Inverters Shutting Down

[HarborBus]

65416542

Last November we made a trip from Yuma, AZ to Marathon in Beaumont, CA to have our awnings adjusted. We drove from Santee, CA the 80 miles to Marathon and on that trip our inverters shut down three times. Marathon replaced the regulator thinking that it was allowing the batteries to charge higher than the 30 amps that the inverters will allow. On the test drive the inverters shut down after just 10 min. They then adjusted the regulators output test drove again, no problem. In March we headed home to Gig Harbor from Yuma by way of Prevost and Marathon. The last 150 miles of our 1800 mile trip, the inverters shut down three times. The last time we were real close to home and when I arrived I discovered that only #1 inverter had shut down that time. When we are plugged in everything operates normally with no faults. Maybe it is my imagination but I think the inverters shut down when we hit a rough section of road. I took the panels off to check and tighten the connections and found heavy corrosion on one of the posts (see pictures). Do you think the corrosion causing enough resistance to cause the inverters to shut down??

[Jon Wehrenberg]

Elliott,

When the bus engine is running your inverters are functioning to convert battery power to AC power such as you get from the generator or shore power. Your alternator supplies charging current to the batteries so their DC voltage is maintained, and the inverters are pulling from those batteries to provide power to your critical house circuits that your converter deemed necessary.

Obviously you must make sure that all your cable connections are clean and tight. Poor or corroded connections cannot deliver the required voltage to the inverter. If I were to start analyzing your problem I would start with the cable connections.

But further information is required. For your inverters to shut down when converting DC to AC voltage high voltage could be the culprit, but so will low voltage. My first question is if the tech measured the voltage output from the alternator and then measured it at the batteries and then measured it at the DC connections at the inverters. If so what were those voltages? Do you have a meter and can you get those measurements? That will be the starting point. I think you problem can be isolated and resolved by methodically doing the diagnosis. I am concerned the tech may have shot from the hip without doing a good analysis.

[truk4u]

What fault is the inverter giving you when it's shut down?

[HarborBus]

My first question is if the tech measured the voltage output from the alternator and then measured it at the batteries and then measured it at the DC connections at the inverters. If so what were those voltages? Do you have a meter and can you get those measurements? That will be the starting point. I think you problem can be isolated and resolved by methodically doing the diagnosis. I am concerned the tech may have shot from the hip without doing a good analysis.

Jon, No his diagnosis was not that extensive. He only measured the the output of the alternator at the regulator, no further comparisons were done as you suggest. I do have a good RMS meter that I can get those values. Tom, unfortunately I didn't check the fault the inverters were displaying. That would have been a good thing to do Huh.:o

[Jon Wehrenberg]

All inverters and their remote panels differ to an extent. If you have an inverter installation in which your remote panel tells you information such as too much or too little DC input power that is critical information to share.

Based solely on Elliott's description above one could conclude when he says he is on shore power and everything is OK that means his inverters are functioning as battery chargers and are passing shore power through to the 120V AC devices.

But since Elliott talks about shutting down when on the road I am assuming they (or one of them) is shutting down when converting DC power to 120V AC power. The analysis (regardless of what the remote panel says) has to start with measuring the DC voltage, and to do that properly we have to determine if Elliott has a 12 volt coach and a single alternator, dual alternators, or a 24 volt coach and a single or dual alternator.

Generically I believe all inverters cease functioning when input DC voltage is too high or too low and he can have either condition present. We also cannot rule out an inverter starting to go bad, but if the shut down he talks about has involved both inverters, then looking for an inverter problem would be down near the bottom of the list because of the odds against two failing simultaneously.

One thing is for certain. To properly diagnose the problem is going to involve a step by step check of the factors which could cause inverters to shut down.

Elliott, we have to assume the technician that replaced the voltage regulator did a diagnostic check that led him to conclude there was an issue. So if there was excessive voltage (not amperage) did you get an alarm on the dash from the Vanner monitor that lit an annunciator light that showed high or low voltage? (To answer this you have to also reveal if your house has a separate dedicated alternator which I suspect is the case if you got not dash indication of a voltage problem). How did you know the inverter shut down? Does it have an audible alarm or do you have a display that is easy to see to alert you.

In your conversion (tell us if it is a 12 or 24 volt house and dual or single alternator) is there a way for you to read house voltage (DC, not AC)?

I think a little time with a volt meter and the problem can be identified.

