MidNite Charge Controller Issue

linnux

Hi, I recently switched the old 12V system over to 24V to add more solar at my off grid cabin. When I turn on the breaker from 1 set of solar panels the MidNite Classic 150 you will see the 'Volts In' increase to 36-37V, but no watts coming into the battery bank. The Classic will display 'Batt Over V' at the bottom of screen. Since my old setup was 12V did the Classic save these settings? In the owners manual the wrong nominal voltage may be selected and factory restore required.  

The 4 - 12V panels are connected in series 2-135W and 2-165W into combiner box each set on 15A breaker. I plan replacing the current panels with 8 - 250W 24V panels. I am also using Magnum MS 4024 inverter and BMK battery monitor. Your help would be greatly appreciated.  

BB.

On page 58-59 of the manual, in S1 dip switch, you can set battery bank voltage (12/24/48/custom):

https://www.solar-electric.com/lib/wind-sun/classic-manual.pdf

But I do not know enough about the charge controller to know if this is the only way.

Also, with most charge controllers, make sure you connect them to the battery bank first, then connect to the solar array (under sun). If you connect the array first, then the battery bank, it can confuse the charge controller.

-Bill

Vic

Hi linnux,

Agree with BB Bill,  that you probably need to Reset the battery voltage.

AND,  you really should Restore Factory Parameters (aka VMM).

Turn off the PV input to the Classic,  and switch off the Classic's battery breaker.
Press the Left and Right arrow keys on the MNGP display,  and while holding these two keys down,  switch the battery breaker to ON,  CONTINUE holding down the two arrow keys,  until you see the initial configuration screen.

Navigate through all of the parameters,  as you will need to change a number of them for your new battery voltage.

EDIT:  Based upon the Vin of about 36 - 37 V,  which should be Voc of the PVs when they are producing NO power.  This seems strange for two 12 V PVs in series,  would expect somewhat higher Vin with good sun on the PVs.  You will be able to test the setup,  BUT,  until you replace the PVs,  as the Classic will not produce maximum from the PVs,  due to low Vin.  Sometimes,  the Legacy P & O Mode on the Classic will help it produce more power with low Vin.

Just be certain that the "24V" PVs are real 24 V PV is wired as 8 in parallel. Almost all 250 Watt class PVs are 60 Cells,  with Vmp of around 30 - 31 volts.<   Most likely you are going to run those new PVs in strings of two in series.

And,  you appear to have quite a number of batteries in parallel,  but a clean looking setup from what we can see.

FWIW,  guessing Vic

westbranch

Agree, a Factory Reset is in order.... it should have recognised the 24 v batteries when you restarted the CC after changing the batteries configuration.  Possibly a Firmware up date too.  If you use the MidNite Local App you can change the nominal Voltage through it as well as stet all your other parameters as well.

go boldly where many have gone before, just follow the instructions..  There are also lots of How to videos on the MN site, enjoy.

linnux

The factory restore did the trick, the system is up and running after countless hours working on this project. With the wiring already in place the only thing left to do is add the 8 - 250W panels on the roof, will wire every 2 panels in series to the combiner box. Thank you all for your help. 

boB

Glad you found the Vulcan Mind Meld (VMM) method...  And it's very good that you will be wiring modules in series to get the input voltage higher than it is now.  The system should be much happier then for a 24V battery system.
boB