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Time for a beefier alt, or do I need another battery?
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<blockquote data-quote="Lasherž" data-source="post: 8705331" data-attributes="member: 679555"><p>I don't think anything on <a href="http://www.bcae1.com/charging.htm" target="_blank">http://www.bcae1.com/charging.htm</a> disagrees with what you said about exceeding the rating. It says, "<strong>As long as the engine is running, <strong><em>all</em></strong> of the power for the accessories is delivered by the alternator. The battery is actually a load on the charging system. The only time that the battery would supply power with the engine running is when the current capacity of the alternator is exceeded or when engine is at a very low idle."</strong></p><p></p><p>I think you have a decent understanding of that, but this example of yours in particular is problematic.</p><p></p><p></p><p></p><p>The alternator is always at the same voltage, usually 13.8 to 14.2v some as high as 14.5v as determined by its voltage regulators. The difference in an alternator under load vs not is the amount of current it's putting out and it's regulated through the resistance of the system (particularly the battery's internal resistance which is why you shouldn't disconnect your battery while the car's running). When the voltage drops, not only is your alternator put at full torque due to low resistance loads from accessories, it's also going to continue a heavier load until the battery is recharged and the internal resistance is once again elevated.</p><p></p><p>It seems like some of that was probably based on misunderstandings so I don't want to come down hard on you, but the example in particular wasn't in line with reality as far as how alternators work.</p></blockquote><p></p>
[QUOTE="Lasherž, post: 8705331, member: 679555"] I don't think anything on [URL]http://www.bcae1.com/charging.htm[/URL] disagrees with what you said about exceeding the rating. It says, "[B]As long as the engine is running, [B][I]all[/I][/B] of the power for the accessories is delivered by the alternator. The battery is actually a load on the charging system. The only time that the battery would supply power with the engine running is when the current capacity of the alternator is exceeded or when engine is at a very low idle."[/B] I think you have a decent understanding of that, but this example of yours in particular is problematic. The alternator is always at the same voltage, usually 13.8 to 14.2v some as high as 14.5v as determined by its voltage regulators. The difference in an alternator under load vs not is the amount of current it's putting out and it's regulated through the resistance of the system (particularly the battery's internal resistance which is why you shouldn't disconnect your battery while the car's running). When the voltage drops, not only is your alternator put at full torque due to low resistance loads from accessories, it's also going to continue a heavier load until the battery is recharged and the internal resistance is once again elevated. It seems like some of that was probably based on misunderstandings so I don't want to come down hard on you, but the example in particular wasn't in line with reality as far as how alternators work. [/QUOTE]
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Time for a beefier alt, or do I need another battery?
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