electrical consumers switched off!!

[GSI-jim]

2002 w211 e320cdi. I drove home from work with no message, got home, went back out 45mins later & dash said electrical consumers switched off. It said it all night while i was out out & didnt go off. Today i checked the batteries, both are 2 months old, rear one had 10.8v before starting, then went up to 11.8v running & occasionally jumped to 12.8 but went back down to 11.8. Front one has 12.3v.
Is this likely to be the reg pack on alternator or can it be something else?
any checks i can do at home?

 

[Dec]

All sounds like a bad alternator.

Do the voltages check on the rear battery about an hour after the car has been driven.

Is your car capable of displaying the voltage in the cluster with ignition on and engine running, like the one in video below and here… On dash voltage display - MBWorld.org Forums

Useful to be able to watch the battery voltage as you drive and turn on/off various consumers.

Dec
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