question

dennisbe avatar image
dennisbe asked

BMV712 problem

I have a camper with two 95 Ah batteries. The batteries can be charged with a 140 watt solar panel, the vehicle's alternator or by a 230 V charger. And a BMV-712 to check. If the BMV displays 100% and I leave the batteries on the charger, it shows -3 Watt and after 10 days 100 Ah consumption. But shows 80% full. I took it to the technician who installed it, he checked and changed it, and now the BMV shows the charge as negative and the discharge as positive!

Any idea what he did wrong?

Settings: Battery capacity 190 AH, Charged Volt 14.5, Discharge floor 45%, Tail current 4.00%

Charged det time 3m, Peukert 1.25, Charge efficienty faktor 95%, Current treshold 0.10 A

Time to go 3m.

greetings, Dennis

BMV Battery Monitor
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

4 Answers
snoobler avatar image
snoobler answered ·

The shunt is definitely backwards.


1654804711531.png


1654804711531.png (105.1 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

snoobler avatar image
snoobler answered ·

The +/- flips sounds like he flipped the shunt around. it probably needs to be flipped back around to the prior config.


Please confirm that the shunt is the ONLY thing attached to the battery (-) terminal with all chargers and loads connected to the other side of the shunt.


If you connected the 230V charger directly to the battery, the shunt could not see the charge current. If you had 3A of loads on the 12V system, but you were charging AT the battery terminals, the only thing the shunt could see is the current leaving the battery, not the current entering the battery from the charger.


A dead giveaway that you've bypassed the shunt would be if you saw the following:

  1. voltage holding steady at float, never going down
  2. SoC decreasing
  3. battery discharging.


The following illustration shows where you should and should not connect the charger.


1654793802185.png



1654793802185.png (59.3 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

dennisbe avatar image
dennisbe answered ·

Hi thanks for your support. I took a photo of the setup. the cable on the left is for Loading (I think)foto-shunt.jpg


foto-shunt.jpg (2.2 MiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

Trevor Bird avatar image
Trevor Bird answered ·

As previously mentioned, the photo shows the shunt is in backwards.

Regards

Trevor

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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