Understanding why your motorcycle won’t start after winter

There’s nothing quite as frustrating as the anticipation of a thrilling ride only to find your motorcycle unwilling to start. The culprit? Often, it’s the battery, having braved the harsh conditions of winter storage. But fear not, for understanding why your motorcycle won’t start after winter is the first step toward reviving your two-wheeled companion.


Understanding the triangle of power

The motorcycle battery is a crucial component in the bike’s triangle of power.

Triangle of Power

The triangle of power consists of the starter motor, alternator and the battery itself. If any of these components are not performing to specification your bike will not start. On a typical bike, the battery has five basic power supply functions:

  1. Starting: supplying power when cranking the engine
  2. Lighting: delivering steady power before engine start
  3. Ignition: supplying power to the ignition system during engine cranking
  4. Charging: operating as a voltage stabiliser to absorb fluctuations in the electrical systems
  5. System support: supporting security systems and ECU memories whilst the ignition is switched off


Understanding why bike batteries fail

Remember, a battery is a consumable item. Just like brake pads or tyres its performance will naturally deteriorate over time until it needs replacing. There are however several conditions that can lead to serious damage and premature battery failure:

  • Excessive Heat: battery temperatures of over 50̊ C dramatically reduce service life. For every 10̊ C rise in temperature the battery’s natural self-discharge rate doubles meaning that it will discharge much faster.
  • Sulphation: continuous discharging, low state of charge or low electrolyte levels can lead to a condition known as sulphation. This is where lead sulphate crystals build up on the lead plates reducing their surface area. Make sure your battery is properly charged and has correct electrolyte levels to prevent this.
  • Vibration: if a battery is rattling around or vibrating excessively its internal elements could be damaged leading to short circuits and premature failure. Regularly check your bikes mounting equipment to make sure your battery is fully secure.
  • Freezing: yes, a battery can freeze, but usually only if it’s not charged adequately. When a battery is discharged, the acid in the electrolyte turns into water which can freeze at 0̊ C. If it freezes, replace the battery as damage and cracking to the case and internal components may have occurred. If your battery is full charged you have nothing to worry about and it can be stored at sub-zero temperatures without issue.

If any of the above conditions have affected your battery, irreversible damage and battery failure may have occurred. In which case, it’s time to replace it with a new one.


How to replace a failed battery

First, remove the old battery. Switch off your bike’s ignition, then detach the negative terminal, positive terminal, fixing bracket and exhaust tube (if applicable) in this order. Finish up by giving the area your battery sits in a good clean.

Now, you can fit your new battery. Double-check that the new battery is the correct specification for your bike here. Then, securely fix the battery using the bike’s bracket making sure that it is firm and will not move or vibrate excessively. Attach the terminals, positive first, and re-fit the terminal cover. If your battery came with a vinyl exhaust tube securely insert it into the battery’s exhaust elbow making sure that any vented electrolyte will avoid the rider’s leg and other components.

Find out more about how to make your motorcycle or scooter battery last longer here.