OT: small engine charging system

"I have a 9 hp honda small engine with electric start. It does not have an alternator as such and the electric starter does not act as a generator so how is the battery charging voltage regulated. My problem is that it is overcharging, putting out up to 16 volts at times. Where is my problem? Thanks. "

I have the same situation with a chrysler 10 hp. I dont think that there is a voltage regulator built into these motors but I may be wrong. The way I handle the problem is, I watch the battery voltage with a monitor while im motoring & when the voltage hits over 14v, I start turning on lights to regulate the voltage.This is probably not the best way to do this but I havent cooked anymore batterys since I started this method. Jerry

I dunno about your particular system and if it can be repaired cheaply but I have a Tecumseh engine with a similar system. The magneto is also the alternator for charging the battery. So the magnet in the flywheel powers both the spark and charging system. If yours is too expensive to fix you may want to consider a zener diode with attached heatsink to regulate charging. This method was used in some british bikes. Kinda brute force and wasteful of power but it works and is simple. You could measure the charging current with an ammeter and then buy a 14 volt zener (assuming a 12 volt system) that can handle the current. The zener connects to the charging wire and to ground. ERS

without knowing more about your application, it's my understanding that small engines use charging coils (under the flywheel), this system is used when the battery is primarily used for just starting the engine. Headlights, directionals, horn, etc use regulators and generators. If you're checking the output without the battery you may be getting a high reading because the battery is used as a balast to complete the circuit. (like mopeds or scooters, they need a battery to balance the output or the system may put out too much power and blow a headlight) If you're checking the system at the battery while running, it should be anywhere between 9-13 vdc, (providing it's a 12 volt system) if it's truly 16vdc, you're charging coil may have a problem. Good luck, walt

I believe you need two zenor diodes in series (facing opposite directions) if you want to regulate the AC voltage from the magneto... and 4 zenor diodes in a "bridge" if you want regulated DC voltage to charge a battery? Virtually all modern snowmobiles regulate voltage, as you say, by using the zenor diodes to dump excess voltage to ground; but with only 1 zenor diode you would have a "dead short" in one direction. In series, one diode blocks 14v from getting to ground in one direction and the other diode would block 14v in the opposite direction... but snowmobiles still run their lights and accessories on AC voltage. An electric start snowmobile uses a special voltage regulator that has an additional 12v dc regulated output. They are relatively cheap ($25) and some will handle up to 200A charging systems (although the headlight, tail light, and instrument lights are always on... for safety). You can try this ridiculously long link, but you must choose a regulator for an electric start model if you want the 12v DC needed for charging your battery:

?show=categoryResult&_requestid=171958 I have no idea whether or not the engine in question was set up to work this way though. David

"Eric R Snow" wrote in message news: snipped-for-privacy@4ax.com...

I've got an older Merc outboard that dosn't regulate the voltage, basically just magnets in the flywheel running past a bunch of coils bolted to the case.

The owners manual points out that the charging voltage will run "high" & to frequently add water to the battery because of this.

Howard.

I agree that it is very important to check the voltage under load but 9 to 13 vdc seems low. Cars typically put out 13.5 to 14.3 VDC. The extra voltage is necessary to overcome the internal resistance of a 12 volt battery.

" > when the battery is primarily used for just starting the engine. Headlights,

If this engine is for machinery, a low charging system should be fine because the batterys only purpose is to power the starter (plus i meant that it may fluctuate between 9-13v). That's why i think it makes a difference what the engine is powering. You may be right though, this was just a guess based on my experience. When in doubt, take it to a place where they service them everyday. walt

If the systen is already putting out 16 volts DC, which is too high,1 zener connected to ground and to the wire that goes to the battery will work. I assumed that the OP was talking abot DC voltage and it being too high. If it is AC then I would use a bridge rectifier and a zener. The system on my Norton uses this exact scheme. Crude, but effective and simple. Cheap too.

All of my tech data shows 13.5 to 14.5 as the expected output range at battery for small engines of 12 volt system designs. Visit my website:

expressed are those of my wifes, I had no input whatsoever. Remove "nospam" from email addy.

Along these lines, I have a snowblower with a Tecumseh engine and I'd like to put a light on so I can see where I'm going when the situation calls for early morning or evening snowblowing. Is there some way to tap into this to power a light? My machine has electric start, but it is a 110v. starter, not

12v. Any suggestions?

Steve

On Wed, 26 May 2004 17:58:45 -0400, "Steve Mulhollan" shouted from the rooftop:

Some engines already have the lighting coil built in. Most don't, but it's worth looking up in the parts break down. Some newer single cylinder engines use a fairly sophisticated ignition system that incorporates a built in alternator, which can be tapped for lighting.

-Carl "If you don't have enemies, you don't have character"-Paul Newman