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Tom Ranson avatar image
Tom Ranson asked

Smart Shunt mid-point monitoring problem

Hi everyone, I have a Smart Shunt 500 A and 4x 6V 240Ah deep cycle lead acid batteries. The 4x batteries are configured in series to provide 24 V. The shunt Vbatt+ is connected to the positive terminal of the first battery in the string, and the Aux is connected to the positive battery of the 3rd battery in the string. Please refer to the borrowed diagram below which shows my configuration. Ignore the battery link from the second battery negative terminal in the diagram as there are only 4x series batteries in this configuration and no parallel ones.


The problem I have is that the mid-point monitoring is showing a deviation of 100.10%, which I understand is impossible in this configuration. It should be only 0.10% perhaps (subtracting the 100%).


I do not understand what I have done wrong here and it seems to be a very straightforward configuration. Is it possible that the shunt is not seeing battery voltage on the Aux connector? That would mean the Vbatt+ seeing 24v, but the Aux seeing 0%, which would result in a deviation of 100% if I understand correctly? I will confirm continuity with a multimeter shortly.


UPDATE: continuity between vBatt+ and Aux to all 4 batteries is good (seeing 7, 14, 21, 28 V from both these terminals to the negative terminalscreenshot-2022-06-28-10-02-33-40-30b6efbd53acd6f2.jpg of each battery).


Or have I just not implemented this correctly?


Many thanks.screenshot-2022-06-28-09-20-29-61-40deb401b9ffe8e1.jpg

SmartShunt
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klim8skeptic avatar image klim8skeptic ♦ commented ·
Check the fuse in the midpoint monitoring wiring.
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2 Answers
seb71 avatar image
seb71 answered ·

Maybe the Aux wire is not properly inserted in the SmartShunt connector.

Also check the inline fuse from the Aux wire and look for corroded contacts there.

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Tom Ranson avatar image
Tom Ranson answered ·

I can't believe it, but that's all it was... A loose fuse holder. I though I had checked continuity through the AUX cable but I must have missed it. Many thanks.

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