How Long Will a Motorcycle Battery Last Without Charging

How Long Will a Motorcycle Battery Last Without Charging? Let’s deep dive and find out!

I’ve owned motorcycles for the past 15 years. In that time, I’ve had to replace my motorcycle battery at least a dozen times. For the longest time, I didn’t realize that I could actually extend the life of my motorcycle battery by charging it when I was not riding.

I used to think that a motorcycle battery would last me about a year, and then I’d need to buy another one. In reality, a motorcycle battery will last much longer than that if you treat it right.

And how long depends on a few things.

Table of Contents

Type of Battery

There are several types of battery that you may use to start your motorcycle. All will self-discharge to differing extents.

Lead Acid

These batteries are typically found in older motorcycles. They consist of several lead-acid storage cells.

While in storage, they will self-discharge the same as any other battery. A lead acid battery will self-discharge at a rate of 5% per month when kept in storage at a moderate temperature.[1] This rate rises as the temperature rises. The danger of battery sulfation increases as the charge drops.

AGM

The majority of modern motorcycle batteries are AGM (Absorbent Glass Mat) batteries. They are a more modern iteration of the traditional lead acid battery. They have improved in that there is no acid sloshing about inside, and they emit fewer noxious gases. Also, they are tougher and more resistant to vibration and shocks, which is important.

Self-discharge affects them as it does any other battery. The AGM battery’s self-discharge rate is around 3.5 percent per month.[2]

Gel Cell

Gel cell batteries are also used for motorcycles. The gel battery does not keep the electrolyte absorbed in a glass mat. Rather, the Gel battery uses a paste within the battery to contain it.

The Gel battery self-discharges at a rate of 2% per month.[3] This is at an ambient temperature of around 20°C. This doubles for every additional 10°C.[4]

Lithium-ion

Finally, we have Lithium-ion batteries. Many consider them to be the future of battery technology. And they do boast competitive advantages over their lead acid counterparts. But there are also disadvantages and inefficiencies.

Not least is the fact that li-ion batteries are also prone to self-discharge when left unused. Lithium-ion batteries lose 5% during the first 24 hours after a charge. Then, they level off at a self-discharge rate of a manageable 1-2 percent per month.[5]

Battery Type	Monthly Discharge Rate
Lead Acid	5%
AGM	3.5%
Gel Cell	2%
Lithium-ion	5% within 24 hours then 1-2% per month

Storage Conditions

The other factor that affects the rate of battery self-discharge is storage conditions. Specifically, the temperature.

The higher the ambient temperature, the higher the rate of self-discharge. This applies to all battery types – they all see an increase in self-discharge, and the rate doubles every 10°C. (18°F).

Why Does the Battery Need Charging?

Batteries suffer from self-discharge. This means that when a battery is not in use, it loses its charge. If a battery is not charged, it will eventually die. To prevent this, you can get a battery charger. Plug it into a socket in your garage and it will charge the battery and counter the self-discharge.[6]

How Long Will It Last Without Charging?

Every time you start your bike, the battery uses some of its charge to turn over the engine. Unlike deep cycle batteries, which can be deeply discharged, the bike battery delivers a quick powerful burst. A typical motorcycle battery uses about 10 percent of its charge to turn the engine over.

Once the bike is running, the alternator sends power from the engine back to the battery, ready for its next use. So, if you are a regular user, the battery should last a long time. It will be able to provide enough energy for thousands of miles of riding.

What if I don’t use my bike regularly?

A lot of motorcyclists are seasonal riders. They may only use their bike during the summer when the weather is good. Or they may use it only once a year, such as for a parade or a special event.

If you rarely ride your motorcycle or are going to leave it dormant for long periods, consider how to look after your battery.

You can leave a battery unused for an indefinite period of time. If you do this, however, you need to remember that the battery will lose its charge over time.

So what happens when the battery runs out of charge? When the battery is completely discharged, it becomes useless. It may have suffered permanent damage.

In this case, you need to buy a new one. And that can be expensive. Which is annoying, especially when it is not really necessary.

When Should You Charge Your Battery?

If your bike is in storage, you should charge the battery every month or so.[7] This will help to preserve the battery and extend its life. It also keeps it topped up so it is ready to use at a moment’s notice. If the battery is getting old, more than 4 years, you may need to charge it more frequently. Once every 2-3 weeks should be sufficient.

Why do batteries self-discharge

Batteries self-discharge naturally. This is not a fault of the battery. Rather, the normal electrochemical reactions within cause a gradual loss of charge.

The chemical reaction within a battery never stops. You cannot turn it off. Since the battery quietly idles when not in use, it takes several months for the charge to entirely drain.

A smart charger supplies energy to offset that internal discharge. And as such, damage to the battery is avertable.

How long should a motorcycle battery last? What’s its service life?

The answer to this is dependent upon how you use the battery and how you treat it. If treated poorly, a battery may last as little as a month or two. But, if a battery is correctly maintained and kept at a status of full charge, it can last between five and ten years.

What is the problem with allowing a battery to discharge

Any battery that discharges too much is vulnerable to sulfation. This is a buildup of lead sulfate on the battery plates. It inhibits and disrupts the performance of the battery.

The only way to keep a battery from sulfating is to stop it from discharging more than a tenth of its capacity. When a battery discharges, it loses its ability to hold a charge, and its voltage drops.

When does my battery become useless

A bike requires between 12.5 Volts and 12.9 Volts to turn the engine.[8] Anything below that you will be struggling. Repeated attempts will only drain the battery further. It will also cause significant wear and tear to your electrical system.

How do I charge my battery

There are a few ways to keep your battery from going flat in storage.

The first way is to fire the bike engine up once a month to use the alternator to recharge the battery. But this might not always be convenient, desirable or practicable. It will also use up gas from your tank.

You can also use a battery charger. A smart charger will detect the amount of charge in the battery and charge accordingly. It will also take into account the chemistry of the battery. It is a much more nuanced way to charge a battery than a ‘dumb’ charger or another battery. It will stop at the end of the charge cycle to prevent damage to the battery from overcharging.

And finally, you can use a battery tender or maintainer. This is a slow charger that keeps the battery topped up and recharges the battery as needed. They are designed to stay attached to the battery. This is the best ‘set and forget’ method there is.