Ending Amps not behaving as expected

[Wxboy]

Let me start by saying I have the June 2012 firmware on my Classic...

Today I changed my EA setting from 1.4 to .2 amps after reading some information from the battery manufacturer.  I also changed max. absorb time from 4 to 6 hours.  The Classic went to float after about 3 hours of absorb time with these settings.  I didn't think the amps got down to .2 before the transition so I forced absorb.  It was then bouncing between 1.0 and 1.4 but went to float after roughly 15 minutes which is my minimum absorb time.  Then I forced absorb again with the same result.  The current never got down to .2 and 6 hours didn't pass so I'm trying to figure out why it kept going into float.  The lowest I saw was .8 or .9 amps for a second. 

I'll experiment more tomorrow but I expect to see the same results.

As a side note I ended up deciding I will change the EA setting to .7 because I have determined my Classic reads about .5 amps too high on the display.  If I account for that then .7 should be a good setting to net out at .2.  Possible enhancement...maybe we could get an offset for the amps out which would then adjust the watts reading for those of us that have done some experimenting and feel comfortable with this?

One more thing.  Since the current bounces around when it's absorbing does the Classic look at the lowest current or the highest current or the average to make it's determination of when it transitions to float? 

[boB]

I think that 0.2 amps is going to be too low because the average battery current must drop below that voltage and NOT
go above that voltage for about 90 seconds.

As soon as the battery voltage (average, reading on the MNGP), rises above your EA setting, it's going to take it
another 90 seconds below that setting to go to float.

Also, on the max absorb time thing, try changing the minimum absorb time to something longer.  Remember
that the Classic starts out at minimum time and counts down to 0 from there if it went straight to absorb.
If it is in bulk, it counts up towards the max absorb time and THEN counts down to 0 from that time
when it finally gets to absorb.  Your batteries may already be charged or close to it so it may be counting
from minimum absorb time so it will go to float faster because of that unless the battery voltage
drops below EA setting for 90 seconds in which case it will go to float faster.

But, 0.2 amps for EA is just too low for the Classic to be able to go below for that usage.
You may also have DC loads that require current from the Classic that can keep it from
dropping below 0.2 amps.  Current bounces around somewhat so that alone may keep
it above 0.2 amps at times and resetting the EA timer/counter.

Later, the minimum and maximum absorb time is going be one number and NOT count up from
a minimum time count if in bulk.   It will just count down from max and when battery voltage
drops below absorb set point, the counter will just stop until the battery voltage gets back to
the absorb set point.

There will be a way to make it do what it does now, (count up and down) but it will be smarter.
Hopefully this code will be coming out in a week or two.

How large is your battery bank in Amp-Hours ??  0.2 amps seems a bit low for a typical
bank.

boB

[Wxboy]

Odyssey recommends .001C for ending amps with no more than 8 hours of absorb time(or 4 hours absorb if there is no EA setting).  C in this case is 136 amps.  I rounded up from .136 to .2.  I agree that it may be hard for the Classic to stay below .2  for 90 seconds but if I set it to .7 then it should be ok?

I'm a little confused on the counting up and down thing.  I thought if the max. absorb was set at 6 hrs. that it would either count up or down once it hit my absorb set point and when it reached the 6 hr. time it would go to float if it hadn't hit the EA setting before that time.  I guess I'll have to pay more attention to this but if it's about to change then I won't worry about it too much. 

Tomorrow I'll increase the min and max absorb time and try things again. 

[Vic]

Hi Wx..

Boy,  .001 X C is an amazingly LOW  EA  value.

And,  did you add a second battery vs your signature?

Here,  have reloaded the FW in each CC,  did the VMM,  and  now,  EA seems to work fine.

boB,  man,  the logs on the Classic are very cool!  Tons of info.  Have not run an app yet,  but it is quite easy to confirm that EA is working well.   Great job on the Classic,  and it just gets better and better!

Thanks,  Vic

[Wxboy]

Vic, I've got two 68ah agm batteries.  I do have that listed in my signature but maybe it's confusing the way I typed it.  I agree that .001C is very low but these batteries seem to be a little different than most.  They also want .4C bulk current for deep cycling applications.  That would be 54 amps for these two small batteries.  A lot more firepower than I have. 

[Vic]

WX,  OH,  yea,  it's right there -- 2!  Thanks for reading it to me.

