View Full Version : low battery help ?

09-12-2015, 03:44 PM
so i buy a new to me mp3... 4044 miles 500cc 2008
brand new battery in may, but i bought a new one ( see below )

day one, started.... 12 miles later, stumbles to a halt battery dead.. trailer it home

day two... charged over night... 20 miles sane thing

day three new battery, fully charged... 22 miles before she dies

day four.. new battery charge both.. put the spare in the trunk... 20 miles, dead battery, switch batteries made it back home

odds are very low i have 2 bad batteries...

but clearly those batteries are being drained as i ride... that, or alternator isn't keeping up..

would bike run on a stone cold dead battery ? or i assume the fuel injection, lock out mech etc need a battery..

p.s. bike seamed to be running slightly hot, the fan turned on more than once without city slow traffic

09-14-2015, 10:57 AM
It is easy to check the charging of the battery with a simple volt meter. Measure the battery voltage before starting, then start the motor. Now, measure the battery voltage with the motor running. The voltage should have been over 12.6 volts before starting the motor and over 14 volts with the motor running. If the voltage does not go up after the motor is started there is likely a problem with the charging system. If the battery was below 12.6 volts before starting the battery is not fully charged to begin with.

09-28-2015, 12:51 AM
first take the battery out and put it on a desk and charge it disconnected from the bike
let it sit for 24h and measure it if its more then 12.4 it should be fine if not the battery is faulty

when putting the battery in connect the drainage from the battery with a ampermeter
it should be 0 when the bike is of or really close to zero due to drainage that the computet, clock and imobilizer take
if you have a parasitic draw you will need to fix that

fire up the bike turn on the head lights and all electrical devices and check the battery voltage
on idle it should be more then 13V and about 13.8-14.7V when the bike is reved up
if it dosnt check the charging system, voltage regulator, fuses (yes batteries often have a fuse between the regulator and battery if
it burns out it wont charge the battery) and check the stator coil and other electrical components that the bike has

often failed parts are a bad fuse, bad regulator, bad connection/oxidized battery terminal, shorted out battery and bad stator coil

the 500s are known for the regulator that often dies when it has to charge a half dead / empty battery but start from checking the cheap parts
also check the trunk switch that can be faulty and lever the trunk light on and discharges the battery (i have a mp3 and i had some minor problems with it that i sorted out myself)