Setting up battery temp compensation:

[finalman]

OK so I've got most things setup for the first run tomorrow but noticed the battery temp compensation value on the classic only goes up to -10.0 mV setting on the classic. Whereas my 12v "SunStone ML 12-250" AGM battery specifies for cycle use -30mV/ Deg C @ 25 Deg  C as pictured in the following link:

http://i478.photobucket.com/albums/rr144/finalman123/Capture_zps0jqgwzis.png

Or if the text is unreadable in the above pic a more cut down version below.

http://i478.photobucket.com/albums/rr144/finalman123/batt_zps1cdp2zhe.png

Ignore the top half of the 2nd picture as that is the Morningstar Tristar setup app. The Bottom bit is from the battery specifications.

So how do I put that into the Classic if it only goes to -10.0.

[Mike W]

I believe the Classic battery temp compensation setting is per cell and your 12V battery would have 6 cells. That would make your required setting 30/6 or 5mv.

[Vic]

I believe the Classic battery temp compensation setting is per cell and your 12V battery would have 6 cells. That would make your required setting 30/6 or 5mv.

YES,  Mike is correct.  The Classic's compensation value is PER CELL.  Although,  -- 5mV/C  seems a bit high for many AGMs,  BUT,  the manufacturer knows all about their batteries.

Vic

[Westbranch]

If you use the Local App you will see it is mV /*C /cell....

[finalman]

OK so I set it up but I don't know if it's working correctly as my absorb is set at 14.7v but when it went to absorb it was either at 14.6v or 14.7v (I was away for a few minutes) @ 10 Deg C.

Shouldn't it have been at 15.15v when it entered absorb because it was 15 Deg C off of 25 Deg C mark. To work it out 0.03mV (-30mV/ Deg) X 15 Deg C Difference = 0.45v temp compensation at 10 Deg C + 14.7v Absorb voltage = 15.15v @ 10 Deg C Enters Absorb Mode.

Is that correct?

If so what setting do I need to check on my classic to correct it?

[Vic]

Hi final..,

In the Classic 'Charge' menu,  check 'Limits'.  Believe that the Limits for temperature compensation are automatically set as your Vabs  for the upper limit,  and Vflt for the lower one.

In the link that you provided for your batteries,  there are absolute limits stated there,  as temperature limits of Temp Comp,   IIRC ...

You will need to calculate what those temp limits equate to as voltage limits,   sorry am in the middle of a project,  need to get back to it ...

Did not recheck the link for your batt,  so hope that the above is approximately correct or better.

Later,  Good Luck,  Vic

[finalman]

OK the battery max charge voltage max high voltage was easy from what I worked out is a max of 15.45v @ 0 Deg C.

To work it out:

0.03mV (-30mV/ Deg) X 25 Deg C Difference @ 0 Deg C = 0.75v temp compensation at 0 Deg C + 14.7v Absorb voltage

= 15.45v @ 0 Deg C.

Does that look correct?

I'm unsure on how to work out the minimum temp compensation voltage though as what happens when the battery is flat or is this value only used when the classic is charging?

UPDATE: OK from what I can gather the battery min charge voltage compensation value from what I worked out is a min of 13.25v @ 40 Deg C.

To work it out:

0.03mV (-30mV/ Deg) X 15 Deg C Difference @ 40 Deg C = 0.45v temp compensation at 40 Deg C
13.7v Float voltage - 0.45v temp compensation at 40 Deg C

= 13.25v @ 40 Deg C.

Does that look correct?

Suggestion for product improvement would be to have and area to enter the battery charge temperature specifications (min and max) somewhere in the T-Comp menu.

[Westbranch]

IIRC you can use the array sizing tool to see the net effect of Min/max local temp by using this tool...  http://www.midnitesolar.com/sizingTool/displaySizing.php

not quite what you are after but what you will actually get as output

[Vic]

OK the battery max charge voltage max high voltage was easy from what I worked out is a max of 15.45v @ 0 Deg C.

To work it out:

0.03mV (-30mV/ Deg) X 25 Deg C Difference @ 0 Deg C = 0.75v temp compensation at 0 Deg C + 14.7v Absorb voltage

= 15.45v @ 0 Deg C.

Does that look correct?

I'm unsure on how to work out the minimum temp compensation voltage though as what happens when the battery is flat or is this value only used when the classic is charging?

UPDATE: OK from what I can gather the battery min charge voltage compensation value from what I worked out is a min of 13.25v @ 40 Deg C.

To work it out:

0.03mV (-30mV/ Deg) X 15 Deg C Difference @ 40 Deg C = 0.45v temp compensation at 40 Deg C
13.7v Float voltage - 0.45v temp compensation at 40 Deg C

= 13.25v @ 40 Deg C.

Does that look correct?

finalman,

Agree with your calculation for Vabs at min temp of 0C.

To me,  would think that one would want to also limit the Absorption voltage when the battery was above 40 C.  So,  IMO, this would be;

15 C temp rise at 0.03 V/C = 0.45 V  (same as you got),  but would subtract this from the 14.7 V nominal Vabs for a final value of 14.25 V.

But,  this is just my opinion.

BTW,  was the issue that you had with insufficient temp compensation of the Absorb voltage due to the Limits setting?

Just my opinions,   Vic

[finalman]

BTW,  was the issue that you had with insufficient temp compensation of the Absorb voltage due to the Limits setting?

That's probably why it went to absorb so early at such a low voltage. Guess I'll see what happens tomorrow morning with the new setting.

[Vic]

That's probably why it went to absorb so early at such a low voltage. Guess I'll see what happens tomorrow morning with the new setting.

OK,  Thanks,  will be interested in how things turn out.
Vic

[finalman]

OK so Battery at 9.5 Deg C it entered absorb with a voltage of 15.2v. Which is a little more then my calculations of 15.165v but I guess the charge controller knows what it's doing.

Any way I'll keep an eye on it now seen as though were at the end of winter and the temps are gonna heat up here in AUS as we head into summer.

[finalman]

Quick question abit off topic but it's to do with my system but at what battery charge state percent should charge controller to go into float mode? My battery is AGM.

I've heard 98% charged \ 2% of the total battery AH capacity. is that OK?

[Westbranch]

FM, you are right tin the ball park, 1 - 2 % of C/20 is  the starting point coupled with Absorb V, time for Abs., and how well charged your bank is...

hth