Does a motorcycle battery charge while idling? Yes…but only if.

Does motorcycle battery charge while idling?
Does motorcycle battery charge while idling?

All the blinking lights, high power LED headlight, self-ignition switch cranking your muscle bike engine, multi-function display panel- all these high power features suck up every bit of juice in your 12V, 18 Ah battery( general specs.). On the other hand, to juice up the battery, an alternator(kind of small generator) is present converting engine power to electrical power when the bike is on the road. But what about when the bike engine is running idle? Will it be of any help to charge the battery or just waste of liquid gold?   

So, Does the motorcycle battery charged while idling? The motorcycle battery doesn’t get charged while idling as the alternator has a minimum requirement of 2000-3000 RPM for generating the desired current of 13-15 Amps to charge the battery as per the datasheet of the battery.

Motorcycle alterantor
Motorcycle alternator

The electrical circuitry installed in the motorbike draws its power primarily from the alternator (small generator coupled with the engine) along with a secondary source as the battery. 

The latest generation of bikes in different categories are loaded with high-end electronics panels, self-start only, high-watt projector LED headlights to have a higher dependence on power from the battery when the engine is off.

In order to generate the power that is required to charge the battery, an alternator is installed. An alternator is a form of small generator closely coupled to the engine, which converts a part of engine power to electrical energy. A part of the converted energy is directly used by the electrical system, and another part is directed at charging the battery. 

In an idle running scenario, the bike carburetor ( a component mixing air and fuel in the right proportion) is tuned to run the engine at minimum necessary RMP so that it won’t die running.

But at such idle running RPM, the alternator is helpless to provide sufficient current for charging the battery.

How can I charge my motorcycle Battery while Idling?

The intention of charging the battery in idle running conditions may turn motorcycles into low mileage and noisy conditions. 

Charging the battery in idle running condition can be done by throttling the bike in neutral at 2000-3000 RPM. Another way is to tune the carburetor (the air and fuel mixing component) for higher idle RPM to charge. 

Both ways will be resulting in a decrease in the mileage of the motorcycle. 

Following the above discussion, one may conclude that if we ignore the other electrical system, the primary reason for the battery is to power the self-start motor to kick off the engine.

After that, the alternator comes in line to power all the electrical systems and battery work as a buffer to absorb excess power when the alternator runs at full RPM and releases deficit power when the bike is in idle running condition.

How long to idle the motorcycle to charge the battery?

While waiting at a red signal, a question may find its way to your thoughts: how long will it take to charge the battery while the bike is running in idle condition?

Working on the assumption that the battery has a specification of 18Ah and the carburetor is tuned to run the engine at such an RPM that the alternator is generating 1 Amp. Hence it will take 18 Hrs of constant running in idle conditions to charge the battery.

The battery may have different Ah ratings depending on the manufacturer and bike requirement. High Ah rating batteries have high power delivering capacity for the equivalent time. Following that, a high Ah rating battery will be taking more time as less current or, say, more current for less time to charge up.

Secondly, the dependency on the tuning of the carburetor directly controls the RPM of the alternator. Tuning the alternator to some higher RPM will deliver more current for charging the battery, and hence this will reduce the time to charge. You can measure the current flowing through the battery by a connecting multimeter in line with the battery and then move the tuning screw of the carburetor to set the desired current.

All these arrangements will work with the assumption in mind that the battery is in healthy condition. A maintenance-free battery (aka dry battery) will do with this assumption. A lead-acid battery (aka wet battery) will be needed to be periodically checked for corroded electrodes, dried-up acid, the low voltage after full charging. If by means you can’t jump the voltage of the battery as mentioned in its manual, it’s better to charge the battery; the battery is dead.

Is it bad to let a motorcycle run idle?

Letting the motorcycle run at idling is not bad until you do it excessively. Excessive and frequent motorcycle idling is bad for both the engine and the environment. With the liquid-cooled engine, a motorcycle will handle the idling better than the air-cooled engine. 

Even at idling, if you twist the throttle for long, then the temperature of the engine will increase; so it should be considered before idling for too long, especially for air-cooled engines.

With an increase in the purchasing power of people launching vehicles in the common man budget, the number of vehicles on the road has increased exponentially. This has the direct consequence of traffic problems at every road crossover. 

Thus due to these situations, riders need to wait in the traffic, letting their motorcycle idling for a longer period sometimes. There are also some newbie riders that don’t stop throttling in that situation.

Thus, it’s important to be aware of the excess wear you could be causing while idling to your motorcycle.


Thus, the motorcycle battery gets charged at idling only if the required power is generated by the alternator that requires 2000-3000 rpm. 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. Protection Status