.

As Byron pointed out, there is some discrepancies between manufacturers specs and reality. I go with specs as a guideline, and real world experience as practice. If the two happen to match.. that's great.
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Old 06-04-2007, 09:54 PM   #11
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wow some debate here! I do like the opinions.

I got it cheap for $120 Canadian (basically new as it was never actually used).

From the research I have done I thought that the large size does not necessarily mean more drain as it is only relevant to the amount of power you are pulling from it?? From my understanding the 1500 watts is there if you need it and not 'consuming' that all the time. It also has an off/on switch.

I'm not even sure what I need one for, I just though if I am going to the trouble of installing a deep cycle battery I might as well get an inverter. A just in case thing I suppose. The only thing I am not sold on is the physical size of the thing. They are not small.

So far I have never even needed a deep cycle battery. Pulling 12 volt power off my truck battery has been fine so far but I don't want to strand myself one day. I am also still looking for a propane heater and the smallest unit so far is only 12x12 inches but the newer heaters require 12 volt power at about a 2.5 amp draw...anyway getting off topic here....

- Kurt
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Old 06-04-2007, 09:55 PM   #12
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Quote:
I have a 1250 watt inverter mounted to the side of plywood in the porti potty compartment
I have this vision of 120v powered toilet.....

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Old 06-04-2007, 10:51 PM   #13
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I did see one chart that showed with low output low efficiencies. I don't remember the numbers but I believe it was close the 10% range, maybe a bit more, of rated power that the efficiency was close to 10%. The specification on another page at 1/3 power was a bit more efficient. I'm sure there's a drop off point, probably different with every size and manufacturer, where the efficiency goes down the tubes. It does take a certain amount of power to run electronics inside the inverter box and all electronics have some losses.


I don't know what a good rule of thumb would be as far inverter power rating and usage. I don't think it would be a good idea to run at 10% or 90% of power rating. Someplace inbetween, I would think.
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Old 06-04-2007, 10:57 PM   #14
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So far I have never even needed a deep cycle battery. Pulling 12 volt power off my truck battery has been fine so far but I don't want to strand myself one day

- Kurt
If was running my lights from my TV I would want to carry one of those jump start batteries. I carry on anyway. Plug it into the cigerate lighter while driving to keep it charged up. Unplug when we stop. Then it's always ready to go.

Shoot, you might even be able to run your lights with that instead of the TV.
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Old 06-04-2007, 11:02 PM   #15
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Looks like my guess about the low power efficiency was pretty darn close. Check this pdf file out. 500 Watt inverter, efficiency starts going down the tube at 50 Watt output (10%).
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Old 06-05-2007, 07:12 AM   #16
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Looks like my guess about the low power efficiency was pretty darn close. Check this pdf file out. 500 Watt inverter, efficiency starts going down the tube at 50 Watt output (10%).
You have a different concept of "down the tube" than I do. It looks to me like the efficiency is pretty darn close to flat linear throughout the entire range after 50w... Very inefficient up to about 30w with a no-load idle draw of 5-6watts which is about 500mA. The graph doesn't have enough resolution but it looks like the efficiency drops by about 7 percent fairly linearly from 50w to 500w. That's not really "down the tube" is it?

Gina says her battery dies "WAY quicker" if she's using the 400w inverter to run her computer than if she's using the 100w inverter. She either has a crap 400W inverter, has a different definition of "WAY quicker" than we do, or her test wasn't scientific.

There's a lot of things one can do to affect the power consumption of a laptop. Whether or not your wireless antenna is turned on, bluetooth, screen brightness, cpu speed profile, playing a movie from a DVD instead of disk, playing a game... I'd be willing to bet there was a difference in the usage or setup of the laptop between her two tests..

I just can not accept that as a general rule, big inverters are _significantly_ less efficient at low draw than a small linverter at high draw... In fact, if this graph is typical of inverter efficiency, then her 100w inverter should have been less efficient at the upper end of its load than her 400w inverter and hence, she should have seen the reverse happen.

If, after a scientific test, Gina finds that her 400w inverter really does suck down her batteries at a much higher rate than the same load on her 100w inverter, I would probably find her 400w inverter faulty.
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Old 06-05-2007, 07:53 AM   #17
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I'd be willing to bet there was a difference in the usage or setup of the laptop between her two tests..
That guess would be incorrect.

I typically never run my comp inverted, only charge it inverted. (I have run in inverted in a "Must do" situation, but those are rare and pretty untypical.. and usually in a running car when I desperately need a map...)

A laptop OFF does nothing current draw wise, other than charging the battery. If I was charging the battery at full depletion vs. one at 95% down, and then coming up with my conclusion, your guess would be correct, however, I typically run down to 45% then charge. So, ... like charge vs. like charge.. running off the same group 24 battery within hours of each other, and showing the same differences consistently afterwards, seems pretty equal to me.

Also, as previously mentioned, the same variances are shown between many sized inverters.. not just the 400 vs. the 100. That eliminates the 400 as the root cause.

Since I installed and actually prefer my LEDs for lighting, I really have no use for inversion other than the laptop. I carry all this fodder "just in case" and have only used them since for infrequent and short use of power tools and small musical instrument amplifiers.. (Which are as a rule.. are not allowed when I camp.. but some of my friends just can't live without for a day... arrgh!)
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Old 06-05-2007, 08:43 AM   #18
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You have a different concept of "down the tube" than I do.
Key words in my post with link to the graph [b]starts to go
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Old 10-10-2011, 09:36 AM   #19
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I ues 14/2 house wire on a 300w inverter, from the battery from april till october use it on a 15 inch flat screen tv and cheep dvd player still lots of power in battery, All the places i go have no hydro hook up.
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