[Ducati] batteries

[rich lambrechts]

Robert noted..

  I currently have a 12V Yuasa
> 4AH, one cell seems bad, so I am looking to replace it. The funny thing,
the
> bike starts on the first kick, but dies when you apply the brake: in
effect
> I have three kill switches: headlight switch, brake-pedal (that one's
> dangerous) and key.
>
> What I was wondering, was whether the charging system would be taxed by a
> higher (e.g. 18AH) battery, as I prefer riding hi beam ON.


Hi Robert...
Unless there is another problem in the wiring...it sounds like yes with a
dead cell...  when you take extra load from the battery via the lights it is
starving the coil of enough juice to fire the plug...  it quits.

The 18AH battery is not going to tax the charging system at all...  you have
to think of it this way..  the battery is a reserve source  ( IE energy
storage)  what taxes the charging system is the current draw of the item(s)
driven off the battery especially if they exceed the capicity of the
charging system or battery, which in the case of an old Ducati single is
nearly so.  It is for this reason I am an advocate of having the greatest
storage capicity available.  Lets say you begine life with a fully charged
18AH battery...  and the system replaces what's used as you run always
leaving you reserve.  In theory..you are just putting back in what the bike
takes out and always have plenty.

It's like a bit of an insurance policy...  remember the 18AH battery will
run the same load for basically 3 times the amount of time as a 6 AH one
under total loss conditions  IE: the charging system quits.

Just the same..with the system working and only able to put back roughly the
same ( and maybe sometimes less) than it draws...  you could discharge the
smaller capicity battery on a long ride at low RPM.  Say you take out on a
simple day ride..lumbering along at lower RPM with the high beam glowing and
it's daylight...the battery may actually be in a low charge state...  An old
friend ( or maybe a georgeous lady) sees you and stops you to chat...time
goes by and the sun goes down...dinner's ready...time to ride home...  you
kick the bike to life.....  turn on the headlight..and it quits....or won't
start at all.... because the battery hasn't got the juice... this is where
the higher capicity batter may save you from a ride home in the back of a
truck as riding several miles with the headlight off in the dark while the
battery is charging is less of an option.

rich lambrechts