Classic Over Voltage Set Point

[boB]

WX, are you running in SOLAR mode ?  If so, there is a new revision coming up that recalibrates the current sense extremely well.

This is done without any extra resting involved which is good.

boB

[Wxboy]

Yes, I am in Solar mode.  Looking forward to the update.  Thanks.

[Wxboy]

The Classic went over voltage again yesterday under the same conditions.  No load, Classic showing Zero watts out but clamp meter was showing about 1.4 amps out.  Voltage limit 60.0 volts.  Temp compensated target 59.8 volts.  I saw the voltage go as high as 61.2 on the Classic while I was watching it.  I was losing daylight as it was happening but every time there was enough light the voltage was going over the limit.  Once I saw it hit 61.2 volts I had to shut down the PV breaker to allow the Classic to reset itself.

Bob, I will email the video to Roy.  The video is dark but it should show what you need to see. 

I can't afford to risk losing my batteries to this situation so hopefully we can work something out . 

[new2PV]

Hmmm, reading all this is making me nervous to purchase a classic if it goes over its set point, as I will be running AGM's.  Its very simple to make a remote disconnect with a wifi  controller box from china ebay  for $60-100 and integrate it a contactor to shut your pv array off or classic etc.   8 channels of remote on  off could come in handy.

[boB]

As long as the Classic is reading close to the real battery voltage, this must have something to do with a setting or temperature comp or
something.  The software doesn't just over-voltage batteries without something making it do that...

Now, it ~could~ be a defective Classic I suppose.   Now that it's about 3 weeks after these posts, maybe the Classic
has been RMA'd and fixed and I haven't heard what was found yet.

Hopefully I hear what happened.

boB

[Wxboy]

boB, the Classic has not been RMA'd yet.  Roy wanted me to try updating to the latest firmware before giving up on the Classic.  I tried that yesterday and it bricked the unit.  I had to go back to the previous version to bring it back to life.  The Classic has demonstrated this charging behavior going back several versions though. 

I made a video and sent it to Roy showing that all settings are correct including the temperature compensated target and the voltage limit and that the Classic was outputting current when it was showing zero output.  That appears to be the issue.  The Classic doesn't stop outputting current because it thinks there is another charging source and it's just along for the ride.  It doesn't limit it's output because it shows Zero output. 

Apparently I'm the only one that's seen this problem or maybe other people haven't seen it because it takes a very specific set of circumstances for it to happen.  The Classic's output power accuracy/reading has to drift off so that it's outputting more than what it's displaying otherwise the problem won't occur.  And it has to drift more than the amount of power that the batteries require to absorb.  Since agm batteries absorb down to a low end amps that makes the issue more likely with agm's or with a very small battery bank. 

[boB]

I made a video and sent it to Roy showing that all settings are correct including the temperature compensated target and the voltage limit and that the Classic was outputting current when it was showing zero output.  That appears to be the issue.  The Classic doesn't stop outputting current because it thinks there is another charging source and it's just along for the ride.  It doesn't limit it's output because it shows Zero output. 

Apparently I'm the only one that's seen this problem or maybe other people haven't seen it because it takes a very specific set of circumstances for it to happen.

Or you are the only one to notice it...

When you see zero output current and the voltage is high, have you looked at the "secret" screen from main status ?
i.e.  Hold down the left-arrow key and then tap the ENTER key.   Look at the two middle (ish) numbers to the right of
the + and the - signs.  These are the RAW battery output currents.  Near zero amps, they should show somewhere
around 40 or so.  I am wondering if the current sense has maybe drifted since last turning on from Resting.

What mode are you in ?  SOLAR ?   Either way, during this time when you see high voltage and zero amps,
have you tried turning the MODE to OFF and back on again ?  Don't need to turn the power off.

New firmware coming up makes the current input and output much better in SOLAR and U-Set modes.
Also networking.

boB

[mike90045]

........

New firmware coming up makes the current input and output much better in SOLAR and U-Set modes.
Also networking.  boB

Does that mean it will transform my 20a input and 35a out to 25a in and 42a out ?   That would be MUCH better 
or does it mean it will report more accurately ?

[Wxboy]

boB, that is exactly what's happening, the current sense drifts during the day, and on many days by the afternoon the Classic is outputting more than it reports.  I haven't changed the mode to off and back again but I've shut the input breaker off to get it to rest and turned it back on and the problem is solved so it is definitely the current sense being off.  That being said I would think you could add something to the software to force the Classic into resting when it goes above the voltage limit as a fail safe. 

