Follow me two classic 150's

[offgridQLD]

I just set up a 2nd classic 150 in follow me yesterday. Watching them today while both in float covering base loads. One the master or should I say the one with the WBJR connected is doing all the work 300w-400w and the new classic is hunting on and off around 0-40w.

I also noticed the time to  trigger end amps using WBJR today took longer to be triggered now with two controllers in "follow me" end amps is set for 14A and usually with one controller the amps would slowly drop to below the "end amp" trigger point and go to flow but today it was hunting above and below 14A . Not so stable.

Is this normal. Any tips to get them both to share the load more 50/50 or at least stop chasing each others tail?

Thanks

Kurt

[dgd]

Kurt,

See the message thread 'load balancing'
Its unlikely this will become available as it has been said its not a priority

I still see one solar Classic providing near all the power while the other sits idle during absord and float.
It gets weird when the wind turbine Classic starts making power as it takes over charging despite plenty of PV power being available. At such times I need to manually shut down the turbine and thats a nuisance 

Followme works great for getting multiple Classics into the same charging state but does not enable anything smart concerning balancing the battery charging between the Classics

dgd

these message posting timeouts are f*****g annoying. I had to post this reply one line at a time.

[boB]

let's see if I get a timeout here...

Try setting the lazy classic's battery offset negative about -0.1 volt and see if that
helps it share a bit better.  Or maybe  -0.2 volts.

Let it think the battery voltage is slightly lower than it thinks it is now.

[offgridQLD]

Thanks Bob,

                   Having one charger do all the work in float isn't to bad as I am sure if the load becomes to large  the lazy one will be called upon to do it's share to meet the demands.  I will keep it in mind regarding the tweak to the voltage set point.

It could have been just that I was watching over the system today but the end of absorb (end amps set point) fluttering up and down was more of a concern. It just seemed to go under 14A (my end amps set point) for a few seconds then one of the charge controllers would spike a little and shoot up to 15-16A not letting it trigger end amps. The loads at the time were very stable so I just got thinking that perhaps it was the two controllers trying to balance between each other that was giving me this over shoot then correction. It did eventually go to float  though it just seemed to take a bit longer. I will watch it again tomorrow and see how it runs.

On a side note I have to say the newer classic 150 has much better main terminal connectors. Considerably more room to fit the thicker wire. They could still be larger but a big improvement as is.

Sure is nice now seeing to of them pumping away at my house bank with 8200w of pv behind them

Kurt

[Vic]

I just set up a 2nd classic 150  ...   I also noticed the time to  trigger end amps using WBJR today took longer to be triggered now with two controllers in "follow me" end amps is set for 14A and usually with one controller the amps would slowly drop to below the "end amp" trigger point and go to flow but today it was hunting above and below 14A . Not so stable   ...   
Kurt

Recently added more PV,  and a second MPPT CC -- the MX-60.  Have also noticed that the Jitter in charge current on the WBjr's status page had increased.  The jitter was enough that it appeared that the previous Shunt EA setting (with only one Classic)  would never be satisfied.   So just increased its value by only 0.2 A (from 11.9 to 12.1),  and that satisfied the EA argument,  and the Classic went to Float within about two minutes.

After watching the two different CCs share charging for a few days,  and tweaking Vabs and Offset settings,  believe that it is very common for multiple CCs will add a reasonable amount to the current jitter ...  it is just the nature of things.

Have also noticed that different loads have a differing effect on this current jitter.   Expect that the exact nature of current waveform of the load,  the way that an inverter tries to regulate the AC output voltage,  and the way that the CCs regulate output voltage and current all have an effect on the observed current jitter  (an voltage jitter) of the CC/s output.

FWIW,  all guesses on my part ...   will probably add an additional Classic to this particular system fairly soon.        Vic
EDIT:   AND,  no time-out this time!!   Thanks!

[offgridQLD]

Try setting the lazy classic's battery offset negative about -0.1 volt and see if that
helps it share a bit better.  Or maybe  -0.2 volts.

Let it think the battery voltage is slightly lower than it thinks it is now.

I played with the voltage offset today. I lowered the voltage offset by 0.1v on the lazy classic and the lazy one did all the work and the other one became the lazy one. So they just switched rolls So just 0.1v isnt fine enough tuning. I think it might be imposable to avoid in float situations

By lazy I mean a lazy classic will show 0 watts then do a pulse of say 150W for two seconds then drop back to 0W every 10 seconds or so where the other classic doing all the work will hum along at 200w reasonably steady.

I don't see it being a big issue  other than the one that is lazy today is my 150 with a reasonable high voltage pv string around 117v loaded input voltage into it. So it's actually running hotter (48c) than the one doing all the work is only ( 40C) .

I handy feature request could be a setting to allow one classic to go to (rest mode) when float is reached and only called upon to wake from reast when the other classic couldnt cover the loads and hold float voltages. Have no idea how or if that could be implemented.

Kurt

[Vic]

Kurt,

I would think that the Classic carrying most of the load in Float would do so,  until the load is so great,  that this Classic could not maintain Vfloat.  Then the battery voltage would decrease,  and would think that at this point,  the lagging Classic would rise to the occasion and supply much more power,  and maintain the output voltage at Vfloat.   It is possible that there might be some toggling of the two Classics,  switching just which one is the leader.

I have not watched this type of situation,  closely.

Yes,  when  Vin increases,  say from 105 to 115 V input to most any MPPT CC,  even at modest output currents,  the  heat dissipated by the CC increases significantly ...  not at all linear.

