Sun Sep 03, 2017 10:26 pm
#1556625
Our aircraft POH states that the "ammeter" is connected between the alternator and battery through a diode. The gauge reads 0 to +ve. I read this therefore as it is an alternator -----> battery load meter.
I need to dig out the wiring diagram but my assumption was that with engine running the alternator provides power to bus bar but NOT via the battery. Hence the only load that the meter should show is that's used to trickle charge the battery. However the POH states that with all electrics on the meter should read about 20A.
Two problems
1) it doesn't ever show 20A. Highest I've seen is aftee running battery alone on ground for long period or after multiple attempts to turn over the engine. Eg when battery is discharged. It soon settles back down to about 2amps once alternator is on. This leads me to believe the alternator does indeed power electrics through a route other than the load meter. Which contradicts the statement in the POH about seeing X amps with all electrics on
2) if the above assertions holds, what's the point of this gauge! If it only shows charge into battery then if the alternator fails in flight you'll see low volt warning so you know your running on battery and I wouldn't hang around to see how much life battery has in it. If battery fails on ground then engine won't start! So it's kind of a redundant gauge?
I need to dig out the wiring diagram but my assumption was that with engine running the alternator provides power to bus bar but NOT via the battery. Hence the only load that the meter should show is that's used to trickle charge the battery. However the POH states that with all electrics on the meter should read about 20A.
Two problems
1) it doesn't ever show 20A. Highest I've seen is aftee running battery alone on ground for long period or after multiple attempts to turn over the engine. Eg when battery is discharged. It soon settles back down to about 2amps once alternator is on. This leads me to believe the alternator does indeed power electrics through a route other than the load meter. Which contradicts the statement in the POH about seeing X amps with all electrics on
2) if the above assertions holds, what's the point of this gauge! If it only shows charge into battery then if the alternator fails in flight you'll see low volt warning so you know your running on battery and I wouldn't hang around to see how much life battery has in it. If battery fails on ground then engine won't start! So it's kind of a redundant gauge?
PPL(A) SEP, MEP, SE/IR, IR(R), Night