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"?
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
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
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 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
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
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