question

Damian Hissey avatar image
Damian Hissey asked

Shunt pcb relocation

Hi all

I'm looking to buying the BMV-712 battery monitor to go in a 4wd.

The display will be mounted in the back of the car, and the shunt will be mounted under the bonnet next to the battery. My concern is the pcb getting wet under the bonnet. Is it possible to remove the pcb, relocate it to the back of the car near the display, then run a twisted pair of wires from the shunt to the pcb?

Thanks

BMV Battery Monitor
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

7 Answers
solgato avatar image
solgato answered ·

You might want to consider mounting it in a project box/enclosure, maybe a waterproof one if you are really concerned. Bud is a popular manufacturer.

Just notch the box for wiring and use grommets to keep it well sealed and wiring from chaffing. You want to keep the negative wire short to the shunt, so suggest you mount the box on top of battery.

Here’s a photo of my shunt installed in a small project enclosure which is strapped to the top of my battery in my solar electric catamaran.


2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

While I've never tested it, I am quite sure that removing the PCB from direct contact with the shunt will cause accuracy issues and should not be done.

I think Solgato's suggestion is a good way to go.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Damian Hissey avatar image
Damian Hissey answered ·

I did consider an enclosure, but unfortunately I don't have much room to work with.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kai avatar image
kai answered ·

Agree with previous posts.... I got forced into a situation where I had to separate the shunt from the BMS and I'm almost certain the noise I'm getting at the BMS is coming from the voltage noise being picked up over the wire run.

The noise in conjunction with non-linear sampling errors can make it difficult to trust the SOC readings... especially your typical current draws are not significantly larger than the noise.

Consider extending the DC cable run so that an enclosure becomes viable.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

dwmarine avatar image
dwmarine answered ·

Hi Damian.

All a shunt had originally to connect the gauge or display was a twisted pair or shielded cable. This worked without issues for many years, with long runs.

Just don't run the cable directly alongside high current DC devices or AC cables if they are present.

Cheers Darren

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kai avatar image kai ♦ commented ·

To reconcile previous comments with this one - if you're just looking at a point-in-time measurement (i.e. you just want to see how many amps is being pushed into/pulled from battery from the BMV), Darren's right.

On the other hand, if you're wanting to use/rely on the SOC/coloumb counting feature, the cumulative error over time can matter, and you really should use the product as designed (direct mount to shunt). BMV is measuring microvolt signals at the low end.

0 Likes 0 ·
Damian Hissey avatar image
Damian Hissey answered ·

Thanks all for your help.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

grim-reaper avatar image
grim-reaper answered ·

What about using some clear PCB lacquer to add some protection once everything is connected, I often use Servisol Plastic Seal 60 to coat PCB's in situations where corrosion might be an issue.

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

boekel avatar image boekel ♦ commented ·

that won't help for the connectors

0 Likes 0 ·