Honda CRX Forum banner
1 - 3 of 3 Posts

· Registered
Joined
·
289 Posts
drnknmnky13 said:
Unless you have a variable sized pulley that would adjust the speed of the alternator to the rate of charge..then no. The alternator spins at whatever speed the belt makes it spin. It produces XX amount of current for a given rpm regardless of the charge level of the battery. The regulator simply adjusts the amount of current it converts (or lets through to simplify things) to the battery. A dead battery would have the regulator allowing full current (up to a point) to the battery... as the battery reaches charged the regulator simply allows less current to flow. But the alternator itself doesn't work any "harder".

Yes if the regulator went bad I would replace the entire unit as a whole. But I wouldn't blame low battery charge for killing it.
The voltage regulator is just that ... it adjusts current produced by the alternator to maintain the regulated voltage (14.5 volts). BTW the CRX has a sensor ("ELD Unit") that measures the electrical load (it is located in the main fusebox under the hood) and under some circumstances (this is controlled by the ECU) the voltage regulator will be commanded to reduce the output voltage from 14.5v to 12.5v. The purpose of this is to save gas by reducing the alternator load. If you were a mad hacker, you could probably hotwire the regulator so that the alternator shut down when you were at WOT. The only reason I know this is because something in my 'rex is busted and the alternator light comes on when it goes to the 12.5v mode. I suspect my ELD is not working right.

The way the voltage regulator actually works, btw, is that it regulates the field coil in the alternator. The larger the magnetic field produced by the field coil, the more current the alternator produces. In a sense this is like having a different pulley size, it's just accomplished electrically. When the regulator dumps more current into the field coil, the alternator pulley becomes harder to turn because it's generating more power.
 

· Registered
Joined
·
289 Posts
drnknmnky13 said:
Unless they changed them recently it doesn't modify the field. It switches the field off and on (it can do this hundreds of times per second). Even if the field were to stay on the entire time (or even if the MF changed like you stated)...it wouldn't make the alternator work any harder. It might make the engine work a little harder as there is more resistance...but the alternator itself is not working "harder".
OK, whether the field is pulse-width-modulated on or off, or varying in intensity doesn't really matter, except that pwm is certainly more efficient as you eliminate the resistance losses associated with transistors or FETs operating in the linear region (i.e. this is why class D amplifiers are so efficient).

And if the field is off, the alternator is doing no work, if it's on 100% of the time, then the alternator is working as hard as it can. Most of the time it's not going to be working very hard as the field will be off 80% or more.

The point I was originally trying to make is that the current output of the alternator is NOT tied to the rpm the alt pulley is spinning. The graph of alternator output vs rpm show maximum output, which is for the case where the electrical load exceeds the alternator output (regulator commands 100% field) or if you have full-fielded the alternator (bypassing the regulator).
 

· Registered
Joined
·
289 Posts
No malice read into any of that ...

Bad battery is most likely problem simply because alternators last a lot longer than batteries ...
 
1 - 3 of 3 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top