Renogy Battery Monitor Problem

I have used the Renogy Battery Monitor 500 A on two trips to Colorado which included several nights of "boondocking." I have a simple system: 2 lithium 100Ah batteries, 2 100 W solar panels (portable), a Victron 100/30 charge controller, and a 2000 W inverter. I have a switch to turn off the charger in my control panel whenever I am using the inverter. Everything worked very well and I was able to replenish batteries by noon most days.

But there is one thing about the monitor that puzzles me: If I use a high draw such as microwave even for a minute, the monitor seems to "go crazy" immediately. It begins to flash and show "0" capacity remaining--flat out empty. It will continue this incorrect display until I use the charger (built into my power center). The minute I plug into power source and use the charger, the monitor begins to display correctly.

I can live with this if I have to--I just won't use the microwave--but I would like to know what may be the cause of this behavior of the monitor.

Edit to say, this is one a 34' fifth-wheel trailer.

Photo is of a normal reading. I will appreciate any comments or suggestions.

I'd take a voltage reading on the battery when using the microwave using a DVM.

But there is one thing about the monitor that puzzles me: If I use a high draw such as microwave even for a minute, the monitor seems to "go crazy" immediately. It begins to flash and show "0" capacity remaining--flat out empty. It will continue this incorrect display until I use the charger (built into my power center). The minute I plug into power source and use the charger, the monitor begins to display correctly.

Click to expand...

Thanks, Bob B for replying, but it is the monitor behavior that I am trying to solve. The batteries and the inverter, by all other indicators are working normally and acceptably even under high draw (microwave is only an example). It is the monitor display that is not working normally or acceptably. In a remote, off grid situation I need a dependable monitor to know the state of my batteries. That is what I am trying to resolve.

Looks like nobody knows.

Does the reading go back to normal as soon as the microwave stops? Do the wires for the monitor go near the microwave oven? Do you have any other devices that will pull as much current as the oven? If you pull the same power with other devices, does the monitor act up? Did it work fine and quit later? Then I would certainly look at every connection for anything that could be loose or getting hot.

It is possible that RFI noise from the oven is confusing the electronics in the monitor. If that is the case, moving it further away could cure it.

If other high loads can cause the issue, I would look to a problem with the wiring and the shunt for the battery monitor. A bad connection at the shunt can cause all kinds of problems.

I would use a separate meter to measure the voltage at the batteries and at the inverter input while under high load. If you are losing more than 2%, the cause of the loss should be corrected. If the loss is just from the wire run, you may be ok, but that is about the most you want to lose. My guess is you are going to have a larger loss across the battery monitor shunt.

Thank you very much, GXMnow, for a very helpful response.

I will concentrate in this message on the direct questions you have raised.

?Does the reading go back to normal as soon as the microwave stops?

This is a very clear "NO." It has only gone back to normal (and correct) reading after charge is applied. I am not sure if this applied to charge from solar or only to charge from AC power pedestal and charger/converter turned ON. The reason I do not know about Solar charging is that I did not have solar connected (we were moving to campground with power so I had packed up.) But when charger was connected and on the reading went right back to normal.

? Do the wires for the monitor go near the microwave oven?

Not really, they go back in the opposite direction and down to the shunt which is in front compartment of the trailer--away from the microwave.

? Do you have any other devices that will pull as much current as the oven?

Yes, I believe I got the identical result from turning on the AC in a brief test.

?Did it work fine and quit later?

Not sure about what this refers to. The monitor worked fine before and after the "crazy" behavior when I used high power through the inverter. It returned to normal after charging power was applied. It has never quit. It still works fine if I just avoid use of very high draw through the inverter.

Let me just add. This monitor works great for me in a totally battery/solar campsite IF I do not use high power draw, so that is easy for me to live with. I would just like to know what causes this behavior immediately when I use a high draw appliance, and why it immediately self corrects when AC charging is applied. I feel sure it is a monitor/display problem because battery capacity/voltage goes back to near where it was before the "problem" when charging is applied.

