From: ` on
On May 17, 1:45 am, Mark Olson <ols...(a)tiny.invalid> wrote:

> On at least four occasions, I forgot to turn the grips off
> and the battery went completely and utterly dead. In each
> case I jumped it from a car, and that seven year old battery
> was still working perfectly when I sold the bike. On at least
> one occasion I was in a big hurry to get going, the battery
> was so low that jumping it from the car wouldn't start the bike
> so I left the car engine running. Nothing bad happened. I've
> heard a lot of people say leaving the engine run will kill your
> regulator or fry some other expensive part, in my experience I
> have never witnessed that. In my locate climate we have LOTS of
> experience with jumper cables.

In the case of jump starting a motorcycle with a discharged battery
from a car with the engine running, the zener diode in a motorcycle
equipped with a permanent magnet alternator and a fully functioning
shunt type regulator would "see" up to 15 or 16 VDC, because the two
batteries are connected in
parallel.

The zener diode in the MC RR would trigger the silicon control
rectifier that shunts one or two phases of the stator to ground, and
the motorcycle alternator's output would be reduced to 1/2 or less,
depending on the number of SCR's in the RR unit.

The SCR has enough internal resistance to shunt excess current to
ground, burning it up as heat.

The SCR takes the load off the power diodes in the MC RR.

If the motorcycle's zener has already blown out, the MC alternator
will have to "duel" with the car's alternator, but there won't be
enough voltage from the
car alternator to cause reverse current through the six diodes in the
MC RR.

But the situation that I was referring to is when the motorcycle
battery is discharged and the car battery is mostly discharged and the
car engine isn't running.

The MC RR's zener diode voltage sensing circuit would *never* trigger
the SCR, because the resting voltage of the car's battery is something
between 12 volts and 12.8 volts.

If the jumper cables are allowed to remain connected after the MC
engine is started, the MC alternator will try to charge *both* the MC
battery and the weak car battery.

Since there is nothing to switch the MC alternator out of the circuit,
it's possible to blow out one or more of the diodes in the MC RR if
the jumper cables remain connected.

For that matter, it's possible to blow out the MC RR diodes if the MC
alternator is forced to continuously try to charge a dead MC battery
under normal riding conditions.




From: ` on
On May 18, 5:56 am, billg...(a)cs.uofs.edu (Bill Gunshannon) wrote:

> I'll fix it one of these days but in the meantime, I'ld rather ride. ;-)

I'd bet a cyber beer that if it came to the choice of fixing a
motorcycle that wouldn't run at all, or riding a keyboard on Usenet,
you'd choose the latter....;-)
From: pokee joe on
paul c <toledobythesea(a)oohay.ac> wrote in
news:PfoIn.4411$z%6.4398(a)edtnps83:

>
> A lesson I've re-learned a number of times on bikes and cars: Even
> a little six-inch ground strap when the ends are corroded/oxydized
> or even thinned due to use might have as much as a quarter-ohm
> resistance. A 300 watt starter motor has a resistance of less than
> half an ohm. In that case, a 12 V battery would lose a third of
> its voltage, ie., 4 V on the ground strap, leaving only 8 V max for
> the starter.

Actually, it's a lot worse than that. Even small starter motors will
draw a locked rotor current of 100 amps or more. That means the
resistance of the starter windings is around .1 ohms and it's not
unusual for larger two cylinder engines to have starters that have
less than .04 ohms. Your 300 watt starter will draw more than 150 amps
initially and have a resistance of less than .075 ohms. That's why we
require starting batteries in the first place, they are specifically
made to provide far higher short term current than deep cycle
batteries.

>
> Cleaning isn't hard, especially with spray-on contact cleaner and
> for helping to keep surfaces clean after re-assembly there is also
> conductive grease for the interior contact surfaces and dielectric
> grease to help insulate the outsides from moisture, some people
> don't bother with the greases, they just use vaseline. Sometimes
> spade or bullet connectors are just loose.
>

The best contacts for carrying high current with minimal voltage loss
is bare metal to metal. Any materials that get in between those
surfaces will increase the voltage drop and reduce the current. There
is no conductive grease on the market that works as well as clean and
smooth, bare metal to metal contact, completely devoid of all
oxidization.

After you chemically clean, then burnish the contact surfaces,
reassemble the connector, then cover the connector from the outside,
with dielectric grease, to isolate the entire metal mass from all air
and moisture. There are several spray-on products, made to coat
battery posts, which are even better for this use.

When someone fills a connector body with grease, then plugs the
terminal into it, they are depending on the sliding contact to force
it's way through the grease and establish a metal to metal contact, in
spite of the grease. Then the grease simply keeps air and moisture
away to prevent future corrosion. That works just fine with the
various kinds of quick disconnects in use, until the female terminal
gets spread from vibration or abuse and weakens the contact pressure.

Vasoline is fine when dealing with rubber or plastics, but never use
it on metal. It is a water saturated grease and will promote corrosion
instead of preventing it.

regards,
Joe
From: Bill Gunshannon on
In article <182e2d14-7afd-43cb-b838-656f6bbd75aa(a)v12g2000prb.googlegroups.com>,
"`" <breoganmacbrath(a)yahoo.com> writes:
> On May 18, 5:56�am, billg...(a)cs.uofs.edu (Bill Gunshannon) wrote:
>> I'll fix it one of these days but in the meantime, I'ld rather ride. ;-)
> I'd bet a cyber beer that if it came to the choice of fixing a
> motorcycle that wouldn't run at all, or riding a keyboard on Usenet,
> you'd choose the latter....;-)

You would loose. :-)

In my spare time I am shade-tree mechanic. Working mostly on classic
sports cars. Computers are what I do to pay the bills and when they
cross over to the hobby domain like the sports cars it is classic
computers. USENET is just something to occupy free time when I am in
the office and not doing real work. :-)

bill

--
Bill Gunshannon | de-moc-ra-cy (di mok' ra see) n. Three wolves
billg999(a)cs.scranton.edu | and a sheep voting on what's for dinner.
University of Scranton |
Scranton, Pennsylvania | #include <std.disclaimer.h>
From: pokee joe on
"`" <breoganmacbrath(a)yahoo.com> wrote in news:dd933f7b-a5e1-43ac-bf6f-
0d011b8f95bd(a)u3g2000prl.googlegroups.com:

> In the case of jump starting a motorcycle with a discharged battery
> from a car with the engine running, the zener diode in a motorcycle
> equipped with a permanent magnet alternator and a fully functioning
> shunt type regulator would "see" up to 15 or 16 VDC, because the two
> batteries are connected in
> parallel.
>

Only if the jumper cables are awg 000 or larger. Even then, you would
need some other kind of connectors than the spring clamps normally
seen on jumper cables.

What actually happens is, the discharged motorcycle battery draws 50
amps or so, resulting in a voltage drop in the jumper cables and
clamps, so the actual voltage the motorcycle harness sees is only
about 13 volts, at most. As long as the motorcycle battery is drawing
a heavy current through the jumper cables, the motorcycle's electrical
system is protected by the battery, just as car batteries used to be
used as voltage regulators and filters for power supplies, back before
the days of electrolytic capacitors and electronic voltage regulators.

If the problem is misdiagnosed as a discharged battery on the
motorcycle and the motorcycle battery is actually charged, then you
can have a serious problem.

regards,
Joe