Hey guys,

Long time since I've posted. 2011 XFR with 75k miles. I normally daily drive this car in the summer. I had it on a trickle charger through winter with the battery connected and in the car. I've since read I should have fully disconnected the battery. The battery is good (AGM, 1 year old).

While on the first drive of the year I forgot to tighten down the battery terminals. Upon tightening them down, I'm now have a BMS issue. The car fails to charge. I took the negative cable (which has a fused connector just like the XF) from my 2012 RR SC. Same issue.

I bought an iCarsoft bidirectional tool to reset the battery as if it was getting a new battery. Drove the car around town and am still getting the same battery draw, so the alternator is failing to charge the battery.

At wits end trying to figure this all out and looking for advice. Should I buy a new ground cable?

Here's how the system works:




TIA

 

Get the oem ground alternator regulator monitor connector for your specific car

 

when you unplug the current sensor the alternator goes to a fixed field.

running vbatt has to stay over 12.3V, that’s the only goal you need to achieve.

 

Do you actually have the "BATTERY NOT CHARGING" message showing on your message centre ? I have just installed a new battery(Canadian labelled AGM similar to US Walmart) in my 2012 XF 5.0NA and I reset the BMS using my VCM and SSD software. I keep battery power on my car during winter storage and I have a tool to keep power on through the the diagnostic connector when removing the old battery.

I have run the car for about 100miles and the BSM is still controlling the voltage at 12.0V most of the time and no message in my Message Centre . I checked my battery voltage across the terminals and it was 12.99V. My assumption is that it will take more time for the BMS to do its thing. The BMS kept the charge voltage between 13.8V and 14.7V all the time when my old battery was in the car.

 

I got a battery warning on the last drive trying to train the BMS. That drive was around town and not on the highway. At one point I did check the battery voltage and it was low, though not the last time I drove the car trying to retrain BMS. That said, I did charge the battery after and it took several days on a 2amp Noco.

 

Interesting, thanks for sharing. So if I disconnect the BMS wiring, I should in theory be ok? I suppose I could assume that if it doesn't charge without the BMW hooked up, it is something else, i.e. alternator, fuse block, rear junction box (I have removed this before and saw no signs of water intrusion)?

I believe it's possible the ~20 gauge wiring (two plug, at least on the 2010/2011) to the BMS is bad and was damaged at some point with battery removal. I might rerun a new lead to see if that solves the problem.