IMO Cetek is the best system, On my R230 SL I’ve got “Cetek traffic light connectors” on both batteries giving an instant view on charge condition. As my auxiliary battery is getting old (2008) it gets coupled up as soon as the car is in the garage but so far I haven’t required to charge the main battery which is a 2018 one.
My CLS is still under warranty and so far I haven’t experienced any problems with the batteries.
My CLS is still under warranty and so far I haven’t experienced any problems with the batteries.