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Jump start it, let it idle for a couple of minutes and you will be good to go.’ That is the advice you get from most people when your motorcycle battery dies. But does a motorcycle battery charge while idling? Read on to find out if it does and if it doesn’t why not.

Every biker has had the unpleasant experience of a dead battery. When this happens, the engine won’t start and none of the bike’s electrical components works.

The standard advice you get is to use jump cables to jump start the engine and then leave it running for a while to let the battery recharge. Jump starting does get the engine running but does idling help? Does a motorcycle battery charge while idling?

In this article, we answer this question with a clear explanation on why we can conclude that a motorcycle battery does not charge while idling.

How a Motorcycle Charging System Works

The charging system in a motorcycle is made up of 3 main components. These are the battery, an alternator and a rectifier, also called a regulator.

Battery

Motorcycle Performance

The battery is the primary source of electric current. It stores it waiting until it is required to start the engine .When the starter button is pressed, stored current flows from the battery to the starter motor, fuel system and ignition system to start the engine.

Although it takes a second or two to do this, it draws a significant amount of current from the battery and there is need to replenish it. Drain may be increased if electrical accessories such as lights are on.

Alternator

The role of the battery is merely to provide the current required to start the engine. Once it starts, it is the alternator which generates electricity to power the engine and other electrical components.

It also recharges the battery to replenish what was spent to start the engine, ensuring it is ready and able for the next time the engine needs to be started.

Rectifier/Regulator

The alternator produces current but it is not in a form which can be utilized. It produces Alternating Current (AC) which must be converted into Direct Current (DC). This is the role of the rectifier. Its regulatory role is to control the current being channeled to electrical components of the motorcycle.

Key Concepts

To gain a clear understanding of a motorcycle’s battery charging process, let’s look at two key concepts. These are idling and RPMs.

Idling:  This refers to the state when the engine is running but the motorcycle is not in motion. You would find yourself idling when waiting in traffic or warming up the engine on a cold day.

Idle speed is the rotational speed the engine is running at when it is on idle.

RPMs: (Rotations of Revolutions per Minute.) This refers to the rotational speed of the engine’s crank shaft which powers the rear wheel through the gearbox.

As the crankshaft rotates, the gears move and this translates to speed for the engine.  The faster the crank shaft rotates, the higher the RPMS and the faster the bike moves. As RPMs increase, fuel consumption of the engine increases.

Minimum RPMs for Charging

As mentioned, the alternator serves to charge the battery to replenish whatever has been spent to start the engine. However, there is a minimum number of RPMS at which the alternator can kick in and start charging the battery.  Below this, the alternator does not do its job even if the engine is running.

With this in mind, the key question then is ‘how many RPMS are required to get the alternator working?’  There is no standard number because it depends on the type of alternator. However, a standard alternator starts producing charging current at 2000 RPMs.

The next question is what RPM speed does a motorcycle operate at when it is idling? It depends on the type of engine you have. If yours is a single-cylinder engine idle speed ranges between 1200 and 1500 RPM. If you have a two-cylinder engine it generally comes to 1000 RPM when idling.

So Does A Motorcycle Battery Charge While Idling?

Motorcycle Battery Charge While Idling

A quick comparison of these figures gives us an answer to this question. An ordinary alternator requires at least 2000 RPMs to start producing current to charge the battery and motorcycle’s idle speeds stand at between 1000 and 1500 RPMs.

From this we can conclude that a motorcycle battery does not charge while idling.In the case of a single-cylinder engine there is a deficit of about 500 RPMs to get it to activate the alternator to start charging. With two-cylinder engines the deficit is about 1000 RPMs.

When the motorcycle is idling, the alternator simply does not produce sufficient voltage to charge the battery. Keeping the engine running for longer does not really make much of a difference. It still doesn’t charge the battery reliably.

Assumptions Made

We have come to with this conclusion on the basis of two main assumptions. If these change the conclusion may be different.

Firstly, we assume that you have a standard alternator which kicks in at 2000 RPMs. If you have a different kind of alternator, it could have a different threshold such that it kicks in at a lower idle speed.

Secondly, we assume that your motorcycle’s idle speed is within the average range. Some bikes have higher idle speeds. Differences could be because you have a different kind of bike or you could have had your idle speed manually adjusted. It can be done.

If you have an alternator with a lower threshold and your idle speed is higher than average, you could end up being able to charge your battery when idling.

What If The Battery Dies?

If you were under the impression that idling alone will help keep your battery charged up, then you may end up with a dead battery. What then? What is the best way to charge it?

The best way to go about it is to put the battery on a charger. It takes anywhere between 4 and 24 hours to charge a motorcycle battery to full charge when using a regular trickle charger. It depends on a variety of factors including type of charger, type of battery and if the battery was completely flat.

Check the level of liquid in the battery. If levels are low, add some distilled water up to the ‘fill line’ before charging. Check the voltage every so often to make sure the battery does not overcharge.

Once it is fully charged, reinstall it and take a good long ride.

Conclusion

Does a motorcycle battery charge while idling? No. There is a minimum number of Rotations per minute below which the alternator doesn’t charge the battery. This is why your motorcycle battery probably won’t charge even if you leave it idling for a long time.

The best way to make sure your battery charges as it should is to take a good long ride out on the road. This way you achieve the required RPMS to get the alternator to kick in and maintain this speed long enough for the battery to have its fill.

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