Title says it all, never had an issue with the charging system until recently but I have a check engine light for electrical load detector and on my S300 I’ll watch the voltage drop from maybe 12.5 tops and go down slowely to now about 10-10.5 after only maybe 30 miles tops. Besides alternator and battery what else could cause a very slow charge like that?

 

eld is built into the underhood fusebox on the firewall.
you need to replace the entire box.
worked for me.

 

Try disabling the ELD in your calibration, see if that changes anything.