Classic is doing a few strange things the last week.
The other day, it was reading 100%SOC, but was still in absorb for a while until I got to End Amps. Why would it say 100SOC if I wasn't at End Amps? It did this for 3-4 days in a row that I saw.
Now, today, it reads 97%SOC and "float." How did I get to End Amps when SOC was less than 100?
I have changed none of my settings.
Ideas?
(Posting this on NAWS, as well)
Hi 2..,
The battery temperature is a component in the SOC calculation. A battery temperature below the Reference temperature (usually 25 C -- 77F) causes the battery to lose Capacity. A temp above the Reference temp should cause the battery Capacity to rise above 100%.
So, the battery Capacity vs temperature COULD be causing this small disparity.
FWIW, Opinions, Vic
Hmm. I thought that since the Classic monitors battery temp that it would take that into account.....
It was rather warm today...95F, and the batteries aren't (yet) enclosed completely in a battery shack
But when it was doing the 100% and still absorbing, it was only about 10F above reference temp...and I never saw any strange behavior this winter when it was cold.
Hi again 2twisty,
Well the Classic DOES take temperature into account, and it is possible that it is this very trait of the Classic that could account for this slight discrepancy in SOC readings.
If you went to the " Temps " page on the MNGP, you should be able to see what the Classic is reading for the battery temperature. If the reading is above the Reference, the battery should show a slight increase in Capacity, and below the Ref temperature the battery Capacity would be reduced.
This may not be all of what you are seeing, but just my thoughts. FWIW, Vic
Yeah, I think I finally wrapped my head around it. Since the batteries are warm and their capacity is reduced, they get to end amps before the shunt says that it's put all the Ah used back in. So, the fact that I am AT End Amps tells me that given the current temp of the batteries, I am at 100%SOC *for that temperature.*
Right?
Quote from: 2twisty on May 01, 2015, 07:52:00 PM
Yeah, I think I finally wrapped my head around it. Since the batteries are warm and their capacity is reduced
Not quite... warmer batteries (within limits) have increased capacity.
I don't know what happens to end amps with higher temperatures. What is important is that your setting for 'end amps', should be checked with an hydrometer (for flooded batteries).
For sealed batteries, you can determine end amps by watching battery current during the late stages of absorb. What that means is that you set the end amps to zero and the absorb time to 'forever'. Then watch the current into the batteries (check every 20 minutes). When the current stops decreasing, you are at end amps.
Then set your controller's end amps to something just a bit higher than the true end amps.
--vtMaps
Quote from: 2twisty on May 01, 2015, 07:52:00 PM... Since the batteries are warm and their capacity is reduced, they get to end amps before the shunt says that it's put all the Ah used back in. So, the fact that I am AT End Amps tells me that given the current temp of the batteries, I am at 100%SOC *for that temperature.*
Right?
twisty,
Just to try to be clear, warm batteries actually have a bit higher AH Capacity than those at Reference temperature, and cool/cold batteries have less Capacity.
When the Classic transitions to Float, the Capacity for the battery being charged is set to the Temperature Compensated full capacity. If the battery is at the reference temperature, the Capacity is set to 100% in the display. If the battery is cooler, the SOC in the display will be somewhat less, and if the batt temp is higher, the display shows a higher SOC.
And, it is not too important to get too wound up in the exact number displayed for SOC, as there are a number of factors that are very difficult to determine about the actual SOC, including the age of the battery, etc.
FWIW, IMO, so on, Vic
Quote from: Vic on May 01, 2015, 09:07:59 PM
When the Classic transitions to Float, the Capacity for the battery being charged is set to the Temperature Compensated full capacity. If the battery is at the reference temperature, the Capacity is set to 100% in the display. If the battery is cooler, the SOC in the display will be somewhat less, and if the batt temp is higher, the display shows a higher SOC.
I hope it doesn't really work that way....
Are you saying that if the batteries are warmer than reference temperature, then the SOC will display greater than 100% when the batteries are fully charged?
--vtMaps
And don't forget the % Efficiency setting has a lot to do with when the batteries reach 100% SOC. You have to put in more AH than you took out to get the batteries fully charged
No it will not display 100% but lets say the battery was 10 degrees C hotter than 25C. It now is 10% bigger than its name plate says. So if the AH in was JUST enough before to get it to 100% it may be falling slightly short now. I too do not know what happens to AH as the battery cools or heats I will try to add that to my list for a battery engineer next time I chat with one
Ryan
Quote from: vtmaps on May 02, 2015, 02:53:22 AM
I hope it doesn't really work that way....
Are you saying that if the batteries are warmer than reference temperature, then the SOC will display greater than 100% when the batteries are fully charged?
--vtMaps
Hi vt..,
Yes, that was what I was saying that I believe to be true ...
BUT, have never seen the battery temps here, rise above the Surrette Ref of 25 C. SO, it is quite possible that the statement that the MNGP would display an SOC above 100% with warm batteries may well be incorrect.
However, some battery manufacturers DO state that their batteries will have somewhat more-than-rated Capacity at temperatures above their Reference temperature, where they rate the Capacity of their batteries, IIRC.
To me, the stated SOC is an interesting aside that the Classic provides (on the MNGP). But the primary use of the WBjr with its Shunt, is to inform one of the number of AH removed from the battery in the previous discharge interval, not the displayed SOC.
Opinions, FWIW. Vic
Quote from: vtmaps on May 02, 2015, 02:53:22 AM
Quote from: Vic on May 01, 2015, 09:07:59 PM
When the Classic transitions to Float, the Capacity for the battery being charged is set to the Temperature Compensated full capacity. If the battery is at the reference temperature, the Capacity is set to 100% in the display. If the battery is cooler, the SOC in the display will be somewhat less, and if the batt temp is higher, the display shows a higher SOC.
I hope it doesn't really work that way....
Are you saying that if the batteries are warmer than reference temperature, then the SOC will display greater than 100% when the batteries are fully charged?
--vtMaps
%SOC is never going to read higher than 100%. The AH Capacity will read higher than the reference AH capacity if the batteries are warmer than the reference temperature.
OK, John,
I stand corrected. Have never seen either the AH Capacity or the SOC exceed 100%. Thanks, Vic
Quote from: Vic on May 03, 2015, 07:36:34 PM
OK, John,
I stand corrected. Have never seen either the AH Capacity or the SOC exceed 100%. Thanks, Vic
My battery temp is currently reading 25.5 C and my 840AH battery capacity is reading 842 and SOC is 100%. My capacity compensation is set to 0.6 %/C