A low or failing battery can cause crazy readings during your testing.
Motorcycle battery voltage when running.
With the battery fully charged and functional it s time to test for battery voltage drop.
A good battery should not drop below 9 6 volts over 10 seconds or so.
Or you may find it s not the battery at all and a charging system problem instead.
The alternator is fitted with a regulator that charges the battery while you ride.
With the ignition on and the bike not running switch on the lights and you should see the voltage drop slowly as the lights use up the power in the battery.
No need to go running to a dealership to spend money.
Now push the starter button and watch what the voltage drops to.
This is a huge part of your charging system.
It doesn t matter if the bike starts or not what you re looking for is a voltage reading.
Your battery may even be holding a charge but it s the cold cranking amps that may determine if your battery needs replacement.
The relationship between your motorcycle battery and engine functions much in the same way as a car battery.
Your charging system is putting out the necessary voltage to the battery during a running condition past idle.
What you are looking for is that all three of the numbers are similar.
The starter should be running at normal speed.
While the starter is spinning observe the voltage.
Replacing the rectifier which converts the alternating current ac from your motorcycle s stator alternator to direct current dc before recharging the battery is also recommended at this time.
Perform a current draw test.
The actual number of the voltage is not terribly important.
A healthy 12 volt motorcycle battery should maintain a range from 9 5 10 5 volts under the load for a good 30 seconds straight.
Be in the know on whether you actually need a new motorcycle battery or not.
Then measure the voltage from tab to tab just like before.
Does your battery seem to be going bad.
However it s important to note that normal riding may not be enough to fully charge the battery after being completely depleted.
You should see the voltage increase on your meter even further up to around to 14 4volts this will vary from bike to bike.
To check for voltage the motorcycle must be running and should be at about 2000 rpm.
With the multimeter on the same settings as above.
If so this is good.
This needs to be correctly charged and tested before you start and troubleshooting.
If your battery is charging perfectly but your motorcycle still seems to keep killing the battery.
Video is your harley davidson or other brand motorcycle seem to be cranking over slowly when starting.
Hook up your dvom in the same manner you did for the standing voltage test and have an assistant thumb the starter.
