Do All Alternators Operate Similar ?

If you find yourself in that condition, you might consider pulling out of traffic every hour or so, shutting down most all of your electrical loads, and fast idling for 5 or 10 minutes.

If you find yourself stopping for long periods, put the car in Neutral and get off the brake. If you are just sitting or creeping in a long line, consider going to your parking lights only (yeah, not quite legal, but it beats stalling out in the middle of a freeway).

If you find yourself in these conditions often, then you might want to get a smaller diameter alternator pulley. This will yield higher alternator RPM for all engine speeds. Also consider buying a new and higher capacity battery.

Ed

Typically, most alternators charge only at higher rpm but I've notice a particular BMW that outputs 13.7 V at low idle with all loads, defrost, fans, high beams, brake lights, power wind. Adequately, charging voltage has to be higher than the battery voltage (respectfully 14.2.-14.4-volts)

Too much stop and go or short trips with many loads may undercharge the battery, not to mention carbon deposits in the combustion chambers that could result in pre-ignition. It won't hurt to shift into low gear or rev the rpm at 1400 or so, just enough to raise the voltage to 14.4 when stuck in traffic. But this might not be enough.

Instead, you might want to fully charge and check the battery at home before a stop-and-go commute.

-- Milo Meineka

Nominal battery voltage, when it will neither charge nor discharge is 12.=

6 volts. In cold temperature the regulated voltage varies among vehicles = but is usually 14 volts to 15 volts.

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All alternators tend to put out less at low RPM. Some are worse than others, and a very common mistake people make when they have a low-RPM charge problem is to buy an alternator with a BIGGER peak amperage rating. In general, if you have the same basic alternator in several different peak amperage ratings, the SMALLER peak amperage rating version will generally have more output at idle than the higher peak-rated version. Say you have an 80 amp (peak) and a 40 amp (peak) version of a particular alternator. The 80 amp version may only put out

10 amps at idle and 80 at 2000 RPM, but the 40 amp version may put out 20 at idle and 40 at 2000 RPM. This is because the higher rated version tends to have fewer turns of heavier guage wire in the windings. Of course its not true if the two alternators in question are actually a different design, say a Nippondenso vs. a Delco vs. a Bosch. The worst things in the world are the "super" alternators sold by car stereo companies. many of them go for huge 'peak' numbers, and are terrible at idle.

Denny B wrote in rec.autos.tech

Just a quick comment, I already answered your question in another newsgroup. When you want to post to multiple newsgroups, put the news groups you want to post to in the header as you are getting ready to post. But limit the number of groups only to those pertinent for your questions or comments. And do try to keep them under 4 groups. That accomplishes several things. First of all, you only need to post once, and you only need to read one group to get all the answers. Anther thing it accomplishes is that everyone who only reads one news group will see the question and the answers from the other groups.

And for those who, for some reason, post from SBCGlobal, please don't. This is the usenet. If you are on an ISP chances are that you have the newsgroup through them. If you don't go to

post from there. It is free, although a little slow. SBC global does not put returns in the lines, so we end up seeing an800 word post in one long line. Very annoying.Thank you, I now return you to your regular scheduled flame war. :0.