Seemingly elementary question I can't find a useful answer to...

But oh so true :-) You are 'charging' it with it's average DC component. And the average DC component of an AC signal is ?

That's the next thing. You are not charging the battery but yet feeding it energy. A battery doesn't move, doesn't shine, so that energy is likely to end up as heat.

If you feed enought energy, almost anything will.

And you figured I didn't "get" that because... ?

So it's not *QUITE* safe to think of it as "half the cycle it's charging, the other half, it's discharging"? That's the mind-picture I was coming up with.

That's what I figured, but wasn't sure, so I asked in hopes of getting confirmation.

Is that any relation to the observation that "Even a brick flies quite nicely when you strap a big enough jet engine to it"? :)

Why not let's just call it a wild-ass-guess, shall we?

Sheesh... Gimme a break, John - It's AC. It may have been 30 years ago that I learned to operate a VOM well enough to distinguish AC from DC, but underneath the extra functions and LCD displays that show you numbers an inch high, instead of needing to squint at a needle and remember which scale you're supposed to be reading from, the basic functionality and methods are still pretty much the same, y'know?

How about the difference between unfiltered DC and DC?

to

Well, it could be and most likely is DC superimposed with AC as one of the rectifier diodes fails in the reverse direction. In this case it will probably still charge the battery if only poorly.

If it is truly AC with a low impedance bi-directional drive on both the positive and negative swing (like a wall plug) then the battery will become discharged to zero. Something will get warm (hot) depending on the actual impedances of the source and battery.

The fact (impression) that the ATV apparently still starts indicates that the battery is not being discharged completely.

You do need to fix it. Sooner or later it will fail completely probably by becoming open circuit and unable to charge anything.

It is unlikely that the battery would do the Cha Cha Cha. The battery and alternator might do the Tango though!

Fine, let's go with "it's exactly what you're saying", just for gits and shiggles. Whether it's AC biased into wiggling above or below the zero line is a detail that just plain doesn't matter - the result is the same: The battery isn't charging, and it's getting hotter than hell.

I checked the empirical data - I put blisters on my fingertips by touching the battery case after having the rig running for a while. Yep, sure enough - It gets hot...

As of this morning, the battery reads somewhere in the 11-14 volt range, no-load, but immediately drops to about 4-5 volts when I hit the starter button.

Which pretty much confirms the "not charging" theory, regardless of whether the juice is a flat line or a wiggly one. (and without any interest whatsoever in whether the wiggle is above or below the zero line.)

It starts - By me pulling on the rope. For the time being, I've disconnected the battery for fear of completely cooking (assuming that hasn't already happened...) or exploding it.

Pull-starting this thing is a stone BITCH, though... If I'm reading right, it's a 400CC engine, and as a rough guesstimate (comparing the effort required to pull the thing to life to the effort involved in, ferinstance, handling hundred pound hay bales or 50 pound feed bags) I'd say it takes close to 250 pounds of pull to fire it up. Not fun...

It's already at the "unable to charge anything" point. Exact failure mode seems pretty much irrelevant at this stage. Doing some online research to find out what fixing it will take is making the idea of "scrap it and find a different one" look like a viable option.

Apparently this failure is common on this model, and according to several boards that cater to the ATV community, trying to find the parts to do the fix is like trying to find hen teeth. And on the off chance that you DO manage to find a source, the prices are through the roof. Never mind the "to do this repair, you must remove the engine from the ATV, then strip the engine down to the point where you might as well go ahead and take it apart the rest of the way and do a full rebuild" factor. Which puts the machine out of commission for what I suspect will be AT LEAST 2-3 days, which in turn puts *ME* out of commission for the duration of the project, which means that the livestock goes hungry, which just plain ain't acceptable, PERIOD! Hiring the job out is likely to cost as much, or more, than just finding a different machine just in the labor charges, never mind whatever the parts end up costing. (again, assuming they can be found)

If only it were as simple as the tractor, or my car: Loosen the belt, unscrew two bolts, unplug one connector, remove one nut holding down another wire, slap new $50-ish unit in place, replace connector, wire, hold-down nut, and two bolts, re-tension belt, 15 minutes plus sending somebody to the parts store have elapsed, time to get back to work!

The Tango, or the Tango Uniform? :)

Unfortunately, either way, I'm afraid that tune is already on the turntable. :(

What about it?

So that we have something to argue about, let's forget about the fact that to a battery, they're the same animal unless the zero line is being crossed. You are aware, that a battery will charge just fine (although it will obviously take longer) off the raw output from a half-wave rectifier, right? Hard to get much less "filtered" than that, no? If we were talking about a 'scope trace, it'd be a different story, sure - and it wouldn't be possible to mistake one for the other unless you were a blind man. But since we're talking about a battery, it's a distinction which makes no operational difference.

Great, you got the cover-all. Here's yer fruit basket.

Look, John, I'm not interested in playing games of theoretical pedantry. In the realm of the lab, or in the math, sure - It's likely to be important. Perhaps even critically important, depending on exactly what's being done/attempted.

Here in the real world, where I'm playing, the distinction is utterly meaningless. I've got a battery seeing what appears to be AC rather than the expected DC. Whether the appearance comes from piss-poor filtering, a total lack of rectification, or AC modulation riding on top of a too-low DC "carrier" voltage means nothing - The battery is effectively seeing AC instead of the DC it wants.

