7 Possible Reasons Your Motorcycle Battery Drains Quickly

Motorcycle battery issues are very common and incredibly frustrating, especially when you’re out on rides, the bike starts losing power and the battery dies out quickly.

However, sometimes the problem with a motorcycle battery that drains too fast isn’t the battery itself, but rather something else with the electrical system that’s sucking the charge out of the battery. More often than not, the problem is something simple, but when it’s not, you have to dig deeper into the electrical system to find the issue.

A sign of a battery losing power may be clicking noises when you try to start the bike up again. This sound means the motorcycle is struggling to draw power from the battery. You could be dealing with a bad or expired battery. However, the battery itself may be fine, but something else is draining the power out of it. 

The video above shows you how to test and replace a motorcycle battery, but ruling out a bad or expired unit, here are some reasons your motorcycle’s battery could be draining so quickly.

You Don’t Turn the Key Off Properly

On some motorcycles, it’s possible to pull the key out of the ignition before it reaches the full OFF position. You think the bike is off and go about your business, but the machine is still running.

As silly as it sounds, it’s not uncommon for people to think a motorcycle is shut off completely without checking, and that can drain the battery. Always check your motorcycle after you’ve parked and taken the key out to make sure it’s 100% shut down. Do a quick walk around the bike after every ride, and check the lights and the dashboard to make sure everything is powered off before you leave. 

There’s a Parasitic Drain on the Battery

When you have too many accessories drawing power from the battery, it can experience what’s known as a parasitic drain or draw. A parasitic draw is electrical equipment continually sucking juice out of the battery, much like a parasite draws from its host. 

Faulty electronic components or power overload from too many accessories can be the culprit of parasitic battery drain. If you added too many electronic gadgets or modifications to your motorcycle on top of what’s already there, they drain additional power out of the battery.

Too many gadgets and accessories on your motorcycle can significantly reduce the lifespan of any motorcycle battery, so check the voltage of the battery with all the accessories and gadgets turned on to see if a parasitic drain is consuming the power out of it. 

The Bike Has a Blown Fuse

A short in a motorcycle’s electrical system can drain its battery fast, even from something as small and simple as a blown fuse. 

Before you go digging too deep into the electrical system, check the fuse(s). A faulty or blown main fuse can shut down all of the electrical components on a motorcycle. Check the fuses one by one with a test light or multimeter to see if they have amperage, and replace any that are blown with new fuses of the same amp value. 

The Regulator-Rectifier is Bad

A bad voltage regulator-rectifier is a common electrical system problem with higher mileage motorcycles, and it could drain out the battery quickly if it's left operating on the machine.

The regulator-rectifier works with the stator to convert AC current into DC current for the battery to charge. When the voltage regulator can’t do its job, the battery won’t get the power it needs to start or run the motorcycle. Testing the regulator-rectifier will help determine whether it’s the cause of your motorcycle’s battery draining out quickly. 

The Stator is Bad

As mentioned, the stator is an electrical component that works with the regulator-rectifier to generate power to the battery for the motorcycle to be able to start and run.

Stators charge the battery while the motorcycle is running, so if the stator goes bad, the bike will run solely off battery power, which would cause it to drain faster. The battery is basically there to start the motorcycle up and power lights and accessories, but once the motorcycle is on, the stator takes over power duties and keeps the battery charged. Test the stator to see if that’s what’s causing the battery to drain.

The Battery has Corroded Electrical Connections

Corroded battery hardware and cables can cause a motorcycle’s battery to drain out faster than it should. Battery corrosion can be caused by overcharging or stem from leaking electrolytes.

Corroded terminals can drain the battery while riding, since there’s a barrier between the terminals and the cable that connects to the stator. Disconnect the battery and clean corroded battery terminals with a wire brush and some battery terminal cleaner. Next, inspect all of the wires that connect to the battery to see if bad connections are the cause of your motorcycle’s quick battery drains.  

The Ground Connection is Bad

Sometimes a motorcycle battery is fine, but the ground connection from the bike to the battery is poor. You'll want to check all electrical ground connections to make sure they’re in working condition.

Problems with grounding can be caused by corrosion and bad wiring, which can prevent the battery from charging or drain it out quickly if the connection is poor. Seek out bad or broken wiring and connectors or exposed wires that could be shorting out the electrical system.

Other Causes of Quick Motorcycle Battery Drain

Heat and motorcycle vibration can damage a battery enough to make it start losing power. If your bike’s battery sits where excess heat and vibrations occur, make sure it’s secured properly to its battery tray, and consider getting a heat shield for it. 

Another potential cause of quick battery drains is taking short, infrequent rides. Using your motorcycle sporadically for short rides doesn’t allow the battery to charge properly due to lack of activity. 

Finally, lack of maintenance can be the cause of your motorcycle’s battery draining out quickly. Keep the battery terminals and connections clean, and check electrolyte levels regularly to make sure the battery is topped off. 

If you’re going to let your motorcycle sit for a while unused, disconnect the battery from the bike to prevent parasitic drain, and leave it connected to a battery tender to keep it charged while it’s in storage.