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Jeffrey A Walker avatar image
Jeffrey A Walker asked

Cerbo GX failure X2

I recently completed my RV system. Every thing worked fine but about 2 weeks after start up my Cerbo GX failed, No lights were on and the GX no longer showed up in the list of components using the App on my phone. I have the power cord attached directly to one of the battle born batteries. I checked the fuse and it's good. I checked the power at the black connector and there is 12 Volts going into the unit. My supplier replaced it with a new unit and all was good after hooking the new unit up, but hat lasted less than 24 hours and the new unit was dead. I have been at a loss as to what is wrong.

I do have a smart shunt in the system and in a previous question Seb71 commented that nothing should be connected to the battery Negative if you are using a Smart shunt. Could my failures be due to directly attaching to the battery?

If this is the case where should I attach the negative for the GX, and have I burned up two units at this point?

Thank you in advance to anyone that can help.

gx device
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1 Answer
wkirby avatar image
wkirby answered ·

Something pretty weird is going on there.
The negative wire being wired directly to the battery should not cause the problem that you are experiencing. That just means that the shunt is being bypassed and the energy consumption of the GX device its self is not being counted. The recommendation to wire all loads to the load side of the shunt is to ensure that their energy consumption is accounted for.

I wonder if there is some sort of over Voltage event if the batteries' internal BMS disconnects, although this would have to be pretty high because the CerboGX can accept a Voltage of up to 70V. If a charging source is charging at full power and then the BMS disconnects, then it's possible to have a high Voltage spike.
Other things to check is that there are no ground loops or ground differentials causing current to flow in the ground plane. If you have a temperature sensor wired is its lug at the same potential as battery negative?
Without knowing very much about how your system is wired, that's all I can think of for now.

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