classic 150 resting

[jenkinswt]

Hello thanks in advance to any help! I have a classic 150 that has been working great up until a few days ago. We had great sun, but was only getting approximately 500 watts out of 1500 watts solar. Then it trickled down to barely 30 watts and then went to resting while we still had decent sunshine. Tried resetting, checking temps, etc. But nothing would kick it back on. Next few days were cloudy but still got some power in. Today it was sunny again and it kicked out after 3.7 kWh. Oddly enough it had 3.8 kWh the last time it kicked out.

It's approximately 85 deg. Fahrenheit where controller and batteries are located. I've had this hooked up since the beginning of this year. Don't know if it's temp related or what. Thought I'd run it by the experts on here!

[Vic]

Hi jenkinswt,

Just to get things rolling,  how about some more details on your system;

1.  Battery voltage?

2.  What is the manufacturer,  model number,  string configuration (number of PVs/string, & number of strings?

3.  When the Classic output seems low,  with good sun,  what is the PV input voltage on the Main Status screen?

4.  What is the Reason For Resting (RFR)#?

Here is a link on the RFR for Classics:
http://midnitesolar.com/Forum/index.php?topic=2034.0

Also,  what is the Classic Firmware version that this Classic is running?

Thanks,   Vic

[jenkinswt]

Sorry for leaving a lot of information out.
Battery voltage - 48
Sharp 250 watt solar panels, don't have the specs handy but basically 24 volt panels ( I know they are higher but you get the idea) I will try to get the panel information tomorrow, as I have 4 more that I haven't installed and can look at them. They are wired in 3 strings of 2. Total of 6 panels currently installed. I was using these same panels last year when I was 24 volt but upgraded things at the beginning of the year.

I can't remember exact input voltage when it wasn't charging but it was in mid 60's while batteries were approx. 50 volts. It showed 0 amps coming in from pv when it had this voltage.

The RFR code was 5, now its 111 for rebooting.

If I am looking in the right location it says Firmware:     
- Classic Rev: 1923

It started working again this evening and it came back on and was putting out almost 500 watts again, then went to resting for awhile and back to about 100 watts. Now its resting again. It seems reasonable tonight though because it is actually quite cloudy. 61 volts in currently, battery is 49.9

[Vic]

Hi jenkinswt,

Thanks for the added info.  Almost all of us start without a signature line of helpful info.

OK,  if the Sharp PVs are like these   ...:
'Sharp 250: ND-250QCS,    250 Watt,  8.4 A @ 29.8 Vmp';  in strings of two,  will often be a bit too low input V for most efficient operation of an MPPT Charge Controller (CC).

So,  if you have the Sharp model number for your PVs,  this would help determine the specs,  and probable performance  of your system.

The above Sharp modules are 60 cells,  and are considered to be about equal to a "20 V" module.   When the PVs are warm or hot,  the Vmp diminishes,  and the  CC is often left with too low an input voltage to operate efficiently,  often at solar peak, around midday.

This may not be the issue  on your system,  if your PVs are 72 cell units ("real" 24 V modules).

Will wait for more info.   Thanks,   Vic

Thanks,  Vic

[jenkinswt]

Okay this might be my issue. I have Sharp ND-250 HAT Panels.
VMPP is 29.98 so must be 60 cell panels.
ISC - 9.03 A
VOC - 37.35 V
IMPP - 8.34

I can understand this diminishing in the heat but to completely halt power I don't understand. For instance when batteries are dropping to 49 or lower and it shows 67 V incoming....I would think it would have a few watts there to keep from resting.

Also we had these panels up all summer last year with a cheap 175.00 controller at 24 volt and nothing similar happened. We had great power. I would think strings of 1 at 24 volt charging 24 volt bank should be identical to strings of 2 at 48 volt charging 48 volt bank would be identical.

I ran all these panels in the midnite sizing calculator before deciding on the classic 150 as it seemed to be a good fit with some room to expand later on. I am considering rewiring to 3 panels per string when I add more panels but I only have 10 panels altogether. Maybe I could find 2 more to match up.

I stayed up late last night and wired in a temporary 120 volt line from a generator I borrowed to my magnum 4448pae inverter. Set it on 10 amps and got fairly charged. This was the first time I have used this feature of the inverter but it went pretty smooth. Got up early and did the same thing then let the panels take over. So far I have put 2.8 kwh from the panels today. Waiting around to see if it quits around 5 pm like the other 2 hot days we had.

[jenkinswt]

Crazy, I was on computer and looked down and local app and seen it was resting. Again we have good sun. 63 v input battery is at 51.8 and dropping now as we have loads on it. I had been trying to do an equalize this time but I believe that's unrelated as I wasn't the last two times. This time I looked at the rfr right away and it was 104:

ReasonForResting = 104  Watchdog WDT reset (only at boot until first RFR)

Any ideas? Its like clockwork for the time of day it has quit every time.

