Alternator has output but battery isn't charging - help!

[WheelyBigBox]

I've been struggling with starting / battery woes for a while. Initially i thought it was just the cheap lion battery from ECP that was at fault, now i'm not so sure.

After multiple short journeys it's no surprise the thing needs a recharge however what i've been noticing is that after long drives (eg 20 miles) the engine would then struggle to restart and i keep noticing it. Yesterday we went out to an event appox 20 miles away, got back to van, it started but i was still aware that it wasn't sounding like a peak performance. Drove home.. This morning it was a bit slower to start. Went to work, finished, got in the van and it really struggled to start. Once running, things like headlights don't seem to be a problem - unless i'm just not noticing.

Got home, got the little'un to come out with the voltmeter before i stopped / charged the engine.. On the engine jump starting points there is 13.9V (well it fluctuates a little between 13.85-13.95V but it's enough to show an output). When i checked the battery, the voltage was 12.05V - yes 1.9V lower than the output voltage from the alternator across the engine.

So the alternator seems to be running but the power isn't making it back to the battery. Is there a charging relay somewhere that has to be turned on or something? - I'm fed up of keep connecting the charger to it each night.

[WheelyBigBox]

Pleasy weasy?

[WheelyBigBox]

Ok so i've removed the earth strap from the battery, it was proper manky looking all over the bolt.

Spent a while cleaning that up with the wire wheel on a rotary tool, also cleaned up the strap itself so that copper could be seen again.. same problem.

Measured the voltage with the red terminal on the + of the battery and black on - terminal. 12.3V. Engine jump points show 14V.

So hooked a jump lead up to the + on the engine then measured it with black probe on - of battery: 12.3V.
Jump lead on + of engine and red probe on + of battery: 14V. So the earth is at fault as the + of the battery is definitely working at 14V.

Then put the black probe on the bolt for the battery earth strap - before the fusable link. Red on the battery: 12.3V - that rules out the fusable link!

Put black probe on the door catch post that the door clings onto when closed: 12.3V.

Finally hooked up the jump lead to the chassis under the van, kept the red on the battery then touched the black to the other end of the jump lead: 12.3V.

Conclusion: Entire chassis has an earth fault between it and the engine. The + supply works if the jump lead is connected direct to the engine for it's - polarity. So somewhere there is a earthing point between the engine and chassis that's not right.

Any idea where i can find it? - Is there a diagram with all the earth points on ?

[Brains_transit]

The earth wire from the starter to the chassis can look fine but the internals can be corroded

[WheelyBigBox]

But WHERE IS IT?

[Frag]

The clue is in the above statement
Goes from starter motor mounting bolt across to near side chassis leg

[WheelyBigBox]

Good point, sincere apologies i missed that!!!

For some reason i had it in my head that it was the engine it was connected to - didn't think of the starter.

[WheelyBigBox]

Lads, I cannot thank you enough!!!!

Been down under and found it, removed it (slightly loose on the starter motor i noticed) and had a good look at it all.

The chassis end was reasonably clean but the starter motor end was an awful state. There were also some mild burn marks on the starter (which i replaced months ago - and did the bolt up bloody tight). Anyways, i introduced both ends to the rotary tool and wire brush to clean them up, then did the same to the bolt heads and threads to ensure maximum conductivity.

Reinstalled, charging like a dream! A slightly higher than previously noted voltage on the engine, i'm now seeing 14.11V which i'm more than happy with.

Thank you all, you've made my day!