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wNCmountainCabin
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205 Posts
Discussion Starter #1
Maybe RV fans can chime in on this one. I have an issue with my onboard Inverter shutting down while off-grid in my motorhome.

Typically, my Magnum ME2012 Inverter and ME-RC remote panel perform perfectly when I park off-grid, or while traveling down the road, powering the fridge, all electrical outlets, and even the microwave. It is connected to my battery bank of 4) 6v deep-discharge batteries, in series and parallel for 12v.

Normally the inverter performs flawlessly, with the AGS starting the generator automatically, as needed, to recharge the battery bank. It's all 'automatic' and is designed to minimize the need to monitor them. The coach's ATS(automatic transfer switch), and the Inverter's built-in ATS, automatically switch power back and forth depending on which is in play at any time - I lose no power to any devices, tvs, or receivers when this happens, which is excellent!

While I do have a LBCO(Low Battery Cutout) feature on the Inverter, usually set at 11.5 volts, and it has reached that point several instances over several years and will 'Fault' with a red light, taking the Inverter off-line until the batteries come back up to at least 12.5 volts, recently I've been experiencing complete loss of the Inverter, but NOT for low battery voltage.

The instances when this happens, which is ONLY when off-grid with no other external power(such as 120v Shore power or 120v Generator power, or even the Alternator power), the Inverter will operate perfectly for a while, sometimes hours, before pre-maturely turning 'OFF', for no known reason.

Now, when this occurs, I typically go to the ME-RC remote panel and look at the readout. It says: 'OFF', and 'DC Volts 12.5'(or similar numbers).
This is not a battery level that would set off the LBCO trigger, and there is NO Fault or red light is present.
Otherwise, it really looks as if someone had pressed the Inverter's push button, turning it off. No other alerts or any information to say 'why'.

If I try then turn the Inverter back to ON, the Inverter will come on for less than a second, and then INSTANTLY turn back to OFF. I've also noticed that the 12v lights in the RV also 'flicker' when this happens.
If I try to do this several more times, it has happened a few times that ALL 12v systems are lost(dead), just as if I had switched off the 12v disconnect.

If I then turn on the coach's engine, and allow the Alternator to come online, the inverter will power on, and continue with no issues. If I turn on the onboard generator, or plug into Shore Power, the Inverter passes thru 120v power, as it should, for the long-term with no issues, and it's internal battery charges also charges the HOUSE batteries, with no issues.
If I then shut off the engine, or unplug or turn off the generator, the Inverter WILL CONTINUE inverting, again for some time, before mysteriously going to OFF for no reason.

____________________________________________________________

My inverter bay has several 'devices' that are part of the 12v system, and that could be suspect for this problem... but I'm no master at determining 'what' these devices are there for, other than some general ideas.

The 5 main devices that are present are:
- a B.I.R.D. Bi-directional Isolator Relay Delay
- a Custom RV Products 12v disconnect(w interior momentary 'Use/Store' wall switch)
- a connector 'block' with the words 'AUX' and 'BAT'
- a WHITE RODGERS Coil 12v D.C. Cont. #586-902 200amp SPNO
- a TROMBETTA 684-1221 150amp SPNO

I 'feel' as the symptoms are such that while the Inverter initially provides 120v output, at least for a while, that the 12v disconnect is not the issue, since the other 12v systems generally continue to work.

A secondary test today showed that if I turned on the Microwave, while under Inverter power, it instantly knocked OFF the inverter, which makes me think that one of the 'coils' within the WhiteRodgers or Trombetta devices could be suspect, otherwise no longer maintaining the needed amperage when the load powers up, IF this is indeed part of their requirements within this system.

))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))

maybe the more knowledgeable brains here can decipher this and help me decide if one of these 'coils' could be the weak link, or, if it's something else all together. : ) Thanks :crying:
 

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5,467 Posts
I would be looking for dirty connections in the 12v feed to the invertors.
You could be lossing just enough to trip the low voltage trip out.
Low voltage high current it is critical that all connections be clean and well made,
A little bit here,a little bit there,and before you know it you have lost enough to trip out.
 

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1,180 Posts
How old are the batteries?



I've seen a low battery cutoff disconnect when the voltage drops below the cutoff voltage, but then, after the load has been disconnected, the batteries recover a bit, back to a point above the cutoff voltage. Makes it look like the batteries are not the problem when they really are.
 

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If the voltage drops enough, many inverters will shut off, then forget the error, as they reset. It's typical of a bad connection or bad batteries. The drop will be quite sudden when under load, but the battery voltage will seem to recover after dropping the load.

Cheers!
 

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wNCmountainCabin
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205 Posts
Discussion Starter #5
I ran some tests today, specifically LOAD tests, to better determine what might be happening with the Inverter:

A) I started with the Inverter ON, and added small loads, such as a tv, receiver, fans, radio and sound bar/bass box, etc... everything worked fine

until

B) I added a small vacuum - POOF! the 12v rv lights flickered, and the Inverter went OFF

C) I also tried a load test with only the Microwave - poof, lights flickered, Inverter went OFF

D) I tried just opening the fridge door, the light came on fine, but when I moved the fridge controller to cause the compressor to come on - POOF! the rv lights flickered, and the Inverter went OFF again.


Now I am assuming that either the internals of the Magnum Inverter are suspect, OR one of the RV's 12v D.C. Cont. coils are failing, otherwise not handling the 'surge' of 12v power properly from the inverter, possibly a cause of the 'flicker' of the 12v lights/12 system, making the Inverter to think that it no longer has 12v power, and shuts OFF.

