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

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it, what's the most likely result? I'm hoping for something a bit more
useful and specific than "you'll end up with a dead battery" - That's
only too obvious.

Should I expect the battery to heat up?

Explode?

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it,

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net
wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it, what's the most likely result? I'm hoping for something a bit more
useful and specific than "you'll end up with a dead battery" - That's
only too obvious.

But oh so true

You are 'charging' it with it's average DC component.
And the average DC component of an AC signal is ?

Should I expect the battery to heat up?

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.

Explode?

If you feed enought energy, almost anything will.

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it,

---
How do you know it's AC?

In article <vhv1l55l698n971m32n675slam0pveq9k4_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it,

---
How do you know it's AC?


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?

In article <vhv1l55l698n971m32n675slam0pveq9k4_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC
to
it,

---
How do you know it's AC?


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?

--
Email shown is deceased. If you would like to contact me by email, please
post something that makes it obvious in this or another group you see me
posting in with a "how to contact you" address, and I'll get back to you.

Don Bruder wrote:

In article <vhv1l55l698n971m32n675slam0pveq9k4_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it,

---
How do you know it's AC?


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?

"Don Bruder" <dakidd_at_sonic.net> wrote in message
news:hirbua$du7$3_at_news.eternal-september.org...
In article <vhv1l55l698n971m32n675slam0pveq9k4_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC
to
it,

---
How do you know it's AC?


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?

--
Email shown is deceased. If you would like to contact me by email, please
post something that makes it obvious in this or another group you see me
posting in with a "how to contact you" address, and I'll get back to you.

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!

On Sat, 16 Jan 2010 00:15:52 -0500, "Michael A. Terrell"
mike.terrell_at_earthlink.net> wrote:


Don Bruder wrote:

In article <vhv1l55l698n971m32n675slam0pveq9k4_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it,

---
How do you know it's AC?


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?

---
BINGO!

In article <9o24l55nh4qsv9mb5ipu1o2n6941gd692c_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Sat, 16 Jan 2010 00:15:52 -0500, "Michael A. Terrell"
mike.terrell_at_earthlink.net> wrote:


Don Bruder wrote:

In article <vhv1l55l698n971m32n675slam0pveq9k4_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it,

---
How do you know it's AC?


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?

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.

---
BINGO!

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.

In article <hissu1$3pr$1_at_news.eternal-september.org>,
"Bob Eld" <nsmontassoc_at_yahoo.com> wrote:

"Don Bruder" <dakidd_at_sonic.net> wrote in message
news:hirbua$du7$3_at_news.eternal-september.org...
In article <vhv1l55l698n971m32n675slam0pveq9k4_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net
wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason,
the
charging source decides to start feeding between 6 and 15 volts of
AC
to
it,

---
How do you know it's AC?


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?

--
Email shown is deceased. If you would like to contact me by email,
please
post something that makes it obvious in this or another group you see
me
posting in with a "how to contact you" address, and I'll get back to
you.

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.

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.

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.

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.)

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

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...

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

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)

sigh> 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!

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

The Tango, or the Tango Uniform? :)

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

--
Email shown is deceased. If you would like to contact me by email, please
post something that makes it obvious in this or another group you see me
posting in with a "how to contact you" address, and I'll get back to you.

On Sat, 16 Jan 2010 22:07:54 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

If I've got a 12 volt lead-acid battery, and, for whatever reason, the
charging source decides to start feeding between 6 and 15 volts of AC to
it,

If you just need a band-aid until you can get a proper repair done,
couldn't you just connect a big-ass diode in series with the output lead
from the regulator?

On Sat, 16 Jan 2010 22:07:54 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

In article <9o24l55nh4qsv9mb5ipu1o2n6941gd692c_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Sat, 16 Jan 2010 00:15:52 -0500, "Michael A. Terrell"
mike.terrell_at_earthlink.net> wrote:


Don Bruder wrote:

In article <vhv1l55l698n971m32n675slam0pveq9k4_at_4ax.com>,
John Fields <jfields_at_austininstruments.com> wrote:

On Fri, 15 Jan 2010 09:08:51 -0800, Don Bruder <dakidd_at_sonic.net
wrote:

A situation I've never encountered, so I've never thought about...

If I've got a 12 volt lead-acid battery, and, for whatever reason,
the
charging source decides to start feeding between 6 and 15 volts of
AC to
it,

---
How do you know it's AC?


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?

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.

---
BINGO!

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.

---
Geez, sorry to get you so upset...

If you just need a band-aid until you can get a proper repair done,
couldn't you just connect a big-ass diode in series with the output lead
from the regulator?

On Sun, 17 Jan 2010 08:31:39 -0600, John Fields
jfields_at_austininstruments.com> wrote:

On Sat, 16 Jan 2010 22:07:54 -0800, Don Bruder <dakidd_at_sonic.net> wrote:

If I've got a 12 volt lead-acid battery, and, for whatever reason,
the
charging source decides to start feeding between 6 and 15 volts of
AC to
it,

If you just need a band-aid until you can get a proper repair done,
couldn't you just connect a big-ass diode in series with the output lead
from the regulator?

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)