Installing inverter system into Montana 3400Rl - Montana Owners Club

Richard · 01-08-2005, 01:42 AM

Hi all,

I was wondering if there's an online schematic and location guide for wiring a deep-cycle battery setup into the existing 120VAC/12vdc electrical panel on montana rv's?

I was a driveability tech in one of my past lives, so I'm not afraid to tackle electrical problems, but I am a firm believer in taking good advice, when available.

Just fyi, I did a search here and on the various rv.com forums and found good descriptions of the relay switching system that kicks in the inverter system when shore power is removed, but not too much *practical* advice for avoiding switching transients, whether to wire all or just some plugs, converter system adaptation, etc.

Hope someone here can point me to a source so that I don't have to re-invent that wheel again.

Thanks,

Richard

NJ Hillbilly · 01-08-2005, 02:25 AM

From what I have seen, many will wire the inverter to 1 or 2 inverter only receptacles. This way they can use the inverter to power specific items like tv's or small appliances. When the inverter is linked to the whole 110v system the loads and total system must be controlled and monitored.

The inverter can't always handle the load or will be trying to power unnecessary items. If the inverter powered the whole system the converter would be trying to charge the batteries using power inverted by them. The perpetual motion machine has not yet been perfected and I don't think this application will prove the theory either

.

Locating a receptacle or two isn't too hard as long as there is access to the storage area. One place I have seen them is in the lower section of the wall near the steps, the wiring can be done from the storage compartment.

Good Luck and I am sure there are some here that have inverters and they will help too.

John

Richard · 01-08-2005, 03:51 AM

Thanks for the reply, John. Gosh, that perpetual motion system sounds great! I wonder if I could plug the truck into it and tow the rig too?

Seriously though, that idea you have about separate outlets for the inverter plug sounds a lot simpler than what I had in mind, namely tapping into the main panel just before the main breakers and rigging a high amperage relay to turn on the inverter and connect it into the circuit once the shore power is removed.

I bought a 1500w xantrax (sp?) inverter from costco for $84 and it can handle surges of up to 2000w which should make it fine for anything but the A/C. Costco has two inverter models for sale right now...the 1500w and the 400w for $24.95. I'm using the 400w model right now in the pickup to power this laptop and it works beautifully just in case anyone is in the market for a good small appliance converter.

Richard

Montana_657 · 01-08-2005, 05:22 AM

I have the 50 amp service. I moved all the essential stuff to one leg, the other stuff to the second leg... then removed the jumper in the change over relay.

The inverter comes on, trips the change over relay and powers the essentials. Things like the converter and air conditioner are on the other leg and don't power up. A spare contact separates the charge circuit from the coach battery and converter.

I can unplug the inverter and plug in a 2000iHonda.. again just powering the essentials, or, I can unlimber my power it all cord, hook the Honda up at the shore power jack and power both sides of the 50 amp panel, so my converter recharges the batteries, both coach and the inverter.

Richard · 01-08-2005, 11:27 AM

Gruffy, thanks for the reply. This is exactly what I was looking for. Is there a webpage that describes the conversion someplace, or did you just think it up and do it yourself?

I'm out driving around Phoenix Az today, looking for a good deal on 2 Honda 2000i's. Are you able to somehow get away with a single Honda? I've read that it takes 2 Honda eu2000i's in parallel to power the A/C.

Thanks,

Richard

Montana_657 · 01-08-2005, 12:01 PM

In the last 18 months I powerd up the AC twice to make sure it hadn't failed. We have a 15K AC and two fantastic fans, plus a 30 inch ceiling fan in the lounge. When we came down to Fla. we decided to strip to shorts and t shirts rather then run the AC. We have hit the low 80's and not been too hot to cope yet. At this point we wonder how hot it has to get.. but in most of the country up north, an Air Conditioner is not necessary unless you can't vent the RV.

