A guide to motorcycle batteries
Tom Vondrasek | 6th May 2023 | 5 minutes to read
Motorcycle batteries have been around since the mid 1960’s. To start a motorbike engine before this time, you needed to manually crank it over by kick starting it or push starting. Some bikes still use this method, although it’s much rarer, with most having electric starters.
Putting on an electric starter motor was a necessity for motorcycles as engine size and compression ratios were increasing, so manually starting a large motorbike engine was becoming hard to do. Instead of kick or push starting, you push a button or turn a key to get the engine going.
You can still manually start most bikes by push starting and some smaller engines even have a kick start lever. More than 60 years later, the principle and even technology is still the same.
To start most motorbikes, you still need a battery. Like a car, once it starts, the alternator or generator kicks in and provides the electrical power, as well as recharging the battery, so you are ready for your next start.
Understanding your motorcycle’s battery is key for maintenance and eventual replacement, here is some important information to keep in mind:
Start Batteries Explained
Electronics
A start battery’s primary role is to start the engine. In a modern motorcycle their secondary role is to keep the electronics alive before the engine is restarted. Even with the bike turned off, there is a small amount of power that the computer uses to monitor systems and make sure the bikes engine is ready to start when turned on. A simple example is the clock, found on the instrument cluster of touring bikes and some other models. It needs power to run otherwise you would need to reset the time every single time you started the bike.
The electronics draw very minimal power compared to starting the engine and will eventually flatten the battery. We are talking months and months of not being used for this to happen and this time frame is dependent on your motorbike battery’s condition.
Battery Power (CCA)
The power required to start an engine is enormous. The battery normally only needs to supply it in short bursts if your engine is healthy. If you have ever tried to start a bike that had a starting problem with the engine, you can hear the battery lose its power the longer you try and start it. That is why short bursts are better than longer duration start attempts. It gives the battery a chance to recover between starting attempts.
This enormous power is measured in CCA or Cold Cranking Amps. Broken down:
- Cold – The engine is cold or has not been started. This takes more power than a warm engine.
- Cranking – Rotating or turning over the engine
- Amps – The Ampere is an electrical measurement for current flow. The greater or higher the number of Amps, the more electricity flows down the cable.
Start batteries all have this rating (they are tested on it). It is the amount of current a battery can supply for 30 seconds at 0 degrees Fahrenheit.
Battery Types
Motorcycle start batteries are all lead acid-based batteries: They are:
Standard Wet Cell – Basically a plastic box with 2 terminals on either side at the top. One positive (+) and one negative (-). It is filled with a liquid acid called electrolyte and has lead plates sitting in the acid. The battery generates electricity and can be recharged. Some batteries are sealed which means there is no need to check the electrolyte levels. Others need to be checked and topped up with distilled or demineralised water.
AGM – Absorbed Glass Mat batteries hold the electrolyte in absorbent fibreglass separators, in between the lead plates. There is no liquid and as the separators are thin you can fit in more lead plates. They are quick to recharge and can be recharged more often than a wet cell.
Engine Size: 2 Stroke and 4 Stroke
Motorcycle batteries are similar to car batteries. The bigger the engine, the bigger the battery needs to be to start it. A 75cc bike motor which has a single cylinder requires way less effort to start than a 750cc, 4-cylinder, bike motor.
2 Stroke Engine – Runs on an oil and petrol mixture and is compressed then ignited on the end of each piston upstroke. As the piston comes down it sucks in the new oil/petrol mixture and expels the exhaust gas at the same time. Then the process repeats itself. As it fires on every upstroke the engine is easier to start than a 4-stroke engine.
4 Stroke Engine – Runs on petrol only and is basically a small car engine. The petrol vapour is compressed and ignited on the end of every second piston upstroke. The piston comes down and on its next upstroke pushes out the exhaust gas. As it comes down it sucks in the new petrol vapour and on this upstroke, it is compressed and ignited. Then the process repeats itself. As it fires on every second upstroke the engine is harder to start than a 2-stroke engine.
Selecting the Battery for your Motorcycle
Selecting the correct motorcycle battery is not so difficult when your old one needs replacing. Being small, you can remove it from the bike and bring it into a store or look it up online. In store, they can match it up for you and get you what you need. There are usually not many choices as the battery space on a bike is small and you need the correct size battery to fit in.
It cannot be too tall, long, or wide and the battery terminals need to match the old battery terminals’ position on the battery. If not, the wiring may not fit. This why having the old battery when doing a comparison is important.
Warranty – Most of the motorcycle start batteries we supply have a 12-month warranty period.
CCA - Sometimes battery CCA can vary. It is important to get a battery with the equivalent CCA rating of your old one. If it is slightly greater, this is no big deal.
When it comes to replacing your motorcycle battery always check your owner’s manual. Most are extremely simple and straight forward and require basic hand tools to remove and replace them.
With computers you can use a small 9V battery to keep the computer going when changing over the start battery. You can get these at auto stores. As mentioned earlier, the battery powers some items even when the vehicle is switched off. If you don’t keep power going when disconnecting the old battery and installing the new, these items may need to be reset (including the clock).
