Does A Motorcycle Battery Charge While Idling?

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Knowing how a battery works on a motorcycle can make life a whole lot easier for any motorcyclist. There are some basic principles about the battery that are easy to follow, but other parts can be a bit more complicated.

Knowing how the battery is charged is important. A lot of riders are aware that the battery is charged while the motorcycle is running, but some wonder if idling provides the same charge.

So, does a motorcycle battery charge while idling? Technically, a motorcycle battery does charge while the motorcycle is idling though it does not provide as much amperage as when the motorcycle is at higher speeds. During a normal ride, a motorcycle provides about 13, 14, or 15 amps while idling only provides less than 1 amp.

Understanding this concept may seem a bit complicated, but if you keep reading I can explain exactly what happens with the battery during an idle and what you can do to optimize the power your motorcycle provides.

How The Battery Is Charged While Idling

Technically, the battery is getting a charge while the motorcycle is idling. But it is such a small amount of charge that it will not be able to top off a battery, especially a battery that is about dead. A motorcycle electrical system is created to keep a good battery topped off but is not designed to charge a dead battery.

If you look at a trickle charger, most of them have a 2 amp setting or a 6 amp quick charge setting which is what your motorcycle needs at the very least to obtain a constructive charge. By your bike just sitting there idling, you’re probably putting in less than one amp. That is such a small amount that if you let your motorcycle idle for 10-15 minutes, you’re really not charging your battery all that much.

Most motorcycles have something called a stator. This is designed to have an output of about 15 volts. The battery is a 12.6 volt battery. If you take a digital reader and connect it to the battery while its running it’ll say something along the lines of 13, 14, or 15 volts. While that is true when the bike is running, it’ll go back down to 12.6 -ish when you turn it off. If the battery was dead before, it’ll go back down to whatever low voltage it had before getting started.

Essentially, the motorcycle is always providing more amperage and voltage than the battery currently has. And it has to do this in order to charge the battery while the bike is running. During an idle, the stator is outputting a small amount of excess amperage that will provide that little charge to the battery, but not enough to do a full complete charge.

The stator is always outputting the 13-15 amps, but the more revolutions inside the engine provides more voltage. That excess amperage goes to power other things such as the lights, spark plugs, and other electrical components. The battery becomes fully charged when the motorcycle is full-on running.

How To Optimize Idle Charging

To say that motorcycle batteries are finicky is an understatement. They can be expensive, so it makes sense that a rider will do everything they can to prolong the life of the battery on their bike.

There are a few things you can do if you wish to provide a little bit more amperage to your battery if you find yourself doing a lot of city driving and have to idle your bike frequently.

You can do this by revving your motorcycle a little while you’re at an idle. This is done by either keeping it in a neutral gear and twisting the throttle to 3,000-4,000 RPM or adjusting the air/fuel screw on the carburetor so it has a higher idle. Revving the engine will provide additional amperage to the battery than just a simple idle, but not as much as it would during a normal ride.

With that being said, many may wonder if it’s good for a motorcycle to rev it like this. In moderation, revving a motorcycle engine isn’t bad. The word revving is short for revolutions per minute that’s happening inside the engine. Revving it is just making the engine do what it’s already doing, just a little faster.

However, revving a motorcycle engine too much (meaning for a long period of time, longer than five seconds per rev) then you can start wearing out the engine. Moderation is key, so occasional revs to give that battery a boost should suffice. Click here to learn more about what happens when you rev a motorcycle engine.

Why Your Motorcycle May Struggle Charging During Idle

When a motorcycle has an issue running, a safe assumption would be issues with the battery. When I first started riding motorcycles, I would always look at the battery first if any of my bikes had trouble starting.

If you’re searching the query about whether or not a motorcycle charges the battery during an idle, you may have run into issues during idling. While the battery is often the culprit of issues a motorcycle can have, it likely isn’t your problem in this case.

The main function of a motorcycle battery is to get the motorcycle started. Once the motorcycle is started, the stator (or alternator) takes over and powers the electrical components on the motorcycle. The battery really has no essential function while the bike is on. So if you didn’t have much of a problem getting your motorcycle started, you’ll know the battery is okay.

If you are experiencing poor idle while out on your motorcycle, the most likely place the issue lies is within the carburetor. More specifically, the carburetor may have a vacuum leak which means there’s too much air in the air-to-fuel ratio the carburetor is giving the engine. The carburetor may also have a fuel leak which leads to the engine starved from the right amount of fuel it needs to run efficiently. Lastly, the carburetor could potentially have a timing issue which means the air/fuel screw needs to be adjusted.

For more information as to why a motorcycle struggles idling or sputters, see my other article by clicking here.

Will Too Much Idling Cause The Battery To Die?

We’ve discussed that the most important function of a battery on a motorcycle is to get it started. Through the system of the stator, the battery is recharged so it can start the battery again in the future. You may ask yourself that if a regular run and normal RPM’s is what charges the battery, what will constant idling do and will it help the battery at all?

If you’re like me, you’ve found yourself in occasional stop and go traffic while riding your motorcycle; this means your motorcycle will be idling a lot. We know that idling does charge the battery, but not to the amount it fully needs in order to completely recharge the battery.

The good news is that all you really need is a few minutes of a good run on the motorcycle for the battery to get the full amperage it needs to recharge for the next start up. Say you are stuck in stop-and-go traffic, you’ll still be using the throttle several times to move the bike forward those few feet. As long as you get those several minutes in of a good run on the motorcycle, you shouldn’t have to worry about how much idling you’re doing.

Similarly, you may just be starting up your bike to brush off some dust and not really need to take it anywhere. If you intend on doing this for longer periods of time or doing it several times in one day, be sure to give the motorcycle a good few revs while it’s stationary so you can ensure that battery gets the charge it needs.

Kyle Cannon

Kyle currently works as a mechanical engineer and graduated with a minor in automotive engineering. He loves restoring motorcycles, has a vast knowledge of how they work, and has sold his restoration projects to customers from all over the United States.

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