A modern motorcycle is only as powerful as its battery. It doesn’t matter how well-tuned your bike’s engine is if its battery won’t hold a charge.
This article therefore lists the most common reasons a motorcycle battery doesn’t charge and how to fix the various problems.
Let’s check them one after the other.
Table of Contents
1. Using an Incorrect Size or Type of Motorcycle Battery
One of the most common and easily correctable reasons a motorcycle battery won’t hold a charge is installing the wrong-sized battery. Wrong battery creates electrical problems and syncing issues.
If a motorcycle battery is too large, it generates extra heat and overcharges your motorcycle’s electrical components. Conversely, a battery that’s too small fails to provide an adequate charge for your bike and drains its electrical system.
Note that running your motorcycle on a wrong-sized battery negatively affects your charging system components – your stator and Regulator/Rectifier.
Also, a faulty charging system can turn around and damage the battery further or, at the very least, fail to recharge your battery while you ride.
Furthermore, motorcycle batteries are manufactured from different materials, requiring different maintenance and charging methods.
For example, lithium-ion motorcycle batteries are less susceptible to dying during inactivity. They require careful voltage and temperature monitoring to prevent the battery from overcharging or overheating, which could hinder its charging capacity.
Lead-acid batteries are more common and cheaper, but they require battery tender charging during inactivity and routine maintenance to prevent corrosion and sulfation.
Whereas lithium-Ion batteries can use over 85% of their capacity during a single cycle before they risk losing their charging power, discharging a lead-acid battery passed 50% can damage it so that it won’t recharge fully.
Solution: Replace the Wrong-Sized Battery with the Specified Size and type of battery
Here are vital points to note:
- Replace your incorrect battery with the type and size specified in your bike’s owner’s manual.
- If you don’t have your manual handy, consult the label on your old battery or ask a technician who specializes in your bike’s make and model.
- Use a high-quality battery, following the maintenance instruction specific to the type of battery–whether lead-acid or lithium-ion.
- If using the wrong size or type of battery damages your wiring harness or charging system, you’ll have to replace the compromised components.
2. Poorly Grounded Wiring
A faulty grounding wire is one of the leading causes of a motorcycle battery that won’t hold a charge. Poor grounding disrupts the flow of juice from your battery to the bike’s various electrical systems and components.
If your battery’s ground connection is compromised, it has nowhere to dump the extra charge it routinely receives from your charging system.
The battery then overloads itself with more charge than it can handle until it dies and no longer holds a charge.
The lack of a fully functional ground wire also causes other electrical failures, such as starting failures, faulty instrument displays, and flickering lights.
Solution: Check, Repair, and Replace Faulty Ground Wires
Follow the guide below:
- Use the wiring schematics in the service manual for your motorcycle’s make and year model to locate the ground wires.
- Inspect the various ground wires in your bike to ensure they’re correctly grounded to metal components.
- Inspect your grounding wires for wear, corrosion, melting, and damage.
- Replace any faulty ground wires you encounter immediately.
- If your ground wires aren’t visibly damaged and appear properly grounded, use a multimeter to ensure the voltage and resistance are reading what they should be.
- Compare our multimeter readings to the test numbers in your make/year model’s manual.
You may also want to check our post on why a motorcycle battery won’t fully charge for better insight.
3. Corroded Battery Terminals
Corroded battery terminals hinder the charging capacity of a motorcycle’s battery by disrupting the electrical connection between your bike’s battery and the rest of its electrical systems.
Whether from exposure to moisture, a lack of battery matinee, or due to a chemical reaction between the battery acid and metal terminals, a layer of rust on the terminals blocks the current’s flow in and out of the battery.
The rust layer not only prevents the battery from receiving the recharging current from its charging system but also lessens the battery’s capacity to hold a charge altogether.
If left unchecked, corroded terminals can damage other cables in your wiring harness, causing shorts and blowing fuses. That said, make sure you also read about why a motorcycle battery won’t charge while riding here.
Proper motorcycle storage habits and routine battery inspections/maintenance will prevent your terminals from rusting in the first place.
Solution: Clean Corrosion Off Battery Terminals Using Baking Soda
Here are tips to follow:
- With the motorcycle off, disconnect your battery terminals and remove your battery from the bike, following your owner’s manual instructions.
- With a wire brush, scrape the corrosion, rust, and dirt off the battery terminals and connector cables.
- Mix baking soda and water until it forms a paste.
- Apply the paste to the battery terminals with the wire brush, scrubbing until the terminals are corrosion-free.
- With clean water, rinse the paste off of the battery terminals.
- Dry the terminals with a soft, clean cloth until there’s no water residue left on the battery.
- Charge the battery with a tender or trickle charger.
- Test the battery’s capacity to ensure it’s holding charge.
