So I seem to have run into some sort of classic bug today.
I'm not running latest firmware yet. This incident gives me more incentive to upgrade.
Lately I've been running some opportunity loads and I also had the absorb time set to 4 hours which is pretty long. The combination meant that for the past week I haven't quite made it to float, and so the auto EQ kicked in yesterday. ( This behavior is due to known issue where auto EQ daily counter gets reset if float is reached -- supposed to be fixed in latest firmware ) Yesterday it did not quite finish EQ and so it tries again today.
Right about when it reached the EQ voltage, the amps dropped from approx 50 down to about 2.
Fortunately I went out there to turn off EQ and adjust the timings and so I discovered the issue within about 2 hours. I first checked for any popped breakers on the input side... nothing amiss.
So then I tried to disable the EQ. I tried stopping and starting it manually several times. No matter what I did, the status screen kept displaying the mode as "EQ MPPT". I tried turning off the PV input and the mode changed to "Resting" after about 2 minutes. Then I turned the PV back on, and guess what... mode returns to "EQ MPPT" and amperage stays between 1 and 3 amps. lame.
I was getting worried I might need to reset the thing and lose all my settings.
Finally hunting around I found "Force Bulk" under the tweaks menu. After turning that on, the amperage returned to normal, and all was well.
I'm attaching a graph from blackbox that clearly shows the event.
One other anomaly I noticed is that my solarvisor script that polls blackbox each minute for battery voltage was unable to retrieve valid voltage info during the event. Yet blackbox's graph code was clearly getting it via modbus somehow. I haven't looked into that any deeper yet.
Why not update the firmware ?
Larry
Your graph does not show the battery voltage during that event so hard to tell what is going on exactly .
Larry
Quote from: ClassicCrazy on July 04, 2016, 11:10:26 PM
Why not update the firmware ?
Larry
I'm planning to. mostly just curious if anyone else has encountered this. It is distinct/separate from the auto-eq daily counter issue.
I wonder if it:
a) is just a one-time freak thing.
b) occurs every time auto-EQ try 2 is reached.
c) occurred due to some sort of overload.
d) is actually fixed by the latest firmware or not.
Quote from: ClassicCrazy on July 04, 2016, 11:11:40 PM
Your graph does not show the battery voltage during that event so hard to tell what is going on exactly .
Larry
Battery voltage just dropped down to normal levels when there is little or no charging and moderate load, ie 52v .. 51.6v. as would be expected. In EQ mode, the amps should have stayed much higher to keep the voltage up/constant.
Edit: oh and actually the graph does show "output voltage" which in my experience is always the same as battery voltage. It is the light green line.
Hi danda,
Just looked at your Graph ...
Is there any Scale Factor on that graph for battery voltage, or other items, or, are the legends to scale?
Please tell us more about your system. PV STC String voltage, battery voltage and type, etc.
Thanks, Vic
@vic everything to scale. nothing funny in the graph.
Normal peak output on a sunny day is 3-3.5 kw. About 50-60 amps at approx 58v.
During the event voltage dropped to around 51.5 and amperage to between 1 and 3 amps. I confirmed this on the classic itself, which was not even operating the fan.
Hi danda,
Fine, thanks for that info.
However, please;
What is the String Vmp, or, how are your PV strings arranged (PVs in series and how many strings), and what is the manufacturer and model number for the PVs?
Assume that you are running Flooded Lead Acid batteries, correct?
Thanks, Vic
Quote from: Vic on July 05, 2016, 05:39:37 PM
Hi danda,
Please tell us more about your system. PV STC String voltage, battery voltage and type, etc.
System uses mixed panels but I matched them pretty well to have similar voltages. Open circuit voltage is around 86.
Battery voltage is 48. forklift battery. 750 amp hour at 6 hour rate.
OK, thanks again danda,
But, what IS the String Vmp, based on the STC Vmp of each PV in one series string? We could guess, but especially with a mix of PVs, could you give the manufacturer and model number of each PV?
From the Graph, it looks like you ran out of Vin when doing that EQ.
TIA, Vic
Also note that your BB curves seem to have no data between about 1245 and 1300. (Its not ideal but BB presently just skips missing data with a straight line.) Wonder if the controller just crashed, a freak surge or something, then it WDT reset after a period? Or did you power it down for a bit?
