XSeries-forum

Why is my ctek doing this on all my batteries..

Are the connections the right way round? The warning light is either - reversed polarity, interrupted charging or not on a 12V battery.

Your BMW battery is very likely AGM - most have been since the early 2000’s. You need to press <Mode> to put it into AGM charging. The charging cycle is different.

My MXS10 died after ten years. It wasn’t charging the battery completely even though it thought it was. The red tell-tale light I have on the permanently installed ‘quick disconnect’ flashed red all the time, so gave me a clue. The battery itself was fine - and still is.

Polarity correct. The mode button won't work either. It does the same thing on 4 different batteries so I think it's fubarred. I'm not having much luck with vehicle electrics at the moment.

Switch cleaner will sort the mode button out.
Hot air gun on the black plastic and it will peel back then a squirt of cleaner and play around with the little button.
Warm it again and stick it back down.
Not sure if it will fix the red light but nothing to lose.

Always thought they were quite robust. Ran over mine about 4 years ago and it does the job

Just bagged the MXS 5.0 on amazon for £60 so that's not bad.