Yea many batts say they want tons of charge current.  Am not familiar with the ones you have,  will look them up on line.  Thanks  Vic

[Wxboy]

Vic, attached is the link to the technical manual for the batteries.  I have the DieHard version but I've read they are re-badged Odyssey batteries.  I believe mine are the same as the PC1500's

http://www.odysseybattery.com/documents/US-ODY-TM-001_0411_000.pdf

[Wxboy]

I just checked the Classic absorb timer and it has 1:45 left.  I set the minimum at 1 hr this morning and the maximum at 7:30.  Based on the timer and the fact that it's been in absorb for 1:45 so far today the Classic is apparently planning a 3:30 absorb time.  Based on my settings I can't figure out why.  I then bumped up the minimum to 4 hrs and the max to 8:30 and the absorb timer didn't change. 

I just reset the Classic since I'm leaving for a couple of hours and set the min. to 3 hours and the max to 8:30.  I then checked the timer and it was counting down from 5 hours.  So I accomplished what I wanted which was to keep it in absorb while I am gone but why did the timer then go to 5 hours when that wasn't either of my settings after I reset the unit?

[boB]

I just checked the Classic absorb timer and it has 1:45 left.  I set the minimum at 1 hr this morning and the maximum at 7:30.  Based on the timer and the fact that it's been in absorb for 1:45 so far today the Classic is apparently planning a 3:30 absorb time.  Based on my settings I can't figure out why.  I then bumped up the minimum to 4 hrs and the max to 8:30 and the absorb timer didn't change. 

I just reset the Classic since I'm leaving for a couple of hours and set the min. to 3 hours and the max to 8:30.  I then checked the timer and it was counting down from 5 hours.  So I accomplished what I wanted which was to keep it in absorb while I am gone but why did the timer then go to 5 hours when that wasn't either of my settings after I reset the unit?

Not sure exactly how it is set but when you reset or force bulk from the tweaks menu, the timer should be filled with the minimum absorb time and
if it is in bulk at that time, the timer should count up towards maximum.

5 hours is inbetween 3 hours and 8:30 hours.    5 hours would be 3 hours plus 2 hours.   Maybe it was bulking for 2 hours when you saw the 5 hours on the timer ??

When the new software comes out, the typical situation will just be to start at the maximum absorb time and spend no  longer than that
in actual absorb.  It will only count down to zero while the battery voltage is sitting at the absorb set point voltage.

If you still want it to do sort of what it is doing now, it will be able to do that, but be a bit smarter and not just count UP towards the
higher time value UNLESS a minimum amount of battery current and some set voltage below the absorb voltage set point (or lower)
is satisfied.   This will keep the timer from adding extra absorb time when the battery voltage is very near the absorb set point
but not quite there because of either large loads or cloudy day or combination of both.

The REAL way to end the absorb time is of course to watch the current INTO the battery terminals while its voltage is at the
absorb voltage.   That will be available when the networked battery monitor is used.  Coming up.


boB

[Volvo Farmer]

The REAL way to end the absorb time is of course to watch the current INTO the battery terminals while its voltage is at the
absorb voltage.   That will be available when the networked battery monitor is used.  Coming up.


boB

Oh, you dogs! Just had to make one more piece of nifty indispensable equipment long overdue in the off grid market.  Someday, we'll look back and laugh at all those arguments about how many hours to spend in absorb. I will be a very early adopter of this thing when it comes out!

[stephendv]

If it is in bulk, it counts up towards the max absorb time and THEN counts down to 0 from that time
when it finally gets to absorb.

I've been trying to follow this discussion, but still not sure I understand 
Does this mean that the "maximum absorb time" setting, actually means "maximum time for (bulk + absorb)" ?

[boB]

If it is in bulk, it counts up towards the max absorb time and THEN counts down to 0 from that time
when it finally gets to absorb.

I've been trying to follow this discussion, but still not sure I understand 
Does this mean that the "maximum absorb time" setting, actually means "maximum time for (bulk + absorb)" ?

Well, hang on to your hat, Stephen !  We're about to make it a bit more complicated but at the
same time either easier OR better, depending on which method you choose to use to determine
Absorb time.

New software coming up soon with the VariMax feature EXCEPT that it will be simple and VariMax
disabled by default...

Instead of going over it again, here is what I typed up on the NAWS forum not too long ago...

http://www.wind-sun.com/ForumVB/showthread.php?17101-Rolls-Surrette-absorption-time/page3

Quoting myself from that page....


