Strange behavior

[SolarMusher]

The input voltage and current displayed by the classic are quite suspect as often when compared to output volts and amps the output wattage exceeds input wattage 

Agree with David, I've seen several times (last time today) 8A output on classic, +9A on my batt monitor and around +9.5A on clampmeter, just one array, no other source.
Erik

[offgridQLD]

I will come back later and update this thread with photos and more detail. But basically I just did some live testing and my accurate(tested  and agrees with another device) shunt is showing 40A going into the battery's while the classic is showing 55A going out. Its all over the place.

I use end amps to trigger float each day. Today just befor I hit float. My pack was showing 13A going into the external shunt. At the same time the classic is showing 21A. That's not good  when the classic is using this data to trigger something like end amps that I have set for 15A and it cant be trusted.

let me get a 3rd and perhaps even a 4th shunt on the line and see what device is telling fibs .

will update later.

Kurt

 

[boB]

I will come back later and update this thread with photos and more detail. But basically I just did some live testing and my accurate(tested  and agrees with another device) shunt is showing 40A going into the battery's while the classic is showing 55A going out. Its all over the place.

I use end amps to trigger float each day. Today just befor I hit float. My pack was showing 13A going into the external shunt. At the same time the classic is showing 21A. That's not good  when the classic is using this data to trigger something like end amps that I have set for 15A and it cant be trusted.

let me get a 3rd and perhaps even a 4th shunt on the line and see what device is telling fibs .

will update later.

Kurt

If the Classic is showing 21 amps and another meter is showing 13 amps, that may be because of external loads.
Unless it got out of here without being tested and calibrated, that much difference just doesn't happen.

You also might want to check your reference shunt/meter.  You also can not measure the common negative
wire coming out of the Classic.  You must measure the positive output wire itself if the PV negative an battery negative
are shared..  If there are no loads or inverters on the battery side, then a negative leg battery shunt should be OK.

Current measurement is not easy and we have gone to great expense to try and get the Classic's output
current measurements very close.  It ~should~ be at least within an amp or so.

That being said, if for some weird reason, the Classic got out of here without being calibrated, then it
could be off by a bunch.  I would hope that would be extremely rare and of course want to know
about it.

Yes, the Classic uses internal shunts and they are our own design and custom parts.

Shunts can be made to work well but you still have to take great care in PCB layout
and circuit design just reading those shunts.

boB

[offgridQLD]

Hi Bob,
          Im not trying to be smart or have a go. I'm sure all effort is taken to get the classic reading as close as it can for its intended purpose. Though I have been seeing some strange output behavior in my numbers so I investigated. perhaps i just got a uncalibrated unit.

  Perhaps this video will prove my point a little more. both shunts are calibrated and read identical , you will notice the inverters shunt is average over 2 or 3 seconds and my 2nd calibrated external shunt and reader samples a little faster but they both agree with each other.  All readings are independent of loads and measuring output amps before the inverter. I also tested my calibrated external shunt reader  along side two other shunt readers that all agree with each other. So that's 4 against one at the moment.

You can see the classic is always showing more amps going into the battery .

link to video
http://www.youtube.com/watch?v=aHZtXVUGL6k&feature=player_detailpage

Kurt.

[Halfcrazy]

My question is are all the other shunts between the classic and everything else or are they between the battery and everything? I ask this just to be sure you are accounting for inverter draw and loads?

Never-mind I was able to follow the video after a couple goes. So the Classic is reading high by 80-100 watts? Seems a little high but? I also don't see how it could have been a calibration issue at Midnite if it ran good for 3-4 months? I would say check it against a couple meters at a heavier load and see what it shows.

Ryan

[offgridQLD]

The inverter was consuming about 5 or 6amps ( DC consumption)  and perhaps 1A or less to keep the batterys at float you can see the -5 A in the inverter LCD that's the inverters DC load at the time so no I am not reading Net or my external shunt would  only be showing 1 or 2A  going to the battery if the classic was correct.

If you like a can tune the inverter off to prove this.

edit: that was a test at under 10A and at 50A this morning it was off by more than 10A though it was off by more at times!