[Vic]

Hi jenkinswt,

Thanks for the info on your system,  and the RFR #.

First,  when the Classic is Resting,  there should be no load on the PVs,  so they should be at Voc for the temperature of the PV cells (yes,  your PVs are 30 cells).

If there are no DC loads directly on the PVs,  it must be HOT there.

Regarding "strings" of one PV on a 24 V system,  verses strings of two on a 48 V system,  one would think that there would be a direct 1:1 correlation.   But,   if the former $175  CC was PWM,  it is easier to see why there would be a difference in operation compared to an MPPT CC.

Most MPPT CCs need a reasonable amount of headroom to operate.

FOR NOW,  why not try changing the Mode to Legacy P&O,  and see what happens,  it may be about 5:30 PM  there,  so try this hopefully,  before Sunset.

Also,  what version of Firmware are you using?

More later,  Thanks  Vic

[dgd]

Battery voltage - 48
Sharp 250 watt solar panels, don't have the specs handy but basically 24 volt panels ( I know they are higher but you get the idea) I will try to get the panel information tomorrow, as I have 4 more that I haven't installed and can look at them. They are wired in 3 strings of 2. Total of 6 panels currently installed. I was using these same panels last year when I was 24 volt but upgraded things at the beginning of the year.

Rewire these panels into two strings of three then that will get the pv voltage high enough under load to let the Classic charge the battery bank.
Two nominal 20volt series connected pvs will struggle to charge a nominal 48v battery bank. Even though you see a no load 67V from the pvs that will drop significantly when taking amps from them to battery charge.
The Classic will detect this and go to Resting state.

dgd

[Vic]

AND,  have no experience with WDT Resets,  but there has been some discussion of them on this Forum.

Those who do data logging of various kinds  seem to see the WDT events on occasion.

Searched for '   WDT Reset   ',  and came up with some hits,  for example:
http://midnitesolar.com/Forum/index.php?topic=2267.msg21501#msg21501

Post from boB  in reply 49  makes some references to these reset,  WDT events.

A number of members here have much more knowledge than I about WDTs and Resting events,  several of whom appear to be on the Forum, just now.

FWIW.   Please let us know how things are going.   Thanks,   Vic

[jenkinswt]

It came back on by itself today after about 20 minutes resting. I didn't touch a thing but it appears it reset because it had 2.8 kwh for today and now its 0. Its 79 or 80 for a high today, were only in Iowa. Yesterday when it quit I tried legacy mode.

Firmware:     
- Classic Rev: 1923
- Network Rev: 1839

I emailed roy at tech support, waiting to hear from him also. The old controller was mppt but cheap. It worked great but not much for settings and was only 40 amp 12/24v.

[jenkinswt]

I will try to get these panels rewired soon to strings of 3. I was actually going to do that but decided on 2 so I could use all 10 panels. Its also about 20' in the air so I have to wait until I have some help juggling the panels around on the roof.

[Vic]

As dgd noted,  the sweet spot for most MPPT CCs,  including the Classic on 48 V systems is about 90-ish String Vmp.

Three 60 cell PVs  are just about perfect for a 48 V battery.  Enough headroom for the CC to have a lot or room for varying light and PV temperature conditions,  and almost no worries whatsoever about cold Voc and lack of production from going into HyperVoc.

Usually,  for systems that are on the low edge of Input voltage,  Legacy P&O works considerably better,  because it sweeps to find the best Power Point,  very slowly.

Vic

[jenkinswt]

For the 10th panel I have, what about wiring panel 9 and 10 parallel. For instance I take 2 panels and wire them parallel and now call them 1 500 watt panel. Would it be mismatched to take the 500 watt, 250 watt and and another 250 watt panel in series? Basically 3 on one string, 3 on another string, 4 on last string? I have a feeling this isn't common and that's why I didn't originally try it.

[Vic]

Sorry jenkinswt,

That string with the fourth PV will make no use of that 10th PV,  as the current from that string will be limited to the Vmp of the other two PVs that have no parallel PVs attached.

This is uncommon,  indeed,  because it makes no use of the added (fourth,  in your case)  PV.

When looking for additional PVs to make additional full strings,  for example,  look for PVs with a Vmp within +/-- 10%,  or better yet,  +/-- 5% for parallel strings.    If you are trying to add two in series with the one remainder 250 Sharp that you have,  the Imp should be +/-- 10% max (5% is better) of the Sharp 250.

FWIW,   Vic

[zoneblue]

Two 60 cell panels will NOT charge a 48V bank (esp ones with such low Vmps), and certainly not with a mppt controller. Itll go for a while in low bulk then just stop. You MUST lengthen teh string size as others have said. If the vmp had been 32 i would have said give legacy mode a go, but in your case, forget it.