--- Manfred: You are attempting to draw on your car experience (watching a voltmeter) and trying predict how the alternator will react in a totally different usage. You would have a much better understanding if you were watching a bi-directional amp meter.
You stated "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!" If you go to: http://www.balmar.net/PDF/Alternator%20Drawings/60- seriesdimensionaldrawing.pdf They have a wonderful drawing of their alternators in various amperage ratings. In The lower left hand corner are the output curves for them. The lowest line is their 70 amp alternator (also shown are 100, 120 and 150 amp alternators) You have to interpolate between the lines, but at alternator rpm (not engine rpm) their 70 amp can produce about 32 amps at 1800 rpm, about 38 amps at 2000, about 60 amps at 3,000, and finally reaches 70 amps at 5,000 rpm. This is a fairly typical curve for many alternators. To me, it is ridiculous to spin the alternator the extra 2000 rpm to pick up 10 amps, in this example. That extra 2000 rpm will significantly cut down the brush life. Note that this is what the alternator can do at those rpms, not what the regulator is telling it to do at any given moment. "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." It is not designed precisely to fully charge 12V batteries. It is designed to fully charge ONE 12V battery of a specific size. It will vary the current based on the current state of charge of the battery, to recharge it as rapidly as possible without doing harm. Higher current rates used when the battery is in a lower state of charge. Lower current rates when the battery is at a high percentage of charge and is being "topped off". The regulator for a specific car will be based on the amp hour capacity of the battery that the manufacturer puts in the car. The Toyota Camry comes with a 65 amp hour battery. So if we are talking about bringing the battery from 95% to 100 percent charge and doing it at a 10 percent rate, the regulator will instruct the alternator to deliver 6.5 amps to the battery. It doesn't matter what speed the engine/alternator is turning at, that is all that will be delivered, because that is a nice slow rate to top off the battery. 5 percent of a 65 amp hour battery is 3.25 amp hours, the 6.5 rate will have it fully charged in half an hour. When you take that same alternator/ regulator and couple it to a 650 amp hour battery (or 10 batteries of 65 amp hours wired in parallel) the regulator cannot tell the difference. You are now 32.5 amp hours away from full and trying to fill it at 6.5 amps. It will take 5 hours of charging without any additional draw on the system to bring the battery to 100 percent. And because you are filling it at 6.5 amps, you are not generating the additional 30 plus amps that you could be generating with a smarter regulator, or one better sized for your battery bank. One solution is disable the internal regulator (or remove it ) and use another regulator or controller that is more appropriate for the larger battery bank. Another option is to lock the regulator into a 100 percent charge rate and then use a dump load controller and dump load to burn the excess generation beyond that which will fit into your battery bank and current usage at the moment. There are additional solutions, but those require an accurate picture of the loads on the system and time of use. Anyway, I hope that this explanation helps. Oso ------------------------ 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/
