2011 CTS4 Coupe, 2014 ELR, 2018 XT5 AWD
Just thought you might want to know this.AGM batteries can, but can other electronics handle the constant voltage fluctuations caused by auto stop/start? I have seen the voltage spike from 11.2 to 15.3 V. With Smart AutoStart it runs at a steady 13.8 V, which would prevent a lot of electronic wear and tear.
The charging system of the vehicle monitors the battery state of charge and state of health. It varies the alternator output to keep the battery charged but not overcharged. It will reduce the voltage to reduce engine load to help fuel economy. It also looks for battery sulfation and will change to a special mode to try to correct for that. It will increase voltage if you turn on the headlights, wipers or other systems depending on the voltage required by those systems. None of this system relies on any moving parts or wear items. It is all software running in the BCM that controls the solid state regulator built into the alternator. The regulator controls the fields current in the alternator to control it's output. If the battery sensor sees that the battery is at less than 80% state of charge the stop start system is disabled and the alternator will increase it's output to recharge the battery.
When you install the smart auto stop you turn off all of these features. The smart auto stop device plugs into the sensor that measures the battery state of charge and constantly tells the vehicle computer system that the battery has less than 80% state of charge. Yes, it disables stop start, that's what you like. It also is telling the alternator it needs to recharge the battery. That's why the voltage ramps up to and stays at 13.8 volts. (An AGM battery is fully charged when it's voltage is 12.8) 13.8 volts is overcharging the battery. That results in excessive battery temperature and extra load on the alternator.
If you are disabling the stop-start system to save wear and tear on the vehicle you are not necessarily doing that.
I don't care what you do, you be you. Personally I wouldn't install the defeat device.