What To Do If Your Motorcycle Battery Doesn't Fully Charge

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Key Takeaways

  • A battery past its expiration date should be replaced.
  • Frayed wires can be a sign of an electrical fault in the charging system
  • How a battery charge depends on how often a bike is ridden
  • Most motorcycles have battery lights to indicate problems with the charging system.

You want to ride your motorcycle this summer but notice the battery seems weak. Here’s what to do if the motorcycle battery doesn’t fully charge.

Without a solid battery powering a bike, nothing will function correctly. Several reasons may affect a battery not holding a charge. A dead battery, corroded terminals, poorly grounded wiring, or even a faulty alternator can contribute to the issue. Battery sulfation can also be a culprit.

Every day, millions of Americans start their motorcycles for the joy of the open road. However, nothing is worse than riding with a battery that doesn’t fully charge because it can mean the difference between riding and pushing your bike down the road. Without solid motorcycle batteries, a bike’s electrical functions can become sporadic at best or fail at worst. Since the battery’s voltage supplies all the electrical energy for your charging system, it is crucial that every motorcycle owner knows when to spot potential issues. What can you do about a motorcycle battery charging at less than full capacity? What are some of the causes of a bad bike battery? Let’s explore this issue and see if we can’t keep you and your beautiful bike rolling down the road a while longer.

In this article...


What Are The Symptoms Of A Battery That Isn’t Fully Charging?

Here are some things to help determine if you have a bad motorcycle battery or if your battery is dead.

The Battery Light Comes On

Most modern bikes have a battery light that flickers on and off (or just stays on), if there is any issue with the motorcycle charging system or how the battery is drawing power. You should take any warning lights seriously.

Trouble Starting

If you insert the key and have trouble starting up your bike, this could indicate that the battery is having trouble sending enough power to the ignition. The ignition switch needs power from the electrical system to work, which can be a sign that the motorcycle’s battery is struggling.

Sporadic Electronics

Many owners report that the first sign that their battery charging might be suspect is electronic hiccups in displays, headlights, or other items. Motorcycles rely on the stored energy from their battery to power things like a stereo, headlights, and a good alternator/stator coil to keep them working. If the headlights flicker or seem spotty, it pays to look over your bike to see if maintenance is needed.

The Bike Dies While Riding

You could have a bad stator if your bike won’t charge while riding. If the stator isn’t functioning correctly, the battery will not recharge while you are riding and can only operate with the current charge it has stored. This situation generally means that after the bike has used that existing charge, it is completely drained and stops powering altogether. (You get stranded).

The Battery Seems Hot to the Touch

It is normal for a motorcycle battery to be warm while charging, but if it seems to be overheating, you could have a serious problem worth investigating.

What To Do If Your Motorcycle Battery Doesn’t Fully Charge?

Fortunately, there are several things that you can do when you suspect that there is a problem.

Check Your Battery’s Expiration Date

Every motorcycle battery has a shelf life, and when it reaches the expiration date, it sometimes fails to hold a charge. Many batteries have operated at a low charge for so long that battery sulfation occurs. This situation happens when lead sulfate crystals form inside the battery and prevent the chemical exchange needed to produce the necessary voltage. The only recourse is to replace it with a new battery.

You should also check the battery casing for any signs of leaking acid. Any bulging, cracks, or leaking battery acid are signs you need a new battery.

Inspect The Battery Terminals

One of the first things you should do is visually inspect the battery for any signs of corrosion. Battery terminals clouded with signs of acid won’t conduct the electrical energy your bike needs to function correctly. (Your battery terminals should be checked regularly).

If you notice any buildup, use a wire brush to clean your connections so that the flow from your battery is consistent.

Look for loose connections on the battery cables. Unfortunately, many owners fail to realize that these cables vibrate loose and might not be making contact as they should. Clean and retighten them onto the battery posts and see if that doesn’t fix your battery issue.

Inspect the Ground Connection

Sometimes a bad ground wire can develop a short or show signs of being broken. If a ground connection is frayed, it might work a little but not at full strength. Replace any faulty ground wires that you find.

Is The Alternator Failing?

The alternator converts the mechanical energy from your bike’s engine into an electrical current. If the alternator is bad, it can prevent the battery from holding a charge. (If your lights flicker or work for a little while but grow dimmer as you ride, you likely have a bad alternator or regulator-rectifier or stator). A technician can use a voltage regulator to determine the compromised component.

Assess the Regulator-Rectifier

As a bike runs, the alternator has to convert the electrical energy (from alternating current to direct current), sending it back to the battery to be stored. A regulator works hard to ensure steady power flows through the system. If it fails, there is too much juice flowing back and possibly overloading the battery. A regulator works very hard because a bike converts a lot of energy. It is not unusual for a regulator to fail after about 20k - 30k miles on them (some bike owners report failures more often).

You can determine a bad regulator by checking the voltage on your battery posts while the bike is running. A typical reading is around 13.5 - 14.5. Rev the motorcycle, and see if you get a higher rating. If your voltage meter shows anything about 15, your regulator is not performing its job and will likely need to be replaced.

A lousy regulator can mean that the battery is overcharging, and if it gets too much juice, it can explode (which is never a good thing), so be sure to have the regulator checked if everything up to this point has looked pretty good.

Inspect Fuses

Sometimes a battery will not hold a charge simply due to a blown fuse. Remove the fuse box cover (most are under the seat) and inspect the fuses individually. You should look for any signs of broken wires inside the plastic housing of the fuse or signs of burn marks on the tongues (melted plastic housing is also a sign). Replace the fuse with one of the same voltage. If the fuses continue to blow after you have replaced them, then you have a different problem with your bike’s charging system.