Can't help you on the panel either, sorry but wanted to let you know where I got my inverter . Not  sure how much your paying for the 2812 but just got my 3012 Hybrid last week from these guys. Their out of stock right now but were out of stock when I ordered and took a week to get.paid $1,600 for it with free shipping.

http://www.imarineusa.com/MagnumEnergyMSH3012M.aspx

using this inverter would make a much easier connection. You can run your incoming power through the inverter and then to panel. This would eliminate having to modify panel other than disconnecting charger.  Manually switch to run your W/H and fridge on gas and only run a/c when hook up to outside power. Hope this helps.

Without a long dissertation, I’d really suggest not modifying the power panel.  While your plan “should work fine,” you seem to understand what you are doing, I’d opt for a separate panel or, as you suggested, feeding the main panel via the inverter change over switch.  I’d really do the separate panel.  This also eliminates the possibly of accidently running the fridge off the batteries when you don’t realize it.

I’d also suggest you think about just how much power the RV fridge, on 120VAC, will draw.  Your battery size, even with the upgrade, really isn’t the best choice to run the fridge even for a day. I’ve got real world numbers to substantiate that opinion. RV fridges use so little LP it really makes more sense to just run them off LP except when you have plenty of shore power.

Using a separate panel also allows you to run the inverter in the UPS mode if you want without concern for flatting the batteries if the HVAC is running and the power dumps.  That's the mode I always use to protect the TV, satellite and IT equipment.

Sometimes the simple way, a separate panel, really is the best – and the safest.  It will also be less work in the long run, IMO.

BTW, so far we are pleased with the MS2812, but I would but in a Trimetric 2025 battery monitor.  Just simpler to use than the MS2812’s optional unit and I think it’s a little less expensive.  But that’s a rather minor point.

Good point about drawing down the batteries if you lose shore power. Since I mostly dry camp and only use a small generator that would usually not be a problem. 

Something to look into, and The next thing I will research, is if the 3012 is capable of charging and passing shore/generator power through wihile the inverter is turned off And will not allow the inverter to come on line if there is a power interruption. I know chargqing and invertering are  separate functions on remote panel.

if that's the case it would seem a sub-panel would not be required. I guess a call to Magnum customer support is in order.

Great

looks like you already know more than I do on this unit and don't have yours yet. Guess I should get to reading since I plan on installing mine pretty soon. Something I always seem to wait until the last minute to do. Looks like that would solve the problem of batteries getting drained.

So if you get the MSH3012 wIll t his change your original installation design plans?

Actually since the MSH 3012 has totally programmable charge capabilities this would work best for lithium since they only need a 2-stage charging cycle. Would just need to know charging parameters from battery mfg. and set those in the MSH 3012. This was one of the reasons i chose this inverter, for optimum charging of any battery type I decide to use.

Google "Magnum MSH3012 lithium batteries" Lots of info on different set-ups

Bill and Linda wrote:

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TheHermit wrote:

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Yes, I would probably just wire it between the source and the panel. That would be the least destructive route and if it causes too many issues i can go from there. I need to read through all the specs and make sure the 3012 can be configured for use with lithium batteries before I would say I am going with it for sure.  In the manual it states that the AC input and output of the inverter must be protected with a max 60 amp breaker. Would this be the breaker on the generator or shore power panel for the input and the camper main breaker for the output? i need to read more.  

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Let me (strongly if I may) suggest if you are going to put the inverter directly on the output of your shore power to feed the panel you install a Progressive Industries HW50C inline before the Magnum.  In fact you should install one of these on the output of the shore cord regardless. (Before the generator changeover switch if you have one.)  Second to tires it is the most important device to protect your rig.

 

http://www.progressiveindustries.net/#!ems-hw50c/cjk6

 

These are available from many sources for far less than the quoted price on the PI home website.

 

I’ll bet you already know about these but if not a read of the manual on the website should do the information trick.  Readout is very handy for monitoring loads and rationing available amps.

 

As to the breaker – they just want the usual input draw and output load breaker to protect the wire and the Magnum respectively.

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 X2

To me, that's a mandatory item.

The EMSHW30C has been on my list. May as well install it while I have everything torn apart.

TheHermit wrote:

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Great idea. A lot of good info. Ran across an interesting thread about alternators and house batteries. My RAM has two alternators and I have no clue how much of that is making it to the batteries but with lithium I can't take the chance. I 'spect i will have to find where that lead taps into the battery circuit and put a switch on it or redirect it to the generator battery. Never ends.

