Kim Neubert wrote:
> I'm searching for why the battery gets low so fast when sitting.
> I spliced a voltmeter between the battery positive post and the large wire
> to the starter solenoid and I'm losing .2 volts with nothing else connected.
> Will that low of drain kill the battery in a few weeks? More importantly
> should there be ANY drain with nothing else connected? There doesn't seem to
> be any continuity between the two large posts on the solenoid, so how can
> voltage be going through?
>
> Thanks for any help.
Be aware of the pitfalls of digital readouts.
It is amazing to see how many people trust the readout of a digital
scale.
The meter says 12.3 so my battery holds 12.3 Volts.
WRONG.
People (like myself) tend to throw away the badly translated Japanese
specs*) that came packed with the meter.
That spec says something about the accuracy of the device (and the
accuracy differs with the range setting too).
My spec may have told something like: "at 20V range; +/- 2% +/- 1
digit".
Doesn't sound too bad eh? 2% isn't much. Well let me do some
arithmetic.
It means that with a real 12.3V inside your battery, the meter may
display something between 12.3 minus 2% and 12.3 plus 2%.
Which is 12.05 and 12.55
And the last digit (cypher) may then be off '1' too,
leaving any reading between 12.04 and 12.56 possible.
It is even worse. Most cheapos only have a three-digit readout,
and the above then becomes 12.1 through 12.6 with an accurate
last digit, but 12.0 though 12.7 with that last digit unreliable.
Especially those people that read 12.0 at their battery start
complaining
about a draining battery. "I just charged my battery, and all by itself
it drops back to 12.0 Volts."
So: What do you mean by: "My battery gets drained". Does it mean you
read a
low voltage with your meter, or does it mean that your bike will not
start.
If the bike happily starts when you read a low voltage, you need a new
meter.
The idea of a measuring voltage drop over the wire was not really a bad
idea for a quick check, but it tells you nothing.
True, when your battery is being drained, and the wire has some
resistance (which
it has) there will be some voltage drop along the wire.
- But because you have no idea what resistance the wire has, it does
not
tell you how fast the battery is being drained (IF it is being
drained at all).
- But because you -probably- have a cheapo meter, that .2V reading
can be off, and the voltage drop across the wire could be 0V or 0.4V
You simply don't know.
- But because you are connecting different materials (tinned probe
and [probably] lead-cladded battery post) you basically create what
is known as
a battery, and measure the voltage that that tiny battery generates.
Take two coins of different materials, spit on one, place the other
on top
and measure the voltage between them.
That is how a battery works.
Now, what can you do?
Switch off everything on your bike.
Unhook the negative post of your battery.
Set your meter to the highest amp setting (probably like 10Amps).
Hook up your meter probe between the negative post of your battery and
the wire that you just disconnected from it.
Read the meter.
If it says 0, you safely can set your meter to a lower amp setting
(probably 3Amps)
Reread and go to a even lower setting if you still read 0Amps.
I would be happy if my meter would read something like 1 milli-Amp.
I have a 12Ah battery, and draining 1mA would mean it takes about 500
days
to get a flat battery. Even if my cheapo is off by displaying '1',
while
meaning '3' it would take 166 days.
I don't know how long it takes for a battery to self-discharge, others
may
tell you that. But I certainly let not sit my battery unattended for
166 days.
If you read something in that 1 to 3 milliamps region, and your battery
gets
flat in a jiffy to the point that your bike won't start, you need a new
battery.
Rob.
*) The spec told me not to unscrew the
back panel. How the hell am I supposed
to insert a fresh battery in that thing?
>> Stay informed about: 1978 650 yamaha voltage loss 
FAQ
Profile
Private Messages
Log in