I am in solar mode. 

[boB]

boB, that is exactly what's happening, the current sense drifts during the day, and on many days by the afternoon the Classic is outputting more than it reports.  I haven't changed the mode to off and back again but I've shut the input breaker off to get it to rest and turned it back on and the problem is solved so it is definitely the current sense being off.  That being said I would think you could add something to the software to force the Classic into resting when it goes above the voltage limit as a fail safe. 

I am in solar mode.

OK, the current reporting will be more accurate but that shouldn't help high voltage regulation.  Current doesn't have anything much to do with voltage regulation (I don't think anyway).

Yes, the update fixes current sense drift which was pretty good to begin with...  WAS anyway.

Anyhow, now it's perfect.

boB

[laszlo]

I have for years used the current limit function on the Classic configured at 63amps and for what's it worth it never tripped my 63amp breakers in/out with over current. So whatever variance there may in current sensing during the day, it's probably in the tolerance range of the MN 63 amp breakers. Wx is trying to show a condition that is *really* hard to catch and reproduce, and I appreciate the fine empirical observations he made and the discussion that ensued.

[Wxboy]

Going back to the problem I had where my Classic was showing Zero watts out and was regularly pushing my AGM batteries over the max. voltage set point, was there ever a firmware version that corrected this?  I realize I may be the only one ever to experience the specific circumstances where this occurred but it did occur and it fried 2 out of 8 agm batteries forcing me to take my bank down to 4 12 volt batteries in series for 48 volts.  I haven't used my classic in over a year because the warranty refurbished model has a loud annoying fan(my original fan sounded much better) and I just don't trust the controller anymore.  I don't want to harp on this but I have to mention the fact that the event that pushed my batteries over the edge happened 3 months after I first reported the issue to Midnite.  Had an RMA been issued in less than 3 months my batteries never would have died.  Had to get that off my chest because I was originally a huge fan of Midnite products and I want to be a fan again. 

The reason I ask if there was a fix is because someone I know is looking at the new Morningstar Prostar 40amp controller and I really want to suggest a Kid or Classic but since this person also has agm batteries I don't want them to have the same problem I had. 

As a refresher this happened late in the day when the Classic was outputting more power than it was reporting.  Eventually the batteries would be in absorb taking only about 70 watts or less with no load.  The controller was outputting the 70 watts or less but showing zero on the screen.  This condition would send the batteries up and up and even the max. voltage set point would not stop it.  2 of my batteries started bubbling internally and then gassed and now their capacity is much lower than the other 6 batteries and they can't be used in the bank anymore.

[BobWhite]

2 of my batteries started bubbling internally and then gassed and now their capacity is much lower than the other 6 batteries and they can't be used in the bank anymore.
[/quote

IS THIS SOMETHING YOU COULD SEE OR HEARD? I USE AGMS AND LOST A FEW THIS WINTER AND LOOKING INTO THE CAUSE BET FEEL I LET THEM FREEZE BY LETTING THE SOC FALL WAY TO LOW BEFORE CHARGING BACK BUT NEVER HAVE HEARD BUBBLING FROM AN AGM, I DO KNOW I OVER VOLTED THEM. BUT STILL LOOKING INTO THE CAUSE OF DEATH.

WALT

[Westbranch]

Walt, the gassing comes from over charging, like an EQ on FLA batteries ....  the problem is AGMs are sealed, but they have a release valve, hence the term,VRLA, valve regulated lead acid, the valve protects you by releasing excess gas H and O2.. 

Hth..

[dgd]

As a refresher this happened late in the day when the Classic was outputting more power than it was reporting.  Eventually the batteries would be in absorb taking only about 70 watts or less with no load.  The controller was outputting the 70 watts or less but showing zero on the screen.  This condition would send the batteries up and up and even the max. voltage set point would not stop it.  2 of my batteries started bubbling internally and then gassed and now their capacity is much lower than the other 6 batteries and they can't be used in the bank anymore.

So how did you establish there was power , the 70watts, going to the bank?
Was that from the WBjr screen which shows actual battery current or maybe a DC clamp ammeter on the main battery cable?
The zero power just shows there was no power being provided by the Classic BUT if the WBjr shows amps flowing into the battery then something else is likely providing that power  OR  if the WBjr is connected wrong way around then the 70watts could be the base (tare or minimum) load.

dgd