Is My Inverter Dead? Xantrex Pro XM1800

[Islandsmith]

Originally Posted by 16ACE27

So are you using a voltmeter to test voltages? Or are you relying on the inverter display?

Yep, a Voltmeter.

[camperguy99]

You have to measure the battery voltage at the same time you measure the voltage at the inverter. My bet is bad batteries. They can test good voltage without a load on them.

[16ACE27]

Originally Posted by 16ACE27

I'm not sure why you are plugging/unplugging SP to troubleshoot the inverter.

If inverter input voltage drops from 12.8 VDC to 7 VDC just by connecting the inverter I would go measure the house battery bank voltage at the same time. If the battery bank reads 7 VDC then you have bad batteries. If it reads greater than 12.0 VDC then you have a bad connection to the inverter.

Originally Posted by Islandsmith

I was plugging in and out of shore power because there seemed to be a difference after each time shore power was attached when on the road. Just to be clear, connecting shore power doesn't change the voltage from the battery bank but it DOES change the voltage that is displayed across the input terminals for the inverter. When the inverter is not connected to the battery cables the voltage there is consistent.

I have pulled the batteries out, tested them and they are fine. I also checked the connections at both ends and they are good. I think there is an error inside the inverter.

How did you test them? Did you use a load tester? Did you check the battery bank voltage with a voltmeter when you had 7 VDC at the inverter?

People are trying to help you but we can't read your mind. The more complete your information is, when you answer questions, the better our information is in guiding you in your troubleshooting. Remember the phrase GIGO?

[Islandsmith]

Originally Posted by 16ACE27

How did you test them? Did you use a load tester? Did you check the battery bank voltage with a voltmeter when you had 7 VDC at the inverter?

People are trying to help you but we can't read your mind. The more complete your information is, when you answer questions, the better our information is in guiding you in your troubleshooting. Remember the phrase GIGO?

I wrote a long reply over the weekend but for some reason it didn't post as I thought. I've re-written it here - I do appreciate the help and apologize for not being clear earlier.


First step was to remove the batteries from the coach, verify the water levels were correct and fully charge the batteries. I then tested the specific gravity of each cell and they all passed. I have NOT load tested the batteries as I don't have a load tester but that's on my shopping list this week.

Anecdotally all of the 12V systems seem to work fine (other than the inverter) and I am not getting any low voltage errors when running the levelers. Slide-outs and drop down bunk are working as expected when not plugged into shore power.

I ran the tests that Judge recommended and can verify the BIM is working. I'm getting charging voltage when plugged into shore power and when the engine is running.

Batteries are now re-installed. I disconnected the inverter and measured the voltage at the cable ends that power it. When not connected to the inverter the voltage there is 12.6V. The same measurement as at the battery terminals.

I then re-connected the cables to the inverter and measured the voltage at the input terminals of the inverter. Result is 7"ish volts. I walked around to the battery bay and measured the voltage at the battery terminals as well as on the downstream side of the fuse - these all measure 12.6V. Essentially it appears that 12.6V is arriving at the inverter but once it is connected something internal is malfunctioning.

With regard to the plugging and unplugging of shore power, I did this because when I plug shore power in there is an audible "click" from the inverter and when this all started it was because the battery charge had dropped and the inverter kept clicking over and over. I did notice that after plugging and unplugging shore power something was changing as the voltage at the input terminals would bounce from 7'ish to 11'ish volts.

(edited to mention) I did notice that power to my fridge and the outlet in the passenger computer desk routes directly through the inverter. With the unit uninstalled I had to tie the AC input to the romex that comes out of the inverter to those locations. Otherwise I have no power, even on shore power.

I'm really open to coaching here - what am I missing in my steps?

[16ACE27]

Originally Posted by Islandsmith

I wrote a long reply over the weekend but for some reason it didn't post as I thought. I've re-written it here - I do appreciate the help and apologize for not being clear earlier.


