Classic entering float with 90% SOC

[dapago]

Hello,

My Classic is entering float with the batts not totally charged (90%). Absorb time is set to 2 hours. Should I just add 30 mm more or are there other settings that need to be changed?

Thanks guys.

[Westbranch]

What does Trojan have for Absorb Time and do you have a WBjr?  I don't see it listed in your sig line...

[dapago]

I don't have a WBjr..Trojan does not tell an absorb time, just a voltaje setting per cel. My settings are set at 58.5v. Sun every days during 8 months a year.

[Westbranch]

looks like you are too low on the Absorb voltage it should be 59.28V (59.3?) and Float at 54.00V... and yes you need to extend the time.   

ADD: Please refer to this Trojan Publication. 59.28V comes from there.
  http://www.trojanbattery.com/pdf/datasheets/T105RE_TrojanRE_Data_Sheets.pdf

Without a WBjr you can NOT use the  End Amps setting in your Classic and get the above voltage values  at    the battery ADD: due to system losses,wire, connections etc.. It allows you to see just how many Amps are really making it into the batteries , not just what comes out of the Classic.

The End Amps point should be where the Amps going In to the battery finally levels out to a flat line, which is normally ~ 1 to 2% of the Ahr rating of your battery.

ADD: The Amps you can see in the MNGP are the total amps the Classic is putting out but not what gets into the battery
.
hth
Do you use the Local App? you can plot the Amps out on the graph...

So if you increase the time to 4 hrs, and watch it for a day to observe the flattening out of the Amps, that will give you a good ball park of the time needed ... then you can back off the time and adjust as needed...

[dapago]

Sorry for my poor knowledge but I don't understand. Trojan says 59.3 for bulk but does not say for absorb. Is it the same?

I do not use the local app but I can check directly on the midnite display. Basically if I well understand, absorb time must be set when voltage In is about ~1 to 2% of the batt amp. In my case ~5 amp In.
I can first increase voltage to Trojan spec for bulk (as suggested) and keep with the 2 hours absorb time and see what happen. If that is not enough, I can  then increase the absorb time.
Now Isnt it better for the batts to absorb at a lower voltage (58.5) and increase the absorb time instead of  increasing the voltage and a shorter absorb time?

[Vic]

Hi dapago,

First,  the battery manufacturer will not be able to specify an Absorb time,  as this time will depend upon how deeply the battery had been discharged in the previous discharge.

YES,  just use that Bulk voltage setting as your Absorb voltage setting in the Classic.

How is it that you determining the SOC is 90%,  with your Hydrometer?

You CAN use Ending Amps without the WBjr,   by using the Classic output amps.   With fairly steady loads on the battery (via the inverter),  and Flooded batteries it is fairly easy to find a good EA setting.  In a household with out-of-control loads,  this will probably not work too well, without a WBjr,  however.

You can set your Absorb time,  based upon  the leveling off of the Classic's output current,  but fairly large changes of loads on the system can make this more difficult to see.

IMO,  it is probably best to use the manufacturer's recommended Absorb,   Float and EQ voltages.  Much more damage occurs when batteries are chronically under charged,  than when a bit overcharged.

Yes,  why not try increasing the Absorb voltage first,  before changing the Absorb time and voltage all at the same time.


Vic

[dapago]

Hello Vic,

Thank you.
Yes I use an hydrometer to check the SG.
How do I set the EA? Do I just enter the value that correspond to 1% to 2% of my batt rating (2.5/5 Amps)?

All the settings in the classic were made by the dealer/installer (absorb @ 58.5V). I asked Trojan about the absorb voltage and here is their answer:
The absorb voltage from the graph below is 2.35 to 2.45V per cell in 48V that is 56.4V to 58.8V. Absorb at 30C should be about 2.35v/cell. Float remains same. Equalization 2.70V/cell every 30 cycles.
Considering Trojan info and in order to get the correct absorb voltage at 25C (because I use Temp Comp in the classic)  I calculated 2.35+0.025V (0.005x5)=2.375 per cel x 24=56.425V for absorb.
56.425V for absorb seems far away from 59.3V recommended here. Even if I take the highest Trojan recommended value (2.45V per cell) that makes 58.8V.
Because I did not get 100% SOC with 2.35V per cell, I raised it to 2.45 (58.8V/cell) as Trojan highest absorb voltage recommend but still i do not get 100% SOC entering float.
Sorry but I have to ask again: should I keep 58.8V as Trojan highest recommended voltage for absorb  and increase absorb time or raise absorb voltage to 59.3 as recommend here and keep with 2 hours absorb time?

