riding lawnmower charging q

[The_Jeff]

Was just given a toro 8-32 riding lawnmower. Was getting unloaded at the dump; I said, put it in my truck.

The thing runs and mows. Had to reseat a couple tricky tire beads and change the battery. I have never before had an electric start small engine, anything. Has an 8 hp briggs, no recoil start, and the battery is the $15 walmart cheapie.

I measure 12.4 volts at the battery just sitting there (ambient fall temps 55'F or so) and 12.7 with the thing running at mid-to-high RPM. Seems like not enough to charge the battery fully.

I have no qualms against putting a manual battery charger on this a couple times a season, but want to know a little more about the charging system on these. Figure the engine spark is magneto based... is the charger just an extra DC pulse from this system? Any regulation? There aren't any lights or other electric frills on this mower. (Yet

)

 

[flatlandtacoma]

The charging coil is under the flywheel. Permanent magnets on the ID of the flywheel generate the current in the coil.

With no lights or accessories I'm guessing it has a very small (1 - 4 amp?) coil.

 

[punisher]

Assuming a single wire circuit, output should be over 13V with a fully charged batt and engine at higher RPM. On the simple systems the output is not regulated so batt condition/charge state and RPM directly effect voltage.

The diode is located in the connector from the stator. Set your multimeter on AC volt and check voltage at the batt. If the diode is good, AC volts should be under 1V, signifigantly higher AC volts mean a shorted diode. Probe on the stator side of the diode and check for AC voltage. I think it should be ~15V AC. The stator is under the flywheel.

You need to get the engine number and search from there to get reliable specs. There are dual outputs, AC only and DC only outputs depending on what accessories the mower has.

 

[SecondMonkey]

Yeah, there's definately something wrong. A new stator (sits under the flywheel) is pretty cheap on ebay and would be a worst case scenario.

 

[Bill Kapaun]

What are the color(s) of the wire(s) on the connector AND the connector color? Briggs has 4 different types of "charge circuits" for these engines.

Most of the simple charge circuits (battery only, no lights) are a single wire with a diode. You basically get a pulsating DC from them. Some have 2 diodes which give twice the pulses.

This should be a 191700 series engine.
What's the ACTUAL model AND type number?

 

[Master ACiD]

i have had good luck rewiring lawnmower charging circuits. usually they are just a simple coil with a diode as someone else said. it gives rippled dc current. ill usually replace the diode with a full wave bridge rectifier and a smoothing capacitor. since i am an electronics geek, i pull the rectifiers and caps out of junk tv's that i find on the side of the road. also use the copper wiring from them. this greatly ups the voltage and current. to combat this increased power, ill fit a cheap motorcycle regulator to the output of the rectifier and capacitor. now it regulates at 14v. perfect charging current.

next upgrade is normally a set of 55w fog lights off a car at the unkyard. they make EXCELLENT headlights for lawnmowers. most lawnmowers with headlights only use a automotive brake light bulb as a headlight. this is weak and barely better than nothing at all. upgrade to a set of fog lights and you can flood the whole yard. makes night time mowing a snap. down in south florida, i mow the lawn as dusk or even later. its too hot for me to mow during the day when its 100 degrees out. i even have a single fog light connected to the rear of the mower, so i can have light when backing up. the rear light is toggled seperately from the front lihts, so its only on when i flip a switch. the front and rear lights are on 2 seperate switches.

my mower has like 3 coils. a ignition coil, a charging coil, and a lighting coil. the lighting coil is only powerfull enough for a single 55w fog, so i wire it to the rear foglight. the front 2 fogs run right off the battery.

if one were frugal enough, ya could wire up a zener diode instead of a motorcycle regulator, but you can usually fund used regulators on ebay for $10. grab one of the 4 wire models off an atv or scooter. the motorcycles with elaborate wiring usually have 6 wire regulators or evben 7 wire, and i dont know how to wire those up.

 

[The_Jeff]

You guys are really giving me something to thing about.

I have to go home and check out the mower. IIRC it's a red wire from the starter solenoid that ends in a glass inline fuse holder (fuse is good) then a wire that disappears into the motor.

Will get engine model number when I look this thing over.

Also am retrofitting a ford starter solenoid as the one in it is nearly toast. This will involve converting from negative switching to positive but I won't let that drag down my figuring out this charging issue.