First step was to remove the batteries from the coach, verify the water levels were correct and fully charge the batteries. I then tested the specific gravity of each cell and they all passed. I have NOT load tested the batteries as I don't have a load tester but that's on my shopping list this week.

Anecdotally all of the 12V systems seem to work fine (other than the inverter) and I am not getting any low voltage errors when running the levelers. Slide-outs and drop down bunk are working as expected when not plugged into shore power.

I ran the tests that Judge recommended and can verify the BIM is working. I'm getting charging voltage when plugged into shore power and when the engine is running.

Batteries are now re-installed. I disconnected the inverter and measured the voltage at the cable ends that power it. When not connected to the inverter the voltage there is 12.6V. The same measurement as at the battery terminals.

I then re-connected the cables to the inverter and measured the voltage at the input terminals of the inverter. Result is 7"ish volts. I walked around to the battery bay and measured the voltage at the battery terminals as well as on the downstream side of the fuse - these all measure 12.6V. Essentially it appears that 12.6V is arriving at the inverter but once it is connected something internal is malfunctioning.

With regard to the plugging and unplugging of shore power, I did this because when I plug shore power in there is an audible "click" from the inverter and when this all started it was because the battery charge had dropped and the inverter kept clicking over and over. I did notice that after plugging and unplugging shore power something was changing as the voltage at the input terminals would bounce from 7'ish to 11'ish volts.

(edited to mention) I did notice that power to my fridge and the outlet in the passenger computer desk routes directly through the inverter. With the unit uninstalled I had to tie the AC input to the romex that comes out of the inverter to those locations. Otherwise I have no power, even on shore power.

I'm really open to coaching here - what am I missing in my steps?

Great write-up and I think I can say now that you definitely have a bad connection in the wiring between the battery bank and the inverter. At this point I don't think you need to load test the batteries as everything else seems to be operating normally. That also indicates the connection between the battery bank negative side and chassis ground is good.

So that leaves:
The positive cable from the battery bank, through the fusible link (or DC breaker) to the positive connection on the inverter, which you have had apart so it should be good when you put it back together.
or,
The negative side of the inverter (again, should be good) back to chassis ground.

You are dropping 5+ volts across a bad connection somewhere above. With the inverter connected and measuring 7 VDC the other 5+ VDC will be seen across the bad connection. If physically possible, with the inverter connected, measure DC volts from the positive side of the battery bank to the positive terminal on the inverter. Do that same for the negative side. Good connections will read 0 VDC on either of those tests. In your case, one should read over 5 VDC - that would be the side with the bad connection.

[Islandsmith]

Originally Posted by 16ACE27

Great write-up and I think I can say now that you definitely have a bad connection in the wiring between the battery bank and the inverter. At this point I don't think you need to load test the batteries as everything else seems to be operating normally. That also indicates the connection between the battery bank negative side and chassis ground is good.

So that leaves:
The positive cable from the battery bank, through the fusible link (or DC breaker) to the positive connection on the inverter, which you have had apart so it should be good when you put it back together.
or,
The negative side of the inverter (again, should be good) back to chassis ground.

You are dropping 5+ volts across a bad connection somewhere above. With the inverter connected and measuring 7 VDC the other 5+ VDC will be seen across the bad connection. If physically possible, with the inverter connected, measure DC volts from the positive side of the battery bank to the positive terminal on the inverter. Do that same for the negative side. Good connections will read 0 VDC on either of those tests. In your case, one should read over 5 VDC - that would be the side with the bad connection.

OK thanks for that, I can definitely run wire under the coach to the battery bank to make the test your suggest.

I am a bit confused how the reading at the cable ends is 12.6V when they aren't connected to the inverter if there is a wiring issue. Is it because my voltmeter doesn't put any load on the circuit? I'm not an electrical expert so this is baffling to me. I just assumed that if I measure 12.6v at the cables when they are not connected to the inverter that once they were connected there should still be 12.6v supplied...and the loss is coming inside the inverter, not from somewhere between the batteries and the inverter.

