W115 Battery Charging System

[abbos]

Afternoon all,

I think I have found another problem with my recently aquired W115.

With the engine switched off the battery registers about 12.2v using a multimeter over the terminals. With the engine started it registers 12.5v.

I have a feeling this is not right as it should be showing at least 13v + when the engine is running I think.

Can anyone help here?

 

[Flash]

Assuming that the battery is new or in good tact could it possibly be an alternator issue or the belt just need tightening?

 

[abbos]

I must admit I don't think the belt is as tight as it should be but assuming it is ok how would I got about testing the alternator (forgive me ignorance)?

I have also read somewhere that this model has some kind of booster. I've not idea what it does but maybe someone could shed some more light?

Thanks,