Author Topic: End Amps setting on multiple Classics charging one bank from three solar arrays  (Read 377 times)

TimBandTech

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So we've got three Classics charging a very large battery bank at about 50% of its max charging current. Per Rolls Surrette new battery manual we are using a very high absorption voltage (60 Volts) for PSOC (partial state of charge) system. To get around overcharging I am hoping that the end amps feature will alleviate by switching to float earlier than the full six hour absoption time. As I recall the computation came to around 5 Amps. We have a Whizbang Junior installed. I've set the End Amps on each of the three charge controllers to 5 Amps. Does this then actually cause a net 15 Amperes ( 5 Amps per CC) to switch over to Float or is the system smart enough to use the battery monitor shunt and if so then do I really need to set all three CC's? I suppose this question also goes into the other settings. To date I manually enter the same data into all three charge controllers when I make a change. Since I've seen the communication link fail twice until power reset I'm very worried about miscommunication. We do not use a LAN and have just the serial ring which does work generally, but when it fails it does not recover. I'm sorry I've jammed more info in here than that title of this thread, but if you have any opinions on any of this I am greatly appreciative of your help. The manual falls short on End Amps details.
24 SURRETTE 2-KS-33PS 2V 2500AH @48VDC, 7kW STC PV  (three arrays) 3 Midnite Classics, one with Waste Not High diversion driving 3kW of heating element at 48VDC through three SSR circuits, Two 6kW XW inverters

Vic

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Hi T B T,

The Classic that is connected to the WbJr/Shunt is the only Charge Controller (CC) that needs the EA value set.  The CCs should have their EAs set to 0.0 Amps.

Each of the CCs need Absorb (Vabs),   Float and EQ voltages set,  individually.   Only the Master CC (the one with the Wb) should need an Absorb,   and EQ  time set.

The above is just based on the systems here that use FollowMe.

Just make sure that the Master Classic is set to use the external Shunt/Wb current,  rather that Classic's internal Shunt.

Cannot say much about Comm errors in the FollowMe loop.   Just make sure that each Classic in that string is running the same Firmware Rev,   and that Firmware  is up-to-date.

As you know,   Absorb time depends upon the Depth Of Discharge of the battery.   Six hours is a very long time,   and may assume that the battery has been discharged to about 50 - 60% State Of Charge,   which is a fairly deep cycle.

The Surrette banks here do use Wb EA,   and this value has varied from about 0.9% of actual battery Capacity (C),   and about 1.65 of C.   This value depends upon the Absorb voltage (higher Vabs = higher EA for proper charge).   Although we have always used a considerably lower Vabs  --  about 58.4-ish V).

All just opinions,   FWIW,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

boB

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Hi Tim...

If you said in an earlier thread I can't remember  but when you say the communications fails, do you mean ALL communications, even with the MNGP ?

Or is it just the Follow-Me that fails ?  OR is it the entire Classic that stops working ?

If the entire Classic stops working until rebooting, I am thinking that it might be one of those that the processor stops when it gets too high in temperature and the latest software update should fix that. 

Rev 2193  /  Firmware Revision Date: Feb 6, 2018


K7IQ

TimBandTech

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Hi Bob and Vic.

Thanks Vic for the End Amps tutorial. I'll try to set it up as you spec. Not sure where the selector is for current sensing but I'll find it.

The LEDs are set so that a long blue indicates a comm error.
Twice now I've gone to the site and the same charge controller always has the long blue.
The only resolution that I have found is to power cycle that charge controller.
I've checked the cables. Having good initial communication is an indicator that the cables are alright.
No other errors are apparent except that the follow me mode has failed due to the communication error. This tends to cause the diverter system to fail, which the customer is more keenly aware of.
As far as I can tell the MNGP is working reliably. I've tried clicking around in it to clear the comm when it is failed.

I'll try to keep a temperature correlation in mind.
It is CC#1 which is comm failing and it has the 'waste not hi' diversion load signalling on PWM aux2 out.
CC#2 is master and has the current shunt and BTS connected. CC#3 has no additional connections.

When things are working properly there are long blue signals going on at each CC, but the short blue does show up regularly. I haven't actually tried to measure their frequency.

Hi Tim...

If you said in an earlier thread I can't remember  but when you say the communications fails, do you mean ALL communications, even with the MNGP ?

Or is it just the Follow-Me that fails ?  OR is it the entire Classic that stops working ?

If the entire Classic stops working until rebooting, I am thinking that it might be one of those that the processor stops when it gets too high in temperature and the latest software update should fix that. 

Rev 2193  /  Firmware Revision Date: Feb 6, 2018
24 SURRETTE 2-KS-33PS 2V 2500AH @48VDC, 7kW STC PV  (three arrays) 3 Midnite Classics, one with Waste Not High diversion driving 3kW of heating element at 48VDC through three SSR circuits, Two 6kW XW inverters

Vic

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Hi TIm,

Regarding changing which Shunt that the Classic will use for the End Amps function,   this is from the latest WvJr Manual that we have here,

"   ...   WHIZBANG JR. ASSISTED CHARGING:
One feature of the Whizbang Jr. is the ability to end an Absorb charge based on Ending Amps. In this mode, if the battery current falls below a programmable threshold for one minute, the Classic will go to Float, meaning that the batteries have been fully charged.
To enable Whizbang Jr. assisted charging, select “CHARGE” from the main menu. Select “ADVANCED.” Press the soft-left key until the annunciator above it reads “SHUNT” (selecting “CLASC” uses the Classic’s internal shunt instead). Press Enter to save your choice   ...   "

Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

boB

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Remember too that if you are only getting a few minutes of absorb using ending amps then your batteries may sulfate.

So be careful with using too high of ending amps
K7IQ

Vic

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Tim,   to bob's point,

Based upon the Absorb voltage,   these Surrettes appear to be Flooded Lead Acid (FLA)  batteries.

So,   at least there is probably a way to measure actual State Of Charge (SOC),   and therefore one can fine-tune Absorb voltage,  EA,   and charge time Limit,   within reason.

Tim,   if you could please give the Surrette battery model number,   and string configuration,   it would make it easier to come up with a fairly good EA value to start with.  It could be helpful to give additional system info,   for PV array,   inverter,   etc.  This can allow more accurate replies to your posts,   and can reduce the number of questions that need answering before replies can be made  --   will save time in the future.   This information can be placed in a Signature,  that is appended to the bottom of every post that you make (you probably are familiar with this ...).

AND,   you can determine the battery bank's Depth Of Discharge (DOD) from  Specific Gravitiy (SG).measurements  using a Hydrometer.   This ease of measurement is large benefit that FLA  batteries offer.

FWIW,  Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!

Vic

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Hi TimBandTech,

Am curious how your Surrettes are doing.

Could you please update us?   Really wanted  to put  this in the  Absorb Time  Thread  under Lead  Acid Batteries Topic,   but    perhaps  this one is better.

Thanks for  any additional info that you can  provide on Absorb V,   time,    SGs,    etc   ...     Thanks,   Vic
Off Grid - Two systems -- 4 SW+ 5548s, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 3X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  Thanks MN for Great Products/Service/Support!