Battery Bank Voltage Change

[hemmjo]

Initial questions;

I have a Classic 150 charge controller in an off grid solar power system. I need to change the battery voltage of the system from 12 to 24 do to an inverter change. 

As I recall, the controller automatically sensed the battery voltage on initial start up.

I have found how to reset to factory defaults in the manual (version dated 1/7/13) page 11.  I am thinking the controller can then be setup for the 24v battery configuration using the Quick Set menu.

I am hoping, if by chance, the controller is powered back-up without reconfiguring for the new voltage, it should not hurt anything, it just will not work?

Some Background information;
I work with a small mission in the Dominican Republic. (http://www.villagemountainmission.org/index.html)
I installed 2 systems into separate buildings in 2013 and 2014. 

The systems are the same, each with 4- 275 watt panels, Midnight Classic 150 controller, 4- 6v 235ah batteries wired for 12v, Iota 12v 55a charger, KISAE 1210 (12v 1000w 2000surge) PureSine inverter. We also have 1 backup generator to run our well and to charge batteries for both buildings when sun is not shining.

Due to growth of the mission we need to upgrade one of the systems to a 24v 2000w 4000surge inverter to run a small freezer. (KISAE 2420 is what we are looking at)

My concern is due to the fact that I cannot be there for the change.  We have a very good, retired, commercial electrician to do the change and reconfiguration.  He is experienced with AC, DC and Industrial Programmable Logic Controllers. Hopefully he will be able to be there for a couple of weeks in case tweaks are necessary for the charging parameters.

Thanks for your help,

John

[ClassicCrazy]

I think the initial setup just gets some ball park settings into the Classic charge controller so it wouldn't cook someones battery .
You should be able to just change the battery charging parameters on the Classic and that would be okay .
Someone else can correct me if I am wrong.

Larry

[tecnodave]

Larry,

That is exactly correct, you can just turn on the classic and go into the input menu and adjust the values to the desired values for the 24 volt bank. The Classic will see an over voltage condition when programmed for 12 volt and connected to a higher voltage, it will go to resting until the absorb voltage is set higher than the battery voltage, then it will begin to charge even before you save that value. I do that sometimes when switching systems and I do not want to lose all my other settings.
David

[boB]

You will want to initiate a Vulcan Mind-Meld style reset to change the nominal battery voltage if possible.

Doing this will also change the battery temperature sense mV per volt per cell compensation to double that of 12V values.

You CAN of course just change all of the settings manually but when the Classic boots up, it will show 12V  system rather than 24V.

If you want to use the auto-sense feature, reboot and as soon as you see the MidNite Solar LOGO on the remote screen, hold down LEFT and RIGHT arrow keys.  The 4 questions of SOLAR vs. WIND and voltages, etc should come up.

If you are expecting large battery temperature changes, you might want to go into the LIMITS menu and raise and lower the maximum and minimum temp compensated Absorb voltage limits.

All just a suggestion.

boB

[ClassicCrazy]

Bob - are you saying that if you initialize on 12v and then change to 24v without re initializing that the Classic will calculate the wrong temperature compensation  ?   That is something I did not consider  .

Larry

[boB]

Yes, although you can go into the Temp-Comp menu and change the amount from -5mV/DegreeC/cell to -10mV

That's for typical lead acid of course.   If he were to go to say, 48V battery, then you cannot go to -20mV without changing the nominal voltage.

Either way can work for this though.

boB

[Matrix]

So the temp comp value for a 24v battery bank is -10mV? 

[boB]

So the temp comp value for a 24v battery bank is -10mV?

Yes but only if the Classic is set for 6 X 2V cells as it would be for a 12V battery.

If the Classic is already set for a 24V battery, then it knows that there are a quantity of 12    2V cells and then all is fine with -5mV per 2V cell.

This is ONLY if you don't want to go through the motions of changing the Classic from 12V system to 24V system by manually changing the default nominal voltage via VMM procedure and reset most of the settings.

BTW, doing the VMM Vulcan Mind Meld does not erase any data logs. Just the charging parameters mainly.

boB