[Gaz64]

I can't see your problem.

If you have say 12.5 volts, then fire up the engine, the battery volts drops to say 10 volts cranking, if you then have a charge rate of 14+ volts, then there must be current flow of some figure.

I think you're chasing a problem that's not a problem.

Does the battery start the engine ok in all conditions?

Does the charge rate have acceptable tolerance to load condition? eg: lights, wipers, ignition system etc.