Is 2nd Inverter Possible ?

Tder1 · 11-11-2016, 09:44 AM

Hi All

Would it be possible and has anyone done it? My 1K watt Magnum Inv/Charger with 2 House Batteries only runs my Fridge right now. I would like to add another 4K Inverter/charger with 4 6v Bats. to run the Coach when boondocking.
2015 Coachmen Encounter, 50Amp. The Inverter/Fridge has a dedicated Breaker in my Panel and the bank does charge from the Chassis Battery when started. Can it be done? under what considerations? It's really been wringing out my Brain for a couple weeks. It's been suggested to strip out the current system and start new but I hate to lose the capacity and remove brand new equipment including my Magnum. If thats the only way, so be it. I'm assuming it may get complicated with all the charging considerations. I'm pretty handy so fire away. Any Suggestions or direction ?
Thanks
Tom D

mlatter · 11-11-2016, 10:11 AM

Yes, it's doable. I question your need for 4000 watts though. What are you planning on running, and for how long? Your battery life from 4 6v batteries will be in minutes, not hours, if you pull anywhere near 4000 watts.

5picker · 11-11-2016, 10:39 AM

Anything is possible.

The added weight of 4 additional batteries (on top of the ones you already have) would have to be seriously considered.

I would probably look for ways to keep what you already have in a top charge state.

Tder1 · 11-11-2016, 03:13 PM

Thanks for the input, No I probably don't need the 4000, I tend to overkill for I'm not sure what will do. I was looking to go live with my whole 120v circuit understanding the need for conservation. Need my Furnace blower, maybe, and my waterpump. I know, we are looking at almost 500lbs of batteries.
What are the major concerns or problems with 2 inverters? Charging? or?
I'm new to this but I figure using 350Ah on the high side. Unless i'm looking at it wrong. What size inverter is optimal?
Should I move this to Tech section of the forums?

Bluepill · 11-11-2016, 03:25 PM

Quote:

Originally Posted by Tder1

Thanks for the input, No I probably don't need the 4000, I tend to overkill for I'm not sure what will do. I was looking to go live with my whole 120v circuit understanding the need for conservation. Need my Furnace blower, maybe, and my waterpump. I know, we are looking at almost 500lbs of batteries.
What are the major concerns or problems with 2 inverters? Charging? or?
I'm new to this but I figure using 350Ah on the high side. Unless i'm looking at it wrong. What size inverter is optimal?
Should I move this to Tech section of the forums?

If you mean your LP furnace, that is powered directly from DC. No inverter needed. Same for the water pump.

Along with additional batteries, you will need an additional charger/converter for them. Your alternator may be strained by keeping 2 battery banks charged, so you may have to use a generator to cover that load if you want to charge while driving.

mlatter · 11-11-2016, 04:35 PM

Is your first 1000 watt inverter/charger isolated from your regular 12v coach battery, or is it the same battery? I am asking this because you may have a situation right now where your inverter/charger and your converter may be both trying to charge the battery. Nothing bad will happen, but you should ideally have only one charger in a system like that. You can pull the fuse for the converter to fix that. When adding the second inverter/charger you will need to disable the charger portion on one of them if they are sharing a battery bank, or you can keep both the ac and dc sides isolated and simply run two systems side by side.

Tder1 · 11-12-2016, 09:59 AM

I have,
1 12v Chassis for Motor with charge relay in line to 6v Bank.
2 6v connected to Magnum MMS-1012 inv/charge
Would like to run them side by side. If I can only charge with Generator thats OK with me. There will be a seperate battery bank for the 2nd Inverter.
Hope thats enough info. If not just ask
BTW. Im not even sure i have a converter? Dont see one anywhere ?
Thanks alot

funfinder5 · 11-12-2016, 01:20 PM

I am guessing your fridge/freezer is electric only (no LP mode). If so that's a challenge right there if you are wanting to go more than a day at a time unplugged, which is pretty much the max your system is setup for currently.

You don't have a bad setup now. If it was me and I was looking for longer 'unplugged' times. I'd add solar as your next step. The goal is to have enough battery capacity for only about a day (night) with enough solar to charge your current bank during the day.

If you add 2X more battery capacity you won't really realisticly be able to change it back up during the day.

With the right solar setup all you'll need to worry about is getting though the night.

Philos3 · 11-12-2016, 03:03 PM

Racking your brain won't help, but expanding your electrical knowledge and electrical systems knowledge would help OR paying for some professional assistance.

A mh basically has three systems...some more than that. The more complex the coach, the more the coach requires electrical complexity.

You have a chassis system, a house 12v system, and a pedestal 110v system. You then have converters and inverters and generators and solar to add options, etc.

Keeping the electrical system consistent with what you have is probably your best bet, rather than adding complexity or doing go arounds.

