I keep having the smart shunt SOC drifting due to cloudy weather. Not reaching absorption and subsequently not resetting to 100 percent.
I get why it’s doing it, and all of my settings are definitely correct, but my question to developers of the software is,
why is the ‘smart’ shunt being so dumb?, surely you can fix the software to read the current in and out AND the voltage to correctly estimate the SOC. It shouldn’t take me with a multimeter and voltage chart to work out the correct SOC when the shunt is clearly able to read the voltage, temperature, current flow and other things to determine the correct SOC?
I love victron stuff and have invested in a very good setup, using the remote VRM to monitor and setup remotely and everything else mechanical works flawlessly. But I regularly get notifications my batteries are nearly flat, when they aren’t!
It’s the software that is letting it down and is frankly disappointing that I have to manually ‘tell’ a battery monitor how to work properly.
I am writing this in the hopes that the developers of the software see the importance of the shunt calculating the voltage and the current
To calculate soc properly. It’s a flaw that even I, a DIY guy with a multimeter and AI can work out the exact SOC based on voltage and current data. I shouldn’t have to , that’s why I bought your smart shunt!
Post a screenshot of your SmartShunt settings here, the type of batteries, your absorption voltage and in what directikn the drift occurs. I have had excellent experience with BMV and SmartShunt monitors but to get the best they need tweaking.
Smart Shunt SOC can drift depending on the settings, and battery type. It should reset to 100% SOC at a programmed voltage, please post your settings and voltage cycle data.
This is what it’s set to ATM, but have gone through so many settings it’s not funny.
I have tried 14.5v absorption 13.4 float on the mppts.
So charged voltage was on 14.2v on shunt.
I have also tried every combination of tail currents, charge detection times, ect. Known to man!
I now have the mppts on 13.4 charged , and absorption. Absorption time 0 mins.
I have tried the no absorption now ( because it’s a lifepo4 battery) and the manufacturer said it doesn’t need absorption, just float at 13.3v
They are 2x 200ah rock lifepo4 batterys.
Max discharge and charge 150a , Max charge voltage 14.6v .
As mentioned. I have tried and tested, tweaked and have followed graphs from the cerbo, tried pretty much everything in every setting on the shunt and mppts for months, it’s cloudy here ATM and it just won’t reliabley indicate correct SOC .
For over a week the SOC drifted down and down even though the voltage at the end of every day charging was 13.3v.
P.s. Yes the shunt is reversed direction. It’s mounted that way.
If you only float them at 13.4V then the charge rate will be quite low. What is normally meant by no absorption is the you charge at say 14.2V but you only then have very little at this voltage before going to float. Personally, I would go with 14.2/13.5 on the MPPT with max absorb time 15 mins and 14.0V charged voltage on the SmartShunt with 4% tail current. These only affect the sync to 100% not the drift.
On the shunt, the Peukert exponent and the charged efficiency can affect the drift. If you are find SOC is drifting down then try 100% charged efficiency and if drifting up then 98%. Peukert exponent also affects the drift but its effect depends on the type of loads seen, shorter high loads or longer low loads. You can try varying this from the default 1.05 and seeing how the system behaves for a few days as the effect is cumulative.
Also. Would it be beneficial seeing all of my VRM data to determine how it should be setup?
I have not shared it before, but I’m sure it is possible to to do.
Just don’t know anymore. I have changed so many things trying to get everything to work as it should, I’m totally lost with conflicting information now.
I have a very good understanding of victron gear and have had it running for a long time. But this… not properly registering correct SOC is driving me crazy! And triggers VRM alerts from alarms I have set up annoyingly.
Ahh. Ok.
I know I can share it by email. And have it set to view only. But if it’s not beneficial then no point.
I can send screenshots of the graphs. Ex. Voltage, current, showing real world info for this setup, but again, only if it’s beneficial.
In the meantime, I have set the settings in the shunt and the Two mppts (the are synchronised)
That you have recommended. It’s worth giving it a shot.
As mentioned it’s very cloudy and rainy here ATM, so I’ll have to try it out over a longer period, but thanks.
Looking at the screenshot, is there anything else you would change in the smart shunt?
Also. There is a tail current setting in the mppts. I haven’t touched it , but could that contribute to anything?
With a short duration absorb, the charged detection time is best at 3 mins.
If you are using tail current to stop absorption then this needs to be set lower than the tail current in the shunt to make sure the mppt stays in absorb until the shunt syncs to 100%, so ideally set this to 2% and see of it works. For tail current to work on the mppt DVCC has to be enabled on the GX device and SVS and SCS turned on so the Smartshunt info is shared with the mppt.
one point: SOC on reset should be 100% not keep SOC, otherwise it won’t reset to 100%. I’d also try a larger tail current of 2 - 5%, and make sure that the Charged detection time is less that your absorption time by 5 min. Charged voltage could be Abs voltage - 100mV, or equal to the float voltage. Also make sure that the Zero current setting is good.
No. When the shunt does an automatic synchronisation it automatically goes to 100% no ifs no buts, nothing the user can do.
The “Battery SOC on reset” setting is if you power off the shunt and on restart it tells the shunt what the SOC should do. The best option is “Keep SOC” so it remembers what it was at shutdown.
All explained in the manual.
@TotalMayhem “SOC on reset” is best set to “Keep SOC”.
