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Discussion Starter · #1 ·
How long will an 18hp Briggs run on a 12 volt lawn tractor battery that isn't being charged?

I am just wondering because I have repowered my old Lawn Chief tractor and just haven't gotten around to finishing up the wiring. It runs great and starts up great, just that the charging and lighting circuit hasn't been hooked up.

The original engine (12hp single) had a single wire whereas the replacement engine (18hp opposed twin) has 2 wires (dc/ac I assume) and I just haven't gotten around to figuring out which goes to which.

So I just wonder if I fully charge the battery and run the tractor to clear snow, how much time would I have reasonably? Does the 18hp engine actually draw power from the battery while its running if the charging circuit isn't hooked up?
 

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I think that depends on what kind of ignition system the engine has. If it's magneto fired, you'll either run out of gas or wear out the engine if you have an unlimited supply of gas. Oil changes might be a problem while the engine is running. With a solid state ignition system that draws from the battery, it'll die a little sooner. Maybe even before the first oil change.

Batteries in most tractors are primarily there to run the starter motor, and that will kill a battery in a very few minutes af cranking. My Onan P220 runs just fine with the battery disconnected completely, once it's started.

Start it up, do the driveway and put the charger back on it when you're done. Better yet, spend a few minutes and get the charging system up and running.
 

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Discussion Starter · #3 ·
How do I know what kind of ignition system I have? I have an older 18HP opposed twin Briggs and Stratton engine.

I'm worried about hooking up wires because I am not sure if I need a regulator installed. My old engine did not have a regular and I believe was a dc system.
 

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A model number posted (here) would probally return the electrical diagram, operator manual, and a lot more accurate info.

Why isn't it charging?
 

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How do I know what kind of ignition system I have? I have an older 18HP opposed twin Briggs and Stratton engine.

I'm worried about hooking up wires because I am not sure if I need a regulator installed. My old engine did not have a regular and I believe was a dc system.
Even my old '71 with starter/generator and magneto has a regulator. Are you sure it doesn't have one?
 

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"The original engine (12hp single) had a single wire whereas the replacement engine (18hp opposed twin) has 2 wires (dc/ac I assume) and I just haven't gotten around to figuring out which goes to which."

Depends, If the dual connector has a diode in line with the "Red" wire, that is the DC to charge the Batt, The other wire may be Black, to run the lights.

To verify, at 2400 rpm you should have 14 + DC measured to ground from the Red wire, and 14 + AC measured to ground on the black wire.

There are about 6 - 7 diffrent configurations with the 18 hp B/S.

The Single wire 12hp probally just charged the battery.
 

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"With a solid state ignition system that draws from the battery, it'll die a little sooner. "

Never heard of such a thing on an 18 hp B&S opposed twin.

IF that engine does not have a carb solenoid, It will run forever without a charging system, will start probably 10 - 20 times. Note that some of those engines had hard cranking problems so that will figure in.

IF you want to know how wires go, contact me at address below IF you like, put in proper format and remind me.

Walt Conner
wconner5 at frontier dot com
 

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Discussion Starter · #9 ·
A little info about my tractor. It is a 1987 Lawn Chief 12/39 that originally had a 12hp single Briggs engine on it. If I remember correctly, it had 2 wires on that engine. One was for the starter and the other was for the charging system. Maybe there were 3 wires, 1 for charging, 1 for starting, and 1 for the starter, I honestly can't remember now. But I don't think there is any type of regulator on the unit at all. The only electrics on the tractor are a pair of those lawn tractor headlights and nothing else.

The 12hp engine blew about 8 years ago and a couple of years ago I bought a replacement engine (18hp opposed twin Briggs, not the V engine) and put it in and have been working on it ever since.

So at this point, I have it running great and everything is working except for the charging system.

I don't have a wiring diagram of the Lawn Chief that I can think of.
 

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Discussion Starter · #10 ·
"With a solid state ignition system that draws from the battery, it'll die a little sooner. "

Never heard of such a thing on an 18 hp B&S opposed twin.

IF that engine does not have a carb solenoid, It will run forever without a charging system, will start probably 10 - 20 times. Note that some of those engines had hard cranking problems so that will figure in.

IF you want to know how wires go, contact me at address below IF you like, put in proper format and remind me.

Walt Conner
wconner5 at frontier dot com
I might contact you but a bit more info about the engine, it does NOT have a carb solenoid. There is a 2 wire plug on the engine that has a red and black wire but that is it other than the wires for the starter and engine kill (I think).
 

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Magneto ignition, so no battery needed for the ignition. I would jump my GT6000 with a Briggs twin and run it all day without even having a battery on it. The lights even worked.
The three wires out of the engine: Single black wire for shutdown, I believe the red one is DC positive, and the black one on the same plug is for lights. The return for both of those is through the block.
 
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