Motorcycle Battery Fault Finding

There are a few common faults that can occur with motorcycle batteries and battery charging systems.

Below are some of the most frequent battery faults with information about what can cause could be and some possible fixes.
If you are thinking of doing your own battery fault finding or related problems on your bike, one of the handiest tools you can buy is a simple volt meter for checking the voltage.

  • No power, even to horn & lights
    • Check the main fuse, located on red lead near the battery.
  • Intermittent loss of power, especially when starting (starts sometimes, won’t start other times)
    • Check the battery terminal connector bolts are tight and secure & tighten if loose (if you can move the connectors at all with your hand there too loose!).
  • Clicking noise when trying to start the motorbike, starter doesn’t turn over
    • Battery charge is to low to turn over starter motor, only activating starter solenoid (the starter solenoid or starter relay is the switch that activates the starter motor, it makes a clicking noise when activated).
      This can also happen if the battery terminal bolts are loose and the bike isn’t making a good, solid connection with the battery.
  • Strong smell of rotten eggs or sulphur when riding
    • Change underwear! Usually a sign that the motorbike charging system is over charging the battery. Stop the motorbike & switch off.
      Do not continue until charging fault fixed.
  • Battery only holds a charge for 1-2 days
    • Possibly an alarm or electrical gizmo draining battery or old battery in need of replacement.
      This can happen sometimes is electrical equipment (like heated grips) are left on or with some pieces of equipment that have permanently on LED indicator lights or similar.
    • Old battery in need of replacing (alot of batteries need replacing every couple of years, especially if the bike isn’t used regularly).
  • Battery is flat & won’t start the motorbike immediately after being ridden
    • Motorbike charging fault (often a fault with the regulator/rectifier).
      Quick way to check, rev the bike with the light on, if the headlight gets dimmer as the revs increase it is probably a charging fault (normally the regulator/rectifier).
  • Starter motor turns over very slowly & struggles to start the motorbike
    • Low charge in the battery, probably in need of replacement or a good charge (once the voltage drops below 12.4 volts, a battery will struggle to start the bike, especially in the winter!).
  • Fitted heated handlebar grips are causing the battery to go flat overnight
    • Heated grips that are wired to a permanent 12 volt wire, so heating 24/7.
      Heated grips
      should be wired to a12 volt ignition wire that goes to 0 volts when ignitions turned off (this means if there accidentally left switched on they won’t flatten the battery).
  • Power to lights & horn but bike won’t start
    • Check if motorbike is in gear, check side stand cut out switch, check clutch cut out switch.
  • Random electrical faults (e.g. some of the clocks not working or indicator lights come on when brake light comes on etc)
    • Possibly a damaged, corroded or loose negative connection causing an electrical short in the system. Follow the black (negative) wire back from the battery and check the connection is clean, intact and solid. It’s likely that other relays or electrical parts will have their own negative connection so these can be checked.
      It could also be a fault with the charging system causing the problems.
  • Sides of the battery are bulging when the bike is running
    • Either a fault with the battery or a faulty charging system trying to put too much charge into the battery.
      Turn the bike off and do not use it until the problem is fixed.
Gel filled battery

The information provided on this page is ‘to the best of our knowledge’ and should not be taken as 100% accurate!!

To keep this page as a free resource for people to use, there are affiliate links (mainly Amazon) throughout the article. These affiliate links help maintain the cost of running this blog (basically, if you visit Amazon through one of the links and buy something, we make a few pence!).


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