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From: Simon Wilson on 15 Sep 2006 17:07
steve auvache wrote:

> Simon Wilson wrote
> > I've got a knackered battery haven't I?
>
> Dunno.
>
>
> > Battery is 12Ah, the lights
> > should draw about 5amps = 2 hours of running or so I would have
> > thought even if it's getting nothing from the alternator.
>
> Just as a matter of interest then, how much current is drawn by the
> various electrical systems on your bike? Knowing this could be a
> useful guide to diagnosing the problem before you start spending
> money on replacement bits. It will only take a few minutes to find
> out as well.

I thought it would be easy at first, but now I realise I'm not sure how
to measure the current drain on the battery with the engine running? Or
do you mean just measure the drain with the engine stopped, which is
fairly straight forward?

--
/Simon
From: Mark Olson on 15 Sep 2006 17:48
Simon Wilson wrote:
> steve auvache wrote:
>
>> Simon Wilson wrote
>>> I've got a knackered battery haven't I?
>> Dunno.
>>
>>
>>> Battery is 12Ah, the lights
>>> should draw about 5amps = 2 hours of running or so I would have
>>> thought even if it's getting nothing from the alternator.
>> Just as a matter of interest then, how much current is drawn by the
>> various electrical systems on your bike? Knowing this could be a
>> useful guide to diagnosing the problem before you start spending
>> money on replacement bits. It will only take a few minutes to find
>> out as well.
>
> I thought it would be easy at first, but now I realise I'm not sure how
> to measure the current drain on the battery with the engine running? Or
> do you mean just measure the drain with the engine stopped, which is
> fairly straight forward?

Assuming the battery is in fact good, measuring the battery voltage
pretty much tells all, charging-wise, except in truly rare cases where
there's an unknown drain somewhere. If when the engine is running and the
lights and accessories are on, the battery voltage is higher than at rest[1],
the alternator's providing enough current to run all loads, plus a bit to
charge the battery. If the battery voltage is lower with the bike running
than at rest, the alternator isn't putting out enough amps. It's really
as simple as that.

Knowing the exact amount of current going into the battery is far less
important than knowing the sign of that current. The same can be said
for measuring the output of the alternator and the load presented by the
system, you've either got enough or not enough... the only folks that
generally get bit by this are the power hungry types who insist on
having photon-torpedo strength main beams and oodles of electrical
add ons, in other words the Wingers and their ilk (you know who you are).

[1] when I say at rest, I mean with engine not running and everything
turned off.

--
'01 SV650S '99 EX250-F13 '98 ZG1000-A13 '81 CM400T
OMF #7
From: steve auvache on 15 Sep 2006 19:24
Simon Wilson wrote
>steve auvache wrote:
>
>> Simon Wilson wrote
>> > I've got a knackered battery haven't I?
>>
>> Dunno.
>>
>>
>> > Battery is 12Ah, the lights
>> > should draw about 5amps = 2 hours of running or so I would have
>> > thought even if it's getting nothing from the alternator.
>>
>> Just as a matter of interest then, how much current is drawn by the
>> various electrical systems on your bike? Knowing this could be a
>> useful guide to diagnosing the problem before you start spending
>> money on replacement bits. It will only take a few minutes to find
>> out as well.
>
>I thought it would be easy at first, but now I realise I'm not sure how
>to measure the current drain on the battery with the engine running? Or
>do you mean just measure the drain with the engine stopped, which is
>fairly straight forward?

If yer meter is good enough then simply in series with the battery if
not by measuring the voltage drop across a known resistance, the main
fuse perhaps and doing sums.




--
steve auvache
i rate dates
From: Mark Olson on 15 Sep 2006 19:37
steve auvache wrote:
> Simon Wilson wrote
>
>>steve auvache wrote:
>>
>>
>>>Simon Wilson wrote
>>>
>>>>I've got a knackered battery haven't I?
>>>
>>>Dunno.
>>>
>>>
>>>
>>>>Battery is 12Ah, the lights
>>>>should draw about 5amps = 2 hours of running or so I would have
>>>>thought even if it's getting nothing from the alternator.
>>>
>>>Just as a matter of interest then, how much current is drawn by the
>>>various electrical systems on your bike? Knowing this could be a
>>>useful guide to diagnosing the problem before you start spending
>>>money on replacement bits. It will only take a few minutes to find
>>>out as well.
>>
>>I thought it would be easy at first, but now I realise I'm not sure how
>>to measure the current drain on the battery with the engine running? Or
>>do you mean just measure the drain with the engine stopped, which is
>>fairly straight forward?
>
>
> If yer meter is good enough then simply in series with the battery if
> not by measuring the voltage drop across a known resistance, the main
> fuse perhaps and doing sums.

If you're going to bump start it you might be able to get away with putting
an ammeter in series with the battery. You do *not* want to disconnect
the battery while the engine is running-- without the battery to stabilize
the voltage, spikes are liable to destroy expensive electronic stuff.

Measuring voltage drops is a very good way of figuring out the relative
magnitude of current flows in charging systems and is usually plenty
accurate.

--
'01 SV650S '99 EX250-F13 '98 ZG1000-A13 '81 CM400T
OMF #7
From: Simon Wilson on 16 Sep 2006 07:20
Mark Olson wrote:

> steve auvache wrote:
> > Simon Wilson wrote
> >
> > > steve auvache wrote:
> > >
> > >
> > > > Simon Wilson wrote
> > > >
> > > > > I've got a knackered battery haven't I?
> > > >
> > > > Dunno.
> > > >
> > > >
> > > >
> > > > > Battery is 12Ah, the lights
> > > > > should draw about 5amps = 2 hours of running or so I would
> > > > > have thought even if it's getting nothing from the alternator.
> > > >
> > > > Just as a matter of interest then, how much current is drawn by
> > > > the various electrical systems on your bike? Knowing this
> > > > could be a useful guide to diagnosing the problem before you
> > > > start spending money on replacement bits. It will only take a
> > > > few minutes to find out as well.
> > >
> > > I thought it would be easy at first, but now I realise I'm not
> > > sure how to measure the current drain on the battery with the
> > > engine running? Or do you mean just measure the drain with the
> > > engine stopped, which is fairly straight forward?
> >
> >
> > If yer meter is good enough then simply in series with the battery
> > if not by measuring the voltage drop across a known resistance, the
> > main fuse perhaps and doing sums.
>
> If you're going to bump start it you might be able to get away with
> putting an ammeter in series with the battery. You do not want to
> disconnect the battery while the engine is running-- without the
> battery to stabilize the voltage, spikes are liable to destroy
> expensive electronic stuff.
>
> Measuring voltage drops is a very good way of figuring out the
> relative magnitude of current flows in charging systems and is
> usually plenty accurate.

Yes my thoughts too. And I don't fancy bump starting a Pan European
ever, especially not with an ammeter and wires dangling all over the
place.

New battery is on, so far it all seems to be behaving, so we'll see.

--
/Simon
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