I have a Victron IP65 Battery Monitor shunt with the optional temperature feature. I currently have the temperature sensor wire connected to a LiFePO4 battery positive post. I have a battery disconnect switch between the battery positive post and a positive bus bar block. My issue is when I disconnect the battery using the disconnect switch I still have a small battery drain which I assume is because the temperature sensor is connected to the positive battery post. Can I connect the temperature sensor to the positive bus bar block which is after the battery disconnect switch? Will the battery temperature still be accurate when the disconnect switch is “on”?
Short answer NO.
The temperature sensor needs the mechanical connection to the battery to read the battery temperature. Connecting it to the busbar will read the busbar temperature.
I have wondered about a variation on this theme (for the same reason as the OP).
In my case I have a BMV 712 with a “regular” shunt and a Victron 12.8 Smart 200 ah battery. Right now I have the temp sensor connected the suggested way (lug on positive battery terminal; small black and red wires to the two shunt push-in terminals)
However, what if one were to connect the lug itself to the negative battery terminal, with the small negative wire straight to the shunt; but then run the positive wire/fuse from the shunt to a positive bus bar (which could be after the battery switch so that then the residual load of it would be cut off when the switch was turned off).
So in other words, the shunt would receive power from the small red wire, but just not directly from the battery, and the lug would still be on the battery to sense temperature (but on the negative terminal)
Would the temp sensor part of the sensor lug work connected to the negative battery post instead of the positive one?
Temp sensors I’ve had in the past have connected to the negative battery post, but they were never set up with both red and black wires going into them. So I didn’t want to change anything without checking.
If the above would work, then that might be a useful solution for the OP and something I would consider as well.
@Coaster You can not do this, the lug on the battery is live and this provides the 12V signal to the voltage sensor PLUS the 12V power to operate the temperature sensor. The black wire is not 0V, it is the voltage signal from the temperature sensor. Your idea will not have 12V power to the temperature sensor.
What you can do is connect a flying lead with fuse to the lug and make sure that the lug was fully insulated so you do not have open positive surfaces. Then attach the flying lead to the 12V bus bar and tape the lug to the battery case where it is away from the negative terminal.
@Coaster The fuse on the flying lead goes close to the bus bar to protect the flying lead should it short circuit and would be 1Amp.
Thanks for the information, pwfarnell.
I feel like the temp info is going to be more accurate attached to the battery lug vs. the plastic outer case, so I think I’ll leave it as is (and remember to pull the inline fuse if need be).
But you satisfied my curiosity about supplying power to the BMV via the positive lead “from the other direction” – i.e. detached from the sensor lug vs. via the temp sensor lug. Thank you.