C3 Picasso, not charging battery

[Wayne_R]

Hi folks,

Have got a really weird one, (well weird for me),
About six months ago C3 Picasso diesel wouldn't crank, naturally thought flat battery, walked to Halfords to buy a jump pack, connected up, jump started car, got in and drove (did a lap of M60), thinking should be sufficient to charge battery.... nope, battery still flat, battery was a cheap eastern European brand that I've long since forgotten, next thought was cheap battery reached end of its life, local dealer stocks Duracell (big name brand right) did the walk of shame carrying said new battery, fitted all good for around 4'ish months then flat battery rears its ugly head, hmmm, gotta be alternator..... ordered a replacement (dealer confirmed fitment) and asked a good friend (hi John) to fit it for me while I stood there looking useless, (existing battery is being charged during this point).

So new alternator fitted, battery charged, Launch X431 pro is showing 14. something Volts coming off the alternator, happy days.... NOPE!!! we get as far as some services just off the M25 (needed a pee) and the car wont crank (flat battery), jump pack come back out, connected up, car fires up and we continue to drive back to Manchester. when we get home i grab simple multi meter from screw fix and it show 11.3V (on battery terminals) WTF

So knowledgeable people over to you, new battery, new alternator, diagnostics shows no faults and charging at 14V, simple multimeter shows 12v & im having to hook a old fashioned car battery charger up after each use.

[Wayne_R]

EDIT / additional info:

I have checked all fuses, all electrical connections (battery, alternator, etc) are tight and free from debris.

Its almost as if the car is telling it's self the battery is fully charged do not overcharge.... confused face.

Thought: what does the smaller electrical connection do?