With the new (overhauled) engine, my original (but overhauled) alternator, and my previous (untouched) voltage regulator, this is what I am finding.
Also, with all loads on, the charging current would go negative when the RPM was reduced through 1100rpm, whereas now it does it at 1200rpm.
I can’t see any possible voltage regulator failure mode which would cause this.
Could it be an alternator drive belt, too loose? It was certainly tight at prop installation (I was there) but maybe a new belt needs a re-tighten?
During flight it is OK, producing 27.7V. That’s another thing: the old one was 28.0V.
Symptoms of an ageing/tired battery? Been offline for a while perhaps, during the overhaul?
Is there a “break-in” for alternator too ?
Didn’t remind that, when I had to change mine. Replacement part behaved just the same.
Belt ? I don’t know how it would slow down positive current appearing.
Was it your first flight after engine exchange ?
How does feel this engine ?
The belt might be slipping until it warms up. Especially if it has some oil or dirt on it. That’s my theory…
A delay in the voltage regulator makes no sense. It is a really simple circuit.
Also the alternator has been rotating for a minute or two, by the time the field current is activated.
2 flights have been done. the first had a short delay – 1-2 secs. The 2nd had the longer delay.
The engine runs great.
If the belt is slipping I suppose you will k ow pretty soon when is shears off 
One really relevant thing is that it needs 1200-1300rpm to charge the battery, whereas previously this happened above 1100rpm.
Providing the field current is maxed out, there isn’t much that can explain that, apart from
This is dead easy to troubleshoot but not if you are prevented from doing work on your plane at your base.
Is it possible the tachometer is overreading on the new engine?
The tacho is a magnetic pickup from the starter gear. Possible but unlikely, especially given the other fault which is the long delay in the alternator coming online.
Are you starting the engine with the alternator CB tripped? Perhaps your overhauled alternator has new brushes with more tension in the springs and the lack of field current during the start phase is allowing the slip rings to glaze slightly, increasing resistance, which then takes a few seconds to break down when you put the alternator on-line by closing the CB. Past experience on 4-engines turbo-props suggest this is possibly your issue. Try starting the engine with the alternator selected ON, just as you’d do in a PA28 and see if you have the same problem.
Are you starting the engine with the alternator CB tripped
Yes – standard procedure. Interesting…. Many thanks.
Would this explain the increased RPM at which the battery charge commences, and the higher current showing during flight? To me the latter suggests that some of the rectifier diodes are open-circuit so there is a lot of ripple.
The battery is good AFAICT. I did a load test on it, and afterwards it settled perfectly at 28.000V to about 30mA, from a power supply. Then it was on a CTEK reconditioning charger.
It could also be a bizzare field CB fault.
