I recently switched from a 12 volt to a 48 volt system and I've noticed several times that the controller is reading about 100 watts lower than what it's actually putting out. Yesterday it was absorbing at 40 watts but 130 watts were going into the battery according to the Trimetric and the Whiz Bang Jr. Sometimes it's very accurate and other times it seems to be reading low by about 100 watts?
Any idea what would be causing this? I never noticed this in 2+ years using the same Classic 150 on a 12 volt system.
Firmware is not the latest revision but the one prior to that.
Wxboy,
I often have switch my Classic from a 12 volt bank to a 24 volt bank and I always do a factory restore when doing this as it will erase data from old system and give the Classic a "clean data sheet" to start with.
This will erase all set points and all entered data so note your setup,
Procedure is simple, assuming you have a Classic with MNGP display panel,
turn off power and P.V. Input breaker, wait 20 seconds, press and hold left and right arrow keys , turn on power breaker while continuing to hold left -right arrow keys until greeting screen that asks you to confirm battery volts. Release arrow keys, renter data , voltage set points mode, etc. Turn on p.v. Input. Go to mode screen, turn on mode ( this procedure turns mode off just in case voltage is wrong)
The Classic will still have some memory of the old system when you do a system change and this procedure deals with that
This is also referred to as a VMM (Vulcan Mind Meld)
If you have a Classic Lite, the procedure is quite different, if you have the lite post again and someone will walk you through the VMM for the lite.
td
td, I'm 99% sure I did a VMM a couple of weeks ago when I made the change but I've changed a lot of things in my system so I'm not 100% certain. I'll try it again tonight to see if it helps.
if you have the Local App working do a check of the voltages etc, before you VMM.
And when you do the VMM shut of the PV as well as the battery power...
hth
Very good observation! I have also reported this, here on a 24v system its more like 50W, and i have actually observed the transition at times, eg:
http://midniteforum.com/index.php?topic=1670.msg14796#msg14796
http://midniteforum.com/index.php?topic=1724.msg15535#msg15535
http://midniteforum.com/index.php?topic=1928.msg17776#msg17776
Most of the time the Iout anomoly gets lost in the noise, but sometimes its very clear.
My view its that it's amps out thats at issue, which flows on to watts out.
Suspect this bug is there but that noone noticed it. Hence have long awaited another report of so i know im not going mad!
Quote from: Wxboy on June 27, 2014, 02:59:32 PM
I recently switched from a 12 volt to a 48 volt system and I've noticed several times that the controller is reading about 100 watts lower than what it's actually putting out. Yesterday it was absorbing at 40 watts but 130 watts were going into the battery according to the Trimetric and the Whiz Bang Jr. Sometimes it's very accurate and other times it seems to be reading low by about 100 watts?
I would think it is a battery voltage calibration issue.
Remember that the Classic will draw some current, too, and the Whizbang and Trimetric will read the same
current but the Classic will be zeroing out its tare draw which ~should~ be taken care of by the PV actually
powering the Classic when it is running (not Resting that is)
You can adjust the battery voltage reading by Offset in Tweaks or by the trim-pot on the top control PCB
in the Classic (gain adjustment)
Also the Classic will draw more tare current at lower battery voltage but it is a lower voltage so the power
draw in watts should be approximately the same as at higher battery voltages.
boB
boB, I don't think it's a calibration issue because most of the time the readings are correct but I have noticed at least 5 times since the change to 48 volts(2 weeks ago) that it can be off by close to 100 watts at times. I am all too familiar with the tare draw of my inverter, Classic, and everything else in my system because I check and double check readings quite frequently.
The other day when it was absorbing at 40 watts and I knew it wasn't correct I shut off the PV breaker, waited a few seconds, and turned it back on and suddenly the Classic was absorbing at 140 watts give or take. Again I never saw this behavior on 12 volts. I would see some drift in the accuracy of the meter as the day wore on but not 100 watts.
I'll see if it happens again today while I'm home.
Since the Watts you see on the main status screen is output voltage times output current in amps, one of
those numbers would have to be wrong.
At 12V nominal, the current necessary for 100 watts would have to be off by quite a bit, or somewhere around 6 to 8 amps.
So, I'm not sure what the deal is here. Let us know if you find out more.
Im with wxboy, its the sudden change-i-ness of it that gets me wondering. You can see this from my trace above. There was a uncharacteristic 6second pause, then it came back reading 50 odd watts low. Vout reading remains the same, vpv reading the same, WbJr reading the same, the only thing that changed, and changed suddenly was Iout.
I didn't notice anything on Saturday but at the end of the day on Sunday it was in absorb at zero watts showing on the Classic and 73 watts going to the battery bank according to the Trimetric. The inverter draws about 7 watts when it's off so the Classic was putting out about 80 watts(1.3-1.4 amps @ 59V). A few minutes later the panels were shaded so it dropped out of absorb to about 50 watts and the Classic relay clicked off because it thought it was putting out zero power and it wasn't maintaining the absorb voltage. When the relay clicked back on it was accurate again. I remember reading that the Classic resets it's shunt readings when the relay clicks off and on so I was not surprised that it was accurate again.
I did not notice if the accuracy drifted slowly during the day or if it was a sudden shift like zoneblue shows in his graph. I would probably never notice this without a graph and consistent loads.
Other notes:
I have no other power sources besides the Classic on this system.
I updated the firmware to the latest version so everything noted here is on the latest firmware.
Quote from: Wxboy on June 30, 2014, 09:27:43 AM
Other notes:
I have no other power sources besides the Classic on this system.
That is what I was going to ask you but you just answered it.
You can look at the secret screen (the one from main status that gives you the RFR Reason For Resting numbers) and
look at the number to the right of the + sign when the Classic is Resting. This number should be between around 35 and 45.
That is the output of the Ibat A/D converter and is noted whenever the Classic comes out of Resting for its reference.
Every ones digit is 0.1 amps and so if it was 40 means it is offset by 4.0 amps. It doesn't mean the Classic is putting
out or taking 4.0 amps, just that this would mean 0.0 amps from starting out Resting.
Anyhow, you might look at this number and see if it jumps around more than a couple of counts when just sitting
there in Resting.