I’ve set my SmartShunt 300A to synchronise at 1% tail current, 56V and 10 minutes. This is with a 600Ah 48V Victron battery bank (2S3P connected with 250mm2 copper busbars). All loads are on the system side of the shunt. Yesterday I watched in anticipation of the shunt synchronising to 100% but after about 30 minutes I gave up and manually set it to 100% because it was just sitting at 99%. The charge current was well below 6A. Any ideas what could cause this behaviour?
Please read the faq’s in this section. It has all the info you need to tune and configure a shunt.
I read the posts here: Shunt / battery monitor not reading the correct SOC/ Amps, missing solar, decreasing daily or other misreading problems
And here: Battery monitor jumping to 100% or reporting a high SOC with low Volts / the BMS shuts down
I couldn’t find any relevant advice - I have the recommended settings for my lithium iron phosphate batteries for Peukert exponent and charge efficiency.
Is there some other FAQ I’m missing?
Those are excellent references and from the FAQ.
If they aren’t helping, I am sure @pwfarnell will be along to share his extensive experience.
The best thing to do is give us your SmartShunt settings as a screenshot and your absorption voltage. Did you confirm that the SmartShunt voltage sat above 56V and the current below 6A CONTINUOUSLY for 30 mins. Your settings are at the more difficult end of the range. If you are absorbing at 56V (which the Lynx NG BMS would do, then set the charged voltage to 55.8V at most, 4% tail current (which is the Victron default) and 3 minutes detection time. These values are much easier to achieve synchronisation with. I have never come across anyone using 30 minutes previously.
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Battteries are Victron Lithium Smart (not NG). Absorption voltage is set at 56.8V on the charger iaw the recommended/standard settings in VictronConnect as I understand it.
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The absorption time is controlled by the MPPT algorithm in the 250/60 charger I believe
You can also save the settings to a file and upload it.
Inside are the trends and we can see the evolution of current and voltages near 99%.
Rename it in order to be able to post it.
Voltage didn’t go below 56V and current didn’t exceed 4A for at least 15 minutes. So I don’t understand why it didn’t sync to 100% after the specified 10 minutes had elapsed.
Yes, but you also had negative currents - discharging - that could interfere and reset the timer…
Like @pwfarnell said, reduce the time for sync…
Nevermind the settings file requested above, it’s all clear from the graph.
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charged detection time is 10 minutes. I waited 30 minutes for it to sync.
From 14:37 to 14:47 - 10 minutes - you’ve had multiple negative currents - discharging.
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So if current goes negative that will reset the charged detection timer? That would certainly cause problems when my fridge cuts in! I’ll try reducing the detection time to 3 minutes as suggested.
Or even 1 minute for confirmation.
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Thanks. I’ll see what happens when the sun is out tomorrow!
So just to confirm my understanding, does the charged detection timer reset when the smart shunt current goes negative?
Yes, Alex beat me to it, when the battery is discharging it is no longer being charged so the synchronisation restarts when the battery starts charging again. This is why a tail current as low as 1% is not ideal, 4% means that you will continue to charge for the next 3 minutes.
Sorry about the 30 mins, I confused your watched for 30 mins with your timer setting. The lower the tail current, the shorter the timer setting should be. If it syncs a little early that is no problem as the charge between 4% and 1% with the Smart Lithium batteries is tiny.
Thanks that’s very clear.