Well, when I say "much better", I mean that feature can be made to work better but still not nearly as good as a real battery current monitor to tell
the CC to go from absorb to float. This is just an option but I believe there is merit for it. I call it VariMax and will be an option in
the next version of Classic code. The up-count timer will be disabled by default but I couldn't just remove that old method completely !

The idea is to let the absorb time increase when bulk time increases ONLY if the battery current when in bulk is above some adjustable preset
value ~AND~ the battery voltage is below the absorb setpoint by an adjustable preset voltage, THEN the counter can count up.
Otherwise, the timer will just stop accumulating absorb time when the battery voltage is not sitting at the absorb voltage.

By default, the current would be higher than the CC can ever put out, (say, 101 amps), and that disables the up-count of the absorb time.
Then, the absorb time will just be a preset time like 2 hours. Of course, when the battery voltage is below the absorb set-point voltage,
the counter will stop counting down towards zero which it needs to do. The battery voltage should be held at that absorb voltage in order
to count as actually being in the absorb charge stage. This VariMax method can even be improved some more but this should be good
enough I think.

I hope this doesn't confuse people too much but I think it's an OK way to keep that feature but also can help keep batteries from
boiling away unnecessarily when the power production is iffy. VariMax may also keep the counter from counting up to maximum
in the morning just because there isn't enough sun power to really be called "bulk" charging with such little available power/current.


boB

[stephendv]

Thanks bob, looking forward to the next firmware release!
In the meantime, I've increase the "maximum absorb time" limit to 7 hours to account for bulk phase too.

[Vic]

So,  regarding EA on one Classic;

Had switched this Classic's Mode = Off for four days.  Then returned to the site,  and switched the Mode = On, late Thursday afternoon.  Min Absorb Time=00:00,  Max time=4:20,  EA=14.5.  Returned to the site Saturday.  Bulk time was about 1:20,  Absorb about 1:20.  The ending current from the Log was about 27.7 A (calculated from last logged Pwr in Abs).  Loads are very light.

Looks to me that this was the Absorb time=Bulk time scenario. I was hoping that setting Min time to 00:00 and setting a reasonable EA value would avoid any possibility of having A time=B time.

I had been "certain"  that I had seen EA work correctly with the above settings,  when doing daily recharge with an EA of 14.5 and Min Abs time=00:00.

So on Saturday,  set a Min time for Absorb,   Forced Bulk,  and it took about three additional hours to get the EA close to the correct range as had been set for EA previously.

SSOOOooooo,  I do not understand just why this is happening.  Had noticed in the past,  that EA did not always seem to be the Abs terminator -- seems unpredictable to me.  And the bank has generally been getting undercharged on average.  EA is really by far the best method for charging the banks here.  If I were at this site every day,  it would be NBD.  But,  am not.  I could guess on a Abs time,  and measure the SGs every time at the site,  and make up any undercharging manually,  or reduce time to accommodate overcharge,  and so on.

BUT,  what is the guaranteed method of completely disableing A=B time??   Does this require using the new FW?

What is the method to guarantee that EA is ALWAYS used,  unless Max Abs time has been satisfied?

On the MX-60  EA is always dominant unless Max time satisfied,  IF,  Min time = 00:00,  and a reasonably high EA is set.  This is the way the current MX charged system always works.  And this approach works wonderfully well.

Curious,  Thanks,  Vic
EDIT:  And sorry,  this msg seems a bit more strident than intended,  but will just say sorry,  rather than trying to edit the post.  Love MN,  just am confused with too little time to devote to understanding this right now.  THANKS,  VB

[boB]

Hi Vic...

I just tried Ending Amps here.   12V battery and no other loads and Absorb was sitting around
3.0 amps.  2:00 hours Absorb time and no minimum time because I had VariMax disabled.

Anyhow, I had the EA set for 2.5 amps and it did not go to Float after quite a while.

I then brought EA up to 3.5 amps and 60 seconds later it was in Float with still an hour and 1/2 to
to from time only.

I think this is the mode you want to use.

The old method where Absorb time = Bulk time was what that was meant for and with Vari-Max
that can still happen sort of, but most people I think just want their absorb time to go for the
Absorb time they set it for.  I think that gone are the days of 00 minimum and preset maximum
time in most cases.   But then the EA appears to work fine too to stop the Absorb early.

In your case, was the battery voltage sitting at Absorb when the battery amps was below the
EA value ?

I would use this latest code with the VariMax mode.  No, actually, I would wait until tomorrow
when we put up the newest beta code with the Follow-Me feature !  It's much cooler !

boB