Short story....

my DSE never had battery issues (not noticable anyway), but now and then randomly during drive it gave an TC error and the info disappeared in the HEVAC dispay.

One morning a few months ago, I got in the car, turned the key, Beeb Beep. Generator failure.... after the glowlight was out, I turned the key to start, car started, not an issue..no lights kept burning (not even the charge light).

I had (and still have) issues with the EAS that some mornings it is on entry height and before I leave My driveway it sits on drive height.... other mornings it takes a few minutes to get to normal drive height, and this was one of those mornings it would not rise, this time not even in the time it takes me to drive towards the main road (5-7 min)...... drove towards the main road, but still not rising (fully)... I stopped, noticed under the bonnet that the compressor was not running and decided to drive home to collect my laptop just in case I'd get an EAS error.
On the drive home I noticed the interior light was dimm and the headlights as well..... allmost home they went to normal brightness and when I got out at home I heard the compressor running and the car lifted to drive height....

I took off to my first customer, 200km drive, and never had any issue during the drive.... switched off the car, went in, about 5 min later I got back in the car to drive around the building to their workshop... turned the key.... nothing more than a click and a verry faint "dsjoeh" from the starter..... Battery dead.... Jumpstarting wiht his thing jumpstartlead and his Volvo XC90 with difficult to reach battery did not work, so I finished my work, walked to a workshop around the corner they got my car (jumpstart with decent cables) and I got a new battery.....

Gilbert warned me to get a new alternator (spoiler now...you were right)

I drove my car for about 15k km in 2-3 months since then, still the TC-error and HEVAC display issue like before, in the first few weeks with the new battery I had once or twice the generator failure in the infodisplay at ignition on, after that never had that, but never the charge-warning light and appearantly, driving that much km allways with lights on, it charged as well... A few weeks ago I measured voltage while I had some time and the voltage was fluctuating between 13 and15,7 volts (TOO high, I know .... shit cheap aftermarket generator..) I had bought an alternator from a BMW 525TDS thinking it would be the same.... when I unpacked it, I noticed it had a different connector for D+ (and switched voltage) SO.... I took the alternator (valeo105A) out of my offroader, and brought it for overhaul to a car elektro repairshop and dropped the BMW bosch 140A at the same time,
The 140 A is going to be in the offroader (will adapt the loom to fit the new connector with switche voltage supply added) and the valeo 105A is as new and I fitted it into my DSE.

Since then no more HEVAC display going blank and no more TC-error messages.....

So yes people...... Battery and Alternator need to be 100% or you get the most incredible inexplainable errors and faultmessages.....