Ending Amps not behaving as expected

[Vic]

Hi boB,

Thanks,

Regarding the MX-60,   it may show this same issue,  BUT  the MX-60 charged system experiences greater DOD,  and has about 60% of the PV that the system that I described above,  so today the MX-60 charged system  dragged along in Bulk all day,  almost made it to Absorb but did not get there.

In considering the situation with the Classic charged system,  it is NBD,  really.  The bank got mostly charged.   And,  probably will not get fully charged tomorrow,  BUT  it might,  as the bank will need more charge tomorrow,  which will be another dark day,  so may spend some time in Abosrb.  NBD.  This system  really needs to be recharged once in 3-4 days due to its light useage.  The main issue to me is the lack of my understanding of just how the charge cycle works.  Have spent many years watching the MXed bank charge,  but its nature is different due to SOC and PVi input,  so,  my expecation is not meeting reality.

However,  there is an extension of this same issue -- the direction from which EA is approached.  The Classiced system had EA approached from below -- a current less than the EA setting.  The fact that this lower than EA current (eventhough the charge current was NEVER above the EA setting)  satisfies EA and causes transition to Float is the same thing that makes ReBulk NOT WORK from Float in most situations.  If one wanted to RB from Float,  one would need to create some substantial loads on the system,  such that the output current from the Classic is greater than the EA setting.  If this is not done,  it appears that RB does NOT work,   because it spends milliseconds or less in Bulk when trying to do a RB,  because EA has been satisfied perhaps before the Classic even tries.

This,  too,  is NBD,  but  if  the Classic was sensitive to the direction from which the EA value was approached,  RB would do its intended function,  as would the Bulk-Float transition noted above.

This RB issue is the same in the MX.  It appears to the system operator that RB does NOT work.  But in reality,  it does not work when a reasonable EA value is set,  when in Float,  with light loads on the inverters.   Again,  NBD.  I did not know why RB on the MX-60 did not appear to work  for years,  years and years,  until stumbled onto it with the Classic.

No wonder it takes a long time to get complex real-time control systems like the Classic into the market.  And this is just one micro small thing,  of which there are thousands and thousands for you folks to figure out and make work.

Thanks,   yammering almost done.   Vic

[offgridQLD]

Guess that due to the high SOC at the start of today's charge (and on almost all other days as well),  that the slow lowish average current Bulk eventually got to Absorb,   and  Absorb current was below EA,  so  went to Float essentially instantly ... 

Just trying to get my head around how this could be a real issue if at all.

My system has low DOD weekdays and I have my EA set to end my absorb and trigger float. Through experimenting with a a very low EA setting (1A) and watching my pack at the same time knowing  my loads. I have found a EA setting (16.5A) it works well for my pack. I have used this setting for the past 30 days and its been very reliable.

My understanding of the issue described in the quote above is.

Say my classic charger managed to reach absorb voltage  and enters absorb but at the time it reached absorb the maximum available output of the PV was less than 16.5A due to very dark/cloudy conditions that the End amp criteria would be met and I would go to float even though the battery has spend little time at absorb.

My thinking of what saves this from actually happening in reality is 16.5A wouldn't not be enough amperage to hold my battery's at 60V ( my packs absorb voltage) for the required 60 -90 seconds to trigger EA. Instead it would trigger back to (bulk) due to voltage dropping under 60v.

Due to the nature of how battery's work. The only time 16.5A is enough amps to hold the pack at 60v is when the pack is 100% SOC so its fine to go to float if it dose.

I don't so how end amps could be triggered when the pack is not full unless you have a way to high end amps setting say 25A for me instead of 16.5A

I could be wrong or missing something 

Kurt

[boB]

Guess that due to the high SOC at the start of today's charge (and on almost all other days as well),  that the slow lowish average current Bulk eventually got to Absorb,   and  Absorb current was below EA,  so  went to Float essentially instantly ... 

Just trying to get my head around how this could be a real issue if at all.

My system has low DOD weekdays and I have my EA set to end my absorb and trigger float. Through experimenting with a a very low EA setting (1A) and watching my pack at the same time knowing  my loads. I have found a EA setting (16.5A) it works well for my pack. I have used this setting for the past 30 days and its been very reliable.

My understanding of the issue described in the quote above is.

Say my classic charger managed to reach absorb voltage  and enters absorb but at the time it reached absorb the maximum available output of the PV was less than 16.5A due to very dark/cloudy conditions that the End amp criteria would be met and I would go to float even though the battery has spend little time at absorb.