[16ACE27]

Originally Posted by Islandsmith

OK thanks for that, I can definitely run wire under the coach to the battery bank to make the test your suggest.

I am a bit confused how the reading at the cable ends is 12.6V when they aren't connected to the inverter if there is a wiring issue. Is it because my voltmeter doesn't put any load on the circuit? I'm not an electrical expert so this is baffling to me. I just assumed that if I measure 12.6v at the cables when they are not connected to the inverter that once they were connected there should still be 12.6v supplied...and the loss is coming inside the inverter, not from somewhere between the batteries and the inverter.

You are exactly right - a voltmeter draws almost no current. The inverter, even in idle mode, draws much more current than the voltmeter. That current is causing the voltage drop across the high resistance connection. V=IR

[Islandsmith]

Originally Posted by 16ACE27

You are exactly right - a voltmeter draws almost no current. The inverter, even in idle mode, draws much more current than the voltmeter. That current is causing the voltage drop across the high resistance connection. V=IR

Ahhh yes, Ohm's law. It's been a while.

[Islandsmith]

I swear I'm not crazy but I think I might be losing my mind. I re-installed the inverter (only this time I connected the ground wires from the AC wires to the dedicated ground mounts on the unit rather than how Thor had done it by just connecting them together).

I ran a long jumper cable from the battery compartment under the rig and into the compartment where the inverter is mounted. Measuring from the negative battery terminal to the negative input on the inverter = 0 volts.

Measuring from the positive battery terminal to the positive input on the inverter = -11 volts. Huh? Let's try that again - I re-positioned the jumper cable on the battery terminal and voila, 0 volts.

OK, let's try measuring from downstream of the fusible link in the battery compartment. 0 volts on the positive side, 12.6 on the negative side.

Here's where it gets strange - I suddenly hear the inverter fans come on. Turns out it was turned on when I connected it and now it's running fine. The display panel shows input of 12.5volts. Could something have been loose in the connection to the inline fuse that I jostled when attaching the jumper cable?

Next headscratcher - after a while the voltage starts to drop because the fridge kicked on. I started the generator to make sure the batteries would charge and low-and-behold - nothing is charging from the generator.

At this point I'm sitting with a beer pouring over wiring diagrams trying to figure out where to go next. The best thing that could happen here is for lighting to strike tonight and cause a total write-off situation.

[Judge]

Originally Posted by Islandsmith

Next headscratcher - after a while the voltage starts to drop because the fridge kicked on. I started the generator to make sure the batteries would charge and low-and-behold - nothing is charging from the generator.

At this point I'm sitting with a beer pouring over wiring diagrams trying to figure out where to go next. The best thing that could happen here is for lighting to strike tonight and cause a total write-off situation.

Do you have any AC power from the generator? There can be two circuit breakers on your generator. If so, maybe one of the two has tripped and it is not sending power to the Converter to charge the batteries.

[Islandsmith]

Originally Posted by Judge

Do you have any AC power from the generator? There can be two circuit breakers on your generator. If so, maybe one of the two has tripped and it is not sending power to the Converter to charge the batteries.

I did not check that but will go back and do so. The fridge seemed to be causing the generator to rev a bit so I just assumed it was sending power.

[Islandsmith]

Here is the wiring diagram for the 12V system. According to this the cables from the battery bank to the inverter should be direct, no fuse.

[Islandsmith]

I swear two days ago when I had this in front of my house the batteries were charging on shore-power. According to this if the converter was not working it wouldn't work on either shore or generator power.

[Judge]

Originally Posted by Islandsmith

Here is the wiring diagram for the 12V system. According to this the cables from the battery bank to the inverter should be direct, no fuse.

The Inverter should be wired directly to the battery but it should also have a fuse or breaker. On my Outlaw it had a Bussman breaker. On my Magnitude it has a battery terminal fuse block.

