Strange behaviour

[wrt]

Hi all. I have had a Standard Midnite Classic running well for at least 5 years now. Today I arrived home in the evening to find it has stopped charging sometime during the day at %80SOC but was sitting at 56.4V (absorb). Real Batt V was 52.5. I have reset the CC and it began charging at 100w (all the light left) normally then after 10 mins jumped back to absorb and shut off. I have not seen this before, I have attempted to reset again this time bulking again then going to float @53.5v and 100%SOC.

Real Batt V still at 52.5, I have never seen this before and don’t know where to start looking. Has anyone has this happen before?
Cheers

[ClassicCrazy]

Harder to analyze when you have lithium batteries because you have also have a BMS  involved since that is also controlling battery behavior.
First place to always start in electrical problems is to check every connection point at breakers - anywhere there is a terminal and make sure everything is tight.
Then you may want to check each lithium cell to see if they are all in balance .
My experience with Lithium is that the absorb cycle can be really short because the battery voltage doesn't have much rise and stays steady.
Not sure how you have your system set up to terminate absorb ( ending amps, time, etc )

Larry

[wrt]

Thanks Larry,
The BMS on mine shouldn’t affect the CC behaviour re balancing cells but regardless, all voltages should still be synchronised as they normally are, so if BMS shuts system down the CC should still report say 53v the same as battery.

Restarted before work this morning CC starts charge as normal for first hour of day then after putting in 2ah climbs the volts on the CC to 56.5 drops off the charge and that’s it. All while the actual battery volts sit at a steady 53v.

The normal regime for my CC is bulk to 56.5 absorption, sits at absorption for minimum time then drops to float @53.5. Now it’s no longer dropping to float, but more importantly no longer appears to be passing any of this on to the Battery, connections all appear to be good, battery is running CC when I isolate panels.

It’s like the CC has had a program glitch and just decided it doesn’t want to play nice with others around it :-) Edit additional info. Could perhaps be a SOC glitch as it’s changing charge modes according to this, so start charge @ 80% rapidly climb to 100% (within 1ah of output) drop to absorb, then a little while later to float, while Battery stays at 80% as not enough charge has been added to alter it

[boB]

I don't suppose you have a secondary charging source running ?

That might explain it if it is helping to bring the battery voltage close to the Classic's absorb set-point.

But if it isn't the case, we will have to think a bit harder !

Do you get full power from the Classic if the batteries are loaded hard so it has to work to bring the battery voltage up to absorb ?

[ClassicCrazy]

Thanks Larry,
The BMS on mine shouldn’t affect the CC behaviour re balancing cells but regardless, all voltages should still be synchronised as they normally are, so if BMS shuts system down the CC should still report say 53v the same as battery.

Restarted before work this morning CC starts charge as normal for first hour of day then after putting in 2ah climbs the volts on the CC to 56.5 drops off the charge and that’s it. All while the actual battery volts sit at a steady 53v.

The normal regime for my CC is bulk to 56.5 absorption, sits at absorption for minimum time then drops to float @53.5. Now it’s no longer dropping to float, but more importantly no longer appears to be passing any of this on to the Battery, connections all appear to be good, battery is running CC when I isolate panels.

It’s like the CC has had a program glitch and just decided it doesn’t want to play nice with others around it :-) Edit additional info. Could perhaps be a SOC glitch as it’s changing charge modes according to this, so start charge @ 80% rapidly climb to 100% (within 1ah of output) drop to absorb, then a little while later to float, while Battery stays at 80% as not enough charge has been added to alter it

The SOC of the Classic isn't used to control charging.
There is a setting in Classic so SOC goes to 100% when it goes to Float. It doesn't sound like yours is set up that way.
I am assuming you have the Whizbang installed ?
It is normal for lithium batteries charging in bulk to go to Absorb for brief time and then to Float.
Are you using ending amps or Absorb time to end the Absorb ?

Larry

[boB]

Thanks Larry,
The BMS on mine shouldn’t affect the CC behaviour re balancing cells but regardless, all voltages should still be synchronised as they normally are, so if BMS shuts system down the CC should still report say 53v the same as battery.

Restarted before work this morning CC starts charge as normal for first hour of day then after putting in 2ah climbs the volts on the CC to 56.5 drops off the charge and that’s it. All while the actual battery volts sit at a steady 53v.

The normal regime for my CC is bulk to 56.5 absorption, sits at absorption for minimum time then drops to float @53.5. Now it’s no longer dropping to float, but more importantly no longer appears to be passing any of this on to the Battery, connections all appear to be good, battery is running CC when I isolate panels.

It’s like the CC has had a program glitch and just decided it doesn’t want to play nice with others around it :-) Edit additional info. Could perhaps be a SOC glitch as it’s changing charge modes according to this, so start charge @ 80% rapidly climb to 100% (within 1ah of output) drop to absorb, then a little while later to float, while Battery stays at 80% as not enough charge has been added to alter it

The SOC of the Classic isn't used to control charging.
There is a setting in Classic so SOC goes to 100% when it goes to Float. It doesn't sound like yours is set up that way.
I am assuming you have the Whizbang installed ?
It is normal for lithium batteries charging in bulk to go to Absorb for brief time and then to Float.
Are you using ending amps or Absorb time to end the Absorb ?

Larry

WRT needs to answer your question, Larry, but AFAIK, most (not all ?) Lithium batteries should be charged when they reach the absorb voltage and then stop after that...   OR go to Float of course which can be any voltage lower than absorb.

Some Li batteries are required to do something a bit different though  I have heard.  I don't quite understand that part yet.

boB

[wrt]

It is normal for my Midnite to reach absorb for a short time then drop to float, under normal circumstances absorb is a really short time and is not really an active part of the charge profile.

As per my Avitar I only run one Classic CC and it has Whizbang. No other charge source, either way, if there was it would be less of a mystery to me because Battery volts would be in sync with the CC ‘s, as an example, This morning charge starts on the CC goes for a very short time volts are normal, then the volts on the CC rise rapidly to absorb (Just the CC not the actual battery) as soon as they hit absorb on the CC they go back to float, leaving the battery uncharged.

Right now my battery is around 52.6 but the CC is floating at 53.5.

[wrt]

I have an interesting update, went to check the CC tonight and found it dead. Checked the Battery to CC fuses and found one blown.
New question, do the HRC style fuses have a lifespan, could it have been slowly letting go over the past few days, allowing enough power through to power up the Classic and allow it to detect the battery, but not enough to allow it to pass charge back ??.

Worth noting I checked these same fuses yesterday while investigating the problem and they where fine. I have tomorrow morning off, so it will either be everything is fine and the HRC fuses have a lifespan, or, the CC has spat the dummy completely and blown its fuse.

Edit...Thanks for the advice guys. Changed both CC fuses and all back to normal.