[HarborBus]

When I was writing the original post I did have momentary brain fade and stated the tech measured amps but I meant volts.............no really I did.:o I have two alternators one small one to charge the chassis batteries and the large on to charge the house batteries. I don't know if the house is 12 or 24 volt, How would I determine that? There is a audible alarm and light on the dash that sounds and illuminates the moment inverter power is lost. I don't think we can rule out the possibility that #1 inverter is getting weak: ("The last time we were real close to home and when I arrived I discovered that only #1 inverter had shut down that time".). I can read house voltage through the Tech Link system. Of-course if the inverters have shut down it reads zero. As soon as I get around here this morning I'll go out and take some measurements with the volt meter.

[BenC]

Did you or the technician take apart, clean and tighten/torque the battery connections after your discovery? Have you observed the inverter shut-down scenario since then? Just curious. Jon is correct. Bad connections act as high resistance (like physically putting a giant resistor in line) in the power delivery line. Resistors "drop voltage" proportional to the current flow value through them, thus the greater the current value (or load) the more voltage is dropped. These problems are not often evident to technicians, if the system is not operating under a large load condition. The effect with corroded or loose connections is that the voltage the down-stream devices "see" will be lower, and can cause invertors to shut off due to low battery. They also use more current at lower voltages to produce the necessary 120v AC power and are succeptible to shutting down on temperature as well. Corroded and loose connections are common problems with all coaches, and all battery and alternator connection inspection/tightening should be considered an annual PM.

[Jon Wehrenberg]

For those that may not know BenC he is an electrical wizard and is with Coach Worx, one of our sponsors.

Pay close attention to what he says because I cannot think of anyone better to deal with electrical questions.

No, I don't get any rewards for saying stuff like that about Ben just telling it like it is.

[Jon Wehrenberg]

Elliott, If I am screwing up here I hope Ben will jump in, but the voltage readings I would like to see are at the alternator output, at the batteries and at the DC input to the inverters. I would like to see you load up the electrical circuits in the bus that are on inverter, and make sure you are not on shore power.

As Ben described if you see a substantial voltage drop between what you see at the alternator, and what is going into the inverter that is likely your problems. If the circuit is unloaded there may be no voltage drop.

Conversely, if the voltage was high, and the inverters see voltage over some value (30 volts maybe) they will also shut down. At least my inverters will.

[BenC]

You are right on track Jon. Thanks for the kind words, by the way.

[Kevin Erion]

If Elliott's Marathon is like mine, and I will guess it is, the 270 amp alternator is 24 volt. This alternator only charges the house batterys. Marathon splits the house batterys up into 2 groups of 3 using 4D size batterys. The invertors are 24 volt and draw from there set of batterys. Just a little more info to help the brain trust! If this is of any help at all!

[Jon Wehrenberg]

That's a vital piece of information Kevin. If I interpret it correctly your inverters each have a dedicated bank of batteries and if Elliott had both inverters shut down I would be led to believe from that his problem relates to something common to both sets of batteries, perhaps they share a common ground.

As Elliott begins his quest to get info hang in there with us to keep our focus in the right direction.

[BenC]

Just to clarify, the house batteries are wired as follows on Marathon, Parliament, Vantare, etc: one group of 3 (or 4 for Vantare) is the "12-volt bank" and the other three are the "24-volt bank" with both inverters (through separate set of breakers or fuses) to the output bus bar or terminal of the "24 volt bank" and chassis ground. The output from the "12 volt bank" is there specifically and only to power the house 12-volt lighting and accessory loads, with a Vanner or Surepower battery equalizer between the 24 and 12v "taps" to make up and keep equally charged the "lower" or 12volt bank. The inverters do not, as such, have their own dedicated batteries. Hope that makes sense.

[Kevin Erion]

Thanks Ben, I was not sure and your explination helps me to understand my bus a little better!

[HarborBus]

Elliott, If I am screwing up here I hope Ben will jump in, but the voltage readings I would like to see are at the alternator output, at the batteries and at the DC input to the inverters. I would like to see you load up the electrical circuits in the bus that are on inverter, and make sure you are not on shore power.

As Ben described if you see a substantial voltage drop between what you see at the alternator, and what is going into the inverter that is likely your problems. If the circuit is unloaded there may be no voltage drop.

Conversely, if the voltage was high, and the inverters see voltage over some value (30 volts maybe) they will also shut down. At least my inverters will.

Here are the reading that Jon requested, these are take with one AC unit running, microwave on, drawing 115 amps. Engine at high idle at 175 degrees.

Alternator output: 27.74V
Measured at Batteries: 27.20V
DC imput at inverters:
Inverter #1: 26.91V
Inverter #2: 26.90V

[Jon Wehrenberg]

Elliott,

You sure do not have any over voltage issues. While I think the voltage drop is a little too large it is not alarming, but I would take the time to clean and re-tighten every DC cable and fitting from the alternators through to the batteries, all the way to the inverters. Don't forget the chassis grouinds.