My thinking of what saves this from actually happening in reality is 16.5A wouldn't not be enough amperage to hold my battery's at 60V ( my packs absorb voltage) for the required 60 -90 seconds to trigger EA. Instead it would trigger back to (bulk) due to voltage dropping under 60v.

Due to the nature of how battery's work. The only time 16.5A is enough amps to hold the pack at 60v is when the pack is 100% SOC so its fine to go to float if it dose.

I don't so how end amps could be triggered when the pack is not full unless you have a way to high end amps setting say 25A for me instead of 16.5A

I could be wrong or missing something 

Kurt

There is no problem or trickery here.   If it takes less than the EA setting to keep the batteries at the Absorb voltage, then the batteries are full.

It doesn't matter if the current comes up from below EA while the voltage rises to Absorb or if the current comes down from above EA while the voltage rises to reach Absorb.

In the first case, where the current and voltage is rising, the batteries were likely almost full already and the available power was low to start with (clouds or whatever)...   In the second case where the current is falling and voltage is rising, the batteries probably needed a full charge and there was plenty of power/energy to charge the batteries.

As long as the EA setting is correct for the DC loads on the system, it works fine.

When using EA to end the Absorb and go to Float, it will work as long as the DC loads on the battery are not higher than expected.  Even if the loads are higher, it is OK as long as the Absorb time isn't way too long.  If this high DC load issue happens only once in a while, then that's great.

boB

[offgridQLD]

When using EA to end the Absorb and go to Float, it will work as long as the DC loads on the battery are not higher than expected.  Even if the loads are higher, it is OK as long as the Absorb time isn't way too long.  If this high DC load issue happens only once in a while, then that's great.

Great that's just how I was thinking it was.

The only time I have seen a issue switching to float with EA is like you say unexpected large DC loads.

I remember one morning i was watching the remote software I could see the amps dropping of below the EA trigger point.  My wife at the same time started doing the dishes (obsessed with rinsing every single cup spoon and knife individually) Making the 500w pressure pump cycle on and off every 20 seconds as she rinsed .  A simple request from me to stop rinsing for 90 seconds and the classic then had a 90 second window of base loads to trigger end amps and switch to float.

95% of time there is a small 90 second or more window of time where things settle back to predictable base loads and EA works fine.

Kurt

[boB]

When using EA to end the Absorb and go to Float, it will work as long as the DC loads on the battery are not higher than expected.  Even if the loads are higher, it is OK as long as the Absorb time isn't way too long.  If this high DC load issue happens only once in a while, then that's great.

A simple request from me to stop rinsing for 90 seconds and the classic then had a 90 second window of base loads to trigger end amps and switch to float.

HAHA !  That's great !  I can just see you telling her to stop washing the dishes while  you wait and watch your CC go to Float !

Thanks for that one, Kurt !

boB

[Vic]

Well,  before posting any of this Bulk-Float observation,  did reflect on it for some number of hours.

In the seven years of watching these two system manage recharge each one using EA as the terminator,  just have never,  ever seen the above behavior - not ever.

There is a camp of folks who believe that a FULL recharge requires a certain time being spent with the charge voltage being held at a reasonable Absorption V.  I am in this camp.  The Absorption stage is noted as finishing the last 10-15% of the recharge,  and is important in helping mix the electrolyte in FLA banks.

The recharge cycle noted above appeared to be just a small bit short of full,   but the numbers are quite small,  and it is difficult to measure small SG differences,  but from experience,  the bank looked slightly undercharged.

With larger banks,  is becomes easier to notice effects of discharges and charges from several prior days.  I was simply unable to access the previous day's Log data via the MNGP  ...  it simply would not display.  Do not use the App to display logged data,  as there is no computer at  this site.  Had wondered if the previous day or two,  the bank was a bit overcharged,  perhaps allowing the bank V in Bulk to rise to Vabs at a lower-than-normal current ...    the date/time data is correct ...   dunno.

On the flip side of believing that perhaps the EA value needs to have been exceeded in order for EA to end Absorb,  realize that on days of low solar power availability,  one can grind along all day in Bulk,  almost reaching Vabs,  but not quite,  and this can really overcharge the bank.

But,  still,  believe that the set EA value should really be exceeded during the charge cycle for a given day,  in order for EA to terminate Absorb.  This would could also allow ReBulk to work when the CC is in Float with light loads (current delivered by the CC below the EA setting),  and as of now RB does nothing in the above situation when EA is "enabled" -- it appears that RB command was totally ignored.