... It looks like the battery V was at about 59 V, and the PVin was about 64 V. This is NOT enough headroom for MPPT CCs to find a good Vmp and operate well ... IMO, the Classic might well have given up on doing the EQ, as the battery V rose too close to Vin.
How long after the Classis's output went to a few amps, did you ReBulk?
Vic
also: 2 arrays on separate breakers.
array 1: 6 strings. mix of 200 watt and 75 watt panels.
array 2: 6 strings. mix of 175 watt and 65 watt panels.
each individual string uses identical panels and open circuit voltage is at or near 86.
Thank,
BUT, what is the String Vmp? The CC does its work, and makes power from Vmp, NOT Voc.
Vmp Vic
And, danda,
A FW Update would not hurt, tracking has gotten better with later revs, believe.
Also, you might try Legacy P&O Mode to see if that helps ... Vic
true that. I hadn't noticed the significance of that straight line before. I was away at the time, so I didn't touch it until a couple hours later, near where the graph returns to normal.
Quote from: zoneblue on July 05, 2016, 07:15:19 PM
Also note that your BB curves seem to have no data between about 1245 and 1300. (Its not ideal but BB presently just skips missing data with a straight line.) Wonder if the controller just crashed, a freak surge or something, then it WDT reset after a period? Or did you power it down for a bit?
ok, I just went out and checked. The lowest string Vmp is 66 and the highest is 71.4.
Quote from: Vic on July 05, 2016, 07:20:09 PM
Thank,
BUT, what is the String Vmp? The CC does its work, and makes power from Vmp, NOT Voc.
Vmp Vic
FW update is on my todo list. Already using P&O mode, thanks.
Quote from: Vic on July 05, 2016, 07:21:49 PM
And, danda,
A FW Update would not hurt, tracking has gotten better with later revs, believe.
Also, you might try Legacy P&O Mode to see if that helps ... Vic
Quote from: Vic on July 05, 2016, 07:08:24 PM
Assume that you are running Flooded Lead Acid batteries, correct?
correct. forklift battery.
Thanks danda,
Am certain that if those are STC String Vmps, that you do NOT have high enough Vin to run an MPPT CC very efficiently.
And, am no expert on the BB, and its data graphs, But, seems to me, that you can see exactly what is happening -- when the battery V got up to about 59, or a smidge higher, the Vmp was down to about 62.5 V.
There IS a bit of a Tracking issue with Classics, sometimes, where the Vin gets dragged down to near Vbat, and this could be part of the issue. BUT, the Voc of your string (well very lightly-load, almost Voc) was about 74 V with a few amps from the array. MPPT CCs want an STC String Vmp of about 85 V or so to be able to work efficiently on warm/hot days, especially with FLAs, which DO require EQing.
Have you considered reconfiguring your PV array stringing? Just to try to keep everything and body happy?
FWIW, Vic
I suppose that is in theory possible but in the past I've EQ'd it at 62v manually without problems and since then I lowered EQ voltage down to 60.
One thing I've noticed is that the PVin always seems to follow the output voltage pretty closely.
In fact, when I first got the classic, I was hearing an annoying chirping a lot and the PVin was often very close to the vOut. Somewhere on this forum I found advice to raise the minimum voltage distance setting ( I forget the exact setting name ). I raised it to about 5v, and the chirping went away and I see what appears to be a larger mppt amperage boost.
Quote from: Vic on July 05, 2016, 07:17:54 PM
... It looks like the battery V was at about 59 V, and the PVin was about 64 V. This is NOT enough headroom for MPPT CCs to find a good Vmp and operate well ... IMO, the Classic might well have given up on doing the EQ, as the battery V rose too close to Vin.
Hi Vic.
That's new info for me, thanks. I thought mppt could pretty much adjust voltage as necessary. I guess it always has to be from significant higher to lower though, eh?
I'm not crazy about reconfiguring arrays due to: 1) physical constraints, 2) wiring hassles, and 3) I want to be able to pop in my old c40 charge controller in an emergency, so arrays should stay not too far from nominal voltage.
But at least now I'm aware of this constraint and can plan/test accordingly.
Further, if this is indeed the cause of the problem, then it would seem to me that the classic should notice an undervoltage situation, protect itself, and display some type of useful error message, rather than freaking out for approx 15 minutes and then putting out a few amps while supposedly in EQ mode. ie, there's still a logic error to be fixed.