*If other high loads can cause the issue, I would look to a problem with the wiring and the shunt for the battery monitor.*

I agree that this is the most likely area for troubleshooting. I had the shunt and monitor installed by RV tech, but I had to move the display into the coach for it to be useful. I am also not confident that ALL negative from the batteries goes through the shunt. However, I will have to say, the monitor displays correctly all the time except for the anomaly which I have indicated.

Again, I appreciate every response. (my birthday is Thursday, I'll be 88, so an old dog trying new tricks.)

padredw said:

Looks like nobody knows.

Click to expand...

While the monitor is acting out, what voltage reading do you get at the battery terminals using a multimeter? Then what reading at the inverter dc positive to negative connections?

padredw said:

?Did it work fine and quit later?

Not sure about what this refers to. The monitor worked fine before and after the "crazy" behavior when I used high power through the inverter. It returned to normal after charging power was applied. It has never quit. It still works fine if I just avoid use of very high draw through the inverter.

Let me just add. This monitor works great for me in a totally battery/solar campsite IF I do not use high power draw, so that is easy for me to live with. I would just like to know what causes this behavior immediately when I use a high draw appliance, and why it immediately self corrects when AC charging is applied. I feel sure it is a monitor/display problem because battery capacity/voltage goes back to near where it was before the "problem" when charging is applied.

Click to expand...

What I was referring to is... Did the monitor ever work properly, even with the microwave load when it was first installed? Or has the monitor been doing this since the very first time you tried it? If it never worked right, even when new, then it could be a wiring problem or a problem with the battery monitor device. The other problem I have noticed with many inverters is that they do not pull a steady current. The current draw from the battery actually ramps like a sine wave, but both halves of the wave pull positive current. Going from near zero current, up to about 1.5 times the average current 120 times a second. At higher currents, my BMS current reading bounces around over 10 amps, but it seems to average it fairly well for the state of charge and amp hour readings. But I could see that kind of pulsing current doing some odd things to some devices.

Another issue could be the grounding. Most shunts are on the negative side of the battery. Is the battery negative grounded, or is the load side of the shunt grounded? If there are multiple charge sources, and loads, is it all grounded at one place?

And as Zil asked, have you been able to measure the voltage at both the battery and the inverter input while the system is under heavy load? That will show if you have an excessive voltage drop anywhere. If the difference is more than about 2%, there might be a bad connection somewhere.

What I was referring to is... Did the monitor ever work properly, even with the microwave load when it was first installed? Or has the monitor been doing this since the very first time you tried it?

Click to expand...

Just time for a quick reply to this question. This a a relatively new install and this is the behavior I noted from the start--in other words, since the very first time I tried to use a heavy load such as microwave or AirConditioner. Not that I would expect to use the Air Conditioner on 2 100 Ah batteries, but the microwave was a real use. Yes the microwave worked fine. It was just the monitor display that bothered me--and made the display of remaining capacity of the batteries of no value out there in the National Park without hookups--until applying charge returned the display to normal.

While the monitor is acting out, what voltage reading do you get at the battery terminals using a multimeter? Then what reading at the inverter dc positive to negative connections?

Click to expand...

I have not tried this reading. I will try to do so and report.

OK. Here goes my best effort to report.
Base= no load, no charge, resting. Monitor See first image below of display
13.2 voltage, 90% capacity
Multimeter reading at batteries: 13.28 v

High load applied (microwave) Monitor see second image
13.2 voltage (same) Capacity 0% -- 0.0 Ah
multimeter reading, slight drop to 13.24

Charge applied, image 3
13.6 v 0% capacity 1.1 Ah
multimeter in full agreement 13.6

If I would leave this charge applied it would climb to 14.?? (full charge) This display and multimeter was taken minutes after charge applied.


Comments: This is basically what I experienced in the field EXCEPT that the display did not reset immediately as I remembered it doing in the actual camping situation. All I can say with certainty is that it did reset at a certain point.

My tentative observation: The actual voltage and capacity of the batteries did not change, (or at most only slightly) and did not change on the monitor display. It is the capacity in % and Ah that is the problem. I know it did not go to 0 (image 2) in a few seconds.

