Since two days ago, my Midnite Classic 150 has been always at "float", no matter what the battery voltage was at. The battery voltage on the LCD display was always the same as what the charge volt was set at (14.1v) although the battery was actually 13.3v. When I set to run on Bulk, within seconds, it would shift out of Absorb into float (because it saw that battery voltage had reached the voltage set as float).
I am not sure which chip reads the battery voltage, whether it is on the communication board or on the power board. I am grateful if someone knows/shares the knowledge. I might have to replace the bad board.
(The positive terminal to the battery was overheated although I was using 2ga wire. That might be the cause). Here are photos showing how it is looking like now. The communication board appears intact.
Hi CountryFit,
It looks like the Positive battery connection on the Classic had a loose/poor connection. This causes some resistance. At high current (perhaps some time ago) any appreciable resistance will cause heating at that connection point. This heating can damage the terminals, causing additional resistance.
The resistance at the battery positive terminal, with current flow, causes a voltage drop between the Classic and the battery. This voltage drop could cause the Classic to incorrectly measure the actual battery voltage.
The power terminals of the Classic blue connector block are NOT designed to accept wire larger than #4 AWG coarse-stranded cable.
Perhaps you can carefully clean and burnish the burned connector terminal/s, and replace the cable with #4 AWG THHN type building wire.
Torque all screw type power terminals correctly, AND re-torque them in about 24 hours.
Do NOT use fine-stranded cable with this type of screw terminal.
This is my read on things, FWIW, Vic
Thanks Vic!
I discovered the overheat on the positive terminal 2 months ago. I slightly enlarged the size and inserted a 2ga wire. For that matter I also called Midnight suggesting making those accepting 2ga wires. But I didn't think the tech support would ever pass my request to anyone/managers (he said "we have been doing this since 1960s..." of course he wouldn't take an external engineer's opinion).
My charge current had been always in about 90a at 12v nominal in 3 seasons a year. Even with 2ga wire, it was still super hot. I even tinned the wire into solid before plugged in and tightened it well, now I saw the wire pvc shield was charred badly. I'll clean it well tomorrow and see if that helps.
Big thanks again!
Steve
The Classic cannot be redesigned to accept 2AWG. There just isn't room. I am surprised your large wire is running hot though. The terminals accept 4AWG. Even at 100 amps, the 4AWG wire should not be running hot.
I have always found that tinning the strands is a bad idea. Solder will cold flow and thus loosen up over time.
Do you have 2AWG running to a breaker close to the Classic? That is the norm and then a 4AWG going to the Classic which is normally only a couple feet.
The battery voltage is read by the processor on the control board. If there is a bad connection at the terminal block, then that high resistance will show up as a higher voltage at the controller and as you saw, a lower voltage at the battery terminals. The processor should see the voltage at the terminal block on the Classic power board though. There is a connection through the 12 pin connectors to feed battery voltage up to the control board to power it and also measure that voltage.
A long time ago I think we saw one Classic with an unsoldered connection from the terminal block. If that happened then that could also cause a voltage drop like this. You could wiggle the connector or the terminal block and see if there is any difference in readings I suppose.
So, with 7 amps or so of current like I see on the MNGP display, there must be some heat dissipated. Say, 14.1V - 13.3V = 0.8 volts and that multiplied by 7 amps is about 5 watts or so and should get pretty warm.
If you can repeat this situation, can you take your volt-meter and measure a voltage drop between the battery plus terminal and that wire ?
The battery negative and PV negatives are tied directly together on the power board and the positive PV input to positive battery output is where all the change in voltage happens. But voltages are measured from minus to plus on the circuit board where the terminal blocks are soldered to.
Even though we have been doing this a long long time though doesn't mean there are still strange and new problems that crop up ! Learn something new every day !
boB
Quote from: Robin on June 25, 2018, 02:39:14 AM
The Classic cannot be redesigned to accept 2AWG. There just isn't room. I am surprised your large wire is running hot though. The terminals accept 4AWG. Even at 100 amps, the 4AWG wire should not be running hot.
I have always found that tinning the strands is a bad idea. Solder will cold flow and thus loosen up over time.
Do you have 2AWG running to a breaker close to the Classic? That is the norm and then a 4AWG going to the Classic which is normally only a couple feet.
This is all good but it sounds like there is a bad connection somewhere. 4 AWG should have very little drop at 7 amps.
And as always, thank you Vic for you valuable input !
boB
Not much to add to what Robin and boB said, The Classic was in float because the positive battery side likely has a bad connection, I would put a call in to tech support today and Kyle or some one can help you get fixed up
Thank you everyone!!
I am posting another photo showing how bad the positive 2AWG was. The right hand end was to the terminal on the board. The left hand end was to the breaker. Obviously, it's been extremely hot. According to your experience, this shouldn't have happened.
Quote from: Robin on June 25, 2018, 02:39:14 AM
Do you have 2AWG running to a breaker close to the Classic? That is the norm and then a 4AWG going to the Classic which is normally only a couple feet.
Yes I use two breakers - one is at the upstream of the controller about 7" away, another is at about 7" downstream.
Quote from: boB on June 25, 2018, 02:40:03 AM
The battery voltage is read by the processor on the control board.
Did you mean "control board" the power board or communication board?
Quote
If you can repeat this situation, can you take your volt-meter and measure a voltage drop between the battery plus terminal and that wire ?
I'll try to replicate the scenario and measure it when sun is up. wiggling it by fingers now, the terminal block appears pretty firm.
Quote from: FNG on June 25, 2018, 07:39:12 AM
Not much to add to what Robin and boB said, The Classic was in float because the positive battery side likely has a bad connection, I would put a call in to tech support today and Kyle or some one can help you get fixed up
Gonna call them once they are open for business.
