Use of Shunt and Whizbang with Multiple Classic Controllers

Started by USCGC3CEN, July 06, 2017, 08:25:51 AM

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USCGC3CEN

We plan to install shunts and Whizbangs to provide increased control of the Absorption charging stage. We have two Classics, controlling different solar arrays (+72 VDC) and charging two battery banks (+48VDC) joined by pos and neg bus bars to support the load.

The two Classics will be wired and configured for "Follow Me". Should we install a single shunt/Whizbang on the Master Classic only, or should we install one on each battery bank neg connection and connect them to both Classics?

If monitoring current will allow us to set End Amps on both Classics, will the Classics end Absorption charging according to current flow or adhere to "Follow Me"?   

Vic

Hi USCG..,

You will only need one WBjr on one Shunt that is connected to the Master Classic.   That WBjr will monitor all current into and out of the battery bank  --  two parallel strings of batteries (as I read it).

You might want to use the Classic String Sizer to confirm that you have sufficient String STC Vmp for a 48 V battery:
http://midnitesolar.com/sizingTool/displaySizing.php

Strings of two 72 Cell PVs may not have a sufficiently high voltage to charge a 48 V battery.

What make and model number PVs are you using?

What type of batteries are you using on this system?   Flooded batteries generally need higher voltages to charge and EQ,  compared to sealed batteries.

More Later,   Thanks,  Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

USCGC3CEN

Vic,

Correction: we are using Canadian Solar CS6k-290 (9 total) panels with three on one Classic (200) and 6 on the other. It's the max number we can install on the existing frame. Batteries are Sun Xtender AGM 104 AH. There are two battery banks of eight batteries. We hope to increase the number of panels in the future. Our load is constant and low- about 2.25 AH.

If we use Follow Me, should we still connect battery temp sensors from both Classics to the two banks? Also- is Follow Me set on both Classics?

Question on connecting negatives- example in Classic manual says that batt neg should not be directly connected to PV neg or load neg. Why? We have no inverter at the site; all loads are 48 VDC.

Steve Farthing
USCG

ClassicCrazy

You may want to consider doing a full reset and restore setpoints every 6 months or so if using follow me if you need 100% reliability . I believe there may be a bug where over time errors accumulate internally in follow me mode and can cause some settings or values to drift.

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable

Vic

Hi Steve,   sorry for my reply delay - busy here;

So,  those CS PVs have Optimizers built-in.

I do not know how to interpret the "data"  on what would normally be called STC Vmp  --  the data sheet gives a range.

Have never used Optimizers on the systems that I'm involved with.

Suggest you contact MidNite Tech Support for their read on how to design your system.

Some Optimizers (Tigo,  in particular)  are not to be used on Classics,  at a minimum.

Sorry that I have so little to offer on the PV design rules for battery-based systems.   Those PVs are normally used on Grid-connected systems.

For Follow-Me,  only one BTS is required,  and need only be connected to the Master Classic.

Yes,  Follow Me  will allow all Classics to transition to Float,  usually within seconds of each other.

Good Luck,   Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

Vic

Quote from: ClassicCrazy on July 14, 2017, 11:08:15 AM
You may want to consider doing a full reset and restore setpoints every 6 months or so if using follow me if you need 100% reliability . I believe there may be a bug where over time errors accumulate internally in follow me mode and can cause some settings or values to drift.

Larry

Hi Larry,   Thanks for mentioning this.   Have never seen it here,  after running Follow Me for a few years.

Is this something that you have observed?   If it was mentioned here,   missed it.
Do you recall just what parameters had changed?

Thanks,  Vic
Off Grid - Sys 1: 2ea SW+ 5548, Surrette 4KS25 1280 AH, 5.25 KW PV, Classic 150,WB, Beta Barcelona, Beta KID
Sys 2: SW+ 5548s, 4KS25s, 5.88 KW PV, 2 ea. Classic 150, WB, HB CC-needs remote Monitoring/Control, site=remote.
 MN Bkrs/Bxs/Combiners. Thanks MN for Great Products/Svc/Support&This Forum!!

ClassicCrazy

Quote from: Vic on July 16, 2017, 07:09:25 PM
Quote from: ClassicCrazy on July 14, 2017, 11:08:15 AM
You may want to consider doing a full reset and restore setpoints every 6 months or so if using follow me if you need 100% reliability . I believe there may be a bug where over time errors accumulate internally in follow me mode and can cause some settings or values to drift.

Larry

Hi Larry,   Thanks for mentioning this.   Have never seen it here,  after running Follow Me for a few years.

Is this something that you have observed?   If it was mentioned here,   missed it.
Do you recall just what parameters had changed?

Thanks,  Vic

Someone I know suggested it .

Larry
system 1
Classic 150 , 5s3p  Kyocera 135watt , 12s Soneil 2v 540amp lead crystal for 24v pack , Outback 3524 inverter
system 2
 5s 135w Kyocero , 3s3p 270w Kyocera  to Classic 150 ,   8s Kyocera 225w to Hawkes Bay Jakiper 48v 15kwh LiFePO4 , Outback VFX 3648 inverter
system 3
KID / Brat portable