Alternator Testing

[a4_jet]

Hi All,
I'm trying to find how much power our current alternator is capable of outputting out of our f3 engine. I'm trying to get some specs on maximum output power, and I also want a way to quantify how much extra power we get when we go to recoil the alternator later in the year. We plan on running some extra electrical equipment on the car in the near future.

Has anybody done anything similar to this? and how did you go about doing this? I have a few idea's about how i could achieve this, but i'm not too sure.

Any help would be greatly appreciated!

[a4_jet]

Hi All,
I'm trying to find how much power our current alternator is capable of outputting out of our f3 engine. I'm trying to get some specs on maximum output power, and I also want a way to quantify how much extra power we get when we go to recoil the alternator later in the year. We plan on running some extra electrical equipment on the car in the near future.

Has anybody done anything similar to this? and how did you go about doing this? I have a few idea's about how i could achieve this, but i'm not too sure.

Any help would be greatly appreciated!

[Wesley]

Electricity isn't my field of expertise, but you could do a poor man's test.

Basically, run the motor, and load the charging system - check the voltage output, and if its still a volt and a half or so over battery voltage, the alternator is still keeping up.

Keep loading it until you end up less than a volt over battery voltage. I'd recommend electric fans or large headlights for this test.

Theres also fancy ways of using math, but what are we, engineers?

[Mike Flitcraft]

As long as it's internally regulated, testing voltage at the battery posts with a multimeter will be the easiest (with the extra load ON) and dirtiest.

You could go into load testing, but I doubt you want to buy the equipment to do so.

[BryanH]

Or you could datalog it..........

http://www.eagletreesystems.com/MicroPower/micro.htm

[Sooner_Electrical]

Or if you have an oscilloscope and some time you could dome some measurements a bit of math. This way you would get just the alternator increase if you wanted that; ignoring all the losses in the system. But since you system has losses then either measurement would do. I would suggest the DMM on the battery with no load and just measure increase.

[Scott Borg]

A clamp-on ammeter is helpful. Be sure you get one that measures DC current, because most of the cheaper ones will measure AC only. I found one at Sears.

-s-

[a4_jet]

Thanks for your replies,

I found the solution to my problem.
Its a hall effect chip that measures the current and outputs it as a 0-5v voltage signal. Apparently you have to order them in lots of a thousand so our electrical faculty just get samples every so often and gets them made up on PCB.
These chips are good for 50A, so pretty robust. Im pretty sure a motorbike alternator is not going to reach 50A, maybe 25-30A max. I'm guessing it is very similar to the clamp on ammeter that you are talking about Scott.

What my plan is to start the car on a fully charged battery then change over to a flat battery which will load up the alternator. Then i will measure the current using the special hall effect chip.

If anybody would like to know the details of the chip i can post it when i get back to uni on monday.

[Chris Boyden]

Allegro micro makes a hall effect sensor that
you don't have to order by the thousands and are already packaged that can measure currents up to 150A or so.

[Scott Borg]

a4_jet, I'd like more info about that sensor. My email is scborg (at) csupomona.edu

Thanks in advance,
-s-

[Chris Boyden]

http://www.allegromicro.com/demo/asek752.htm

$20 bucks

Same thing without the overhead....unless you like to do things the hard way ????

Clamp on meters are nice....because you don't have to put them in series.