Re: GPZ500 No Spark!


oldgeezer wrote:

In the parallel situation, if the bike battery it is 'empty' and so old
that it cannot hold much charge, it will drain your car battery fast.
Your car battery will output many amps to your bike battery trying
to charge it.

No, that's not true at all. If you jumper your car battery to the
motorcyle battery and the car engine isn't running, the car battery
voltage will be somewhere between 11.9 volts (dead battery) and 12.8
volts (fully charged *resting* battery).

So, a "dead" motorcycle battery will only get about 0.9 volts from a
fully charged resting car battery and the charge rate (if any charge
takes place) will be at a very low rate.

When charging a dead motorcycle battery from a variable voltage
charger, you want to crank the voltage up to about 20 to 25 volts to
see if *anything* happens. If you see a charge on the ammeter, reduce
the voltage to about 15 or 16 volts to get the
*slow charge* rate on the sticker on top of the battery.

You could end up with warped plates in the car battery because
of the high current it then puts out.

Plate warping and lead shedding occur with a battery is charged at too
high a rate. That would never happen to a resting car battery while
hooked across a dead motorcycle battery.

When people do this parallel setup with cars, which is the
normal way it is done, then the guy with the good car always
starts his engine first and runs it a high revs, so that his generator
helps his own battery.

The reason for running the car's engine is to use the excess voltage to
charge the
battery in the *assisted vehicle*, as a fully charged resting battery
would take about 24 hours to equalize its charge with the dead battery
*if anything happened at all.

Really dead batteries need to be *shocked* into life with higher
voltage than you imagine. Refer to what I said about variable voltage
charging.

Check how fast the bike battery starts bubbling when you have it
on the charger. If it bubbles within a few minutes, it cannot hold
charge and you have to buy a new one.

The only reason I can imagine for a battery to begin bubbling
immediately would be if there were shorted plates.

There is a lot of misinformation about what can happen if you jump
start a motorcycle using a car battery and nobody else seems to realize
what will happen except me.

I will say this over and over and over.

The danger is to the motorcycle's alternator and the rectifier diodes.
Since motorcycles do not have a generator switch like an airplane, the
alternator is connected to the battery through the rectifier regulator
at all times.

If you jump start the motorcycle with a car battery that is, say,
half-charged, the motorcycle alternator will then try to charge the car
battery *and* the dead motorcycle battery.

This could lead to a damged alternator stator or blown diodes.

So, the absolute best way to solve the dead motorcycle battery problem
is to charge the motorcycle battery, do the capacity test you described
with a headlight across the battery terminals, and, if the battery
fails that test, replace the battery with a fully charged new battery
and go from there.

.

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