And so on.  This is NBD,  just something that have not ever seen with the venerable MX CCs.   Using CC EA  is always a compromise,  as varying loads do affect the real charge current delivered INTO the battery bank.  But batteries are teriffic integrators,  and all that is needed for battery health is the average recharge,  not just one on a single day.   Thanks,   Vic

[offgridQLD]

is important in helping mix the electrolyte in FLA banks

I was under the impression EQ would get this mixing done.

On a weekday when my bank is usually only 95% SOC in the morning. Due to very light overnight consumption. I see 1hr or so at bulk returning around 2.5kwh or so into the battery then I hit absorb voltage 60v and I'm usually pumping 30A into the pack at the start of absorb but it take little time perhaps 1hr for the amps into the battery  to drop to the 16.5A EA setting triggering float.

I feel the battery is getting 100% charged but the question of electricity stirring- gassing due to being held at a high absorb voltage   for a particular length of time its beyond me 1hr of electrolyte mixing at absorb voltage or  say 2 or 3hrs mixing i haven't ever seen any study's to determine the difference. i do know they get a good mix up when you do a EQ.

Factory specs for absorb on my battery's is reasonably high at  (60v) so they do get some mild gassing - stirring during the absorb even if it is only for 1hr or so.

Kurt

[Vic]

Hi Kurt,

Well,  I did not mean to say or imply that the Absorption stage was soley to mix the electrolyte,  but the gassing during Absorb does mix the electrolyte,  and it is an important function  that ocurrs during that last part of a charge cycle.

EQ  is a very active mixer,  but is usually done infrequently (if one is lucky).

Thanks,  Vic

[boB]

Vic, I think I know what you want added to normal old Ending Amps method of operation...

When the battery voltage rises to the absorb voltage and the battery current is already
under the EA setting like in your post, below, you would like it to take longer than
60 or 90 seconds.   THAT would be your MINIMUM absorb time.   Am I right

To my knowledge, there should not be any more time required in absorb as long as
the current that it takes to be AT the absorb voltage is below the EA setting, but I
understand what you are talking about I'm pretty sure.

Not a bad idea really.  Just not sure if it's absolutely necessary.

Who knows ?  It might even get in there at some point.

Thanks for the idea.

BTW, today I tested the EA along with the ReBulk and they both appear to
work fine.  Remember that the ReBulk will not take effect in Float but will
require the CC to be in "FLOAT MPPT" with the battery voltage below the
actual Float set point.

Or, maybe you meant something else instead ??

boB

[Vic]

Vic, I think I know what you want added to normal old Ending Amps method of operation...

When the battery voltage rises to the absorb voltage and the battery current is already
under the EA setting like in your post, below, you would like it to take longer than
60 or 90 seconds.   THAT would be your MINIMUM absorb time.   Am I right

To my knowledge, there should not be any more time required in absorb as long as
the current that it takes to be AT the absorb voltage is below the EA setting, but I
understand what you are talking about I'm pretty sure.

Not a bad idea really.  Just not sure if it's absolutely necessary.

BTW, today I tested the EA along with the ReBulk and they both appear to
work fine.  Remember that the ReBulk will not take effect in Float but will
require the CC to be in "FLOAT MPPT" with the battery voltage below the
actual Float set point.
boB

Hi Bob,  Thanks for thinking about and considering the low current EA situation.

Agree,  I would like to see much more time than 60-90 seconds spent in Absorb in this situation.   Min Absorb setting should be Fine. And,  also agree that it is not absolutely necessary.  Daily full recharge is not necessary.  But,  when there are a number of days in a row with fairly low PV (or other RE) power input,  it may be helpful to get some real Absorb time for the batteries.  The situation with this bank is not too common,  so am not asking for you to build something just for my situation.

Regarding Re-Bulk when EA is ENABLED,  with the 6-29-12  FW,   RB seems to work like I'd like to see it work -- from Float --,  only when current delivered by the CC exceeds the EA setting.  This is from Float,  not FloatMPPT.

While,  I am not a real Control Freak,  I would like RB to do a real RB when I ask the CC to do it.   This is often done when one is trying to see just how something does work,  or that something resulted in the battery not being fully charged,  and  one needs to take another shot at it on a given day.  If the initial Bulk had been done,  the Bulk part of RB will only last a few minutes,  and not harm the bank by beating on it too hard in a single day.

To me,  even if EA is enabled,  and one asks the CC to RB,  I'd like to see the CC do a RB from Float,  even if the CC output current is well below the EA setting.  When there is ample PV input,  if only the CC would TRY to do the RB,  the current would rise well above the EA setting,  and all would be well.

