Problem sorted out by measuring voltage directly at the ignition switch.
Took some effort to put a wire from the steering pedestal
back to the engine bay. But finally I was able to get the job done and started the engine for the first time.
Output was around 60A at 850rpm. So that's looking good.
What I noticed is that when only the ignition is on, there is a rising current
which I can see on the BMV (alternator linked directly to the LFP bank, which has a shunt). After about a minute the current
stops rising at around 4A. The only consumers when ignition on, is the instrument panel with its two lamps (oil pressure warning, charging
warning lamp) plus tank and hour meter.
Could it be that the current is coming from the alternator
, so to say as a result of the building "excitation voltage"?