- Reinstall your motorcycle’s battery and start your bike to test it out.
4. Crystalized or Sulfated Battery Acid
Another problem resulting in the failure of a motorcycle battery to hold a charge is battery sulfation. Battery sulfation is when the battery’s lead-acid crystallizes and accumulates on the battery plates and exterior.
Sulfation occurs as a result of repeated discharging and recharging, overcharging, and undercharging. It could also happen due to the act of depleting your battery to empty and failing to restore it for an extended period.
Just like rusted and corroded battery terminals and cables, sulfate crystals interfere with the smooth current transition to and from your battery.
In time, sulfation impairs the battery’s internal resistance, voltage production, and refill capacity. This makes it hard for the battery to hold a charge, and it causes frequent starting problems for your motorcycle.
Solution: Replace the Sulfated Battery
In some cases, riders can dissolve the sulfate crystals with a high-frequency pulse from a desulfator or a specific type of battery charger. That said, replacing the sulfated battery with a new one is far easier and more common.
Follow these steps to prevent your new battery from developing sulfate crystals:
- Keep your battery at a full charge at all times without overcharging it.
- Refrain from only partially charging your battery.
- Store your motorcycle in a cool, dry place, tendering your battery during long periods of inactivity.
- Inspect your battery’s voltage regularly.
- Keep your battery terminals and connector cables clean.
5. Excessive Engine Heat and Vibration
Excessive engine heat and vibration can make a motorcycle battery to stop holding a charge by damaging the battery’s internal components.
Suppose your engine is producing more heat than usual. In that case, the heat build-up can potentially evaporate the electrolyte formula inside the battery, reducing its capacity for storing electrical energy.
Engine vibrations can shake your battery around, loosening and cracking your battery’s internal plates and causing short circuits and leaks.
Some batteries are more durable against heat and vibration than others, and your motorcycle manufacturer considers this when choosing the ideal type of battery for your model.
That said, various engine failures can cause an increase in engine heat and vibration, which can spoil your battery, reducing its ability to hold a charge.
Solution: Install Heat Shields or Rubber Mounts
If your battery is damaged due to excessive heat and vibration that results from an engine failure, we suggest you repair the engine problem before replacing your battery to avoid killing your new one.
If the heat issue is there to stay, ask your mechanic if there’s a more heat-resistant or durable type of battery that fits your bike.
- Install a heat shield and rubber mounts to lessen the battery’s exposure to heat and vibration.
- Inspect your regulator/rectifier and stator for any damage.
- Employ a trickle charger or battery tender to maintain a full battery charge at all times.
6. Neglecting Battery Maintenance
Neglecting the basics of battery maintenance can reduce your motorcycle battery’s ability to hold a charge by degrading its overall performance.
As mentioned earlier, failure to keep the battery terminals free of rust and corrosion via regular cleaning can corrupt your battery connection. The corruption could be enough to reduce the electrical contact between the battery and your various electronics.
Furthermore, if your battery’s electrolyte levels aren’t inspected and topped off appropriately, your electrolyte levels will lower over time, lessening the battery’s capacity for energy.
Solution: Replace Battery and Follow Manufacturer-Suggested Maintenance Steps
Here are tips to follow:
- Replace your corrupted battery with a new, high-grade battery that fits your motorcycle.
- Clean the battery terminals regularly.
- Inspect your battery’s electrolyte levels per the battery’s instructions, topping off as needed.
- Charge your battery during inactive periods.
7. Dead or Expired Battery
Whether from damage, corrosion, neglect or because it reached its cycle limit, a slow or expired motorcycle battery will no longer hold a charge.
Electricity in an electrolyte-filled battery is produced through a chemical reaction. Therefore, a dead battery typically results from evaporated or leaking electrolytes, which impairs the numerous battery cell’s ability to produce an electrical charge.
Battery plates are the components that store electrical energy. If the battery is damaged, its internal plates can crack, causing short circuits and leaks that drain the battery and hinder its ability to recharge.
An expired battery is a battery that has passed its cycle limit, meaning it has discharged and recharged enough to wear its capacity.
All batteries expire eventually, and once they do, they need to be jumped or recharged manually until they lose their ability to hold a charge at all.
Motorcycle batteries typically last between 200 – 300 discharge cycles before they expire, provided they’re recharged intermittently while riding by your bike’s charging system.
Solution: Replace Expired Battery With a New One, Following Suggested Maintenance
Tips to follow:
- Keep new batteries charged during periods without use.
- Keep battery cables and terminals clean.
- Refill electrolyte levels as needed, per battery manufacturer’s instructions.
- Store motorcycle and battery in a cool, dry place to extend their life.
On this note, make sure you also read about what to do when your motorcycle battery has been inactive for a year here.