Dead Battery.

looking at the specs of 2 bike manuals i have on the shelf here

ZXR750

14.5volts @4K RPM

RGV250
13-15.5v @ 5K RPM

i think you will find at higher revs the current output will be higher

almost all of them

idle speeds are generally 1500 or less

alternators are built small and generally dont have such a huge supply
in excess of what is required in a bike environment due to space and weight
restrictions

the probs a lot of people face which is coming into cars now is that between
EFI, Fuel pumps,
lights etc that is a huge current drain

as an example think the duke was using 20+ amps just running all the above
crap

FYI cars are going to go to think IIRC 48V as this way less current is
required with the higher voltage
and in turn smaller cables are required through the car also then a weight
and space saving

first car i heard of this was the late 7 series BMW's they run water cooled
twin? alternators
to cope with all the electric crap in the car

it takes a while after starting a bike to recharge the battery back to the
capacity of what was used to start it

 

"Johnnie5" wrote

higher

I think Charlie may be looking at car specs where 1500 engine rpm will
have the alternator turning at 3000 rpm or more. On most motorcycles
the alt turns at engine rpm so your figures of 4 or 5K are about
right, though I think the Guzzi reaches it's max output at less than
3000. However that equates to over 90 km/h in top gear. Hardly what
you would expect to do in traffic. At idle, most bikes will be
discharging the battery if the lights are on.

Theo

 

Surely it depend's on you'r jetting?

Conehead

 

"Conehead" wrote

Oh dear, I've misplaced an apostrophe. Please accept my humblest
apologies.

**** off Coney!

Theo

 

Theo Bekkers said....

TB> I think Charlie may be looking at car specs where 1500 engine rpm will
TB> have the alternator turning at 3000 rpm or more. On most motorcycles

Actually, I was looking at my own bike. The lights would dim and then be
at their brightest below and above around 1,600 rpm, when I was having
the battery problem.

But yeah, just looked up the specs for my bike's charging system.
Regulated voltage 12.5 - 15v as measured at 5,000 rpm.

 

I have found recently on my bike that the indicators which i previously thought weren't
working correctly after i changed my rear indicator stalks. Were just not getting quite
enough voltage to go from continually-on to blinking when waiting at the lights and idling
(1400rpm idle). I found a tiny twist of the throttle and about 300rpm more and the alternator
was making enough power for them to work correctly. so now when at the lights i just once
in a bit touch the throttle lightly while waiting.

I havent bothered measuring the charge as it seems to be behaving itself for the most part.
Mike.S

 

"Charlie Haughs" wrote

Charging systems are about amps not volts.

Theo

 

I wouldn't've believed that except my Trump used to do the same thing.
It would pushstart on the first step but just would not electric start!
Clem

 

Same thing happened with a loaner Yamaha 650 I used. Engine turned over
easily on the starter motor, but it wouldn't fire unless the kick-starter
was used.