wrong mode

[EW Zuber]

I installed a dual inverter Outback system at a remote lodge. There is a 1.75KW array with an Outback controller and a 3.75 KW array with a Midnite controller. I have the Midnite and Outback absorb voltage set at 58.8 VDC. However while the Outback is in Bulk at ~56V the Midnite goes into Absorb. After a couple hours at this voltage it goes into float while the Outback is still in Bulk so we are not realizing the full advantage of the 3.75KW array. I increased the Absorb voltage on the Midnite to 59V just to see what would happen and there was no change.
I did notice a burned resister smell coming from the Midnite the first time I fired it up.
Next step, I think I will swap it out with another Classic to see what happens.

[Westbranch]

do you have a WBjr?
What are the other Classic settings other than Absorb
Does setting the Classic higher  by another volt or 2 make a change?
What are the SGs on your battery?

[boB]

I suspect this has to do with either voltage reading differences OR maybe, battery temperature compensation
differences.   Do either or both of the controllers have a battery temperature sensor connected up ?

You can view the Classics' target voltage based on battery temperature change from 25 C  by going to
the CHARGE ---  T-COMP ---  VIEW menu.  There used to be (still there ?) a menu in the Outback controller
(MISC) where you could view its target voltage as well.

Also take a Fluke meter (or suitable volt meter) and see if there is a difference at the battery terminals
of readings from one controller vs. the other.  I think that one of them is probably reading higher or
lower than the other and if so, that is most likely the problem.  Either way your batteries are getting
charged so that's good at least.

Both charge controllers can be adjusted slightly so that they both agree, unless that smoke you smelled
had something to do with this.  We try to add a bit of extra smoke to each Classic so there should be some
left in it.

boB

[EW Zuber]

Thanks for the replies. I checked the Midnite temp comp settings and they are apparently factory set at 5mv per degree C.? With the batteries at 30 degrees C that is only about 35mv difference if I read it correctly. Now if that were .5V per degree C it would account for something.
I looked at the Outback display but it is an old MX30 and I couldn't find the temp comp anywhere.

[boB]

Thanks for the replies. I checked the Midnite temp comp settings and they are apparently factory set at 5mv per degree C.? With the batteries at 30 degrees C that is only about 35mv difference if I read it correctly. Now if that were .5V per degree C it would account for something.
I looked at the Outback display but it is an old MX30 and I couldn't find the temp comp anywhere.

The -5mV per degree C is for each 2 volt battery cell.  So, if you have a 12V battery, multiply that 5mV by 6 to
get the full voltage change per degree C.

So, at 12V battery and 5 degrees C rise (25C to 30C)  that would be  30mV times 5 = a drop of -0.150 volts.

24V battery would be double that or, -0.300 volts

48V battery = -0.600 volts  etc...

boB

[EW Zuber]

boB, thats good to know. It's a 48V system so that would put the voltage at about 57V T comp. Going to try and get out there before the season ends and see what another Classic does.