Recommended Backup Alternator

I am installing a backup alternator on the vacuum pad. I have the EXP119 engine. Any recommendations on which Alternator to order. I am assuming it will be 30 or 40A. The only recommendation I have so far is for the Plane Power (Hartzell) FS1-14.

I recommend the very nice 20 amp B&C standby alternator and associated voltage regulator.

If your ship is like most dual screen EFIS systems, your panel will be drawing perhaps 10 amps with everything up. Add LED nav/strobes and landing lights you will be perhaps 15 amps steady state load. This alternator has plenty of output for unlimited flight.

I like it over the larger units as it just fits better on the vacuum pad.

Carl

I just installed the Monkworkz 30 amp unit on one of our airplanes, and am quite impressed - tiny and powerful. Have flown it a couple of times, and it does exactly what it is supposed to do - and will carry all my normal loads if I turn off the main alternator.

Full review coming in some future edition of Kitplanes….

Paul

Does a back-up alternator wear the same way the primary alternator wears? Maybe I should take one step back, does the backup alternator produce power as long as the primary alternator is functioning? I'd hate to lug around a back-up alternator only to have to replace it at the same interval as my primary because its been spinning all those hours but went essentially unused.

B&C “20 A” alternator

BTW the B&C “20 A” alternator is capable of 30 A at cruise RPM on a Lycoming.

My vacuum-pad alternator summary here.

PS: Bob Nuckolls recommends using an LR3 vs SB1 regulator with a B&C wound-field vacuum-pad alternator. Set it to a lower voltage so it idles if both alternators are online and so it will maintain charge level but not use its capacity to charge the battery if the main alternator is offline.
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