question

andreholgersson avatar image
andreholgersson asked

Why is SmartShunt showing high state of charge but low battery voltage?

Hi!

At 16:30 the other day, someone pulled my shore line.

I had an alarm set that should notify me if SOC went lower than 50 percent. That didn't happen. Instead I got an alarm when the voltage was about 8 volts. Is my settings messed up or is one/both of the batteries toast?

I have two Victron 110Ah AGM batteries in the service bank. The SOC apparently does not reflect the reality. How can about 0.2A load deplete two 110A batteries in 14 hours?

Time remaining also seems quite off. It suggests that I have about 90 hours left when the battery voltage is around 8V??!

Graphs below is home assistant, and data is pulled by mqtt from the cerbo gx.

Running Cerbo GX v2.90 & Smartshunt v4.08

Settings are as follows:

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cerbo gxSmartShunt
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1665782067200.png (50.1 KiB)
1665782846059.png (34.8 KiB)
1665782860082.png (36.2 KiB)
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2 Answers
JohnC avatar image
JohnC answered ·

Hi @andre.holgersson@callisto.nu

I think there may be something wrong with your batteries, or something else in your system.

The shunt figures appear to be in the ballpark for the applied load. Coming off a ~14.0 'float' and the V collapsing like that is indeed unexpected. And then when you reapply charge the V goes instantly to target V with just 11A and tapers quickly. This indicates the ~95% SOC shown then isn't far off.

The batts may have dried out, and if you're applying that flat 14.0V continuously there's a fair chance of that too.

At the shunt, your Charged V is a bit low and Tail too high, and that will cause the big SOC step your graph shows. With the 4% Tail setting you're telling it to sync to 100% at <8.8A at a low >13.2V.

Or you have a phantom load that's bypassing the shunt. But the evidence doesn't really suggest that.

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andreholgersson avatar image
andreholgersson answered ·

Many thanks for your input! I have a multiplus 12/800/35 that charges the batteries with default settings. Most of the time it is in storage mode, and charges with 13.2V. As there is a constant load from the Cerbo GX and the LTE modem, charge occasionally goes up to 13.8 or 14 volts to top them off. The batteries are barely 2 years old and have only one complete discharge cycle. Do you think I should contact my dealer and claim warranty replacement?

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JohnC avatar image JohnC ♦ commented ·
@andre.holgersson@callisto.nu

I wouldn't abandon them just yet. I'm not a big fan of storage mode for long periods on Pb's, and they may benefit from a bit of regular cycling. Like down to 80% or so (If you can get there!), and they may improve. Might take quite some number of cycles, but if they've dried out that won't help much. I'd have to look it up to be sure, but I don't think the SShunt registers full cycles til it gets down to like 65%, so shouldn't impact the cycle count.

I note from other posts you have a Multiplus, and if you're up to the challenge you could set up Assistants to do this by using the IgnoreAC functionality. This could also bring ACIN back on immediately if that V failure reoccurs. You could target 80% SOC and see what happens. If it improves keep going, if it gets worse the batts are probably done for.


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