Whizbang Jr off by several amps [SOLVED]

[phxmark]

***UPDATE***

Issue has been resolved.  Turned out the bolt holding the battery cable to the shunt was not fully tightened down.  It was snug, but it could be moved.  It was enough to interfere with the WBJr readings, but not enough to upset the Magnum BMK readings.




I recently installed a system in my friends house.   

I am using a Magnum Mini Panel with a MS4024PAE and a Classic 200.

The Whizbang is installed across the shunt that came pre-installed in the panel.  There is also the Magnum BMK installed across the shunt.  The WhizBang is always several amps lower in reading than the BMK.  I tested with no solar and the inverter/charger in the off position and the BMK showed zero amps while the Whizbang showed between -8 and -9 amps.

Any ideas?   Do I have a defective Whizbang?

The shunt is the proper 500/50 shunt.

Thanks.

[zoneblue]

Minus 8 or 9 amps.  The WBJr has thus far proven reliable.  So somethings screwy with yours.

Have you tried removing the magnum shunt, to see if its interfering in some way. How long is the magnum cable, and did you connect it under the standoffs? And you sure its in the right way. I guess all the obvious questions.  Do you know that the magnum reading is closer to reality, ie measured with a clamp meter as well?

Maybe Bob will chime in, hes the expert...

[phxmark]

The inverter reports it's own current draw, along with the BMK.  If I turn off the solar so there is the just inverter drawing from the batteries, the BMK and Inverter readings line up within about a half amp.  The WhizBang is off by several amps.  I verified all connections to the shunt and even tried a different shunt.  Still the same result.

I have basically the same setup at my house and the WhizBang is only off by about 1 amp from the BMK and inverter.

Any help would be appreciated.

Thanks.
Mark.

[zoneblue]

Inverters are not known for their current measurment accuracy. Bob has previously said that the accuracy of the WBJr shouldnt be far off that off the deltec, which is much much closer than "an amp". My testing with 0.1% meters has not shown up any such anomoly.

So again i say something is up. But the only way to be sure which is right is to use one at a time with a decent multimeter across the shunt. Measure the mV, times that by 5000, and thats the true reading in amps. The power system for the WbJr is drawn from the tiny data lines, so any other gear that draws any kind of current at all off the WbJr is likely to upset it. So other monitors used in parallel with WBJr need to be the kind that have a very high input impedence. Which i should have thought was most of them, but im not familar with the magnum product.

Until you can rule out an issue with your setup, we wont know if the unit is faulty or not.

[phxmark]

Something is not right with the WhizBang readings.  Even with the inverter off and in charge mode, the WhizBang does not show a positive reading unless the charger is putting out more than 9 amps.  The BMK and charger in the inverter both show positive readings when the batteries are charging.

The Magnum mini panel came with a Deltec Shunt pre-installed and the BMK also included a Deltec shunt.  I swapped the shunts do be sure.  I even had the BMK disconnected and the WhizBang still showed incorrect readings when the batteries were charging.  I verified the WhizBang is installed properly since it is installed just like the one in the system at my house.

The Classic and MNGP have the latest firmware installed.

I opened a support ticket with Midnite to try and get this resolved.  I may pull the Whizbang from my system and put it on my friends system to verify.  Don't really want to do this since it is a pain to remove and install the WhizBang from the shunt.

[zoneblue]

So you have two different shunts? Ok. Not sure id do that, youre just adding ohms to the line. But anyway im still not sure how you know its 9amps toolow, what did you measure it with?

I ask becuase when i had an odd reading it turned out to the classic amps that was at fault, not the wb amps. Moral of the story: the WB is usually  the better data. However yours may be faulty, but still interested to know how you measured it.

[phxmark]

It is just one shunt in the mini panel.  Both the BMK and WBJr are hooked to it. The BMK came with a shunt in case there wasn't one already installed.

I did more troubleshooting and Midnite is going to RMA the WBJr.

The Inverter has its own amp meter, the BMK reads amps and the Classic reads amps.  All of those reading jive, it was just the WBJr that was reading up to 9 amps lower than all the rest.

[phxmark]

***UPDATE***

Issue has been resolved.  Turned out the bolt holding the battery cable to the shunt was not fully tightened down.  It was snug, but it could be moved.  It was enough to interfere with the WBJr readings, but not enough to upset the Magnum BMK readings.

[zoneblue]

Good to hear. If it was loose enough to upset the WB,i wonder what other havoc it was causing. Loose connections can be  suprisingly bad, and even cause fires.

[phxmark]

Everything else was working.  The BMK was working, the inverter was working, batteries were getting charged.  It was loose enough to probably cause a bit of noise that the WBJr couldn't handle, but not enough to upset anything else.  I figure that the BMK as well as the inverter have really good filtering in them, but the WBJr doesn't.

[zoneblue]

The WBJr as you know only has one wire, and this makes its other connections into the circuirt very  important.

You said it was the battery wire that was loose, not the wb screws right? That kind of connection has a higher resistance and that one small area and can overheat. You did seem rather to be trying to fault part of your kit when it was the installation that turned out the cause. Sometimes cause and effect struggle to relate in this kind of fault finding. Lesson learned!

[phxmark]

Yes, the battery cable connecting to the shunt was loose.  Not enough to cause any overheating or sparking, but just enough to interfere with the WBJr.  It was snug, but not fully tightened down.  I noticed it when I went to remove the WBJr from the shunt.  Once I fully tightened down the bolt, the WBJr read within an amp of the BMK.

The BMK does have additional capacitors and filter coils in it.  The WBJr just has a capacitor on it for filtering.

I am just happy that it is working now.

[boB]

I am kind of surprised that with just the battery minus not quite tightened that the WB Jr. would be off with its current readings
especially if the 2 screws that go into the WB Jr. from the side of the shunt are tight.

The battery negative IS the WB Jr's negative connection though so maybe that has something to do with it.

The WB Jr. has a capacitor, yes, but it also has digital filtering.

When everything is tight and proper, the WB Jr. should be as good as you can get for accuracy of reading current.
As accurate as the shunt is anyway.

Thanks for this info !  This may very well help troubleshooting in the future.

boB

[phxmark]

I am kind of surprised that with just the battery minus not quite tightened that the WB Jr. would be off with its current readings
especially if the 2 screws that go into the WB Jr. from the side of the shunt are tight.

The battery negative IS the WB Jr's negative connection though so maybe that has something to do with it.

The WB Jr. has a capacitor, yes, but it also has digital filtering.

When everything is tight and proper, the WB Jr. should be as good as you can get for accuracy of reading current.
As accurate as the shunt is anyway.

Thanks for this info !  This may very well help troubleshooting in the future.

boB

It just drove me crazy trying to figure it out.  The BMK has its own separate sense wires and power wires, whereas the WBJr uses the shunt as its negative and the Classic as its power source.  I took the BMK apart and there are some caps, coils and resistors on the sense line for filtering.  Since the BMK has its own power wires going back to the source, the loose negative batter cable didn't affect it.

[zoneblue]

the WB Jr. should be as good as you can get for accuracy of reading current.
As accurate as the shunt is anyway.

For the deltecs, that is +/- 0.25%, which is more accurate than ~95% of DMMs in the world.