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Mon May 09, 2011 10:02 am

Hello,

I finally have my race car running. The engine has a generator on it, but currently it's not hooked up to anything to charge the battery. I'd like to hook it up.

I need to run wiring for the regulator and idiot light. I was wondering if a LED would work instead of a light bulb for the light?

Thanks
Tom

Mon May 09, 2011 10:54 am

Nope....the resistance in the light is integral to how the charging system works. An LED has a .5-.6 volt drop in the forward direction when turned on and needs a current limiting resistor to work with 12v but is basically infinite resistance the other direction. The system is looking to put 12v on it's side of the the bulb while the bulb itself is supplied with 12v battery power. When the system runs and is charging the bulb sees basically the same voltage on each side so it goes out (technically). The reality is there is always a tiny disparity in the voltage on either side of the bulb so there is always current flowing toward the 12v supply to the bulb and that is what induces the field for charging.

If I misstated any of that please feel free to jump down my throat as it's been years since I even thought about HOW the Gen system works at it's deepest level. Usually just hook it up and go with no issues.

RC

Mon May 09, 2011 12:26 pm

The circuit below is designed to make LED work as indicator lamp with ALTERNATOR... You might try it for generator...

Quite frankly though a GENERATOR with REGULATOR does not need the initial pulse of 12 volts to start producing electricity as a ALTERNATOR...I do not see why a LED will not work with generator circuit if wired correctly...

Dale

Mon May 09, 2011 4:34 pm

Thanks for the replies guys.

I posted because I too was not sure that a generator needed the same 'excitation' as an alternator to function.

Thx for the diagram Dale, that helps.

Tom

Mon May 09, 2011 8:23 pm

Yes it will work I have one. My buddy Pete made the circuit. It is super bright. We used high power white LED's and then replaced the lens with clear green lens.
We did the oil light and blinkers too!
Led's rule!
MG

Mon May 09, 2011 11:17 pm

I've had 6v LEDs in the dash of my '63 Bus with a generator for a couple years.

The battery hasn't run out yet. :)

Tue May 10, 2011 6:45 am

I'm using 2 LED side marker lights for my idiot lights on my buggy with my alternator, and I wired the same lights on another buggy for a friend using a generator. Both work fine. No problems with them not charging.

brad

Tue May 10, 2011 8:39 am

Cool! Thanks guys.

I wanted to use LED's because I of the brightness of the super bright LED. Need to be able to see them without actually looking at them. Going to use them for both oil and gen/fan warning lights in my race car.

Thx
Tom

Tue May 10, 2011 9:26 am

Flat4Tom wrote: Cool! Thanks guys.

I wanted to use LED's because I of the brightness of the super bright LED. Need to be able to see them without actually looking at them. Going to use them for both oil and gen/fan warning lights in my race car.

Thx
Tom

That's why I used them, and in an open top car it's even worse trying to watch for a light.

brad

Tue Nov 12, 2019 8:40 am

Sorry to drag this old topic up, but wanted to be sure.

I have a engine with generator, NOT ALTERNATOR

if i replace the charging light bulb with a LED. Will it charge or does it need an extra resistor in parallel?

Thx

Tue Nov 12, 2019 9:05 am

Generator will work, alt. no.

Tue Nov 12, 2019 9:12 am

Awesome, thanks!

Tue Nov 12, 2019 9:52 am

They are tricky, I work with a electronic engineers and I had a few blown bulbs. They broke the glass out and installed LED s. I wanted super bright for my oil pressure. He used what looked like a clear LED that when lite was Red.

Problem was for some reason the Oil light was reverse polarity vs the other gauges????? I put it on the side and started to install the other LED s and noticed my Volt gauge lit up RED?????? By mistake I installed the LED that was for the OIL.

So the Polarity was reversed-- could be my car because over the years I made a lot of mods to the electrical system I may have taken power from the Oil wire.

They are Diodes and have polarity.

With all those toggle switches do you think I know what I did!!
I even reverse the ON to a NO

Tue Nov 12, 2019 12:01 pm

Dale M. wrote: The circuit below is designed to make LED work as indicator lamp with ALTERNATOR... You might try it for generator...

Quite frankly though a GENERATOR with REGULATOR does not need the initial pulse of 12 volts to start producing electricity as a ALTERNATOR...I do not see why a LED will not work with generator circuit if wired correctly...

Dale
If using an LED with a generator you will still need to keep the blocking diode shown in your diagram (1 amp, 200V) because when the car is turned off the voltage across the indicator is reversed (the ignition side goes to ground and D+ is at about +12 volts.) Most LEDs can only handle about 5 volts reverse without damage. This momentary reverse voltage is why a normal generator charge light goes on when a Bug is turned off.

Tue Nov 12, 2019 1:02 pm

I installed LEDs into the oil and gen lights on my Type 3. They light up faster and brighter. They work fine and have for a couple of years. They are reverse polarity.

The dash turn signal lights do not flash with LED bulbs, however. Externally everything is fine, but I'll have to put back incandescents into those two sockets one of these days.

Tue Nov 12, 2019 1:31 pm

KTPhil wrote:
The dash turn signal lights do not flash with LED bulbs, however. Externally everything is fine, but I'll have to put back incandescents into those two sockets one of these days.

is it a case of just needing a resistor? I use small led turn signals and I had to add a ballast resistor thing to the circuit otherwise they wouldn't work, something about led's not drawing enough current so the system won't accept there is something there.. I dunno, all i know about electrical is that when the magic smoke comes out, you need to buy new parts.. ;)

Tue Nov 12, 2019 1:59 pm

Yes, there are lots of posts about using a LED bulb for the alt/gen warning light and it not providing enough juice for charging-do a search.

Tue Nov 12, 2019 2:21 pm

tattooed_pariah wrote: KTPhil wrote:
The dash turn signal lights do not flash with LED bulbs, however. Externally everything is fine, but I'll have to put back incandescents into those two sockets one of these days.

is it a case of just needing a resistor? I use small led turn signals and I had to add a ballast resistor thing to the circuit otherwise they wouldn't work, something about led's not drawing enough current so the system won't accept there is something there.. I dunno, all i know about electrical is that when the magic smoke comes out, you need to buy new parts.. ;)

Yes, that's probably it, but those resistors are heaters and I don't like them for safety reasons. It's just easier to replace the bulbs in the dash pod. The T/S indicator doesn't need to be bright and fast-acting the way I like the idiot lights to work.

Fri Nov 22, 2019 8:44 am

LEDs as generator light is a bad idea because of 2 main issues:

1 - the generator light has to work in both polarity directions; one (the straight) to advise about generator non charging; with inverse polarity, to advise that generator is working but something is wrong in regulator or wiring to the ignition key.

2- the generator light has one terminal directly on the D+ from generator and on this terminal there are a lot of voltage spikes, either negative and positive, due to the collector rotation. So a LED will last not so much as expeted.

A filament bulb is the best solution also with generator.

Fri Nov 22, 2019 10:56 am

I run Both, The stock one and a K4 super bright LED. 900+ miles and no issues. I knew not to try it without the stock bulb in place.