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I bought my Craftsman Lawn Tractor (917.270940) new in October 2000. It has been reliable and required minimal replacement parts over the year. In the past few years it’s been used more as a tractor and less as a mower. Now it’s used mostly for hauling firewood and branches from point A to point B, with a lot of starts and stops and very few long run times.


While the charging system works as intended, with short run times, and frequent starts & stops the alternator barely keeps the battery to full charge. This unit has a dual circuit alternator (393474) with 3 amps to the battery and 5 amps to the headlights—which I have never used & don’t plan on using.


Is there a way to boost battery charging with this alternator? What I am thinking is to connect both wires (red & black) from the stator together and run them both through a bit larger diode. This, I am hoping, will boost the battery charging amperage.


I would appreciate the forum’s comments, suggestions, or alternatives for my situation. Thank you. bob
 

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I am not an electrical engineer, but have a thought that may help. You can get rectifier/regulators that were designed for Kohler engines for less than $20, I think. If you connect the stator output to the two 'in' terminals of the rectfier/regulator, and connect the output to the battery "+" terminal, you should have increased and regulated power charging the battery. I am not clear on connecting both outputs to the same terminals as I don't know the 'phase' of the AC output if they were to be connected.
If you do rewire, and consider each output a separate leg of the AC output, with a common ground 'in the middle' like a center tap transformer, that may do what you want. I think it might take some rewiring of the coils in the stator, but you would have to know its electrical layout.

Here is a current listing on DaRiver:
https://www.amazon.com/Voltage-Regulator-Rectifier-Kohler-10-S/dp/B01K9Y2M3O

tom
 

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Tom: thank you for your thoughtful post. I think you touch on the key factor, (the phase of the two AC outputs), on whether this will work.

The frequency of the two stator outputs would be the same—both directly proportional to engine RPM. The phase of these two is unknown, so maybe install another, separate, diode on the 5 amp headlight output and combine these (connect them together) after the diode rectifiers. That is combining them as DC.

My particular Craftsman has a 20 hp. Briggs & Stratton engine (461707) but your provided link to the Kohler Regulator Rectifier with two AC inputs and one DC output may do the trick. My B&S has no regulator and only one rectifier diode on the 3 amp battery charging circuit.

Combining the two AC voltages, after rectification, I think eliminates the phase problem. I very much appreciate your alternative idea! It seems like a reasonably cheap solution which may work & help in keeping the battery charged. bob
 

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Very creative idea!! Being conservative, I'd put an inline fuse prior to the new rectifier, cheap insurance to save the stator windings. JIC.
 

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If money is not an issue then Briggs actually sells a little box that plugs into the dual system connector and boosts the amps. It's been discussed in some forums. Not sure if I saved the part number somewhere.
790292. They call it a rectifier/regulator for the dual system. Search briggs site faq for alternator_specifications.pdf
Briggs and Stratton Regulator Part No 790292
 

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Discussion Starter #6
Thank you all for sharing your knowledge!

I was unaware of the B&S 790292 Regulator/Rectifier; DB Electrical sells & delivers the unit for $12.95 (not a big $ issue); some additional cross reference parts numbers include: Arrowhead Electrical Products: ABS6004 and 230-22148.

This (790292) regulator/rectifier is for use on dual circuit alternators and has 2-prong male & female connectors which attach to the stator wires/connector and wire harness. This device does nothing to the 5 amp AC voltage (black wire) for the headlights, it is still AC and unregulated; the headlight voltage bypasses the device entirely with the looped through black wire (see photo 790292).

Photo 790292

The input to the device is on the yellow wire & its output is the red. Inside this gizmo are a full wave bridge rectifier (4 diodes) and a resistor with Zener diode to make a voltage regulator. This device does not require (nor IMO should it have/use) the existing diode heat shrunk on the red 3 amp stator output wire. My guess is this rectifier/regulator (without using the existing diode) would provide a bit more charging amperage (4-amps?).
 

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the connectors take care of everything. I suspect that the black is the bypass for the AC so it's the DC from the diode that goes in and then out of the box. It has been discussed but my guess is that it increases the current by reducing the voltage (keeping the fixed power about the same)
 
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