Battery voltage on dash different from Off Road Pages

[Marco#1]

Does the battery voltage on my dash display come from a different sensor than the battery voltage displayed on my UConnect Off Road Pages?

I was driving home today and had my Off Road Pages displayed on the radio, and the battery voltage displayed on the dash, and noticed they show generally similar readings, but they are absolutely not the same. I thought maybe there was a lag on one, and watched for that. The voltage on the radio seemed to move faster, meaning a quicker response time or more frequent updates, but that doesn’t really describe what was happening.

While coasting, radio voltage would pretty much snap to 14.4v as soon as I took my foot off the gas, while dash voltage would gradually tick up to either the same voltage, or a tenth of a volt less. Stopping at a red light, radio voltage would snap down to 13.3v while the dash would slowly tick down a few tenths at a time until reaching the same voltage, then maybe show a tenth lower as I sat at the light.

The two readings never diverged for very long, but I am pretty much convinced they are not getting data from the same place. It’s definitely not a simple case of one lagging or updating less frequently than the other. The dash reading, which seemed to either lag or update less frequently, would also show a different reading for 5 or 6 seconds straight and the radio reading would never show that number.

I can’t seem to find any info on this so I was hoping someone here would have some thoughts.

Sponsored

 

[THAW]

Both are likely taking readings from the ECU, but using different polling, smoothing, and/or rounding/averaging.

 

[Marco#1]

Update after this morning’s commute…

Sometimes the dash reading seems to lead, sometimes the radio reading seems to lead. Sometimes the dash reading clicks up and down a tenth while the radio reading is stable, sometimes the radio reading fluctuates while the dash reading is stable.

@THAW, I think what you said makes complete sense. I figured the same. But the readings really do seem to be somewhat independent despite being connected to the same electrical system. Hoping someone can tell me for sure whether both are coming from the same source.

 

[Jeep Wick]

Update after this morning’s commute…

Sometimes the dash reading seems to lead, sometimes the radio reading seems to lead. Sometimes the dash reading clicks up and down a tenth while the radio reading is stable, sometimes the radio reading fluctuates while the dash reading is stable.

@THAW, I think what you said makes complete sense. I figured the same. But the readings really do seem to be somewhat independent despite being connected to the same electrical system. Hoping someone can tell me for sure whether both are coming from the same source.

I don't have your answer but I do know the canbus is probably a part of it. Everything goes through a local network of sorts, so it depends on which modules are prioritized in the traffic.

 

[Carolina Jeeper]

One screen may update slower than the other. Battery voltage changes especially right after engine start up, shut down or after things are turned on or off. So, one screen may be just displaying a voltage that hasn't been updated. Basically it's possibly just a screen update rate issue.

I would be concerned if it never changes or the two are far apart and maintain that difference. Being a little different may just be the result of how the CAN bus works. I see this lag in some of the screens in machines I work with that have a CAN bus.

 

[AndySpill]

Marc:

Likely off topic and tangential, I imagine both systems you cite are reading, independent of mechanism or CANBUS priority frequency, a composite voltage of both batteries, provided you have them both connected on your 2018.

That same reading, during ESS events though, will only show the voltage of the ESS battery.

Food for thought.

 

[Marco#1]

All great points, which I agree with. But quite honestly, I don’t have any concerns. I’m simply curious about how the system is set up. I find this interesting and I generally like to know how things work.

 

[AndySpill]

All great points, which I agree with. But quite honestly, I don’t have any concerns. I’m simply curious about how the system is set up. I find this interesting and I generally like to know how things work.

Perhaps it's that our CANBUS has been smoking cannibus.

Sponsored