We'll be talking with Magnum tomorrow to see what their ideas might be.
 

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Registered
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I ran some tests today, specifically LOAD tests, to better determine what might be happening with the Inverter:

A) I started with the Inverter ON, and added small loads, such as a tv, receiver, fans, radio and sound bar/bass box, etc... everything worked fine

until

B) I added a small vacuum - POOF! the 12v rv lights flickered, and the Inverter went OFF

C) I also tried a load test with only the Microwave - poof, lights flickered, Inverter went OFF

D) I tried just opening the fridge door, the light came on fine, but when I moved the fridge controller to cause the compressor to come on - POOF! the rv lights flickered, and the Inverter went OFF again.


Now I am assuming that either the internals of the Magnum Inverter are suspect, OR one of the RV's 12v D.C. Cont. coils are failing, otherwise not handling the 'surge' of 12v power properly from the inverter, possibly a cause of the 'flicker' of the 12v lights/12 system, making the Inverter to think that it no longer has 12v power, and shuts OFF.

We'll be talking with Magnum tomorrow to see what their ideas might be.

The refrigerator compressor, microwave and vacuum all present heavy loads, especially when starting. Since the 12VDC lights flicker, that says to me that the 12V input to the inverter is dropping below the point where the inverter is able to operate, causing things to shut down.



It doesn't sound like the inverter is the problem. Your 12VDC source isn't able to deliver the power that is needed.
 

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Njuneer
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870 Posts
You will get absolutely nowhere until you figure out that using a meter will point you to the problem. I suspect others will have the patience to explain how and why but at this point I cannot even suspect anything is wrong with the inverter.
 

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wNCmountainCabin
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205 Posts
Discussion Starter #8
Here's the latest:

Thor sent over a wiring/device diagram for the Inverter and Battery bays - and I've confirmed the wiring of the WhiteRodgers coil, the BIRD, and the RV CUSTOM 12v latching relay disconnect. These are all for the HOUSE side of the system and/or tying in the AUX connection with the Chassis batteries, with an internal switch.

Thor does not, though, specify or make any note of the Trombetta coil, though I've determined that it may only have a role within the 12v Fuse Panel within the coach, not the Inverter, 12v disconnect, or BIRD. Since the slide system, a Schwintec brand high-torque motor-driven set of three slide mechanisms, is powered thru the 12v system, I can only imagine that this coil is in relation to that 'power', thru the slide switches, and the energy required.

I did confirm that MAGNUM does not require or recognize any need for any type of external 12v D.C. Cont. coil between the House battery bank and the Inverter - it is already built to handle the load itself.

BATTERIES:

I finally realized that while the House batteries all seem to 'read' the appropriate voltage of 6.3 or so, at rest, that making an additional step of testing each batteries three cells might give more info.
I used the hydrometer to test each, and found that battery number 4, in the rear, has two suspect cells, reading on the very low end of the scale - not good.

In talking with Thor, and Magnum, and others in the RVing world that have more battery knowledge than me, it seems that while even the batteries are showing a full 'charge' level, and may work just fine for smaller loads, once a larger load, especially a 'motor', is brought online, these low cells can cause the whole bank to fail to provide the required power to the Inverter, possible creating a seemingly 'sudden' and instance loss of power.
Makes sense, maybe, though I imagine I could also perform another test and simply remove two of the batteries from the mix, including the suspect battery of course, and see if the same 'cut off' or loss of momentary 12v occurs, more-or-less to confirm the theory.

If this was an immediate need for me to correct, I'd probably already just replaced the battery, but my 'do it yourself' instincts and the fact that the motorhome is in storage allows me to take some time to not only confirm the real problem, but apparently start to better understand the system as a whole. Nice.
 

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wNCmountainCabin
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205 Posts
Discussion Starter #9
SUCCESS...

I've found that one of the four 6v House batteries in the motorhome has two 'low' cells, possibly bringing down the voltage enough when a large load is required thru the Inverter to cause a momentary loss of voltage, cutting OFF the Inverter.

I'm now trying to 'revive' the suspect battery - we'll see ...

as for the other devices in the Inverter bay:

- B.I.R.D Bi-Directional Isolator Relay, which senses the levels within the two battery banks(Chassis and House) and decides which to allow Charging to, or both...
- WhiteRodgers 12v DC Continuous coil, which is the relay that the BIRD uses to either open(disconnect the two battery banks), or close(connect both banks)...
- Trombetta 12v DC coil, which is the relay that the dash 'AUX' switch uses to momentarily combine the two battery banks, as needed(starting the generator, or engine, on low levels, etc) I actually used this to TEST the theory about the dead cells in one of the House batteries bringing down the voltage - holding down this switch, with the inverter ON, and adding a large load(microwave), and the Inverter held up, performing just as it should with both battery banks online...

- RV CUSTOM PRODUCTS 12v automated Disconnect, which allows my to Disconnect the House 12v items within the motorhome via a doorside momentary switch...this is a magnetized LATCHING relay, which is why it has a 'momentary' three-way switch, for either CONNECT(USE) or DISCONNECT(STORE).

I now temporarily wired two of the good house batteries in SERIES, and the Inverter performs just as it should, with large loads, such as the fridge compressor, a vacuum, and the Microwave, all at the SAME TIME. Once I get the fourth battery back up to par, I'll wire the battery bank in SERIES and in PARALLEL, as originally installed, for more battery amp hours at 12v.

...
 
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