Resting in middle of day

[offgridQLD]

I will paint the picture ...

It was early afternoon on Sunday 1:30pm and my battery's were on float just idling along. The classic was charging around 400w to the battery just covering a few small loads in the house and keeping the battery's at float voltage.

It was a very sunny day I went out to the workshop and started my air compressor 2800w load as I have done many times before without issues. With 4000w of PV  what normally happens is the classic usually just ramps up its charge output to cover the load to maintain float voltage.

Not this time. The classic was showing resting and not putting anything into the battery. Why?

You can see its captured in the graph below it drops to zero. Showing resting on the classic LCD display for about 5 or 6 min before coming to life and pumping 2750w into the pack.



Its the 1st time in almost I have noticed anything like this and its not I big deal as it looks like it sorted its self out but I would like to understand what happened

[Halfcrazy]

I am surprised at the 6 minutes? It looks like the battery was in absorb or Float when the air compressor started. I assume this surge was seen as a small "OCP" if you will an the classic stopped charging for a bit.

Few questions.
What firmware version in the Classic?
What serial # (roughly) is it?
What is the sweep interval in the Solar Mode set for?

Ryan

[offgridQLD]

The 6min is a guess as it was already showing (resting) by the time I walked from the compressor to the classic. I'm guessing the 6 min by lining up on the  data logging time line. using the data logging picture I posted above. you can see when it drops to zero watt charging at 13:36 and starts charging again at 13:42 so that's why i say 6 min.

It was just a bit odd having a 2800w load on my battery and watching the charge controller resting as the battery voltage slowly dropped. Then it sprung to life and gave it all its got to recover the loss.

"OCP" .... whats that?

Classic 150V (rev 4)   
MAC: 60:1D:0F:00:1D:34
Device ID: B426 C482

Firmware:     
- Classic Rev: 1070
- Network Rev: 1024

Kurt

[Halfcrazy]

OCP = Over Current protection.

Can you give me a rough serial #? Also can you look at the sweep interval time in the Mode?

Ryan

[offgridQLD]

Sorry, sweep interval is (3) I'm not at the location at the moment to get serial number but purchased the Classic new on 29th October  2012.

So as the classic went to cover the sudden load to try and maintain float voltage it tripped its self into over current. Strange as it was only a 55A load on a 48v battery and  output current limit is set at 86A. My 4000w system at 48v isn't capable of reaching 86A

Kurt

[dgd]

.... Strange as it was only a 55A load on a 48v battery and  output current limit is set at 86A. My 4000w system at 48v isn't capable of reaching 86A

Maybe that 55A is when compressor is running but there is a much higher surge current at startup?
Enough to OCP the Classic 

Dgd

[offgridQLD]

Maybe that 55A is when compressor is running but there is a much higher surge current at startup?
Enough to OCP the Classic 

Dgd

I don't get why I would be having a (OCP) situation of the classic.

I understand motor start up surge loads but it's not like the classic is running the air compressor directly by itself. My 6000w continuous 12,000w peek inverter is the device powering the compressor its the inverter and 63kw of battery that's taking the surge loads.

The classic is just a charger and can only create its own (charging) surge based on what it decides to do with the available PV power at the time and I have 4000w of PV . So looking at data logging for voltage at the time the compressor started the battery's sagged to from 55v to 52v. So lets just say the classic responded to this and dumped everything it had available to try and get the voltage back up to 55v(float) so potentially that could be up to the max available from thePV = 4000w /52v = 72A. Realistically it would be less.

The strange thing is my plasma cutter consumes more than double what my air compressor dose. I haven't noticed any issues when running that and for brief moments (under 30 seconds) The air compressor actually runs at the same time as the plasma cutter.

perhaps I am missing something?

Kurt

[Watt]

Maybe that 55A is when compressor is running but there is a much higher surge current at startup?
Enough to OCP the Classic 

Dgd

I don't get why I would be having a (OCP) situation of the classic.

I understand motor start up surge loads but it's not like the classic is running the air compressor directly by itself. My 6000w continuous 12,000w peek inverter is the device powering the compressor its the inverter and 63kw of battery that's taking the surge loads.

The classic is just a charger and can only create its own (charging) surge based on what it decides to do with the available PV power at the time and I have 4000w of PV . So looking at data logging for voltage at the time the compressor started the battery's sagged to from 55v to 52v. So lets just say the classic responded to this and dumped everything it had available to try and get the voltage back up to 55v(float) so potentially that could be up to the max available from thePV = 4000w /52v = 72A. Realistically it would be less.

The strange thing is my plasma cutter consumes more than double what my air compressor dose. I haven't noticed any issues when running that and for brief moments (under 30 seconds) The air compressor actually runs at the same time as the plasma cutter.

perhaps I am missing something?

Kurt

Have you checked all your connections?  Also, what size battery bank do you have?  What was the surge current to the inverter while starting the compressor?

[offgridQLD]

All the connections are fine. The battery is 63kwh made up of 24 x 2v 1330AH cells for 48v 1330ah. No measuring device I have is fast enough to capture the surge spike of the compressor starting. perhaps if I downloaded the inverters logs it has a fast sample rate option that would pick up the starting spike.  Though the compressor has a big capacitor on the motor and a mechanical soft start feature so I don't think its spikes all that bad. My watt meter on it shows around 2800w at start up then it settles down to around 2400w. well within the c20 range of the battery's.

Kurt.

[Watt]

All the connections are fine. The battery is 63kwh made up of 24 x 2v 1330AH cells for 48v 1330ah. No measuring device I have is fast enough to capture the surge spike of the compressor starting. perhaps if I downloaded the inverters logs it has a fast sample rate option that would pick up the starting spike.  Though the compressor has a big capacitor on the motor and a mechanical soft start feature so I don't think its spikes all that bad. My watt meter on it shows around 2800w at start up then it settles down to around 2400w. well within the c20 range of the battery's.

Kurt.

I'm not familiar with the soft start you have but, that compressor starting on single phase will have a surge.  Surge could be 3x or more running watts but who knows for sure.  I have a fluke meter which measures surge and min/max voltage I use when I have doubts.

[offgridQLD]

Yes I understand induction motors surge at start up but what dose that have to do with my classic charge controller? The classic shouldn't care less what the inverters doing.

Kurt

[Halfcrazy]

What "Can" happen is if the Classic is wired into a battery bus with the inverter and then there is a common set of battery cables to the battery, When a very large surge hits the inverter the Classic will see the battery voltage as nearly 0 for a split second and dump its Caps instantly to try to charge the battery. This is much more pronounced on high voltage inputs like a 200 or 250.

I do not think this has anything to do with your case though as OCP should just force a sweep and track right back to MPPT voltage.

I suspect yours was just an anomaly caused by the classic being in absorb or float and the load coming on. In the future after or during an event like this you can check the reason for resting by holding the left arrow and hitting Enter. The top middle number is the RFR. Please realize the Classic stores only the "LAST" RFR so in your case you could have checked it anytime until the next "resting" event.

Ryan

[offgridQLD]

Great thanks for that it sounds reasonable to me. If it ever happens again its good I can see why. Though as long as it recovers I'm ok with that .

Kurt.

[perronotto]

thank you