question

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woody06 asked

Battery current reading reverse of DC system current with REC-BMS

Hi,

I have a REC-BMS communicating with a Cerbo GX over the can bus. (side note, for anyone else trying this I had to ignore the manual and use the VE bus rather than the can bus, and to set the speed to 250k instead of 500k)

The BMS has a shunt resistor and there's only one place the current is measured. The data is sent over the VE bus to the cerbo gx. While discharging, the battery current says it's charging and is the exact opposite of the DC system current. DC system current is the correct sign.

I just updated the firmware on the Cerbo GX to V2.94 and the issue persists.

Any thoughts?

img-1247.jpg

cerbo gxBMSVE.Bus
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1 Answer
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woody06 answered ·

Figured it out! It was a combination of incorrect leads on the shunt and not understanding the sign convention for the DC system. After switching the shunt leads it now reads a positive number for the DC system and says "from battery", along with correctly stating "discharging" under the battery percentage.

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