Author Topic: How do you test a DC shunt?  (Read 2825 times)

Trukinbear

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Re: How do you test a DC shunt?
« Reply #30 on: October 21, 2020, 08:24:42 PM »
No, I bought the stuff from three or four different vendors. A short SMA backplate, and the twin classic side plate, the E-panel came with the shunt installed, but not with the leads to the Sunny Island (those were in the SI box). I installed the DC side breakers, WhizBang Jr, and a couple of busses for the PV...along with the MODBUS/Canbus adaptor in the E-panel, and now the three MNSPD's, and the MNBDM too. I'm afraid the E-panel will have to come off the backplate to R&R the SI.
SMA Solar Sunny Island SI6048
JA Solar 330W 72 cell panels (18)
Classic 250 (2)
MODBUS/Canbus comm adaptor for Sunny Island
SMA-OG E-panel
WhizBang Jr
MNSPD300V (3)
Atkinson GSCM mini-i
Onan Quiet Diesel QD-8000
Monterey 986Ah 'Big Sur' 24-125-11 48V battery
Off the grid on the PNW coast

FNG

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Re: How do you test a DC shunt?
« Reply #31 on: October 22, 2020, 09:23:20 AM »
It has been a few years but I was the one that worked with SMA on this project. We worked with Roy Dynghan and Kristen over at SMA. The SI is a very fickle beast on SOC and it uses SOC for everything (Not always a good thing)

What I know and have in my notes:

You can use the SI COMM for current calculations but SMA at the time didnt recommend it as the classics are not calibrated like a shunt. My personal system uses the shunt and an SI Comm but I set the SI up to follow the shunt not use the classics.

I suspect there is more than one way to skin the cat but thats how Roy had me set it up when we designed the SI COMM

Trukinbear

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Re: How do you test a DC shunt?
« Reply #32 on: October 22, 2020, 02:23:59 PM »
Do your Classics, Sunny Island, and battery hydrometer all agree on your SOC? Mine NEVER agreed...
SMA Solar Sunny Island SI6048
JA Solar 330W 72 cell panels (18)
Classic 250 (2)
MODBUS/Canbus comm adaptor for Sunny Island
SMA-OG E-panel
WhizBang Jr
MNSPD300V (3)
Atkinson GSCM mini-i
Onan Quiet Diesel QD-8000
Monterey 986Ah 'Big Sur' 24-125-11 48V battery
Off the grid on the PNW coast

Trukinbear

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Re: How do you test a DC shunt?
« Reply #33 on: October 22, 2020, 02:46:12 PM »
Curious how far back this was. I bought my SI last August and when it arrived it had old firmware, which I updated. Perhaps they changed something in the firmware update?

This is from SMA:
The battery SOC issues may be influenced by a few factors. For one, the battery SOC is recalibrating down to 20% due to low voltage. I've attached graphs of SOC and voltage to this email. Note the battery voltage dipping as low as 45 V at times. These drops correlate with the SOC recalibrations. SOC recalibrations can be caused by improper programming and/or weak battery cells. I've attached the SI Battery Management document to this email, which explains causes and remedies for SOC recalibrations in detail. Ignore the mention of programming the C10 capacity, as this only applies to non-US Sunny Islands. I recommend a few actions for addressing the SOC recalibrations.
Confirm the battery capacity is set to the C20 rate. If you are not sure if 986 ah is the C20 rate, please contact the battery manufacturer to confirm.
Your initial comment indicates that you have installed the Midnite Com Adapter for the SI, but the parameters show that you also have a shunt programmed. The SI can work with *either* the Com Adapter or a shunt, not both. If you want to continue using the Com Adapter, you must deactivate the shunt programming in menu 225 Battery Current Sensor. Additionally, to ensure proper communication to the Com Adapter, you would need to set menu 250.28 ChrgCtlOp to SMA. You can only change menu 250.28 while the system is in Standby.
Load-test the battery in order to determine if there are any weakened cells. I have attached a short article describing how to perform a load-test with a voltmeter.
SMA Solar Sunny Island SI6048
JA Solar 330W 72 cell panels (18)
Classic 250 (2)
MODBUS/Canbus comm adaptor for Sunny Island
SMA-OG E-panel
WhizBang Jr
MNSPD300V (3)
Atkinson GSCM mini-i
Onan Quiet Diesel QD-8000
Monterey 986Ah 'Big Sur' 24-125-11 48V battery
Off the grid on the PNW coast

FNG

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Re: How do you test a DC shunt?
« Reply #34 on: October 26, 2020, 04:58:47 PM »
My SOC was always within the margin of error yes. SMA has a SOC% and then they have a Margin of error % also.

Trukinbear

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Re: How do you test a DC shunt?
« Reply #35 on: October 26, 2020, 05:49:24 PM »
Mine was often off by 50-70%
SMA Solar Sunny Island SI6048
JA Solar 330W 72 cell panels (18)
Classic 250 (2)
MODBUS/Canbus comm adaptor for Sunny Island
SMA-OG E-panel
WhizBang Jr
MNSPD300V (3)
Atkinson GSCM mini-i
Onan Quiet Diesel QD-8000
Monterey 986Ah 'Big Sur' 24-125-11 48V battery
Off the grid on the PNW coast