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To utilize all those available amps from the second alternator you will need to run a bigger, dedicated cable to the rig batter bank, IMO.  Seen this done and if you travel a lot it can charge the bank really well during the travel period.  If you don’t travel much – or relatively short time length periods – might not be worth the effort.  Do the math as they say.

TheHermit wrote:

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My concern is with over charging as I cannot turn the alternator off. Hopefully the drop in voltage with the thin wire is enough to make it a none issue. Will have to put a meter on it and see what is getting to the batteries.

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 Good point. Just wanted to let you know IMarine has one MSH3012 in stock right now @ 1575.00. i know they usually have trouble keeping them in stock

Bill and Linda wrote:

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TheHermit wrote:

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My concern is with over charging as I cannot turn the alternator off. Hopefully the drop in voltage with the thin wire is enough to make it a none issue. Will have to put a meter on it and see what is getting to the batteries.

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Luis:

 

I truly believe you may be over thinking this. (“Ask me how I recognize this tendency.”)  If you just use the charge wire that is in the 7 way connector, pin number 4, all will “just work fine.”  You really don’t need to do a thing except make sure the in-vehicle fuse is installed that feeds this line.  Some OEM’s don’t always install this fuse.

 

Like you will have with the Trimetric, I’ve been monitoring the batteries with the “pin 4” charging for years and have never seen the batteries overcharged even after a long day of travel.  The only way this might happen slightly is if the truck batteries were really flat, the trailer bank were not, but the trailer bank would still only take so much through the wire.  The first and second alternator will output only what is required by the 3 stage regulator in the truck.

 

Just traveled close to 400 miles today and when we arrived the battery bank was at its usual 100% on the Trimetric with the battery temp at 82 degrees and the ambient at 85. (That's with the solar panels working on a fully sunny travel day as well.)  Just not a problem in the real world, IMO, as the new trucks actually have “smart” 3-stage chargers in them as commented above - basically like better quality solar controllers.

 

BTW, I do disconnect the truck at night so the truck batteries are not part of the house battery bank in case of a power outage and the inverter kicks in. (That’s one reason.)

 

My 2 cents

Bill

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Bill,

What type of batteries do you have? I think Luis was planning on using Lithium batteries which have a very different charging parameter than lead acid. I read they do no liked  being charged at too high of a voltage and if they are it can shorten the life. Not sure if the alternator will put a higher voltage that lithium can handle but at the cost of litlium would definitely want to be sure. 

Luis, 

If you are going lithium batteries, you might want to check if the battery management system (BMS) will make sure the voltage  from the alternator does not exceed acceptable limits. That would be a good question for whichever mfg. you choose

Mobile Greg wrote:

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TheHermit wrote:

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My concern is with over charging as I cannot turn the alternator off. Hopefully the drop in voltage with the thin wire is enough to make it a none issue. Will have to put a meter on it and see what is getting to the batteries.

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 Good point. Just wanted to let you know IMarine has one MSH3012 in stock right now @ 1575.00. i know they usually have trouble keeping them in stock

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 Thanks for the heads up. I have been watching it and going back and forth on picking that up but over the last couple of weeks i ordered all the components for this next phase and now realized I am just about tapped out for the month. At least I have everything i need to make it inverter ready.

Bill and Linda wrote:

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Mobile Greg wrote:

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Bill and Linda wrote:

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TheHermit wrote:

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My concern is with over charging as I cannot turn the alternator off. Hopefully the drop in voltage with the thin wire is enough to make it a none issue. Will have to put a meter on it and see what is getting to the batteries.

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Luis:

 

I truly believe you may be over thinking this. (“Ask me how I recognize this tendency.”)  If you just use the charge wire that is in the 7 way connector, pin number 4, all will “just work fine.”  You really don’t need to do a thing except make sure the in-vehicle fuse is installed that feeds this line.  Some OEM’s don’t always install this fuse.

 

Like you will have with the Trimetric, I’ve been monitoring the batteries with the “pin 4” charging for years and have never seen the batteries overcharged even after a long day of travel.  The only way this might happen slightly is if the truck batteries were really flat, the trailer bank were not, but the trailer bank would still only take so much through the wire.  The first and second alternator will output only what is required by the 3 stage regulator in the truck.