Something new observed. I do not remember the inverter shutting down in the field (maybe it did). But on my two tests, the inverter shut off power soon after the microwave was turned down. At the camp, I believe we used the microwave without that shut-down. That was in a real life situation not in a controlled trouble shooting situation

It is the remaining capacity which is most important in camp without hookup and using only solar for charging.

Solution to this point: DO NOT USE THE MICROWAVE Is there any better solution????

Attachments​

• 
  Base.JPG
  106.5 KB · Views: 0
• 
• BON1.JPG
  94.1 KB · Views: 0
  
  
  
• 

The image links are not working for me.

Can you also try measuring the voltage at the input terminals of the inverter? The test you did does show that your battery appears to be in good shape. But we don't know yet if there is a drop somewhere in the system to the inverter. Do you have a DC clamp amp meter? If you can good amp reading with a separate meter, does it match the reading on the battery monitor? I am starting to think the shunt is bad or needs to be calibrated on the monitor. If the shunt has any extra resistance, or the calibration is off, it could be reporting a higher current than is actually being drawn. For small loads this is not a big problem, but what it means on a larger load is the calculated battery capacity will drop much faster than it actually is.

Your picture in the first post does show 184 amp hours remaining, so this is probably all good, but figured I would ask to make sure. Have you gone through the settings on the battery monitor to tell it what the battery capacity should be? On my BMS it had a field in the app to enter the Amp Hour rating. If this number is lower than the actual capacity, it will drop the remaining percent faster than actual. Here is a link I found to the manual.


They are calling the shunt "the sampler". Page 5 of the PDF (page 04 of the booklet) shows the wiring

Page 7 (06 in book) shows the user settings.

If all of the settings are correct for your battery, then I would suspect that the shunt voltage is too high for a measured current. On the page between these two, under operation, there is a calibration procedure. When the battery is at full charge, hold in the up arrow key for 3 seconds and it will set that as the full set point. If you pull 1 amp for an hour, it will subtract 1 amp hour. I do not see any place to calibrate the current shunt. It just says,

"1. Connect and check the current: Power on after completing the connection as shown, the screen should display capacity percentage. If the screen has no response, please check the connection. Then charge or discharge the battery and check whether the display current is equal to the actual current. If the deviation is large, please check the connection."

I would check it at a few different fixed current levels. Maybe try a few small lights, for a low amp reading, then maybe 100-200 watts on the inverter. And then the microwave. In each case, the clamp on amp meter should be close to the amp reading at the middle bottom of the display. If it is not, the shunt may be bad. If the connection was ever loose, it could have heated it up and damaged it.

I have been busy with other things so have not been watching this monitor display, BUT sometime in the last hour or so it has reset and now reads 100% which is correct as I had charger on. Based on past experience it will work normal UNLESS and UNTIL I turn on high draw on inverter (microwave or Air Conditioner)

Hope these images will work. 1. base at rest 2 and 3 reversed. 3 = microwave on BUT fuse/breaker has shut power off. 2 = charge on

Yup, those pics work.
Looks like your entered capacity is 200 amp hour.
The right pic of the 3 is only showing 1.61 amps being drawn. Just 21 watts. Oh, the microwave breaker tripped off.
What did it show for current with the oven or A/C running?
In the middle pic, it shows charging at 44.8 amps. Is that from your solar? What current does the charge controller show? Is 610 watts about right for your charge source?

Have you gone through the settings on the battery monitor to tell it what the battery capacity should be?

Click to expand...

Yes according to the manual and I am confident in that setting.

exactly as you have quoted:

On the page between these two, under operation, there is a calibration procedure. When the battery is at full charge, hold in the up arrow key for 3 seconds and it will set that as the full set point

Click to expand...

and

"1. Connect and check the current: Power on after completing the connection as shown, the screen should display capacity percentage. If the screen has no response, please check the connection. Then charge or discharge the battery and check whether the display current is equal to the actual current. If the deviation is large, please check the connection."

Click to expand...

All this has checked out correctly from the beginning. It works correctly when in camp EXCEPT for the one thing I have pointed out.

I would check it at a few different fixed current levels. Maybe try a few small lights, for a low amp reading, then maybe 100-200 watts on the inverter.

Click to expand...

