Smart Shunt Data and VRM Display

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ako asked Mar 25, '23

Smart Shunt Data and VRM Display

I connected my new Smart Shunt yesterday and thanks to clarification on some aspects by Axexandra I understand it better and it seems to be working well with a few exceptions .

Average discharge: The cumulative Ah drawn divided by the total number of cycles

Total charge cycles: The number of charge cycles over the lifetime of the battery monitor. A charge cycle is counted every time the state of charge drops below 65% and then rises above 90%

My SOC is only ever less than 70% on the rare occasion we had a bad day weather wise so it seems that the Average Discharge will never be correct . History shows Deepest Discharge , Last Discharge and Cumulative Ah Drawn but nothing displayed for Average Discharge . Is there a work around .

This morning is the first time I can look to see how my batteries performed last night on Victron Connect . There is no TIME REMAINING shown , just – , is that because the Solar is charging at the moment and its only relevant at night when there's no input .

I changed the default Battery Efficiency from 95% to a more realistic 85% , what data is this information needed to calculate .

Do I need to set the Peukert factor with shallow discharges , my normal consumption at night is at most 3% of Battery Bank capacity .

Lastly , why does the VRM Dashboard occasionally become corrupt with a different layout and has anyone found a way to restore it , its been this way for 12 hours now and I have tried Logging out , Turning off my Internet , Unplugging the Cerbo , nothing has any effect . Its the same on Windows Laptop with different browsers and Android phone .

Many thanks to anyone who can assist .

SmartShunt

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Answer 1 · 2023-03-25T10:21:35Z

JohnC answered · Mar 25, 2023 at 10:21 AM

Hi @AKO

Yes, the Charge Cycles count needs some work. I still have zero cycles on mine after several years. I think the 65/90% thing could be applied successfully to the zone above the set Discharge Floor, which would in most cases be more appropriate, and also give a defacto adjustment.

The Time Remaining only applies under discharge, down to that same Discharge Floor.

Presuming you have Pb batteries, your 85% Charge Efficiency might be a little low. I'm not sure how this is handled, but it's not the same as batt round trip efficiency. Adjust it upwards when the 100% sync requirements are met before the calculated SOC gets there under it's own steam. And vice versa. You won't get this right overnight, and may even find it changes seasonally if your batts are subject to temp variance.

The default 1.25 Peukert is probably too high if you're discharging lightly. It will apply a 'credit' to your SOC, and possibly not show how deeply you're really going. This can be calculated from batt specs (Victron app), and even then I go a little lower to err on the safe side.

I can't help with the VRM display. Never seen that.

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Answer 2 · 2023-03-25T12:15:09Z

ako answered · Mar 25, 2023 at 12:15 PM

Thanks John , i have just encountered another situation that i dont know how to get around . It says that the unit will synchronise battery to 100% when 3 parameters are met

Voltage

Tail Current

Time

My adsorption voltage is 28.8 and i followed the instructions and set the charge voltage 0.3 volts lower than that at 28.5v

What happens is once the adsorption voltages is reached the current reduces until it goes into Float then the Voltage drops to 27 volts . The problem is that when the tail current is reached the voltage is to low to meet the criteria so will not synchronize .

My tail current is 1.85 amps but i have been at around 1.3-1.5 amps for ages and battery percentage has only reached 97% so far although it has been rising steadily it will be a while before its at 100% . I do not know if my batteries will actually be 100% full or not and if they are is there a chance of overcharging them as they are AGM and vulnerable to overcharge .

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JohnC ♦ commented · Mar 25, 2023 at 01:52 PM

@AKO

You have to decide whether to sync at Absorb or Float. Then set the Charged V to suit. This can get a little tricky with a low Float, then Temp Compensation in hot weather can reduce that gap. Passing cloud can hold up V with sluggish batts, while Amps drop, so you may need to increase the Time to prevent premature sync with cloud.

I've flooded batts, and drop to Float at ~3% A/Ah. That's about 99.0% SOC for me, and I sync at 0.6% (for 5 min) to pick up the last 1%. That's at the lower Float V, so the Tail% is lower. You may not be so fussy, and this Tail figure is well below the default 4%.

Your 97% suggests you need a higher Charge Efficiency setting (I've said that). You just need to get to know you batts and how they behave with the Amps they can accept at various V's. Patience, hey. Your batts won't overcharge at Float V, so long as it's not set too high.

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Answer 3 · 2023-03-26T08:00:36Z

ako answered · Mar 26, 2023 at 08:00 AM

Very interesting John , i can see you have mastered the Shunt so as to configure it to produce what you need to see . From your SOC settings i now have a better understanding myself . I am going to use Float Voltage -0.3v @ 5 Mins , i did read that it takes account of Temperature Compensation so cold weather shouldn't be a problem .

I was disappointed to see that the Average Discharge will not function if batteries don't fall below 60% SOC and if it does occasionally then it will be well out because it will be averaging the total Consumption by far fewer cycles , im surprised they set the bar so high , with batteries being so expensive im sure a lot of users like us keep our SOD lower than required so they last as long as possible .

I am considering reducing the Battery Bank setting to 1/4 of what it actually is to be able to see the Average Consumption , the Time Remaining will be out but as its not that helpful anyway im not concerned about that , not sure what other data relies on it being correct , hopefully nothing important .

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JohnC ♦ commented · Mar 26, 2023 at 10:14 AM

@AKO

Yeh, I grabbed a Smartshunt when they first came out, solely to give me a batt Amp reading for my mppt to use to finish Absorb. The SOC gets thrown up everywhere in big figures, so it challenged me to tune it. Now I'm not happy if it's out by more than 0.2% SOC when it syncs. :)

Average discharge doesn't mean much to me, but if I wanted it I'd just use the total Ah or kWh discharged in the History, and divide it by the number of days since history was reset (I'd have to go find that). Then all the minicycles that may happen within a day (like with large load or passing cloud) I'd be forced to wonder about.

So I don't. I can tell you're a thinker, and that's great. How you choose to run is for you to determine. These are still great devices, and changed the way I treat my batts.

Thanks for the heads up on that Temp Comp thing. I looked years ago, maybe changed since?

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Answer 4 · 2023-03-26T15:51:09Z

ako answered · Mar 26, 2023 at 03:51 PM

Reducing the Discharge Floor would also make the Time to run calculaion inacurate if it was ever needed but it should also work in providing an average Consumption as the calculations are done on the active part of the SOC , just need to adjust it so that the SOD is always greater than 35% of that .

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