Voltage Drop on Starting

[Grahamm]

If you've a voltage of 10v once the engine is running it still points to a duff charging circuit

It's fine when it's running, but it's the initial drop when I press the starter that seems to be causing the problem.

If I've got the following right, you should be able to see a video clip of what happens here:

https://drive.google.com/file/d/0BzSHRSa...sp=sharing

The voltage is fine to start after it's been charging on the Optimate, but when I hit the starter the side-lights dim, the volts drop to 8.51, however (in this case) there's enough to get it to start.

The problem is when I've been out and it's been sat around for a while not charging, at which point it may be sluggish to turn over or just fail to start as you can see here:

https://drive.google.com/file/d/0BzSHRSa...sp=sharing