You guys want to play the pedant game, you go right ahead and enjoy yourselves. Meanwhile, I've got more important things to worry about - like how to transport the several hundred pounds daily of feed to (and resulting "output" from) 20-odd head of horses who don't give a tinker's dam about electrical theory except in regard to how it bites them on the ass when they back into the fence.

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Well, I guess you'll just have to replace the whole unit. How about getting one of those diesel "mules" Kawasaki?

Somewhere above I saw that you have 20 horses? Perfect short term solution: Hitch up a horse to a cart or even to the ATV and you can deliver hay all day long, just like the old school. What the hell did your grandpa do?

to

My first guess also. But I didn't mail it, as I realized that a rectifier in series with the load also forces the source to carry DC too. As OP mentioned an altenator, forcing that to carry DC may have very serious consequences, And the alternative (one diode in series and one diode over the source to carry the other halve of the wave) may have rather serious consequences also (over current situation by almost shorting half the wave)

I thought about that, but doesn't that have the potential for some pretty severe consequences to the magneto, and/or the wiring from it? Seems that it would be effectively shorting it out each half-cycle, which I can't imagine being anything like good for it. Assuming, of course, it isn't fried already... that oddball 6-ish volt reading I'm seeing at low RPMs has me wondering if it isn't a three-phase setup, with one or more of the phases fried. On second thought, if that's the case, where's the 15 volts coming from when I wind up the engine? (pardon my stream-of-conciousness...)

Of course, if I try the diode trick, there's the "fun" of trying to find one that can handle the 410 watts the magneto is supposedly rated for. Let's see... 410/14 is a little under 30 amps, if I haven't misplaced a decimal point. Biggest diode I can put my hands on right now (Without going downstairs into the parts box to look for sure, I think the biggest diode I have on hand is either a 1N1005 or 1N1006) is rated for an amp or less. Somehow, I suspect all the "magic smoke" would leak out of one of those in a matter of milliseconds if I dropped it into the mix. I imagine I could find/order something designed to go in a welder, but that's likely to be fairly pricey, and take at least a few days to arrive. Damned if I do, damned if I don't...

OK, that's what I suspected, as posted in my other message - I thought about doing just that, but then had the suspicion that it might cause other/more troubles.

I'm not CERTAIN if this thing has an alternator or a magneto - Both terms get used on the spec-sheet I found, but I don't know if either can be trusted, since it APPEARS to have been put together by a third party, rather than being an actual "Yamaha approved" document. If there's an official Yamaha document available online, I haven't managed to find it yet, but I'm still looking.

In article , "Bob Eld" wrote:

We're looking into that general idea. Meanwhile, it's "pull-start or nothing" for the forseeable future.

Heh... While I'm qualified to drive singles, doubles, 4, 6, and 8 horse teams (Including having driven one of the Budwieser Clydesdale hitches, and the Coor's Belgian hitch, both in full regalia), the horses here are all the "prissy" types - they jump and do dressage, they (turn on the most scandalized "Bonnie Blueblood" inflection you can) DON'T pull wagons, perish the thought! That's just plain beneath their dignity! Or so they'd tell you, anyway. None of them are harness-broke, so it would be a pretty good rodeo for the first few weeks, I'd imagine. Never mind getting the harness and rolling stock to hook 'em to.

You'd be AMAZED at the price of horse-related leather work... Hell, I'm in the biz, and *I'M* frequently left speechless when I see the prices horse-folk pay for horse-related leather goods! As an example, one of the boarders here just recently bought a headstall - Not a full bridle, with bit and reins, JUST the part of the bridle that the bit and reins attach to. If you were *EXTREMELY* generous (and rather creative, besides) with the measurements, you *MIGHT* be able to figure out a way to call it 50 square inches of leather. Throw in half a dozen "Chicago screws" (Basically tiny nuts and bolts, but chrome-plated, and made with no sharp edges, so that no matter what happens, they can't damage the horse), four buckles, a few inches of stainless steel wire, and a few dozen yards of thread, and you've got the whole thing. The price she paid for it could have easily kept me AND my two horses fed - and fed WELL - for a month, with money left over for a couple trips to the movies. A decent harness can run into the price of a car. And that's just the harness - never mind the bits, bridles, lines, and hookup hardware that doesn't come as part of the basic "harness" package. You don't even want to know about how much the price jumps when you move from the plain-jane "working grade" gear into the "show grade" stuff with all the silver and spots and crystals and crap... Just thinking about those prices is enough to give a guy nosebleeds and altitude sickness! On the other hand, there IS the entertainment value to be considered - I can imagine the scene... Jane Boarder drives up to see her precious high-points jumper hitched to a cart full of shit. She immediately goes into full freak-out mode, causing her blood pressure to jump so high that her head explodes like a cantaloupe in a microwave oven...

Of course, the downside of that is me being the one who would have to sweep/scrape/shovel up and dispose of the mess...

ting

Couple of other ideas that might be worth considering, at least as temporary get-outs from having to replace the whole shebang. Both involve DISCONNECTING the faulty alternator or dynamo. First, spend maybe 50 bucks or so on an old banger (ObUSA : junker) from a scrapyard. Something with maybe a knackered chassis or bodywork falling to bits, but with an engine that still starts and runs reliably. Tow it home and park it up next to your ATV. Couple of jump leads, connect the two batteries together and start the ATV off the junker's engine. Or get a 12v charger and charge up the ATV's battery overnight, and start it up off the battery alone in the morning.

Cheers, Pete.