Photo taken at same time. Shunt 1 on the inverter is  befor the load  (it's not NET) Net is shunt 1 number minis the  (INV AMP) - load number



kurt

[Halfcrazy]

Ok so at the time in the video the batteries where essentially taking 0 amps. The inverter was using all the classic was making? I would be interested to see if it still shows off by the same 1.5 or so amps when it is making say 30-50 amps?

Ryan

[offgridQLD]

Yes it was actually 5.2Amps not 6 A (you can see this on the inverter LCD in the video) so the battery's were taking around 1A or a little less to hold them at float.

[boB]

Kurt, in that video I am seeing the Classic saying about 2 amps higher than your meters.
About 8.5 amps vs about 6.5 amps...

Try that again, but go to the Classic's mode menu and turn it off and back on again or
maybe, in main status, press the ENTER button to force a sweep.  I think it may do
a zero re-cal at that time also but for sure if you turn it off and on again.

   The offset is what the zero calibration takes care of.

Thinking out loud here....
If this was a gain error, then at an actual 13 amps I would expect to see
about 17 amps output and not 21 amps from the Classic.

Thanks !
boB

[offgridQLD]

Ok bob,
            I have removed the external shunt reader (it was very temporary setup - dangerous with cover off wires every where ) I did it just to prove my inverters external shunt 1 readings were  ok.

So now I will do your test but just compare classic  to inverters shunt 1 as we know its good now.

It doesn't look to be a offset shift its more like a 10% shift . though its not that consistent. I will make some more comparisons at different AMP levels   10 - 20 - 30 by applying loads while on float.

Back soon....

Kurt
         

[boB]

Well, if that Classic really does have a gain problem, I can tell you what pot to turn.

If gain problem, then it's going to be off more amps at higher output and off by
lower amps at low output.

boB

[offgridQLD]

Thanks bob i just did your test.

batterys on float consuming 1A to hold float 

I tested .. as close as I can get jumping up and down between the two meters but you get the picture. The classic is roughly 20% over the shunt 1 at different loads.

Base loads 4.8A shunt 1 vs 6.4A classic

water pump + base loads  14.1A shunt 1 vs 17.8 classic

water pump + toaster + base loads 45A shunt 1 vs 55.7A classic 

Gain problem? What pot do i need to turn?

Kurt

[boB]

Thanks bob i just did your test.

batterys on float consuming 1A to hold float 

I tested .. as close as I can get jumping up and down between the two meters but you get the picture. The classic is roughly 20% over the shunt 1 at different loads.

Base loads 4.8A shunt 1 vs 6.4A classic

water pump + base loads  14.1A shunt 1 vs 17.8 classic

water pump + toaster + base loads 45A shunt 1 vs 55.7A classic 

Gain problem? What pot do i need to turn?

Kurt

You will need a fairly small, adjustment screwdriver.

The left side towards the front is a hole gaining access to the trimpot labelled GBATT.
(see picture)

Turn very slightly counter-clockwise (I think) and watch the current come down.

Easy now... be careful !

Make sure the offset hasn't been affected (it shouldn't) by turning mode to off
and back on again to recheck the reading.  If it reads closer, great.

boB

[dgd]

The left side towards the front is a hole gaining access to the trimpot labelled GBATT.
(see picture)

boB

So does the trim pot labeled G-PV adjust the current input reading?

Dgd

[boB]

The left side towards the front is a hole gaining access to the trimpot labelled GBATT.
(see picture)

boB

So does the trim pot labeled G-PV adjust the current input reading?

Dgd

Yes, but it is gain, not offset.  For the input, the error is more of an offset problem which would be
a software fix.

These adjustments are usually cal'd as good as can be at the factory and shouldn't normally be
tweaked.  It appeared as though offgridQLD  has a gain anomaly that should be fixable.

I would not advocate adjusting these unless you really know what you're doing and have
a good reference.   I'm not sure how good those meters are that offgridQLD has, but if
he absolutely trusts them, then, so be it.

boB