12-23-2025, 03:11 PM
(Edited 12-23-2025, 03:27 PM by Jared Hartzell.)
Good question Sam, we really don't need alternators bigger than 65 amps, I think even 65 is overkill in most builds with LED lighting systems. I haven't measured the current draw of all systems together (that'd be interesting to know, continuous load has to be less than 25 amps with a good battery based off 37A installs). But, I wonder why anyone would want to use a 90A other than just to have it (and the added weight/wiring/fuses or breakers).
Wish we had Al Yard on here to answer this question! His inbox is full on the other forum, if anyone can contact him—please have him join us!
Also as a side note, I rev up to ~2,100 engine RPM to energize the alternator/regulator so it can excite the rotor field and reach cut-in; at idle the alternator speed is too low for stable regulation. We should see 13v to 14.2v on the FADEC display, which typically seems to read about .1 volts lower than measuring at the battery posts. Keep in mind if you have the traditional thermostat setup like I do, do not to exceed 2,400 rpm until the thermostat opens, as stated in the flight manual. Once you're at flight rpm, the alternator should have a very stable output.
Monitoring voltage in our helicopters is vital. If we're not charging properly during flight, it's only a matter of time before the engine quits. I did test this in a hover before with the bad regulator (anxiously waiting for a hover auto) and my Odyssey AGM battery was able to handle a full flight at hover for 1.5 hours from a fully charged state without quitting.
Wish we had Al Yard on here to answer this question! His inbox is full on the other forum, if anyone can contact him—please have him join us!
Also as a side note, I rev up to ~2,100 engine RPM to energize the alternator/regulator so it can excite the rotor field and reach cut-in; at idle the alternator speed is too low for stable regulation. We should see 13v to 14.2v on the FADEC display, which typically seems to read about .1 volts lower than measuring at the battery posts. Keep in mind if you have the traditional thermostat setup like I do, do not to exceed 2,400 rpm until the thermostat opens, as stated in the flight manual. Once you're at flight rpm, the alternator should have a very stable output.
Monitoring voltage in our helicopters is vital. If we're not charging properly during flight, it's only a matter of time before the engine quits. I did test this in a hover before with the bad regulator (anxiously waiting for a hover auto) and my Odyssey AGM battery was able to handle a full flight at hover for 1.5 hours from a fully charged state without quitting.