Magneto wattage

turbofiat124

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Does anybody know right off hand how much wattage the magneto produces on a 21 hp Intek Briggs? This would be on a lawnmower without a power take off.

Reason I ask is I'm going to build me a shade cover for my Husquvarna. It already has mounting holes for one, but I'm going to make my own out of some threaded rod and fiberglass.

I would love to mount some sort of fan underneath the cover to blow air on top of me to keep me cooler.

Some B&S engines like push mowers do not even have a magneto.

My Husquvarna does not have a power take off which to me anyway is not really the correct terminology. I always thought a power take off was a driveshaft on a tractor (or small lawn tractor) that runs an implement. Where a power take off on a riding mower is an electromagnet clutch which engages the blades when you pull a knob out instead of using a lever.

I've heard if you blow the engine on a lawnmower with a power take off, if you use a donor engine from another mower, your supposed to use the magneto from the blown engine or find an engine that produces enough current to operate the clutch. Otherwise it will discharge the battery and eventually the blades won't engage. I find it hard to believe an electromagnet clutch would pull that much current. So it must not be that much.
 

Rivets

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Turbo I think you have your terms mixed up. Almost every small engine has a magneto (CDI COIL) to provide spark. You can’t run anything else off a magneto. I think you are talking about a charging system (stator and voltage regulator) which are used to keep the battery charged and provide power fo4 accessories, such as lights, PTO, etc. Briggs has six different sizes depending on the engine size. They are rated in amperage, not wattage.
 

turbofiat124

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You are correct. The magneto is the ignition system not the charging system.

I think this is what I would need but i'd first need to check to see if it fits my engine.

https://www.ebay.com/itm/Briggs-Stratton-592831-Alternator-/332556660054?_trksid=p2349526.m4383.l4275.c10#viTabs_0

I guess I could wire in a shunt wire and ammeter guage from the current charging system going to the starter and hook the fan up to the battery and see if the needle on the guage goes into the discharge range. That would tell me if fan would pull more current than the charging system could provide.

The easiest thing would be to test how many amps the fan would pull and compare that to known data. So far I have not turned up anything about the current alternator's capacity.
 

bertsmobile1

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Briggs alternators are all coded by the shape & colour of the plug and the wires that go into them from the engine
You should find most of them here.
Briggs fitted different alternators to the customers requirements.
It is one of the things that the code part of the model number refers to.
But you need the parts book then check the alternator section and you will see which numbers had what alternators.
 

bertsmobile1

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The AC to the lights is not regulated either,
This is the most common system because it is cheap and very durable.
It uses the battery as a voltage regulator and that takes a toll from the battery.
IT also makes it difficult to fit accessories as the supply from the diode goes from 0 V DC to 14 V DC then back down to 0 again followed by nothing for same time then back 0 to 14 & back to 0 .
Some will cope quite fine while others will not, all depend upon how they are wired inside.
So in a nutshell you have 3 x 12 = 36 watts to play with without running down your battery, however you will not be recharging it either so when you have finished mowing it will need to go on a battery charger.
You get 50 to 100 starts from a battery depending upon how easy the mower starts and the condition of the battery.
You can change the stator to upgrade the system .
 

txzrider2

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I used to have a "pith" helmet, I think that is what it was called...bought it at sharper image and it had a fan pointing at my face made into the brim... had a solar cell on top to run it... it made me look like quite the dufus ... but I never cared since it really worked to keep me cooler in the sun.
 

turbofiat124

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The AC to the lights is not regulated either,
This is the most common system because it is cheap and very durable.
It uses the battery as a voltage regulator and that takes a toll from the battery.
IT also makes it difficult to fit accessories as the supply from the diode goes from 0 V DC to 14 V DC then back down to 0 again followed by nothing for same time then back 0 to 14 & back to 0 .
Some will cope quite fine while others will not, all depend upon how they are wired inside.
So in a nutshell you have 3 x 12 = 36 watts to play with without running down your battery, however you will not be recharging it either so when you have finished mowing it will need to go on a battery charger.
You get 50 to 100 starts from a battery depending upon how easy the mower starts and the condition of the battery.
You can change the stator to upgrade the system .
I can connect the fan I have in mind using to the battery and measure the current draw and do the math and see if it exceeds the charging capacity.

I'll check with a guy I work with who has a sideline lawnmower repair business and see if he has any used staters that came off a lawnmower with a power take off. That might be enough to run my fan. I still can't imagine an electromagnet clutch would need a larger charging capacity to avoid discharging the battery.
 
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