According to your wiring diagram, you have a 300A terminal fuse block. It should look like this and it should be on the battery post with the positive cable to the Inverter attached to it.

[Judge]

Originally Posted by Islandsmith

I swear two days ago when I had this in front of my house the batteries were charging on shore-power. According to this if the converter was not working it wouldn't work on either shore or generator power.

Your Converter should work on shore power and generator power. If a circuit breaker is tripped on the generator, the Converter would not have power with the generator but it would have power with the shore power and charge your batteries.

The Converter has its own AC breaker as well. If that breaker is tripped, it would not work on shore power or generator power.

One other thing..... the Converter has a couple Reverse Polarity Fuses (usually 40A). If you accidentally crossed the battery cables when you were troubleshooting the Inverter, you could have blown the Reverse Polarity Fuses for the Converter and that would prevent it from charging the batteries.

[Islandsmith]

Originally Posted by Judge

The Inverter should be wired directly to the battery but it should also have a fuse or breaker. On my Outlaw it had a Bussman breaker. On my Magnitude it has a battery terminal fuse block.

According to your wiring diagram, you have a 300A terminal fuse block. It should look like this and it should be on the battery post with the positive cable to the Inverter attached to it.

I do have one in-line but I will need to get inside the battery compartment a bit more to see what the A rating is.

[sthursto]

Question:

Someone said "I could not even get the slide out after driving several hours unless I was plugged into shore power or the generator was running because the house batteries were drained."

My question is how does connecting to shore power or running the generator give more power to the DC side of the electrical system? I thought power from either of those sources would run the converter to
1) charge the batteries (but that would take time)
2) I guess the converter also sends power to the DC side (even without any batteries) - is that what gives more power to the DC side?

3) So hooking up to shore power or running the generator should also provide more than enough power to the Lippert leveling system that runs on DC power? Thus I should not see that stupid "low voltage" message on the Lippert system.

4) one last question on Lippert Leveling - Has anyone had wire connection issues that caused it to say low voltage when that was not the true issue? If so, do you happen to know where the wiring was loose or poorly connected. We had someone work on the system and they disconnected all the plugs and reconnected them and it worked for a day. Then stopped again. I think it could be a corroded wire connected at one of the many connection plugs.

Thanks for the help, you forum members are the greatest!!
Scott

[16ACE27]

Originally Posted by sthursto

2) I guess the converter also sends power to the DC side (even without any batteries) - is that what gives more power to the DC side?

Scott

Yes, the converter can run any/all DC loads. And yes, you can substitute the converter for running the engine for the leveling system (low voltage) condition.

[Judge]

Originally Posted by sthursto

Question:

Someone said "I could not even get the slide out after driving several hours unless I was plugged into shore power or the generator was running because the house batteries were drained."

My question is how does connecting to shore power or running the generator give more power to the DC side of the electrical system? I thought power from either of those sources would run the converter to
1) charge the batteries (but that would take time)
2) I guess the converter also sends power to the DC side (even without any batteries) - is that what gives more power to the DC side?

3) So hooking up to shore power or running the generator should also provide more than enough power to the Lippert leveling system that runs on DC power? Thus I should not see that stupid "low voltage" message on the Lippert system.

4) one last question on Lippert Leveling - Has anyone had wire connection issues that caused it to say low voltage when that was not the true issue? If so, do you happen to know where the wiring was loose or poorly connected. We had someone work on the system and they disconnected all the plugs and reconnected them and it worked for a day. Then stopped again. I think it could be a corroded wire connected at one of the many connection plugs.

Thanks for the help, you forum members are the greatest!!
Scott

The people that had to be on shore power or generator power to get their slides out had their BIM’s wired backwards from the factory. As a result the slide controller did not see enough voltage to unlock the interlock. Getting AC power to the Converter allowed enough DC power to release the interlock.