Alternator question

[Razzar]

Running a chevy 10si alternator on a 6.5hp engine. Would there be a significant loss of power running an alternator on this small of an engine. I am trying to use a stator magnito but might not be able to find one that fits

Thanks

 

[anderkart]

Depending on how many amps it puts out, It could take as much as 3 or more HP to spin that Alternator to its full output level.

Once your battery was fully charged (and you werent running any lights or anything) the alternator would then spin very freely with hardly any power loss to your engine.

 

[Doc Sprocket]

Thanks, Anderkart! I was wondering that myself... I knew that a functioning alternator added a load to the engine, but I had no idea how much, nor did I know that the load was proportinal to demand. I wonder how that works- Is the magnetic field actually that difficult to overcome? And-
Could you put the alternator on a switch (likely requiring a relay/solenoid) to de able to bypass it and get full horsepower when you want?

 

[truesprocket]

Thanks, Anderkart! I was wondering that myself... I knew that a functioning alternator added a load to the engine, but I had no idea how much, nor did I know that the load was proportinal to demand. I wonder how that works- Is the magnetic field actually that difficult to overcome? And-
Could you put the alternator on a switch (likely requiring a relay/solenoid) to de able to bypass it and get full horsepower when you want?

a 6.5hp would easly push it but an old VW generator motor would be better for any reason I could think of & a 6.5hp would probably not laber to much running 2 or 3 of eather, atleast I'm thinking a 6.5 is atleat that good or maybe far better, 4, 6 but a sepperate belt with a tensioner you could disconnect for hills or sand, if it's electric start it will have a charging system so you don't have to recharge it to use it & you can add the kit if it isn't electric start, most are set up for it even if it doesn't come with it, like lawnmore tractors with lights same idea. good luck! let me know what happens & try it!

 

[truesprocket]

my picture

hey guy's how do I show a picture instead of just my handle

 

[Linksep]

Volts x Amps = Watts

746 Watts = 1 HP

6.5 HP = 4,849 Watts

4,849 Watts / 14.4 (Charging) Volts = 337 Amps (Assuming 100% efficiency.)

Quick googling shows me the 10si, 12si, 15si 17si all mount the same and they are rated 40-120A. With less current draw they take less power to spin, so you should be fine. However, it WILL draw some power, and if you have a bad battery that doesn't accept a full charge or run lots of lights it will sap engine power all the time. If you'll notice the missing power or not I can't say.

 

[anderkart]

Thanks, Anderkart! I was wondering that myself... I knew that a functioning alternator added a load to the engine, but I had no idea how much, nor did I know that the load was proportinal to demand. I wonder how that works- Is the magnetic field actually that difficult to overcome? And-
Could you put the alternator on a switch (likely requiring a relay/solenoid) to de able to bypass it and get full horsepower when you want?

Your right, at higher output levels the rotor is spinning in a higher magnetic field.

Most of these 10SI alternators have Self Energizing Voltage regulators and will keep charging even if unplugged. You could try installing a super heavy-duty switch (or relay system) in-line into the alternators rear output post, but the internal voltage level would spike and that might end up damaging the Alternator.

Something you could try for free here is to take your Alternator apart, (just remove the 4 little 5/16" through bolts/the Stator stays with the rear half) and somehow cut/tap into either of the brush's wire leeds, and then reconnect them through a toggle switch. Cutting the signal to either brush would stop the Alternator from charging and not damage anything.

FYI:
When your ready to reassemble the alternator, theres a little trick you'll need to know about... You'll find the brush holder has a very small hole you can poke a (straightened-out) paper clip through to hold the brushes back away from where they normally ride against the rotors slip rings. Slide your paper clip in from the from the small matching hole in the alts. rear case , then instal the Alternators back half, and simply pull the paper clip out to relese the brushes.

You'll find you can reinstall the Alternators back half in your choice of 4 different positions. Just select any clock/position that gets the wiring connections located where you want them.

All you'd need to do for wiring this up is conect the Alternators rear (Bat) post to your battery + post with 10 gauge wire. And then where the 2-wire plug goes in, just jumper/connect the Alternators 2 male plug conectors together. Most of these 10SI alts will work this way to make it an easy 1-wire instalation.

 

[anderkart]

hey guy's how do I show a picture instead of just my handle

First click on Quick links you'll find up near the top of any DIY forum page.
Then click Edit Details.
Then click on Edit Profile Picture and upload any pic from your computer or off-site photo host.

ps:
You'll first have to edit your pic to a very small size (100x100 or 64KB) to use as your Avatar.

 

[motor_head]

All you'd need to do for wiring this up is conect the Alternators rear (Bat) post to your battery + post with 10 gauge wire. And then where the 2-wire plug goes in, just jumper/connect the Alternators 2 male plug conectors together. Most of these 10SI alts will work this way to make it an easy 1-wire instalation.

that will work but will drain the battery when it's not charging

the #2 pin on the picture needs to be switched so when your motors off you also turn the switch off so you battery doesn't get drained

 

[Razzar]

Thanks everyone for the info. I was thinking that i might added a flywheel housing on the end of the drive shaft out of the engine. I would run a seperate stator off of it and use it that way as a alternator. Has anyone tried this, i was thinking that this would cause no real stress to the engine provide the charging i would need. It would need some modifying to get it to work but i think the principle looks sound.Has anyone tried this.Also if running a tav 30 is there any room left on the end of the shaft to mount it?

