Adding a hardwired Inverter to my new 5ver....

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Dec 12, 2008
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OK, so when the new 5ver gets here next week, I am considering adding a hardwired Inverter to the electricial system to power the TV and such while dry camping.

Does anyone have any advice for doing this?  How big of an inverter did you use?
The key is to limit the size of the inverter to what you actually intend to power. Inverters are most efficient at their rated amount. This is most important for dry camping.

I had a 2500W inverter and found it very inefficient because the biggest draw that I had was our 1000W coffee pot. When my wife uses her 100W hair curler the efficiency is about 50%. I ended up buying a 1000W pure sine-wave inverter. We've been very happy with it.

When you say "and such", does that include the microwave - even for a few minutes and what else.  A list would help.  Also this may impact the number of batteries needed.
It will probably be just TV, satellite box, DVD player, and maybe a computer. For coffee we usually run the gen, or just make it on the stove.
Count the max concurrent watts you will need and size the inverter about 20% above that, just to give some head room. Your list so far is only 300-400 watts at peak load, so a 500-600 watt inverter would do it nicely. I suggest going for a pure sine model, which should not be too expensive in that size range.

There is no point in getting more inverter watts than you have battery to support, so also consider the number and size of the battery bank. Maybe expand it somewhat if you really expect to do any boondocking.

The big challenge in inverter wiring is making sure that the inverter can never attempt to power the circuits at the same time as shore power.  The simple way to do this is to connect the desired circuits directly to the inverter and always run them that way, even when shore or generator power is available. Let the converter/charger re-supply the battery amps as fast as you use them. Many smaller motorhomes are wired in this fashion - it saves cost and is foolproof.  Otherwise, you need to add some sort of switching to the circuits , basically a double pole, double throw switch, to make sure they can connect to either shore or inverter power source, but never both at the same time. The wiring diagram to do this is simple, but getting access to the circuits after the RV is built can be a nightmare.
There are basically two schools of thought.  First is a whole house inverter and second is dedicated inverter.  I went the dedicated inverter route.  I located and mounted my inverter, and then ran dedicated circuits to where I wanted power.  Behind each TV is where mine are.  I then using a simple lable maker marked the outlet as to the type of power is supplies.  When we get to a dry camping spot, it is a simple matter to turn on the inverter, plug in the power strip and go.  No worries about double feeding a circuit because i forgot something.  A whole house inverter requires some form of either an automatic transfer switch or a 4X4 box with a 30/50 amp outlet mounted to it that is fed from the inverter.  When you arrive you just plug in your shore power cord, turn off everything you do not want to power and go.  Your choice which you might find the most convenient.
This inverter would probably suit you nicely:

General rule of thumb with inverters is to figure the amperage draw from the battery as 10% of the the rated watts load. In other-words, A TV that draws 150W will have a load of around 15A on your house battery. 4 hrs of TV will cost you around 60AH.

This is a good tool to have onboard to check the actual amp load at your battery:

This is also a great tool for checking the actual output of the solar panels as well.
Well Sarge you're considering doing exactly what I did about four years ago on our toy-hauler.

What I did was pick up an inexpensive Cobra 1k inverter off Amazon.  I wired it up in the front basement gen-set compartment so that it was isolated from the batteries for safety but only had to use 3' of what I recall was 2ga battery cable.  From there I purchased bulk exterior extension cord rated for 20 amps (10ga?) and ran the line under the rig bringing it up through the garage floor and into the entertainment center area.  The inverter uses it's own outlet box in the entertainment center area and when we switch to boondock mode I simply unplug the power strip that has the DVR, TV, Sound System and cell phone chargers on it from the rig outlet and plug it into the inverter outlet.  The combined draw of ALL of those componenets is only 170 watts by the way.  Last year I decided that our garage fridge (which is dedicated to adult beverages) needed to have a way to stay on during travel so I broke into the inverter line and installed an additional outlet in the garage to run the all important fridge.  Surprisingly enough that 3cf fridge only draws 110 watts.

Last summer we spent almost three months in northern Idaho boondocking in a cow pasture and that inverter proved that it was one of the best things I've ever done to customize our rig.  I will say that while boondocking we DID NOT run the garage fridge simply because that 110 watt draw would have put a significant beating on the batteries, besides if you're boondocking you have to at least make some sacrifices so cutting down on cold beer storage was one of those.

