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Old 04-19-2012, 09:35 AM   #1
Singleprop
Scraping Paint
 
Join Date: Nov 2007
Posts: 131
Zero amps charging at idle RPM, good or bad?

here is a question that has bothered me a bit and it relates to some other alternator questions that I have posted previously:

My engine idle is 650 RPM, with 1:2 pulley ratio it will give me about zero amps available for battery charging with an Electrodyne G-150 alternator at about 1300 alternator RPM. An equivalent 150 amps Delco-Remy/Prestolite has about 50 amps output at the same alternator RPM.

I consider this "lack of charging" at idle as excellent since it does not put any load on the engine just after it has been started, thereby reducing the wear on the cold engine. As we all know, 80% of the wear on an engine happens when it is cold, so "no charging" seems to be a way to reduce this wear.

Others have commented on how good it is that their alternator is capable of putting out large charging amps (say 50-60 amps) at idle, and several manufacturers use this as an argument for how good their alternators are.

For a trawler, which uses the engine for a looooong time every time it's being used, the charging amps at idle seem to me as being a useless argument for evaluating a trawler's alternator, but I would like to ask the clever guy's on the forum about their considerations and experiences.

Thanks
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