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orangecrush avatar image
orangecrush asked

VE Direct Cable Hack

I have a BMV 702 in which I re-purposed an available in wall Cat5 cable to create my UPT RJ12 connection to the round display module. This used 3 of the 4 twisted pair in the Cat5 cable and has worked flawlessly. I am now adding a Cerbo GX next to the shunt and would like to leave the round remote display in place but also connect to the Cerbo GX. I am assuming I can do this by connecting the VE Direct port out of the round display and running that to one of the Cerbo GX inputs. In order to do this I am thinking about trying to re-purpose the remaining twisted pair in the Cat5 cable to return to the location where I have the shunt and Cerbo GX and adding 12V/Gnd there before plugging into the Cerbo. Anyone have a since as to whether any of this will work, or if I am crazy for trying, or both?

BMV Battery Monitor
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nebulight avatar image
nebulight answered ·

First off, ve.direct is 3.3v on the BMVs, not 12v. You've only got 2 wires and the VE.direct port has 4 wires: RX, TX, Ground and 5V. However I think the power needs to be coming from the ve.direct product, not the cerbo, but I could be wrong on this. If I'm right, then you won't it won't work as you've only got two wires left. I guess you could try to inject the power going into the cerbo, but I wouldn't.

Bottom line, is I probably wouldn't risk this, but it's up to you.

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wkirby avatar image
wkirby answered ·

The input on the CerboGX will definitely need all four wires coming out of the BMV unit.
You need +3.3V, Tx, Rx and GND to go from the BMV to the CerboGX.
The 3.3V is required to power the outward facing side of the digital isolator at the VE.Direct port on the CerboGX.

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orangecrush avatar image
orangecrush answered ·

OK. Plan B. Can I connect a bluetooth dongle to the ve direct port on the BMV 702 and have that connected via bluetooth to the Cerbo?

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nebulight avatar image nebulight commented ·
You can't currently connect devices to a cerbo via bluetooth so that's not an option.
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Mike Dorsett avatar image
Mike Dorsett answered ·

Whilst sharing data from the shunt to the BMV and the Cerbo is theoretically possible, you have a problem in combining the Tx data from these units to the shunt..

retaining the round BMV display with the cerbo is not a good idea.

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