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offrocker avatar image
offrocker asked

SmartShunt 500A voltage varies when connected via app

I have a SmartShunt (500 A), and I am connecting to it via the Victron iOS app. The SmartShunt has firmware 4.08 and Bluetooth firmware 2.37. I also have it connected to a computer via the VE.Direct port.

When I connect via the app, the reported voltage immediately drops by about 100 mV. The voltage then rises, and a small (< 2 A) charging current goes into the battery. After a few seconds, the current drops to 300 mA. This then continues until I disconnect the app. About 30 seconds after disconnection, everything evens out and returns to normal.

I also have a Blue Smart Charger, and the charger and shunt are connected to a VE.Smart network. When the app is connected, the charger is raising its output by 100 mV. I observe this 100 mV difference via a second app connected to the charger as well as via an independent, non-Victron voltage monitoring apparatus.

I am not sure, but this issue may have begun following the recently released update to the SmartShunt's Bluetooth firmware.

Does anyone have any advice?

Is it possible to downgrade firmware? (I am a software developer, and I doubt it is, but I'll ask anyway.)

Also, is it possible to calibrate the SmartShunt's voltage reading? Mine is low by about 1%.

SmartShunt
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JohnC answered ·

Hi @offrocker

This could be symptomatic of high resistance in the power lead (the one with the fuse in it). Check all the connections there, and maybe change out the fuse (1A, not 100mA).

I very much doubt that firmware is the issue, but it is possible to 'zero' the shunt if you're devious enough to falsify a zero.

There was a batch of BMV's (I think) that mistakenly came out with 100mA fuses, and showed similar issues to what you describe.

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offrocker avatar image offrocker commented ·
I'm pretty sure you're right. I pulled the fuse from the temperature sensor's power lead and measured its resistance at 59 ohms! It's only 100 mA, as you suspected. I'll replace it in a few days with a new fuse. Thanks for the help.
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