I am somewhat unfamiliar with the intricacies of the alternator-regulator, and I am putting together the final touches on the following configuration:


  • Engine is a ULPower 520is with an integral 50A alternator and regulator, of which 15A is used for engine related systems and support (net about 35A, these systems are powered from the main plane bus, battery a bus, and/or battery b bus, depending on the load involved). The ULPower alternator is self contained - no external field wire is available for control (hence, its always on - period).



  • Installing a B&C 40A alternator with a Primary LR3C-14 regulator (I have a VP-X as well in the plane). Hence... both alternators are continuously enabled.



  • There are two batteries, on their own contactors, which are brought to a parallel bus (main plane bus), which then powers the starter and most non-engine plane systems. Both batteries are 16Ah EarthX units.



  • The B&C will be attached to the VP-X, so it will get field power and voltage sense from there (as if its a primary alternator).


Key questions:


  1. What is the behavior of both alternators in this configuration? I assume that the B&C need to be set to the exact same output voltage as the ULPower alternator (~14.8VDC).
  2. Do the two alternators just balance the bus load, or are there nuances on this? For instance, if the total load is 60A, that load has to be shared across the two alternators as the load is not (and practically cannot) be easily segmented to only one of the alternators. In reading some online articles, it seems that both alternators will constantly "seek" and output will vary slightly back and forth, but this should be a non-issue.
  3. I have the ULPower regulator output on the main bus, as opposed to one of the two batteries directly. Is this preferable, or should the regulator go onto one of the two batteries directly (before the contactor)? If, yes, then I assume the B&C regulator should go against the second battery?


Thanks!!!