That really looks like the loose connection meltdown I had in my E-Panel.....ALL due to a loose connection when the classic was putting out ~ 50 Amps.
Did you re-torque the connections after 24 ~ hrs??
Quote from: Westbranch on June 25, 2018, 12:34:04 PM
That really looks like the loose connection meltdown I had in my E-Panel.....ALL due to a loose connection when the classic was putting out ~ 50 Amps.
Did you re-torque the connections after 24 ~ hrs??
I was certainly aware of the importance of the tightness and did tighten it a few times since 2 months ago.
Maybe my current was too high - about 90A during the peak hours everyday when it was working.
Quote from: CountryFit on June 25, 2018, 02:08:10 AM
...
I discovered the overheat on the positive terminal 2 months ago. I slightly enlarged the size and inserted a 2ga wire ...
Steve
Hi Steve,
It is quite possible that there was insufficient Torque on the original #4 AWG cable, and that heating damaged the positive bat terminal of the Classic, causing further heating.
I do not know if the Classic PV and battery terminals are Tin-plated aluminum, or copper. But, reaming out the battery positive terminal, would have removed any plating. If the base material is Al, that could well represent a very poor connection.
As Robin noted, usually, Tinning copper cable ends that terminate in screw terminals is a bad idea. The screw terminals are designed to compress the cable strands, which would increase the contact area and reduce resistance. The solder is not very compressible, and could create more of a point-contact.
Please avoid tinning cable ends of screw terminal connections, as well as for crimp terminals.
Just my opinions, Good Luck. BTW, as you can see, MidNite Engineering and Tech folks to listen, AND give feedback. Vic
Quote from: Vic on June 25, 2018, 02:21:13 PM
I do not know if the Classic PV and battery terminals are Tin-plated aluminum, or copper. But, reaming out the battery positive terminal, would have removed any plating. If the base material is Al, that could well represent a very poor connection.
The terminals appeared to be aluminum. I saw the flakes when I reamed it. After this time, I'll keep it as how it comes from the manufacturer.
Quote
as you can see, MidNite Engineering and Tech folks to listen, AND give feedback.
I really like this board! And very grateful for everyone's big helps!!
Steve
One thing that comes to mind, the box lug is aluminum and is screwed to a tin plated copper buss bar from the bottom side, Drilling that box lug out would reduce the screw length and amount of threads that screw has left to hold it onto the copper buss bar. It could also potentially loosen that screw connection, the resistance issue may have been between the box lug and the copper buss bar inside the classic.
Quote from: FNG on June 25, 2018, 04:47:48 PM
One thing that comes to mind, the box lug is aluminum and is screwed to a tin plated copper buss bar from the bottom side, Drilling that box lug out would reduce the screw length and amount of threads that screw has left to hold it onto the copper buss bar. It could also potentially loosen that screw connection, the resistance issue may have been between the box lug and the copper buss bar inside the classic.
Good point! I actually had to grind off the tip of the screw so to have enough threads to held the wire. I did that two months ago.
Quote from: CountryFit on June 25, 2018, 10:14:04 AM
Quote from: boB on June 25, 2018, 02:40:03 AM
The battery voltage is read by the processor on the control board.
Did you mean "control board" the power board or communication board?
Quote
If you can repeat this situation, can you take your volt-meter and measure a voltage drop between the battery plus terminal and that wire ?
I'll try to replicate the scenario and measure it when sun is up. wiggling it by fingers now, the terminal block appears pretty firm.
The one processor is on the control board. Top board.
The Classic terminal block is not designed to accept any 2 gauge wire. Only 4 gauge and even then, only solid or
small number of strands at 4 AWG. Maybe the problem had something to do with putting 2 AWG into the Classic
TB ?
And before going to Float, the Classic will usually go to Absorb for a while. Do you have the Ending amps set to
other than zero in the advanced menu maybe ? That would also cause the Absorb to go to Float prematurely if
the battery voltage rises at the Classic.
boB
Quote from: boB on June 25, 2018, 05:26:58 PM
And before going to Float, the Classic will usually go to Absorb for a while. Do you have the Ending amps set to
other than zero in the advanced menu maybe ?
The ending amps was set to 15A.
Hi gents, I would like to update to you all that my controller is on the way to Midnite. This should take care of the issue of terminal block. And we can close this thread.
I'm really indebted to you on this. Wish everyone the best!
One thing I thought is if reaming out that hole with a drill could snag the terminal and jerk it maybe breaking solder joint ? Anyway I am sure Midnite will find the problem and you will be charging again soon.
Let us know what the problem was when you get it back.
Larry
I've always liked the gripper terminals, where the set screw presses on a metal plate, which mashes into the wire. Seems solid, the screw does not drill through the stranded cable,
Another update -
I got the unit back and installed. It works great and the heat at terminal block appears subdued - warm not hot. I switched to 4 gauge welding cables.
It proves again that Midnite is a great company!
Thank you all!
Quote from: CountryFit on July 08, 2018, 02:08:53 AM
The Classic terminal block is not designed to accept any 2 gauge wire. Only 4 gauge and even then, only solid or
small number of strands at 4 AWG. Maybe the problem had something to do with putting 2 AWG into the Classic
TB ?
Like boB said #4awg with small # of strands, if your welding cable is fine strands and more than about 19 of them, then another failure may be headed your way. The Classic Terminal Block was not designed for the finer stranded welding cables...
It uses industray standard THHN or THWN type "Building Wire" available from Home Depot or Lowes or an Electrical Supply house and is sold by the foot. Yes it is stiff, yes it is a pain to get into the Classic terminals, yes it is a pain to bend & route in the Classic wiring box. Using welding cable and admitting it may void your warranty if the terminal block burns & melts. That means a paid repair, paid shipping, can be a real pain. Just FYI...