From what have read about the KID when paired with another,  believe that they work as a parallel pair,  not two separate CCs that communicate ...   as I read it.   This approach would probably help several CCs share charging more equally,  I think (?).

FWIW.  Good Luck,    Vic

[boB]

OK.  Will see if  we can make the alternate classic go to resting if not doing any work
in Absorb.  It would have to stay that way for around 1 minute or so before it went
back to resting.  A CC should not be holding a battery at absorb or float and be
putting out 0.0 amps.
boB

Try setting the lazy classic's battery offset negative about -0.1 volt and see if that
helps it share a bit better.  Or maybe  -0.2 volts.

Let it think the battery voltage is slightly lower than it thinks it is now.

I played with the voltage offset today. I lowered the voltage offset by 0.1v on the lazy classic and the lazy one did all the work and the other one became the lazy one. So they just switched rolls So just 0.1v isnt fine enough tuning. I think it might be imposable to avoid in float situations

By lazy I mean a lazy classic will show 0 watts then do a pulse of say 150W for two seconds then drop back to 0W every 10 seconds or so where the other classic doing all the work will hum along at 200w reasonably steady.

I don't see it being a big issue  other than the one that is lazy today is my 150 with a reasonable high voltage pv string around 117v loaded input voltage into it. So it's actually running hotter (48c) than the one doing all the work is only ( 40C) .

I handy feature request could be a setting to allow one classic to go to (rest mode) when float is reached and only called upon to wake from reast when the other classic couldnt cover the loads and hold float voltages. Have no idea how or if that could be implemented.

Kurt

[offgridQLD]

If this proposed (Rest lazy CC feature) was added. If a lazy classic was to go to rest and then a load came on say I switched a pump on and the non resting classic couldn't handle the load would the resting classic come out of resting and help?

Utube video of lazy classic on float
https://www.youtube.com/watch?feature=player_detailpage&v=3q76ALTdtCQ]www.youtube.com/watch?feature=player_detailpage&v=3q76ALTdtCQ]https://www.youtube.com/watch?feature=player_detailpage&v=3q76ALTdtCQ

Utube video of lazy classic after voltage offset was lowered 0.1v. Notice now the other classic has now become the lazy one after 0.1v offset change.
https://www.youtube.com/watch?feature=player_detailpage&v=TWj5WTQ694k]www.youtube.com/watch?feature=player_detailpage&v=TWj5WTQ694k]https://www.youtube.com/watch?feature=player_detailpage&v=TWj5WTQ694k


Kurt

[boB]

UH OH  KURT !!!   I accidently edited YOUR post !!  Please re-post your links !
I have never done this kind of screwed up thing before so please forgive me !

I was trying to reply to your post !

Sorry about that !

[offgridQLD]

No prob fixed

Kurt

[dgd]

OK.  Will see if  we can make the alternate classic go to resting if not doing any work
in Absorb.  It would have to stay that way for around 1 minute or so before it went
back to resting.  A CC should not be holding a battery at absorb or float and be
putting out 0.0 amps.
boB

I see this same situation reasonably often. The almost zero output Classic will hover around zero output in Absorb but when a load comes on line the 'lazy' Classic  usually makes up the power.
I don't think forcing it into resting state would be of any benefit because if it woke up due to loads appearing would it not go into bulkmppt? This would mess up the absorb state the other Classic is managing
Or will it move straight to absorb stage when it sees the battery voltage and just return to zero output state?
Would the real solution be some sort of charging management where the absorb and float current is ratio'ed between the Classics?
just IMHO

dgd

[offgridQLD]

I see your point regarding absorb.  Perhaps my idea wasn't the best. I was thinking for for when the battery's are in float. But res same issue with the resting classic going to bulk again....was just a thought.

My concern isn't that they both have to be doing a perfectly even share in (float) I'm not that pedantic that I have to see a 50/50 split in float output watts.

My concern was that by having one classic hovering around 0w and pulsing to 20 - 100w for a few seconds and back down again to 0w basically doing nothing might not be healthy for it as I noticed the lazy classic today was getting a little hot doing nothing.  So the idea was to find a way to avoid this (if at all it is a problem)? My system at times can be on float at 9:30Am so the lazy classic could be doing this for 6-8hrs.

Kurt

[Vic]

...

My concern was that by having one classic hovering around 0w and pulsing to 20 - 100w for a few seconds and back down again to 0w basically doing nothing might not be healthy for it as I noticed the lazy classic today was getting a little hot doing nothing.  Kurt

Hi Kurt,

Well,  believe that one Classic is running a fairly high Vin.  When this Classic has little or no load,   the Vin goes to Voc (for the temperature that the PVs happen to be,  then).   Even with low current output,  the CC is very inefficient at this point,  and will get warm/hot.   One "solution"  would be to load the PVs,  or the battery.   Loading the PVs should decrease the Vin.  IIRC,  the lagging Classic has a string Vmp of 117 V (?).  Have not taken the time to look at the videos.

We have somewhat similar situation here,  with string Vmp of 106 V ...    FWIW,  Vic

[offgridQLD]

Vic,
      The new array is 21 - 200w panels  for  4200w, 7 strings of 3s, VOC is 136v, VMP is 110V, on a 48v battery. Even in winter the VOC is typically no more than 125v on a coolest of days when on float as we have very mild winters (subtropical climate).

Loading the battery isn't usually a issue when we are at the house as we have a electric car that's a handy place to dump kwh's into. Though at this stage the home is a weekender until we move their full time. So base loads and 8200w of pv to recover them in clear sunny weather  float comes around very fast.

Perhaps just shutting down one controller (the one on with 110v VMP) over the weekdays is a short term solution.

Kurt