The inverter was wired via trial and error.
We figured a 2kw would run the microwave and went from there. The weight determined 3 batteries was the max we can carry. We can get up and make one pot of coffe and one toast each... then hit the road to recharge... or start the genny.... works for us... most of the time the genny stays stored.

Go Pokes · 01-08-2005, 04:29 PM

We have 1400w inventer. Bruce installed it in the front of the basement opposite the battery compartment. We have had added 2 additional batteries for a total of three. He ran a sixteen gauge extention cord, zipped tied in placed through the basement to a separate wall pull (which he also installed) in the w/d closet. Then we put a 7 cubic foot freezer into the closet. He wired the inverter directly into the battery bank with a 40 amp inline fuse using six gauge wire. The inverter will run the freezer for approximately 12 hours. He bought the inverter from Camping World for $59.00.

We used a cheap square wave inverter to power up appliances. Suggest a sine wave inverter for electronics -- even though they cost around $300 so you do not burn up the electronics.

Richard · 01-09-2005, 02:39 AM

Hi Gruffy,

Well, maybe I'll just get a single Honda eu2000i then. Like you, I don't envision using the A/C all that much. I much prefer fans if anything and A/C makes it difficult to sleep for me. I used to work for Honda so I'm very familiar with the Honda bulletproof reputation and if my new one is anything like the ones I remember, it'll probably last longer than I will.

I agree with your method of trial and error on the wiring, but I'm surprised that you don't get more than a couple of cups of coffee and toast out of 3 deep cycle batteries! I guess I should sit down and do the a/h math to figure out if I'm going to have enough juice to run the tv/dvd for the boys at night, plus the fans, etc.

Thanks,

Richard

Richard · 01-09-2005, 02:50 AM

Hi Marilyn,

Thanks for that detailed description. We have been thinking about outfitting that closet space next to the front door with either a washer/dryer or a second refrigerator.

We have 2 special needs boys and the reason we've chosen the rv lifestyle to travel is that their diets are very stringent and contamination from gluten/casein (wheat/dairy) is a real problem when trying to eat in restaurants. They're also immuno-compromised so the cleanliness factor of public places like restaurants and hotels can be a problem too.

Did you buy a standard freezer or one made specially for RV use?

I'll be sure and check the quality of the sine wave output of the Costco inverter I bought. I hadn't thought of that, but you're probably right about the square wave output.

(sidenote: believe it or not, I actually HAVE a handheld Fluke DSO (digital storage oscilloscope) with us....long story, don't ask......lol.....but, if you happen to see us on the road and want to check your sine waves...don't hesitate to ask.)

Thanks again,

Richard

Montana_657 · 01-09-2005, 10:10 AM

We refrigerate at the farm with the modified square wave inverter just fine. The only problem we have is with some compact flourescents. Computer and ink jet work fine also.

I think we have made out as well as we have because both in the 5er and the farm, the inverter is as far as possible from the load. The capacitance in all that wire tends to block the higher frequencies and smooth things out a bit.

Go Pokes · 01-09-2005, 02:34 PM

Hi Richard,

We just installed a freezer purchased from Sears. They had both a 5 cubic foot and a seven cubic foot freezer that would fit into the closet -- of course we choose the bigger one. It was almost was too deep for the closet. Bruce had to modify the closet bi-fold door into two separate doors which open in the middle-- because the bi-fold design would not allow the freezer door to open wide enough. The freezer works great and is a real handy.

Like you have special needs travelers with us at times. Our grandson has breathing problems and public places and motels can be a problem. Hope to see you on the road sometime.

Montana_2785 · 01-10-2005, 01:28 AM

Hi Guys,

I have a 4 things to mention regarding only getting a little toast and a couple cups of coffee from three batteries.

1) The faster you go, the less you have.