I'm pretty sure you were not pulling 115 amps unless you are talking about DC at 24 volts. At 24 volts a heavy load on the inverters would be around 200 to 250 amps, or 40 to 50 amps AC.

[HarborBus]

Yes, I was referring to 115 amps DC on 24 volts. I know it wasn't a huge load but I couldn't run my front AC unit because the cover leaks and is on order, in the mean time I have it covered with plastic. What voltage drop would be acceptable? Is there a torque value on the battery connections I should be using or just clean and tighten them by feel? I know what the maximum voltage the inverters will allow before shut down is 30 volts, what is the minimum?

[Jon Wehrenberg]

I cannot answer the minimum voltage. The owner's manual should have that information.

An almost one volt drop to me seems large. If Ben is reading this I hope he jumps in with what he sees from his experience. Remember, the engine was running and the alternator was maintaining the voltage, yet it dropped between the alternator and where you measured on the batteries, and then some more to the inverter. You didn't say if you were on fast idle, but if you were I don't think there should have been that drop. If on low idle I think I could understand it because the alternator needs RPMs for output.

I had some goofy inverter actions recently and I found a number of the original cable and terminal connections that needed both cleaning and tightening. I would surmise you do not have a single point of problems, but more likely need to start at the alternator and just insure everything is clean, free of corrosion and tight. I cannot quantitatively define tight, but would expect to see it quite tight. I also coated all the connections with battery terminal corrosion protection after I got everything clean and tight.

[phorner]

As an aside to this general discussion, battery terminal and other electrical connections do need to be checked on a fairly regular basis.

I have a 72 volt electric car that has 6 wet cell batteries. I check the water levels at 3 to 4 week intervals and check all the terminals for corrosion and tightness at that time. It amazes me that almost without fail, nearly every battery connection that was tight less than a month ago will still allows a smidgen of tightening upon inspection.

I don't know whether it's the vibration from driving or just the nature of the connections but they almost always can use at least minimal torque to bring them fully snug...... until next time.

I wouldn't be real surprised if this was the case with all battery/electrical connections to some degree.

[HarborBus]

Here are the reading that Jon requested, these are take with one AC unit running, microwave on, drawing 115 amps. Engine at high idle at 175 degrees.

Alternator output: 27.74V
Measured at Batteries: 27.20V
DC imput at inverters:
Inverter #1: 26.91V
Inverter #2: 26.90V

Jon the measurements were taken with the engine at fast idle(see Quote). I will set about the task of disconnection all the cables one by one, clean and tighten. I appreciate the time you have taken to work through this with me. Additionally I also appreciate all the impute I have received from everyone else. I to hope Ben weighs in here before I have to undertake the removing cleaning and tightening of all the connections. I'm still at a loss for a definitive answer as to why the inverters shut down and I'm not really fond of the shotgun approach to a problem but sometimes it can't be helped. Ben where are you??

[JIM CHALOUPKA]

There is a specified torque for the battery connections. I don't remember what it is. Some POGer referred to it awhile back, maybe it was Bruce, 0533??????
You could call the battery supplier, I guess.


JIM

[Jon Wehrenberg]

Elliott,

Some of the stuff we experience and have to deal with is not crystal clear. As our coaches have gotten more sophisticated and reliant on electrical and especially electronic devices terminals, connections and grounds become an important part of reliability. Paul brings up a very good point and that is how our battery cable connections seem to loosen in a short time period. I can tell you from our manufacturing of the temporary power outlets that have electrical cable connections internally that are torqued to specific values at the factory precisely, within a very short period of time the connections have to be re-tightened. Campground owners all face the need to do so.

Compare our coaches that probably have electrical connections in the thousands that are bouncing those connections up and down the highway, subjecting them to temperature variations and potentially corrosion from the elements and its a wonder we don't have more severe problems.

Checking your house cable connections is a PITA, but absent anything else we can point our fingers at it appears that might be your problem. It appears to have been the same problem I had and although I could not find a single bad connection it was likely the accumulation of a lot of less than tight or clean connections.

[HarborBus]

Jon, Ofcourse your right, like Evy always says it's like a small earthquake going down the road. All the systems and equipment are getting a good shaking constantly while under way. Thanks again for your help.