[Westbranch]

dapago, please re read post #3... I made some additional comments to clarify what i typed, some of it was not clear enough  after I read Vic's comments. Sorry about that.

I would go back to Trojan and ask them which is correct the published document or his response to your inquiry. There is some inconsistency there.

My final sentence is what I believe you should do. 

In addition I recommend a WBjr , it is a very good tool..

[dapago]

Thank Westbranch. I attached the diagram Trojan sent me. It seems absorb voltage should be between 2.35 and 2.45 per cell as showned on  this diagram. Still confused.

Vic: could you please explain: You can set your Absorb time,  based upon  the leveling off of the Classics's output current...

[Westbranch]

dapago, you asked

could you please explain: You can set your Absorb time,  based upon  the leveling off of the Classic's output current...

Looking at the graph you posted, down on the right side, the red line is the Amps going into the battery. 
The horizontal part of the line you see is what we are calling ''leveling off''.
It tells me that the EA is from 1 to 3% of the battery capacity.

You need to keep track of the time that Absorb started and when the leveling started. 

That time, in minutes,IIRC, will be what you enter into the EA location on the MNGP.

[dapago]

Westbranch.
Thank. But what the point entering the EA set point in minutes if absorb time does the same thing? It might be a typo error and I suppose you were referring entering the EA set point in Amp.

To make sure I did understand correctly:
1. Set the absorb time limit by monitoring when the CC enter absorb stage until leveling off. Enter this time period (in minute) in the absorb time limit set point.
2. Set the EA set point to 1% to 2% (~1.5%) batt capacity. In my case 225Ahx1.5%=~3.5 Amps.
Is that correct?

An other question.
EA set point has the priority over absorb time limit. Does that means then when the EA set point is reached, the CC just does not charge anymore the batt (meaning 100%SOC) until absorb time set point is reached  or does it enter float mode or bulk depending on the loads?

[Vic]

Hi dapago,

In general,  using EA to end Absorb,  is a good approach,  because the amount of Absorb time to fully charge a battery depends upon the Depth Of Discharge (DOD)  that the battery experienced in the previous discharge.

On many systems,  the DOD will vary quite a bit from day-to-day.  So the required Absorb time would also vary quite a bit from day to day.

The graph that you posted,  shows measured battery charge current.  IIRC,  you do not have the WBjr,  so,  if your system has varying loads,  using the output current of the Classic will not be a clear indication of the actual amount of that current that is flowing into the battery.   Depending on the size of the other loads,  the CC output current may give an adequate indication of the battery current plateau.

If you were not going to use EA to end Absorb,  then,  noting the amount of Absorb time required to reach that plateau,  could be used as an approximate Absorb time setting in the CC (and not try to  use EA).   But,  again,  this required time may well vary from day-to-day,  or week-to-week,  depending upon the DOD that the battery has experienced,  compared to the DOD of the battery when you observed the amount of time that took to reach the charge current plateau.

Without the WBjr,  that actually measures the battery charge current,  by using a Shunt,  EA can still be used,   when Flooded batteries are being used,  and with systems that have either predictable loads,  or  with loads that cycle.

This may be too many words.  Hope that some of it makes sense.
Vic

[Westbranch]

amps that were received by the battery ...

The CC will stop ABSORB when it reaches either the time set or the measured EA.

sorry have to go and I see most of my post disappeared, more later if needed.

[Vic]

YES,  the EA function is an OR  --  either the set Absorb time set ends the Absorb,  OR,  the EA reaches its set value,  and ends Absorb,  which ever one happens first.

AND should have also mentioned,  that when using EA,  one should set the Absorb time to a value that will usually be more than would ever be required.

Off to work.   Vic

[dapago]

Vic. To make it simple. Should I just set the EA to 7.5 amp (~ 3% of 225ah allowing a small continuous load on the batts [2 fridges, sound system on all the time] and the absorb time to 3 hours?

Unfortunately in my location I can not get the WBjr or have to wait until somebody would bring it back to me from the US.