One thing to keep in mind is what percentage of your battery bank's capacity are you drawing when these high drain appliances are operating. I've included an excerpt at the bottom of this post from:

http://www.windsun.com/Batteries/Battery_FAQ.htm

(sorry, the table columns won't stay tabbed in this forum)

Bottom line: a 1400watt inverter running at full capacity will be drawing somewhere in the neighborhood of 140+ AMPS from your battery bank (I checked in our kitchen just now and our toaster oven draws 1660 watts and the coffee pot is 825 watts as an example). Also, don't forget to take the inverter inefficiencies into account!

Assuming that your 12V batteries are in the area of 100amp hours each, you are drawing a pretty high percentage of your total capacity. The higher percentage of your total capacity you draw, the more Peukert's Effect has to be taken into consideration. Peukert's Effect can vary quite a bit from one battery model to another so you can't really "take an average" and apply it to your batteries. Poorly made (as opposed to inexpensive) batteries with a high internal resistance will have a more pronounced Peukert's Effect. If you are REALLY interested, you can do a rough calculation yourself by drawing your batteries down at two different known rates and calculate the effective energy provided each time....

Or, if you can find the a manufacturer's data sheet that shows the Peukert's ratio directly, or shows the AH capacities at two or more rates, you can calculate it that way without the Mr. Wizard experiment...

2) Battery Construction.

Batteries that aren't rated in Amp Hours, but use Reserve Capacity instead, >>typically>at least

Montana_2821 · 01-10-2005, 04:00 AM

Wow Eric, I have worked around electicity most of my life, for a power company, but you educated me on batteries well beyond what I thought I knew. Thanks for the link and the discussion. I'm pretty sure when we replace our existing battery it will be with two golf cart batteries.

Thanks

Richard · 01-10-2005, 04:05 AM

Hi Eric and Mary Lou,

Thank you for that extensive and exhaustive discourse on batteries and charging. Yes, I bought Costco deep cycle batteries, leaving the 6 volt golf cart batteries on the shelf. Perhaps I shouldn't have been so hasty. I'm well aware of the fact that the printing on the label doesn't necessarily reflect the product inside. lol.

Richard

Montana_657 · 01-10-2005, 04:54 AM

That's where you have to do the math when you design your system... then if money is no object......

Or if cost, availability and nation wide warrenty become a practical consideration and you end up at CostCo. I think Richard will be well served by his system..... may not be the optimum but he's up and running....

Montana_2785 · 01-10-2005, 07:19 AM

Gruffy, I agree with you. I've just learned enough about the subject to know a few of the bigger factors that limit performance and run-time for small inverter systems and wanted to pass them on. Also, it is possible to have too large a battery bank. It needs to be sized such that it will routinely get discharged to a "comfortable" level. Deep enough discharge to keep the battery in good shape, shallow enough to prevent premature deterioration. A lot of the information on inverter systems are for stationary installations where you don't have to worry about a weight budget. Some of the considerations for stationary systems need to be filtered against our mobile nature.

For my own system, I currently have some rather "lofty" ideas that I'm sure will get cut down once I get a weight budget established and get ready to part with $$$.

I just like to push the numbers around first to see what kind of performance is available at the various combinations of equipment. That way I know how close to the edge I'll be running once I commit $$$ to the project. It's FREE to just push numbers around

Montana_657 · 01-10-2005, 11:43 AM

Yeah... me to but the beer budget makes me forget about the champagne.... but a cat can look at a queen...can't it??

Montana_2048 · 01-30-2005, 02:29 PM

Richard; It sounds as though you are looking to do essentially what I did. Installed a 2000 watt inverter on the basement ceiling running the wires through the wall behind the 110/12 load panel. Purchased a 30A transfer switch from CW, routed 110 from inv through transfer switch to the leg of my 50A service which controls just about everything except the ac's (2), washer/dryer etc. The only big load is the occasional use of the micro. I haven't figured out if the converter is still trying to charge the (2) group 27's and (1) group 24 or not. My rig has an additional 50A transfer switch up front to split park power from my onan. I also installed 150watts of solar panels which for me is almost a "must have" with any inverter I have owned.

Regards..... Roy

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