Voltage drop on cable to BMV 712

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xels asked Apr 19, '20

Voltage drop on cable to BMV 712

Hello,

I have just put the BMV 712 smart into operation.

I use the 10m cable to the shunt which was included in the package.

When I measure the voltage on the shunt (between B1 and ground) I get a correct value (in this case 13 Volt).

But the BMV 712 only shows 6.6 Volts and the display flickers (apparently the voltage is too low for operation).

I checked the cable to the shunt, the cable between B1 and battery plus and the fuse contacts. Everything seems to be ok.

What could be the problem here?

How can I solve the problem?

Thanks a lot

warm greetings

Martin

voltage

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Answer 1 · 2020-04-20T05:55:22Z

nigelfxs answered · Apr 20, 2020 at 05:55 AM

Some BMV712 units were shipped with the wrong fuse - it should be fitted with a 1A fuse. One can get a large voltage drop if one uses the (incorrect) 100mA fuse.

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Answer 2 · 2020-04-20T12:26:14Z

xels answered · Apr 20, 2020 at 12:26 PM

Hi,

the fuse is ok (1A) but i changed it for sure, with no sucess.

The power between plus (battery protector) and ground (shunt) is about 14,4, volt.
The power between B1 and shunt ist about 14,3 volt

The power which is shown at connecting the bmv712 is about 6,6 volt.
After the backlight is switching off it goes to 11,1 volt.

After connecting with bluetooth to the bmv the power goes to about 4,7 volt.

What happens with this piece of ..........

Pleas help

Thanks with best regards

Martin

img-20200420-121418.jpg (1.7 MiB)

img-20200420-121343.png (334.0 KiB)

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Answer 3 · 2020-04-20T12:27:11Z

xels answered · Apr 20, 2020 at 12:27 PM

Aditional i changed also the connection at the shunt (left to right)

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Answer 4 · 2020-04-21T05:39:44Z

xels answered · Apr 21, 2020 at 05:39 AM

Any suggestions?

1

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harold commented · Apr 21, 2020 at 08:35 AM

As your V changes when you use more power (light, bluetooth) I realy think you have a restriction some where in the cable or connections

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