Trying to start a motorbike with a car battery can “fry” it. We will show you how to do it correctly and safely.
First of all, keep in mind that if, when you press the starter button, there is “no” battery left, the lights will not come on and there is not even be a hint of movement with the starter motor, you battery might be dead and you may not be able to recharge it.
But first of all, let’s learn some operating principles from the battery specialists who work side by side with the Repsol Honda Team in the MotoGP World Championship.
Batteries are devices that store electrical energy in chemical form and release it as direct current in a controlled manner.
All types of batteries contain a positive and a negative electrode immersed in an electrolyte, and the entire set is in a container.
Most batteries are lead-acid, which means they have positive and negative electrodes made of lead compounds in a dilute sulphuric acid electrolyte.
Lead-acid batteries are secondary batteries, which means they can be recharged after they have been discharged.
There is also a wide range of lithium batteries for motorbikes. They are lighter than lead batteries, they resist discharge better and they have other advantages, although they do not work as effectively when the ambient temperature is too low, always below 0 ºC. Gel batteries also include this element to the electrolyte so that it solidifies.
Primary batteries can be discharged only once before they are to be disposed of, like some types of radio and torch batteries.
In lead batteries, the positive electrode is composed of lead dioxide and the negative electrode of porous lead.
When an electrical load (e.g. headlights or a starter engine) is connected through the battery, current flows through the battery electrolyte and through the external charge.
This causes the battery to discharge, which causes the chemical composition of both electrodes to change to lead sulphate.
Sulphation is a normal part of battery operation and occurs when the battery is discharged. When the battery is recharged, the sulphation (lead sulphate) is converted back into active material.
If the battery is left discharged for a period of time, this sulphation slowly transforms until it cannot be converted back into active material, and so after charging, the battery will not be able to return to its original performance.
If the sulphation is severe enough, the vehicle will not start. This is the problem usually referred to as sulphation.
To recharge the battery, current must be passed through it from an external source of electricity such as an alternator, dynamo or charging unit.
This way, the lead sulphate is transformed back into the original materials: lead dioxide and porous lead.
As the battery charges, electricity begins to break down (hydrolyse) the water in the electrolyte into its constituent elements, hydrogen and oxygen, which are released as a gas. This is the reason why batteries release gases when they are charged.
If you do not use your motorbike regularly, a conventional battery can lose about 5% of its charge every month.
Although it is often believed that batteries get more discharged in cold weather, it is actually the opposite, and the rate of self-discharge above 25ºC is doubled for every 10ºC.
So, if you do not use it much out of season, and you do not use a charger with a maintenance program, you should drive it from time to time.
But even if there is still some charge left, the motorbike may not be able to start due to lack of power in the demarreur.
If the motorbike’s battery has been discharged because it is somewhat deteriorated or due to external circumstances, such as being stopped for a long time, you can recharge it.
This is something you can do yourself, of course, but with certain precautions.
After closing the ignition and accessing the receptacle where the battery is located, it is best to disconnect the terminals using a screwdriver and/or a suitable tool.
Always start with the negative (-), the black wire, and continue with the positive (+), the red one.
The most modern batteries are usually “maintenance free”, and do not require their caps to be opened to fill the cups with distilled water.
If it is not the case, do not forget to replenish the water levels before recharging it.
In any case, it is very important that the charger is the right one.
It is best to use one of the modern “smart chargers” for motorbikes.
If they are of the Ctek or Optimate type, they eliminate the danger of overcharging and decide how much current to give to the battery depending on its condition.
As mentioned above, these chargers also act as battery “maintainers”.
Our motorbikes’ accumulators (the lead ones, but also in the long term, the new lithium ones) always appreciate being near one hundred percent of their charge.
Lead batteries stay in better condition if they are charged, and they appreciate being recharged gently, just like smart devices do.
Indeed, as the charging current must not exceed one tenth of the total capacity of the accumulator, the process can take a few hours..
These chargers provide, in addition to the typical spring clips, cables that can be left fixed to the terminals in order to be accessible to the outside and to be able to be “plugged in” every day or in case of being stopped in your garage for a long period.
Never plug the charger into the mains before connecting the charger cable clamps to the battery terminals.
After disconnecting the charger from the mains and removing the clamps, first screw the positive cable of the motorbike -remember, the red one-. Finish with the black negative (-) one to prevent, as in the case of the first disconnection, any possibility of short circuit.
Once on the road, if your motorbike’s alternator charges correctly, the battery will replenish itself after a few kilometres.
Header photo: Al Ibrahim | Flickr