question

will-bunce avatar image
will-bunce asked

Why is my BMV712 smart displaying incorrect low voltage of 'AUX' / starter battery ?

I returned from a weeks holiday, only to be awoken hours after falling asleep by a low voltage alarm.

Having disabled the alarm, a today checked the voltage directly on the starter battery terminals and found it to be fully charged, (13v) as it was still receiving a trickle charge from solar.


connections all seem secure and tight at battery and on shunt, could it be a faulty RJ45?

I have fairly recently replaced the pcb board on the shunt after water came in to contact with the shunt and shorted it, however the new pcb installed and everything has been working fine for a few months, and bo there has not been further water ingress.

any help greatly appreciated.


cheers

BMV Battery Monitorstarter battery
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5 Answers
aowaller avatar image
aowaller answered ·

Mine did the same. Haven't figured it out yet.

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ronhanson01 avatar image
ronhanson01 answered ·

Are both the house and starter connected to the same ground? Ive had that happen when they were not

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will-bunce avatar image will-bunce commented ·

yes they are, the starter negative connects the the end of the leilure bank

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Pieter Boomsma avatar image
Pieter Boomsma answered ·

As you mention your board had contact with water, you could check your cable between the shunt and the BMV itself. I think there is corrosion on the terminals of the cable (or inside the connector), you can easily check this by replacing the cable with another one.

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Justin Cook avatar image
Justin Cook answered ·

@Will Bunce, check the voltage at the end of the start battery power lead to the shunt; there's a good chance that you have a half-blown fuse in the power lead, which will lead to erratic voltage being delivered to the aux port of the PCB, which the BMV display will interpret as low starter vbatt, since all the display can "see" is the voltage being delivered through that power supply wire.

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Martin Keogh avatar image
Martin Keogh answered ·

Check the red monitoring cable and fuse. Mine was faulty from the factory and was reading the incorrect voltage

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