I must admit that on the trips we have actually taken most of the use of small lights, etc. has been directly from DC from the batteries. That is, the inverter has not been involved. I do not leave the inverter on so as not to use the power it would draw. I will follow up on trying some of the various loads with the inverter.

What did it show for current with the oven or A/C running?

Click to expand...

I missed that reading entirely, running back and forth from display to battery testing. It tripped pretty quickly.

In the middle pic, it shows charging at 44.8 amps. Is that from your solar? What current does the charge controller show? Is 610 watts about right for your charge source?

Click to expand...

That if from connection to my 30 amp household current with the charger on. My solar is 2 100w free standing panels. I usually get a reading over 150+ I have the Victron charge controller with wifi to my phone. I can't remember the high readings. Anyway, I have checked the controller readings consistently and they support the fact that the voltage from the batteries in in sync with the voltage shown on the Renogy battery monitor.

My solar panels are packed away right now, but I don't believe using them would be different (except for time for recharge) from the AC charger I used for tests this morning. -- It was cloudy anyway

A personal note. Thanks for sticking with me. I am really not stressed out about this. I have a work around, but I do like to solve mysteries.

Did some readings with inverter

Photo 1 with light on P 2 with refrigerator P3 Microwave (1.6Kw) P4 after tripped
I did reading with TV (65 w) and slide out (500+ w)
Everything worked and displayed correctly until MV tripped.
Inverter is 2000 w. rated.

No worries. I do a lot of trouble shooting for my job. If I am hands on a system, I can usually track the issue pretty quick.

These pics show 51 watts in the first pic. That seems like a lot for just lights, but not crazy. 356 watts for a refrigerator is a bit high, but if it just started, and the light and such are still on, that is not too bad. My full size kitchen fridge draws just over 200 watts running.

Now the third pic. 129 amps, 1,6000 watts. WOW, that is a lot of power on a 12 volt system. The time remaining display is still showing 53:42 which sort of fits, if it is minutes and seconds, but it is actually hours and minutes. In the first pic 3.76 amps for 53 hours = 199 amp hours. Makes perfect sense. In the second pic 27 amps for 28 hours = 756 amp hours, oops. I think it needs a bit of time to update the calculation. I think that is also what happened in the third pic. It takes longer to update.

What actually tripped to stop the microwave? Is it a circuit breaker in the inverter? An external breaker between the battery and the inverter? A breaker after the inverter? Just a self resetting overload (in what device)? If the breaker is one of the surface mount lever breakers, I am seeing a lot of bad reviews. I ordered a 150 amp, and they kept sending me 40 amp units with a 150 amp sticker on the package.

It just seems odd that the voltage display went blank in the 4th picture. But it is still showing the 129 amp current. Maybe you can record a video of the screen as you turn on the microwave and see what it does for the whole time from power on until the trip shut off. The 129 amps looks good for the power, so the shunt seems to be accurate. If the display makes sense until the trip, it could just be the trip off is just confusing it and causing some kind of reset. How long does the air conditioner run? What current does it pull?

What actually tripped to stop the microwave? Is it a circuit breaker in the inverter? An external breaker between the battery and the inverter? A breaker after the inverter? Just a self resetting overload (in what device)?

Click to expand...

I think this is a highly relevant question, but I don't know the answer yet. It does reset pretty quickly, but I don't know in what device. The problem is that the battery monitor does not reset until charge is applied. I don't think it is a breaker in the power center--I did check that. I am inclined to the possibility of this being a breaker IN THE INVERTER.

The 129 amps looks good for the power, so the shunt seems to be accurate. If the display makes sense until the trip

Click to expand...

That's right. The display makes good sense until the trip.

How long does the air conditioner run? What current does it pull?

Click to expand...

I will try that this afternoon. Funny thing, I thought we used the microwave. I don't remember the tripping, but when you are fixing lunch and several things going on at once--that is different from the kind of trouble shooting I was doing this morning. I also remember the Air Conditioner running--just using huge amount from batteries through inverter--but I do not remember anything tripping. This morning is the first time I was clearly aware of some device tripping. I could not swear to any of my memories on actual boondocking.