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post #3 of Old 10-13-2004
GordMay
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High Output Alternators

As Zeph said - yes & no.
There are several conditions that limit the output of an alternator, including: Altí Speed, and Batt. Acceptance.

Alternator speed is a function of engine speed and pulley ratio. Most Alternators are designed to provide full output at about 6,000 RPM, so you wonít get full output at anything under about 2,500 RPM engine speed (assuming 2:1 pulley ratio). Altí current output varies as the inverse of the square of speed - so a 35 A rated (@ 6,000 RPM cold) alternator, turning at 4,000 RPM (66%) will only put out a maximum of about 15 Amps (0.66 x 0.66 = 0.4356%) & (35A x 0.4356 = 15.246 A).

Acceptance rates vary proportionally with battery size. A larger battery (more A/H capacity) will accept more charging current. A small battery bank will not benefit (much) from a High Output alternator.

HTH
Gord
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