For example, replace batteries with better quality batteries and more of them. Upgrade the inverter to a more powerful inverter.
=======
Some may argue with me, but most coaches, unless customized, come out of the factory based on the assumption you will be attached to a pedestal in an RV park. There are all kinds of ways to add boon docking capabilities to your coach and I recommend you don't plug and play, but go to someone who is highly qualified in electrical systems and can help you plan out a complete, well thought through set of upgrades for boon docking.

Note: an electrically savvy buyer can recognize a jury-rigged coach and if smart will take a hike.

markb422 · 11-12-2016, 07:12 PM

All inverters have efficency ratings meaning a percentage of the power from converting is waisted in resistance, heat and cooling fans. With mulitple inverters you need to add the efficencies or waisted power of each unit and include it to your need calculations. For each inverter you add, you could be doubling the amount of waisted energy.

Oscarvan · 11-12-2016, 07:57 PM

Quote:

Originally Posted by Philos3

Racking your brain won't help, but expanding your electrical knowledge and electrical systems knowledge would help OR paying for some professional assistance.

Best advice so far. I am reading a lot of lack of basic electrical knowledge on this thread. And increasing the complexity (not necessarily the same as improving) of an RV electrical system requires more than basic knowledge.

Not to be a complete jerk I will answer the original question:"Is it possible to add a second inverter?" The short answer is "yes".

Someone asked "why?"...... very good question. My answer: "no idea".

If I understand it correctly, what the OP wants to do is extend his off-grid endurance. Yes, you could add a second battery bank with a second inverter.

Now, here's the key part..... except for possibly sharing a 12V source the two shall NEVER MEET. The two inverters will never be in phase (one of those basic electrical knowledge items) so having them end up in the same place will NOT produce a usable 120V current. May even fry them, have to think about that. So, you'll have to re-work your 120V system. From what OP says I think he wants to have the fridge on one system and everything else on another. This requires separating the fridge out of the 120V service panel into it's own panel with breaker.

Where this gets interesting is what happens when you plug into shore power or run the generator. A small fortune of quality 120V "either/or" selectors and detailed knowledge of the why and how would be required to take the inverters out of the equation and now powering both 120V circuits unless, of course, both inverters are of the smart sort. Would have to do some more thinking here.

As I said the two could share a battery bank but to create endurance this bank would have to increase in size. OP wants to add a separate bank, no problem. Where it gets interesting is how the one converter/charger now installed is going to keep up with this increased capacity, not to mention the alternator, assuming you want to be able to charge off the engine while driving. Me thinks at least one additional battery charger would be required.

So, buying more stuff..... panel/charger/inverter/switches or auto switching, cabling..... And more things taking up space and more wiring to add to the spaghetti.

I don't see it.

Now, if OP would have asked the question: "How can I increase the off grid endurance the best way......" Many of us (as some already did above) would have said:

Increase size of house bank by adding same type size batteries, replace inverter with higher capacity smart inverter/charger. Ebay old inverter. Done.

Blackhat6mike · 11-12-2016, 07:57 PM

I always go with "overkill" as I never know when I might just need it even if for only a short time. It's there!
I have a 5,000/10,000 watt inverter working off of 5 x 125 amphr 12vdc batteries. The battery bank is charged by either/and/or a 75 watt converter, 600 watts of solar panels, truck's 150 amp alternator.
I haven't turned on my converter in over a year as the solar keeps me at or above 12.5 vdc even after hours of running several 120vac appliances. The A/Cs are another story but they will run well off the inverter, I just don't do it.
I've been asked by several people why I use such a large inverter? The answer is because I can. Just because it will run a steady 5,000 watts doesn't mean I EVER will, buy it is there if and when I need it. Its no different than having a 2,000 watt inverter and drawing 1,500 watts, the outcome is the same , 1,500 watts used.
IMHO, solar is the answer to most all electrical setups. Works for me! I just can't say enough for solar. I have yet to hear of anyone that went solar that regretted it. I have, however, heard many that have never used solar, talk it down.

Tder1 · 11-13-2016, 06:06 AM

You are so correct. What I have now is just good enuff for my Fridge which is 120v only. The more you try to add and keep everything running consistent is my problem and why I turned for your advice. Unless your an electrician or engineer the whole thing could be daunting. I am working with someone who wants to strip out all my current equip and start over with one system. I do plan on adding Solar but next year. Just getting thru the winter now. I see the power consumption of the inverters has a detriment to the available power. I have decided to let him remove and start over with more Batts and a larger Inverter. easiest work around, otherwise as you say i will be continuing to wrack my brain. 4 x 6v 225Ah 3k watt Aimes. What do you think about equipment? Not sure about the Aimes. Consumption is a bit high and quality?? Not against more $$ for a Magnum or Xantrex. just double the price.
My biggest user.. 2TVs and 1 Satellite Rec. , Fridge.
Yes, perhaps I should have asked a different question, I guess the answer is:
"Increase size of house bank by adding same type size batteries, replace inverter with higher capacity smart inverter/charger. Ebay old inverter. Done."

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