Briggs Charging Modification?

I have your standard Briggs Dual Circuit alternator on the MULE. Two outputs off the alternator. One remains AC for lighting, one gets clipped to DC with a diode for charging. What if-

I were to ditch the diode, and run both circuits through the inputs of a bridge rectifier? Would I not then double my DC current availability? Are the two circuits in phase with each other, and if not, will it create a problem? Are there any other foreseeable issues with the idea? Thanks!

That is a really good question. I contemplated using a diode on the lighting circuit to make it DC to charge a battery that would be for lights, horn, etc. But in reality I'll probably eventually spring for LED lights and just use the battery.

Maybe you could use two rectifiers and combine the output.

Here's another one, will led's work on a/c?

The answer is in whatever circuitry they are put together with... AC will probably smoke LEDs if they are hooked up raw.

wikipedia has a good article on the function of LED lights as a whole - probably a good thing to read given the question of a/c power sourcing them:


https://en.wikipedia.org/wiki/Light-emitting_diode

Guys you are in luck. I happen to be bit of a electronics engineer. So maybe I can put some light on things. Yes leds can run on ac , the are just a diode that emits light so they can run on ac or dc as long as you also use the correct sizes resistor along with them or they will fry. As for using two different ac sources with a bridge rectifier. It can be done. And it will increase the amp output as long as the voltage is not to high to point it would try to over charge the battery. Probably the best option would be a two phase rectifier regulator from a motorcycle.

goesman wrote:

Guys you are in luck. I happen to be bit of a electronics engineer. So maybe I can put some light on things. Yes leds can run on ac , the are just a diode that emits light so they can run on ac or dc as long as you also use the correct sizes resistor along with them or they will fry. As for using two different ac sources with a bridge rectifier. It can be done. And it will increase the amp output as long as the voltage is not to high to point it would try to over charge the battery. Probably the best option would be a two phase rectifier regulator from a motorcycle.

Well, that makes 2 of us. Not so much an engineer as a technician... but we run the same field (lol). Now, what I might be able to add to this is that everything I've understood about running such a device in that fashion depends on voltage stability and heat buildup. So basically they'd have to stay at a constant of about .707 to 1.0 (70% to 100% efficiency @ 12v) to function for more than a few minutes without burnout. Best bet IMO is to avoid the lighting circuit of the engine, run the rectifier to the battery then wire the lights direct to a switch and the battery. I did something similar in my camp trailer and I could run those LED lights independent of the 12v generator I rigged up or the inverter, heck I could even run them directly off of the solar panel I rigged to keep the battery topped up. Same principle applies here I think.

As far as the rectifier goes, check out the ones from Kohler OHV engines. Essentially the same thing you're talking about goesman, 2 inputs, one output. According to the diagrams I have, 1 input is a/c, 1 d/c and the output goes direct to switch/battery for charging. 15A on most of those too.

Well then, I shall have to keep my eyes out for a bridge, and give it a shot. Thanks for the input. Now, some output-

I can attest that LED's will run on AC. Years ago, I built a wee little polarity tester using some alligator clips, two LEDs and some resistors. The LEDs were wired in parallel, opposite each other. DC+ would light the green LED, DC- lit the red, And AC lit both.

Any luck converting that Ac to Dc Doc?

I've been so busy working on other things, I haven't touched this again. HOWEVER-

I recently laid hands on an oscilloscope, so when I actually get around to it, I can probably get some solid answers.

Well on a more simple path(and assuming that both wires output 14v AC) do you think I could add another diode to the Ac wire and charge two batteries. Have one for starting and the other for accessories. Having them wired seperately of course.

Weird... But possible. Athough, if you DID keep the two systems completely isolated, you could run the heck out of whatever accessories without the chance of running your starting battery dead.

Doc looky here. Does this shed some light on the subject.
http://www.smallenginesuppliers.com/html/engine-specs/briggs/briggswiringexplanation.pdf

No, I am already familiar with all of that, but I thank you for the effort! No matter where I look, I just cannot ascertain the phasing of the two alternator circuits. In the spring when the weather improves, I'll break out that oscilloscope and find out for sure!

I believe what you have is a "Dual Curcuit" Alternator. The circuits are not connected to eachother and therefore not necessarily 180 out of phase like you want for the rectifier / regulator. There are many different ones according to the B&S Chart. I even thought about running two of the 1/2 moon styles...

I dug pretty deep and ultimately realized that I need to buy the right one for my purposes. I found this one on ebay:




It's a 696458 Alternator and a 691185 Regulator. It's the strongest you can get for a 28ci motor. I'm just hoping I've got the big magnets in my flywheel.

Yup- dual circuit. Trust me, I've done a TON of homework on this. I got the big magnets on ONE of my two oopy wheels. On the other, I took the magnets right off. For what is basically beer-league racing, I thought I might completely remove the charging system for weight and rotating mass savings.

My original question boiled down to a curiosity, not a need. Since no one has yet been able to actually answer it, nor have I found the answer online.

The simple answer is no. BUT: What you would have to do to run a bridge rectifier like the one I just bought would be this: Determine whether the "other end" of each wire is connected to ground or eachother. They want to go to each other, making the entire thing one circuit NOT connected to ground. Then they would be opposing phase and able to power a bridge rectifier. The problem with the shunt rectifier is that 1/2 the energy does back to ground. You already knew that though!   

Didn't I effectively say that in my first post? LOL...   

Hey, if there's one thing I'm good at, it's chasing my tail! Especially when it comes to electricals.   

I would experiment with a lighting coil if I had one. The two I do have were the 1/2 moons, so maybe I could have run a bridge, but most likely only a shunt. So yeah, like I said, I just gave up and ordered the one I really want!

Speaking of charging systems I have a Q, if my motor was made to run a regulator do I need to keep it on there? Or can I bypass it by useing a switch on my dash and keep a eye on my volts?

The very first thing that comes to mind is this: The regulator is actually a regulator/rectifier. By eliminating it, you are eliminating DC- instead you will be getting AC power. You would need to add a diode or bridge rectifier in order to have usable DC.

Definately an interesting concept for those of use that put 6" subs in the hood of our mowers.. hehe.. hint. hint..

thanks doc.

Doc Sprocket wrote:

The very first thing that comes to mind is this: The regulator is actually a regulator/rectifier. By eliminating it, you are eliminating DC- instead you will be getting AC power. You would need to add a diode or bridge rectifier in order to have usable DC.

So, yes. If you do this it will work. Keep in mind that the lower power alternators do not have a regulator because they do not have enough power to boil (overcharge) a battery. They are the ones with just a diode in-line next to the connector and just pump .5-5 amps constantly (depending on the alternator and RPMs). I' pretty sure you wouldn't have to keep an eye on those.