Absolute jewel, B+C SD20S with beautiful shock absorbing drive ripped off from vacuum pump. Using a B+C LR3C linear regulator with adjustabel setpoint and OVP. "NOT CHEAP" but IMHO worth every cent. Output on both identical when heat soaked, but linear regulator eats a little current compared to internal switcher. Can count on 18 amps realistic when heat soaked, and unrealistic 60 amps when dead cold for only moments. Thx. Bill at B+C for testing!
914 gear ratios:
Accessory pad 1 revolution for 1.842 crankshaft revolutions (.54 of crank)
Prop shaft 1 revolution for 2.43 crankshaft revolutions (.41 of crank)
(ALTERNATOR RPM) - (HOT OUTPUT (14V) AMPS) - (ROTAX CRANK RPM)
2,000 RPM 15 AMPS 3,684 RPM
2,500 RPM 24 AMPS 4,605 RPM
3,000 RPM 29 AMPS 5,526 RPM
3,500 RPM 32 AMPS 6,447 RPM
Need to take losses of LR3C off above.
Note for a while B+C SD20 and SD20S got a bad reputation for a low output. First off Bill tests when they get hot, which provides a more useful and realistic number. Then he made a mistake! He was touting output for 28 volts and had it marked as 14 volts!
Here is 28V output for alternator RPM
2,000 RPM 0 AMPS
2,500 RPM 4 AMPS
3,000 RPM 12 AMPS
3,500 RPM 20 AMPS
Bill never measured losses of a switcher, but said a switcher is more efficient, thus has less loss than a LR3C, albeit with much more noise than the linear LR3C. When asked of approximate loss off published SD20S output, said he never really measured but said the more amps you output the more loss. When I pushed for an approximate loss at 15 amps, 20 amps and 25 amps, he thought perhaps 1.5 amps, but probably never more than 2 amps.
He notes on LR3C warning light, make sure you can read whatever you select in bright sunlight and viewing angle catches your eye. said 500 ohm resistor in series allows use of LEd without it glowing when off.
Y10-02-22