Typically we would run our Honda 2000 for between four and six hours per day to keep the batteries up.  The satellite TV and DVR stayed on pretty much 24/7 and occasionally we'd run out of power in the wee hours of the morning but it was never a big deal.  On average over the course of our stay we averaged burning less than one gallon of fuel per day and that included running the Onan 5.5 occasionally when the temps warranted having the A/C, which only occurred three or four times.  By the way, we run two Wal-Mart marine batteries, nothing fancy.

Since I've followed your posts on the forum for some time I'm pretty sure that you're more than capable making this upgrade but a little tip here just in case you weren't aware:  DC doesn't travel well at all, keep the connection from batteries to inverter  as short as possible and use stranded wire.  If I had it to do again I WOULD NOT have installed mine inside the gen-set compartment.  When running the onboard gen-set the heat from the gen-set causes the cooling fan on the inverter to run non-stop. So far it hasn't hurt it but I probably should have installed the inverter away from the heat source of the gen-set.  AC travels very well and likes solid core instead of stranded wire (another thing I didn't do) so Romex would be best rather than bulk extension cord.

In conclusion, you really don't need a pure sine wave inverter if you're not running any electric motors.  There's NO need to buy a huge inverter for what you're planning on putting power to. my opinion if you don't mind opening a compartment to push the on/off button on the inverter and unplugging a power strip from one outlet and plugging it into another there really isn't any reason to go through all the work of installing a auto switching system either, keep it simple and when something fails it's a lot easier to track the problem.

Let us know what you wind up doing.
Sarge, read this guys blog and rants and you might decide you need 2.  A large one for the whole rig and a smaller one for smaller popular loads like the TV, laptops, and phone charging.
Wow, you guys are awesome!  I need to digest all this info before making any decisions. I'm sure there will be lots more questions!
I installed my inverter in the basement bay with the batteries and hard wired it to the batteries. I connected the output to a 30 amp, outdoor receptacle. Now, I plug my cord either into shore power, or the generator, or the inverter. This was a lot easier than trying to rewire all of the AC circuitry. I added a remote switch so I can turn the inverter on or off from inside.

The one possible pitfall, is remembering to turn off power to the converter prior to plugging in to the inverter. Otherwise, the converter is pumping current into the batteries while the inverter is pulling current out. Both units have losses, so the resulting loop will discharge the batteries fairly quickly.

Once, I forgot, with predictable consequences. To avoid repeating that mistake, I connected the coil of a normally closed relay to the inverter output and ran the power to the converter through the relay contacts. Now, the converter automatically turns on or off as the inverter turns off or on.

In my preliminary looks so far, and based on a lot of the info suggested here, I like the Magnum 600 watt inverter. A little more pricey than some, but a solid performer with a good rep.  I will know better when the rig actually gets here next week.
I went and found it to have a look after I posted the question.  YIKES!!! They like that thing A LOT!!!

So is the auto switching feature supposed to turn it on when you're not connected to shore power and visa verse or does it have something to do with the converter?
That Magnum is an inverter/charger with automatic switching for 20 amps.  That may be more function than what you need to occasionally power some electronics, but it neatly solves the 120v source switching problem.  And gives you a high quality 30 amp, 3-stage charging system as well. Maybe a bit small on charging to replace the trailer's OEM charger, though.

Once you get the trailer you can look over the wiring and determine how easy or hard it will be to add your own power switch, which can be as simple as a double pole, double throw switch you can buy for around $30-$40. Couple that with a 600 watt, pure sine, standalone inverter for around $150 and you could be in business fairly cheaply.
Thanks Gary, I will get back to you when I have some more info.  I do agree that the Magnum is more pricey than most, but I do like the fact that it is American made.
The Magnum is priced like other units of its type, but it may be more function than you need. I assume you already have a perfectly good converter/charger in the new trailer, but maybe an upgrade there wouldn't hurt either. In that case, tho, you would probably want a bigger inverter to get more charging capacity, at least 50A worth.
Yep, I will find out the specific details in a few days when I get her home.  I think I will be starting with 2- 6 volt batteries for power in the rig. 
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