B&S Intek Dual Charging System - DC charging voltage

g0uihsteve

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  • / B&S Intek Dual Charging System - DC charging voltage
Hi from Steve.
I’ve owned an MTD J/136 ride-on lawn tractor for a few years. About 2 years ago the battery went bad so I replaced it. During this current season, again I noticed the battery wasn’t in very good condition. It didn’t hold the charge until a few days ago gave up the ghost.

Thinking the charging circuit could be at fault, I investigated further. This particular Briggs and Stratton engine is a 13hp Intek with a dual circuit charging system. I’m familiar with electronics and electrical apparatus and am comfortable working in this environment so measured the output from the alternator.

There are 2 output wires on this setup, one is AC which runs the tractor lights, that shows a nice 14v AC under load dropping to around 11.5v on tick-over so all ok there, however the DC line includes a pretty crude rectifier diode affair [presumably to convert AC to DC] on the 12v line to the battery.

It looks like a 1N5408 from the various online info I have which is a 3A 1000v standard rectifier so nothing special. I have 100’s in the workshop.
Putting the DMM on the output shows 12.9v on tick-over, but 16.7v under load. In my book this is a recipe to wreck a battery pretty fast. If it was around 14.8v then I’d be looking elsewhere for the problem.

The current output is fine at 2.6A. Suppose I have a choice here. I could build a properly regulated output which would be fairly easy or the dirty method would be to use more than one diode in series to drop the voltage as each rectifier will drop the volts by 0.7v – to get more in the right area.
I have a bunch of 10 amp 1000v rectifiers [10A10] that would suit – rather overkill though.

My question is – does anyone have any info on what the [correct] charging output voltage is expected to be on this setup. Personally, I think anything over 15v could potentially shorten the battery life fairly quickly.

Best - Steve
 

Richie F

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  • / B&S Intek Dual Charging System - DC charging voltage
Amps and volts are inversely proportional.
Higher voltage in a DC charging circuit means amps are low.
How do you have AC voltage tractor lights ?
Your charging coil is AC that is rectified into DC to run the mower.
Unless the coil is a DC unit.
If you have a voltage regulator you are going from AC to DC.
 

StarTech

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  • / B&S Intek Dual Charging System - DC charging voltage
Yes the voltage is a little higher than it should be. The only solution is to add the Briggs 790292 regulator (about $45) to provide voltage regulation plus boosts the 3 ADC system to 5 ADC. OR you can build your system but amps may not increase or add two or three silicon diodes.

And Richie it is a dual circuit stator. One circuit is for charging and the other circuit is for incandescence lighting.
 

g0uihsteve

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  • / B&S Intek Dual Charging System - DC charging voltage
Thanks for the replies everyone.

Richie: The dual circuit is both AC and DC outputs. StarTech is correct that the mower lights run off the AC output of the alternator. High voltage > low amps – yes I get that, but over 16v DC is certainly not right. There is no regulator in this circuit. You can see that because a diode is certainly NOT a regulated output. All it does is rectify the AC to DC [and very badly on its own]. To me this looks like a cheap ‘get-by’ Friday afternoon solution. Even a bridge rectifier would have been a better solution and that wouldn’t cost more than a couple of $.

StarTech. No point in me spending big $$ on a B&S regulator when I can build my own for about $5.
I have a 10-amp LT1038 variable regulator semi-conductor and with a couple of resistors and smoothing caps will do just the job.

Rivets: There’s 15 to 16v+ DC coming out whatever the load. Agreed a good battery just acts like a capacitor and smooths everything out. I’ve seen your PDF link which is a ‘how too’’ rather than any tech data on what the output should be at factory spec.

I was actually more curious about what the factory specs were on the output voltage. It would be pretty easy if B&S said something like ‘DC output from the alternator is ‘X’ volts and ‘Y’ amps. Would make things pretty easy.
Ok - am going to build my own regulator. I’ll let you know what I build and how well it works.

Cheers for now,
Steve – Peterborough UK
 

Rivets

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  • / B&S Intek Dual Charging System - DC charging voltage
In a perfect world Briggs would supply those specs, but as you know this world is not close to prefect. Sorry for wasting your time.
 

Hammermechanicman

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  • / B&S Intek Dual Charging System - DC charging voltage
In a perfect world Briggs would supply those specs, but as you know this world is not close to prefect. Sorry for wasting your time.
I am wondering how the charging system worked fine for a couple years then all of a sudden starts overcharging? Some magnets, a coil of wire, a diode and a battery. I wonder which one is now defective.
 

tom3

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  • / B&S Intek Dual Charging System - DC charging voltage
Usually goes the other way, voltage drops. Wonder how a bridge rectifier would work in that circuit?
 
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