[BenC]

Being that this coach is a Marathon, there is a 300 amp dual battery isolator between the alternator and the batteries. Depending on the current through the isolator's diodes, the isolator can drop as much as a volt at it's current rating. So, with that in mind, the voltages seem pretty normal. Also characteristic of a Marathon, with the house batteries in the back tag axle compartment and the inverters in the front bay, the cable length in between can result in another half a volt drop at near the inverter's output rating of 33 amps AC. With the roof a/c and microwave, what was the inverter's "LOAD CURRENT" reading? If you get over 33 amps (AC) then remember you are in the "grace period" of intermittent output only, not continuous. The inverter can shut down on "OVERCURRENT" or high temperatures if the load stays above 33 for an extended period. The chart is in the inverter Owner Manual for exactly how long versus how much over the continuous rating the unit is producing. I would, however, strongly recommend, as was mentioned, the cable/terminal tightening and cleaning. I consider this an annual PM for any coach with Trace 4000 watt inverter. Hope this helps.

[HarborBus]

Ben, Yes it helps and thanks for getting back on this for me. FYI since my coach is a 40' XL II the batteries are located in the same bay as the inverters (Bay 2) which is approx. 25' from the alternator. I did not check the AC Amps draw(I'm assuming what you refer to a "current Load") when I did the testing. I only recorded the DC Amp draw at 115 Amps. Additionally when the inverters shut down on the way home the 3 times I had nothing running in the bus that would be considered high draw.

I will clean and tighten all connections and check the inverter manuals for the chart that you refer to.

[HarborBus]

Update..............The overcharge condition that I experienced for almost a year and a half is finally solved. I had several facilities, including Prevost Mira Loma, look at this problem to no avail. It cost me about $1500, but there were many many hours spent on this that I wasn't charged for. Prevost Mira Loma even changed out the alternator for a new one, with no change in the condition they put mine back in, a total of about 4 hours "no charge". On our way home in April of this year I finally took it to Marathon in Coburg and they fixed it. The 270 Amp alternator was not sufficiently grounded with the mounting bolts. They added a grounding cable from the case directly to the chassis ground lug. We now have about 1700 miles on the coach since then and problem is solved. Thanks to all that gave me your input.

[JIM CHALOUPKA]

Update..............The overcharge condition that I experienced for almost a year and a half is finally solved. I had several facilities, including Prevost Mira Loma, look at this problem to no avail. It cost me about $1500, but there were many many hours spent on this that I wasn't charged for. Prevost Mira Loma even changed out the alternator for a new one, with no change in the condition they put mine back in, a total of about 4 hours "no charge". On our way home in April of this year I finally took it to Marathon in Coburg and they fixed it. The 270 Amp alternator was not sufficiently grounded with the mounting bolts. They added a grounding cable from the case directly to the chassis ground lug. We now have about 1700 miles on the coach since then and problem is solved. Thanks to all that gave me your input.

Elliott, did Marathon give any indication that your coach should have had the additional grounding, added now for you, from day one of conversion by them?

Seems to me that had they done things correctly, you would not have had all that trouble!

JIM

[Woody]

Elliott,

Some of the stuff we experience and have to deal with is not crystal clear. As our coaches have gotten more sophisticated and reliant on electrical and especially electronic devices terminals, connections and grounds become an important part of reliability. Paul brings up a very good point and that is how our battery cable connections seem to loosen in a short time period. I can tell you from our manufacturing of the temporary power outlets that have electrical cable connections internally that are torqued to specific values at the factory precisely, within a very short period of time the connections have to be re-tightened. Campground owners all face the need to do so.

Compare our coaches that probably have electrical connections in the thousands that are bouncing those connections up and down the highway, subjecting them to temperature variations and potentially corrosion from the elements and its a wonder we don't have more severe problems.

Checking your house cable connections is a PITA, but absent anything else we can point our fingers at it appears that might be your problem. It appears to have been the same problem I had and although I could not find a single bad connection it was likely the accumulation of a lot of less than tight or clean connections.

FWIW my 12 alternator just had a catastrophic failure caused buy the fastenings on the fuse block loosening up and apparently sending some sort of surge. This fuse was on the fwd engine room bulkhead and I have never thought of tightening it up.

[HarborBus]

Elliott, did Marathon give any indication that your coach should have had the additional grounding, added now for you, from day one of conversion by them?

Seems to me that had they done things correctly, you would not have had all that trouble!

JIM

No Jim, as a matter of fact it is just the opposite they said that most of the time the ground through the attachment bolts (four of them) are sufficient to ground the case. It's just my luck I guess.

[MusicianTrader]

this thread was amazing. years later im having this issue on my 1994 Vogue. Common denominator here is an alternator. I just installed a 12v 65A for my house batteries as the old one was dying. New 1 didnt have the same grounding bolt so i jerry rigged it. My inverter #2 shuts off as soon as AC power is removed. I will check tje ground as soon as bus comes back from Houston.
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