Regarding RB working from Float-MPPT,  seems to me at that point,  an RB is moot,  as there is not  enough current available to even maintain Vfloat,   is it not??

It is true that there are several ways to cause  another  Bulk/Absorb  for example,  sertting Vfloat to the desired Absorption V,  but then it is up to the operator to terminate this new cycle,  by resetting Vfloat to the real desired V.  And there is always shutting off the PV and Batt breakers,  and re-powering IIRC,  and think that there is another way that you may have described which creates a second Solar Day on the same date ...  But,  to me RB should DO an RB when requested by the user,  and doing it from Float would be good.  I CAN turn on some heaters to get the CC output I above the EA setting,  and,  am certain that this has worked with the older 6-29 FW,  from Float with less than EA current.

Another NBD thing,  but to me as it is,  when using EA,  RB just appears to NOT work.  (I had felt the RB on the OB MX-60 simply was broken,  as have never seen the MX RB,  probably since I always use EA on those,  too).

OK,  enough,  THANKS!   None of this stuff is to get too wound up over,  just little things.   Vic   K6IC

[Rngr275]

This opinion is from someone who is still very much a rookie in the world of all things associated with batteries, charging, solar and off grid. But I am a fast learner and climbing my learning curve as fast as I can.

Everything that Vic posted is what I assumed was the way it worked when I started trying to learn/program the charge parameters on the CC.

ReBulk: If I (or anyone) goes into the menu and manually ask for a Re-Bulk, that is what should happen. At that point the operator is taking over from the logic/algorithims, or any programing in the CC. One would only go to that menu and do a rebulk for a specific reason; to put more juice into the batteries... now. The owner/operator does though have to take on and accept the responsibility to monitor and turn off the manual Re-Bulk.

On the EA front I am leaning towards Vic's thought process here but because I am so new I am not as versed as he is. I do know that when I have a number of days with light use the voltage rises quickly and I am not in absorb very long (EA met) but when the SG is measured the batteries are a little on the low side. This is where I think there would be a benefit to getting more than a couple minutes of Absorb.

[Halfcrazy]

You are confusing ReBulk with Force Bulk. If you Force Bulk manually that's exactly what happens the CC starts a new Bulk charge algorithm. ReBulk is an automated way to do this. It is a battery voltage lower than float. What happens is if the cc goes to float and a load or clouds intervene and the battery voltage drops to or below the ReBulk setpoint the cc will start a new bulk charge.

Ryan

[Rngr275]

That is why I wrote the first sentence in my post. 

I guess I got confused when Vic talks about "To me,  even if EA is enabled,  and one asks the CC to RB,  I'd like to see the CC do a RB from Float,  even if the CC output current is well below the EA setting." I guess I am not sure what this is then....

And the learning continues.

[boB]

If the ReBulk set point voltage is at or above the Float voltage, then there is no reason to have a Float voltage.
Set the Float voltage above the ReBulk voltage in that case.

The Float voltage must be at least one tenth (0.1)  volt below the Absorb voltage.  Normally they will be quite
a bit more different than this.

Making the EA time be variable is a possibility here though.

boB

[Vic]

You are confusing ReBulk with Force Bulk. If you Force Bulk manually that's exactly what happens the CC starts a new Bulk charge algorithm.

Just lost a post ...   otra vez ...

Ryan,  YES,  you are absolutely correct.

While I DO know how ReBulk works,  I WAS definitely using the WRONG term for the command that I was referencing.

So,  First am very sorry to go on and on,  whining about something while using the wrong term for the command.

SO,  was referring to the command in the Tweaks menu called Force Bulk.

Speaking of Force Bulk -- FB --,  it is this command that appears to be sensitive to EA being enabled,  and when in Float with CC output currents below the current setting for EA that the CC appears to ignore the FB command. It must be that the CC does not even try to start a new Bulk,  because if it did,  in almost all situations,  the CC output current would rise well above the EA value when there is reasonable sun available.  It appears that the Force Bulk command is just ignored.  Assume that perhaps the FW looks for an EA value,  and if this is satisfied,  the new Bulk is not begun - guessing of course.  Could also be that the new Bulk is started but the FW notes that the  CC current is at/below the EA value,  although one might think that there would be the 60-90 second dwell time ...   and so on.  Dunno.

SORRY for using the wrong term,   and wasting valuable mental bandwidth of Forum members and MN Engineering and Tech.

Thank You  for the help,  Vic