Hi Oso, > Spinning it at that speed, the brushes are not going to last very > long, 6-8 weeks would be my guess. If you cut the speed to about 3000 > rpm, the alternator should still produce 50-55 amps and the brushes > will last a little longer, say 12-16 weeks.
I fear that a 70A alternator running at half its rated speed will definitiley NOT produce 50-55A, but rather will end up with insufficient voltage to put ANY current at all into the battery bank! It depends on the specific alternator, of course, but if it's rated at 6000rpm, I would not count on it being usable at all at 3000! About the brush problem, I understand there are some brushless car alternators now. > If you hook the alternator to a big battery bank, your bigger loss of > generation will come from the internal regulator on the alternator. > As you get up somewhere near the 13 volt mark on the battery, the > regulator will cut way back on the output, despite the rpm. You will > never get the large bank "fully" charged. Here I think you are very mistaken! The regulator in a car alternator is designed precisely to fully charge 12V batteries. Typically, the alternator output is regulated to 14.4V or thereabout. This can certainly charge a battery bank to full capacity, and the problem might be opposite to the one you mention: You might slightly OVERcharge the batteries! The 14.4V level is great for cars, which typically run for only one hour a day or less. In a microhydro system, running 24 hours a day, this rather high voltage would lead to higher water consumption in the batteries. If they are of the open cell type, that's just a maintance issue, requiring water to be added perhaps once a month. With sealed batteries, if anyone fancies to use them, it might be better to modify the regulator so that it regulates to 13.8V instead of 14.4V! Of course, the issue of low efficiency of car alternators remains. Manfred. ---------------------------- Visit my hobby website! http://ludens.cl ---------------------------- ------------------------ Yahoo! Groups Sponsor --------------------~--> Get fast access to your favorite Yahoo! Groups. Make Yahoo! your home page http://us.click.yahoo.com/dpRU5A/wUILAA/yQLSAA/FGYolB/TM --------------------------------------------------------------------~-> Does your company feature in the microhydro business directory at http://microhydropower.net/directory ? If not, please register free of charge and be exposed to the microhydro community world wide! NOTE: The advertisements in this email are added by Yahoogroups who provides us with free email group services. The microhydro-group does not endorse products or support the advertisements in any way. More information on micro hydropower at http://microhydropower.net To unsubscribe: send empty message to [EMAIL PROTECTED] Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/microhydro/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
