Duff Battery?

Arrived at work this morning with bike idling a bit slowly. It was around
900rpm, usual idle is 1200. Engine ran for a few seconds then died.
Starter made an asthmatic wheezing sound then stopped. Bollocks, thought
I.

I have now gone out and checked the battery, 12.2 Volts. Started on the
button and showed 13.6V to 13.9V while running. The readings were a bit
variable with trying to hold leads on and rev at the same time.

This says to me that my alternator is fine and that it will get me home
(22 miles) as long as I don't use the lights and that the battery is just
goosed. I am right, aren't I?

 

gazzafield wrote

This is not far enough away from OK to really be an issue, of itself.
Although to give it proper meaning it has to be stated in context of how
long since it was last giving Amps and/or how long since it was last
receiving Amps. Note the use of capitalization and plural.

This is a bit low but high enough to suggest some charge will be getting
to the battery.

Tick over and 3K of choke assisted revs, no faffing around with
throttles.

Pretty much the conclusion I would first jump to, although the voltages
don't quite tally. I wouldn't care to comment on your chances of
getting home though.

 

I don't think it is weird at all. I have had duff car batteries recover
overnight enough to get the car started and they have been truly
knackered. It'll be something in the chemicals. I'm sure a chemist will
be along shortly to explain.

 

Average voltage on idle for a 12v system(Bike or car")should be around
14.2v to 14.6v.Suspect faulty Alternator/Rectifier-regulator and or
the battery.

HTH

 

If you took those reading with the meter connected to the battery
terminals, then they are too low, 14.4V is a good reading.

If you measured them battery positive to frame, you may have detected
duff, corroded or loose connections, or an earthing problem probably
at the battery end.

Another indication of an earthing problem, amongst others.

Disconnect the battery, and find the big heavy lead that run to the
starter motor, and the battery-to earth lead. Undo them, clean them
up, put them back together, and coat with (protectant of your choice).

Charge the battery at (capacity/10) Amps until it is gassing freely
and the terminal voltage is steady. Reconnect to bike, switch on
headlight for a couple of minutes (to remove 'surface charge'), switch
off headlight, and with no current drain from the battery, check the
terminal voltage. Anything less than 12V is bad battery news, 12.6V
and you're in the clear.

HTH