2021, CX-30 Grand Touring FWD Dark Gray
Well John---After I found this post here about a german car maker having this exact same problem since 2004--I am guessing the start of adding so many different sensors to their cars...and now my CX-30 having somehow similar issues. In my own personal case--after I run around my own car--example, while cleaning it and or washing it...which never before caused similar problems to my previous cars--unless of course I was playing my electronics at full blast--which I sure did when I was younger."-although if we think about it--accumulated events leads to battery failure to start the car" This is correct, but only part of what the engineers are trying to prevent with "smart charging systems". One thing often overlooked is that when a battery ends up staying low state of charge, it's total lifespan can be significantly shortened.
I have been watching the battery in my CX for several weeks to gain some insight into Mazda's system and it's not that different from a number of manufacturers. They don't keep the battery at 100% state of charge, in fact it appears that 80-90% is the target based on this chart. View attachment 1921
That actually makes a lot of sense because the battery isn't just for starting the car. It helps prevent voltage spikes (it's technically speaking the largest capacitor in the car) in the vehicles systems when it can readily accept any charging current, and it also supports system power under conditions where vehicle demand is higher than the alternator can produce.
Without writing a whole class on smart charging systems here, a test that can be run by any owners willing to do so would be to park the car with the hood open after having just been driven. Measure the battery voltage. This voltage "should be" relatively high (over 12.8v in most cases). This would be considered "surface charge". Remeasure the voltage after the car has sat for an hour. Some decrease in the battery voltage is expected because of both the surface charge dissipating and some normal parasitic loads as modules went to sleep. Repeat this measurement at two hours, three hours, and four hours without disturbing the car and waking modules up. By now everything should be stable and the batteries true state of charge should be reflected by the chart above. If your battery checks out lower than 12.28v, a 60% state of charge then you will be seeing the battery saver message earlier which means the system will not let you keep the doors open, or run the radio (accessory mode) as owners have been describing. That's enough for now, lets see what the battery state of charge is for the owners having issues.
However--I did hear some beeping and funny noises while I was washing it. Have no idea what those noises were coming from--But, having some experience with electronics--there seems to be some sensors running (operational) where they should be none...and are being activated by my close presence to to car...those are my two cents.
All car sensors should have a condtion in order to be active and/or running. They all should be completely non-operational if the car engine is not running + seat belts locked.
Doors, hoods and rear doors do turn a light on--however, we know most cars (since many years back) shut this light off automatically after few minutes-in case we accidentaly leave them open--of course, to prevent killing the battery by accident.