 

[anderkart]

that will work but will drain the battery when it's not charging the #2 pin on the picture needs to be switched so when your motors off you also turn the switch off so you battery doesn't get drained

As long as It has an SE (self energizing) type regulator that most rebuild shops have use since the 1980's, there wont be any drain with this setup. If the Internal Regulator in Razzar's 10SI Alternator is not a Self energizing type, it wont charge at all with a 1-wire hookup and its 2-wire plug will require the usual battery/ignition feed to function.

I never actually checked for a drain with a non-SE equipped regulator/1-wire hookup with this type of Alternator, (because it wouldn't charge anyway) but you may very well be right and meybe it would cause a drain.

I retrofitted literally hundreds of 1-wire 10/12/15/27-SI Alternators on all kinds of different vehicles over the 17 years I worked at an Auto Electrical/Alt-rebuild specialty shop. Part of our testing procedure was to double check for drains before and after all charging/starting system type repairs.

The only drawbacks we found with 1-wire hookups on these types of Alternators were: when first starting the engine, you had to rev it up a bit (2000 rpm or so) to get the Alternator charging, but besides that they worked just fine otherwise.

 

[nerfo]

If a guy were to use a 10si alternator, could you use a small ATV or lawnmower battery AS your battery? And if all you were running were two 55 watt lights, that would only put an amp load of 7.8 @ 14 volts on your alternator... So, assuming the battery is fully charged, and we're not running two, 12 inch subwoofers with a bazillion watt amplifier with a 00 gauge wire for power, and 100% efficiency from the alternator... we can assume that 110 watts divided by 746 watts/hp = .147hp to operate two typical fog lights. So, big whoop? Is my math right? Do I know what pulley sizes I'm using? (no, I dont.) Is this something I REALLY wanna do? He!! yeah it is!

 

[nerfo]

A cheapie "wal-mart auto aisle" volt meter would be a handy addition to something like this. Oh crap... now I want to put a fuel level sender on a clone engine.

 

[anderkart]

Yeah you could run a small (12volt) ATV or lawnmower battery with an automotive Alternator. The Amp Hour/CCA of the battery wouldn't really make any difference in how the Alternator charged. Once the voltage regulator sensed battery was fully charged and the voltage up to around 14.2, the Alternator would pretty much stop charging and wouldn't present much of a load on the engine. At that point any 12v. accessories you operated would drop the systems voltage down and the voltage regulator would sense this and immediately send whatever field current was necessary to maintain the system at 14.2 volts.

I didn't double check your math but it all seemed about right to me.

Your pulley diameters would definitely be something to consider.

Installing a volt meter would be a cool option to monitor things, you could also opt for wiring up an Idiot-Light with most any automotive Alternator.

I just sold a clone powered fun kart (it had a black colored Homelite brand clone engine) that had a factory installed, float type, mechanical fuel level indicator all built into the tank. It was a pretty cool setup I'd never ran across before.

 

[dcook3333]

I haven't spent a lot of time looking into the alternator thing, so forgive me if this is answered somewhere else. If there is a comet drive on the engine's output shaft, where can you put a pulley to run the alternator belt?

 

[anderkart]

I've seen some Centrifugal clutch manufacturers offering belt drive models with dual/triple pulleys, but i dont know of any chain-drive clutch models that also have a drive pulley. (although a good fabricator could probably weld something up...)

 

[dcook3333]

Thanks, Mine is a regular comet 40 drive. I haven't had the battery/lights on it long enough to know if juice is going to be a problem yet. And not worried about it too much as the recoil starter works just fine, too.

But, if I have to go there.... Thinking about finding a belt drive to go on a standard 1" keyed shaft. Then I'd take a short piece of that kind of shaft and bore a 5/16 hole all the way through the center. Then take that pulley and shaft and stick it inside the Comet drive (the engine output only goes part of the way through the drive). Hold it all together with a long bolt into the engine output shaft.

We'll see. If charging becomes a prob.

 

[anderkart]

Hey dcook, I just took a look at your Frankenbuggy thread pics and got a different Idea that might just work for ya. If you installed a Serpentine pulley on the Alternator, and also a couple well-placed automotive Serpentine Idler pulleys, I was thinking you might be able to drive the back side of your Alternator belt directly from the flat outer hub portion of your 40-series driver...

I'd think you'd want your 2 Idler pulleys located (right directly above and below your driver) so the back side of your Alt-belt wrapped around like half of your driver for a good grip, and then also located close enough to act as guides keeping the belt centered. As long as the Alternator didn't have a super high output level, I'm thinking you'd get enough grip to drive it this way.

Some of these serpentine Idler pulleys are equipped with spring loaded brackets to tighten the belt so the Alternator wouldn't have to pivot. These Idlers can get kinda pricey new but you could probably score some good used ones from an automotive wrecking yard cheap. Then you'd just need to take some measurements and find the right length Serpentine belt.

 

[dcook3333]

Anderkart, good idea... using the comet drive to run the back of a serpentine belt. What it will come down to is space. That whole assembly can bounce up and down with the swingarm, so need to be careful. Yeah, it's hard to believe there is clearance enough for that swingarm to move fully with the big engine and tranny, but it does... barely. What it will take is a good solid half hour of me staring at it to come to an answer. Somehow zoning out helps.