kelvin sensing

Thread Starter


Joined Aug 2, 2012
could someone please post a pic of how to implement a kelvin connection to measure battery voltage directly at a 12v lead acid battery and connect that to a pic18f4523 controllers a/d?
I've attached my charge section and bvolts is from my battery but the voltage drop while charging is causing me to not accurately sense the real battery voltage.

should the a/d vref+ and vref- be connected at the battery terminals
via a 5v regulator?

I would really appreciate any help.



Joined Mar 14, 2008
For a Kelvin connection you need a differential type input. You connect the two differential leads to the battery terminals. The measurement then does not see any voltage drop due to cable resistance Since I believe the PIC does not have a differential input, then you need to add a Instrumentation (differential) Amp buffer, such as one of these or these, between the battery and the PIC input.