Does any of your cars provide a 12V current reading at the battery?
Or a temperature of that battery? These could help diagnose 12V
battery issues early. But the voltage is normally sufficient to
estimate degradation.
I have dozens of items relating to the 12v battery - but as far as I can see it's all logged history of charge cycles including SOC and temps start and end of charging cycles.
eg:
#define I3_RES_EDME_STAT_E1_12V_BATTERIE_TEMP_LADEBEGINN_WERT (RXBUF_SCHAR(69))
#define I3_RES_EDME_STAT_E1_12V_BATTERIE_TEMP_LADEBEGINN_WERT_UNIT '°C'
#define I3_RES_EDME_STAT_E1_12V_BATTERIE_TEMP_LADEBEGINN_WERT_TYPE char
// Set 1 (last) - temperature of the 12V battery when starting the 12V battery charging process / Satz 1
// (letzter) - Temperatur der 12V-Batterie beim Starten des 12V-Batterie Ladevorgangs
...
#define I3_RES_EDME_STAT_E1_12V_BATTERIE_SOC_LADEENDE_WERT (RXBUF_UCHAR(81)/2.0f)
#define I3_RES_EDME_STAT_E1_12V_BATTERIE_SOC_LADEENDE_WERT_UNIT '%'
#define I3_RES_EDME_STAT_E1_12V_BATTERIE_SOC_LADEENDE_WERT_TYPE float
// Sentence 1 (last) - state of charge of the 12V battery when the 12V battery charging process is ended (= state
// of charge when starting if charging is not possible) / Satz 1 (letzter) - Ladezustand der 12V-Batterie beim
// Beenden des 12V-Batterie Ladevorgangs (=Ladezustand beim Starten wenn Laden nicht möglich)
I can't find anything specifically for temp and SOC "right now".
Steve