vtecvfr avatar image
vtecvfr asked

SmartShunt Battery Settings??


I have a 12 V battery bank consisting of 8 6V 370 ah FLA batteries.

Other than changing the battery bank AH size, I think all the other settings are the defaults.....See below attached.

Can someone comment if the settings are accurate?

Thanks in advance.


cerbo gxSmartShuntVictronConnect
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3 Answers
snoobler avatar image
snoobler answered ·
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Wayne avatar image
Wayne answered ·

Looks pretty good, the charged voltage may be a bit low, if you notice it syncing early you might need to raise that a bit..

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JohnC avatar image
JohnC answered ·

Hi @Vtecvfr

I note you've asked this before. Still struggling?

What you really need to do is grab the manual and try to understand what the settings are for. For best results they need tuning to your own batts, and only you can do that.

These are my own FLA batt settings (48V version). And they work very well after a lot of fine tuning. They're my batts, not yours, but should be closer for you than the defaults..


Similar CV to your 13.2V. I decided i want to sync in Float (not Absorb), so set to lower than Float, and out of the possible temp-compensated range of Float. I'd leave that where it is.

The default Tail is too high. I'm still in Absorb then. My true Tail is like 0.5% (at the set CV), so 0.6% works fine. I might raise it to 0.7% in the shorter days of winter, cos I run out of daylight time to fully complete.

The 5m CDT is a little higher to avoid sync at times of unstable sun. You'd need to watch what your V and I does in a dynamic situation to understand this.

True Peukert you can derive from your battery specs. Your 370Ah should be a 'C20' rate. Ideally find a C100 rate, but maybe even a C5 or C10 is available. Run that through the Peukert calculator (on Victron website).

Optimistic at 95% CEF. If you're not drawing your batts down lower than (say) 80% SOC daily, then you'll need lower, else you'll wind up to 100% SOC before fully charged. And if you're not watching the Tail I, the downward drift in true SOC (as distinct from reported SOC) can add daily.

And yes, it can change with how far you draw your batts down daily, and batt Temperature between winter and summer might also need tweaks for a 'perfect' result. We usually learn to live with a middle-o-the-road compromise though, so Good Luck finding yours..

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vtecvfr avatar image vtecvfr commented ·

Thanks for the detailed reply.......and yes I am still playing with the parameters. Made a few tweaks based on your settings/input....

I also included the batteries I am using....MK-8L16-DEKA.pdf


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snoobler avatar image snoobler vtecvfr commented ·

IMHO, when using the Peukert calculator, you should avoid the C100 value unless you actually expect to use it. Given that many systems don't have 4 days of battery power with loads that do not exceed the C20 rating, I find it impractical and misleading. When used, C100 produces optimistic values. I like C20 and C5 when I can get them because I'm likely to be working between them in most cases.

The 8L16 has C5 of 275 and C20 of 370.

The calculator yields 1.27.

If there's an error, I'd rather have more than the system says than less.

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JohnC avatar image JohnC ♦ snoobler commented ·

Hi @snoobler

I'm up for a friendly discussion on this. There are many posts on this forum asking why the Ah discharge shown in VictronConnect never matches the shunt SOC. Peukert is largely responsible for this of course, but the complaints are invariably 'too high SOC', indicating all the complainants are using less than C20 discharge rates.

Now 50% SOC is generally considered a low point for discharge for pb's, but 75% is better. Using my 225Ah bank as an example, and drawing down at C50 for an overnight 12h means 225/50x12 = 54Ah. Around the 25% max drawdown I target, but a little less given the 225Ah is effectively larger than that at C50.

Poke holes in my means of expressing this as you will, but it ain't C10 or C5, it's in the C20 to C100 range. We all use higher discharge at times, and this can impinge, but there's an average somewhere, and it's almost always lower than C20 discharge rate.

I agree though that the 1.09 Peukert seems low (I checked it and it's correct). And I think sometimes makers are a little careless with rounding etc with stuff like this.

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