Quote from: Vic on July 05, 2016, 07:48:57 PM
Thanks danda,
Am certain that if those are STC String Vmps, that you do NOT have high enough Vin to run an MPPT CC very efficiently.
And, am no expert on the BB, and its data graphs, But, seems to me, that you can see exactly what is happening -- when the battery V got up to about 59, or a smidge higher, the Vmp was down to about 62.5 V.
There IS a bit of a Tracking issue with Classics, sometimes, where the Vin gets dragged down to near Vbat, and this could be part of the issue. BUT, the Voc of your string (well very lightly-load, almost Voc) was about 74 V with a few amps from the array. MPPT CCs want an STC String Vmp of about 85 V or so to be able to work efficiently on warm/hot days, especially with FLAs, which DO require EQing.
Have you considered reconfiguring your PV array stringing? Just to try to keep everything and body happy?
FWIW, Vic
Hi danda,
Fine on all. zoneblue wondered if the Classic had "crashed" IIRC. You Monitoring Whizzes are far ahead of me ... so dunno about that.
BTW danda, what IS the FW Version in the Classic?
Understand about not wanting to re-wire your present PVs, but perhaps you might want to consider doing it anyway, and perhaps do a hack back to lower Vmp, if you needed to revert to a PWM in an emergency.
Here, on one system, during the design process, considered trying to run an early MPPT CC (the OB MX-60) with strings of two 35.4 Vmp PVs in series, for a String Vmp of about 71 volts ... felt that this was just too low, and went with three PVs per String for a String Vmp of 106 V. This is pushing the high end, for most climates, but the Classics seem happy.
Perhaps others will chime in, but just my opinion that you need about 85 - 90-ish String STC Vmp.
FWIW, Vic
The ever observant Vic is onto that Vmp issue. Vmp of 66V is cutting it too fine IMO. Remember that in hot weather the Vmp drops. When your PV amps are high the array home run cable drop is at max. Near the end of bulk, and the beginning of absorb when the battery voltage and current demands are highest, this is where i would expect to see issues there. So the fact that your "accidental" EQ occured bang in the middle of the day, might be a clue.
My two old c40 workhorses never had a problem with the voltage. oh, and auto-EQ worked great from day 1. :-D
This seems to be a downside to MPPT that I had not considered (for my system). That said, I'm not yet fully convinced it was caused by the voltage given that I've manually EQ'd in warm weather before with the classic. Even the previous day, which was auto-EQ try 1. Next time I do a manual EQ, I'll pay closer attention.
For the sake of moving forward, let's say inadequate vmp was the underlying cause. It still seems to me that this is a condition the classic should detect, protect against, and warn the user of. And the observed behavior seems a serious bug.
I'm thankful for the diagnosis which definitely helps me plan and work around. But I would also hope that midnite fix this erratic behavior.
Hi danda,
SO, what is the Firmware version running on your Classic?
Thanks, Vic
Quote from: danda on July 06, 2016, 11:28:18 PM
My two old c40 workhorses never had a problem with the voltage. oh, and auto-EQ worked great from day 1. :-D
PWM works best when the Vmp is around 17V per 12V of battery. That allows a few volts off for heat, cable and controller loss. In this situation you cant just swap in a MPPT. And 60 cell panels dont work well per 24V using any controller. There just isnt enough leeway, and the controller will ride teh IV curve leftwards and downwards where it settles on a reduced output. There is one guy who uses 60 cell panels with LFP and PWM, (LFP doesnt need quite as high voltage) but still he trades off a little reduced power at near full charge, to get a really high level of efficiency during the larger part of bulk, when you most need it. Obviously this needs careful tailoring of strings to achieve, you lose the flexibility of mppt. But in terms of total throughput effciency you cant beat PWM when you can manage to match the module Vmp to battery voltage.
With your strings varying in Vmp this also makes the controller choose a compromise of sorts, so that might be a factor here too.
Peoples experience with mppt varys. While the rule of thumb is to go one battery voltage higher for Vmp, the odd person has reported acceptable results using legacy mode, and o thers say that the Morningstar MPPT controllers can run closer to Vmp. I have no experience with either. Both Outback and Morningstar's have excellent power efficiency curves, which are worth a study on the matter.
As to the cause of your glitch im not real sure.