 

Just traveled close to 400 miles today and when we arrived the battery bank was at its usual 100% on the Trimetric with the battery temp at 82 degrees and the ambient at 85. (That's with the solar panels working on a fully sunny travel day as well.)  Just not a problem in the real world, IMO, as the new trucks actually have “smart” 3-stage chargers in them as commented above - basically like better quality solar controllers.

 

BTW, I do disconnect the truck at night so the truck batteries are not part of the house battery bank in case of a power outage and the inverter kicks in. (That’s one reason.)

 

My 2 cents

Bill

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Bill,

What type of batteries do you have? I think Luis was planning on using Lithium batteries which have a very different charging parameter than lead acid. I read they do no liked  being charged at too high of a voltage and if they are it can shorten the life. Not sure if the alternator will put a higher voltage that lithium can handle but at the cost of litlium would definitely want to be sure. 

Luis, 

If you are going lithium batteries, you might want to check if the battery management system (BMS) will make sure the voltage  from the alternator does not exceed acceptable limits. That would be a good question for whichever mfg. you choose

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Lifeline AGM’s 6 volt.  Indeed, do check your charging parameters but I don't think this is a problem.  Advise if you find otherwise.  If it is, just pull the fuse in the truck.

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 Bill, over thinking? Me? More like my middle name! I currently have two Interstate 12v lead acid but yes I am setting this up to install two GBS III 200 amp lithium batteries. GBS III Link.  I have a tendency to get a little paranoid about charging sources. From what I have read lithium is not very forgiving.  So is pin 4 only used for charging? 

The BMS will monitor for over discharge as well as over charge. I am installing two contactors that will be controlled by the BMS, one on the positive cable from the batteries and one on the negative right after the shunt. However I want to avoid having the BMS tripping the over charge contactor if I can help it. I plan on using the over charge contactor to isolate the negative battery terminal from the Inverter and the solar charge controller. This way the loads won't be affected.DC Electrical Plan Link.

TheHermit wrote:

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 Bill, over thinking? Me? More like my middle name! I currently have two Interstate 12v lead acid but yes I am setting this up to install two GBS III 200 amp lithium batteries. GBS III Link.  I have a tendency to get a little paranoid about charging sources. From what I have read lithium is not very forgiving.

 So is pin 4 only used for charging? 

The BMS will monitor for over discharge as well as over charge. I am installing two contactors that will be controlled by the BMS, one on the positive cable from the batteries and one on the negative right after the shunt. However I want to avoid having the BMS tripping the over charge contactor if I can help it. I plan on using the over charge contactor to isolate the negative battery terminal from the Inverter and the solar charge controller. This way the loads won't be affected.DC Electrical Plan Link.

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Pin 4 is designated to feed 12 volts to a trailer from the tow vehicle.  Just +12 “all the time” from most vehicles. I.e. not usually on the ignition key but YMMV.  How it is used, if at all, in the rig is determined by how they wired it.  But in the past 40 odd years I’ve been doing this I’ve always found the +12 from the connector in a trailer going right to the 12 volt bus (hopefully via a fuse) just like it were a battery charger or converter.  If you removed the trailer batteries you would still have +12 to run lights, etc. from the truck’s +12 - (albeit not for very long).

BTW, trailer batteries are used to supply the +12 to the emergency brake-away switch.  I’m sure you know that but just commenting . . .

All the 12 volts, via a fuse panel, is usually tied together one way or another unless there is a diode isolation stack which is sometimes present in motorhomes to isolate the vehicle batteries from the house battery bank so you can start the motorhome if you run down the house batteries.  Never seen one in a trailer from the OEMs.  Just keep all in mind with your design as might be appropriate.

TheHermit wrote:

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Good to know. I requested electrical schematics from the manufacturer and what I got was a couple of Fleetwood (which the camper is not) floorplan drawings with a bunch of hand drawn lines and scribbles. Could not believe it. Called and asked if they had real schematics and they said no. I am sure they have something better than what they sent but then again when I pulled out the breaker panel and looked inside it looks just like what they sent. A mess.

Anyway, I will have to plug it into the truck and see what it sits at. Like you said it may not be an issue. 

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Welcome to the real world of RV’s.  No, I seriously doubt they actually have anything much better than what they sent you and this has nothing to do with any particular manufacture or price point – at least any price point I’ve been involved with.  Just saying . . .

In the "old days" Airstream did a pretty good electrical schematic manual.  Not saying there are none now, but I haven't seen one that is rig specific in sometime.