How To Fix A Motorcycle Battery Draining Overnight? – 7 Fixes!

All motorcycles come with 12 volts rechargeable battery (li-ion or lead-acid) that cranks the engine. The electric power generated from the motorcycle stator recharges the battery when you ride it. But, sometimes, the battery discharges overnight due to wiring faults and other reasons.

If your motorcycle battery drains overnight, you’re reading the correct guide. Because I recently fixed the overnight battery draining issue on my Royal Enfield Classic 350. I’ll share some easy solutions to fix any motorcycle’s faster battery drain problem.

So, why does your motorcycle battery drain overnight? A motorcycle battery will drain if you do not turn off the ignition switch, there is short in electrical wiring, battery terminals have corrosion, too many accessories are attached, or regulator-rectifier has gone bad, or the battery is faulty.

How To Fix A Motorcycle Battery Draining Overnight?

If your motorcycle is not cranking with starter switches, it means the battery is discharged. You can jumpstart your motorcycle with another vehicle.

But jumpstarting is just a temporary solution. In this guide, we’ll troubleshoot the actual reason why your motorcycle battery is draining when not in use and provide you with a working solution.

1. Faulty Ignition Switch

If your motorcycle battery is draining overnight, ensure you turn off the ignition key. The battery drain may occur if your faulty ignition switch doesn’t cut off the power supply to electronic accessories.

Solution:

To ensure that the battery is draining because of a faulty switch, remove the ignition fuse from your motorcycle fuse box or disconnect the ignition key connector. If the motorcycle battery is still draining, it means the problem lies somewhere else, and you should inspect it further.

2. Corrosion At Battery Connections

The second most common reason a motorcycle battery drains overnight or while riding is corroded battery connections (at terminals and grounding). If the battery terminals are corroded, some current leaks through the spark, which discharge the battery.

Solution:

Locate the battery and check its terminals. If battery terminals are corroded, clean the rust with the help of sandpaper and tighten the screw. Similarly, if there is corrosion on the grounding frame, clean it with sandpaper and tighten the bolt.

3. A Short In Electrical System

If you look underneath the motorcycle tank and handlebar, you’ll see a bunch of wires that supply power to different electrical accessories attached to the motorcycle. If any positive wire is scratched and touches the body, it will generate a spark (which causes battery draining).

Solution:

Dealing with the electrical wiring system of a motorcycle is not easy. You have to check the short in different wires. So, first, perform a continuity test between the positive wire and grounding with a multimeter.

The continuity sound on the multimeter indicates the short circuit; you need to find out and fix it. I would recommend you to take professional help.

4. Too Many Electrical Add-ons

Everyone does aftermarket modifications to make their motorcycle more appealing. But, adding too many electrical accessories increases the power consumption, draining the battery faster. If any electrical add-on is directly connected to the battery, it will always drain your battery.

Solution:

It’s better to keep the manufacturer’s light and avoid any aftermarket accessories. Disconnect any extra-installed accessories on your motorcycle and check whether the battery draining issue is fixed.

5. A Faulty Regulator-Rectifier (RR Unit)

A rectifier-regulator converts the AC current into DC and regulates the voltage. It also prevents reverse current flow to the stator.

A faulty regulator-rectifier (RR unit) will create problems in charging the motorcycle battery. If your RR unit is faulty, it will not restrict the reverse current flow, and your battery will discharge overnight.

Solution:

If your motorcycle regulator-rectifier is faulty, replace it immediately because a faulty RR unit will not charge your battery and can also damage the stator.

6. A Bad Stator/Alternator

All motorcycles come with a stator and alternator system that converts mechanical energy into electrical energy. The stator has a strong magnet, and an alternator coil rotates.

The alternating current (AC) goes into regulator-rectifier units and is converted to direct current (DC), which powers all the accessories and recharges the battery.

If your motorcycle stator/alternator is faulty, then it will not generate electricity and your battery discharges while riding.

Solution:

You need to visit a professional mechanic garage to get your motorcycle stator/alternator replaced.

7. Bad Battery

The average life of AGM batteries on a motorcycle is approximately 2 to 3 years; however, battery lifespan depends upon other factors too. Your battery may not hold the charge if it is over two years old. That’s why your motorcycle doesn’t start in the morning.

Solution:

You need to replace your motorcycle battery. Check the amperage rating of your battery and buy a replacement from Walmart, AutoZone, or any online platform.

Do Motorcycle Batteries Drains When Not In Use?

All the electrical accessories are turned off when you turn off the ignition key. But modern motorcycles come with theft control and electronic control unit (ECU) that continuously takes some power from the battery.

That’s why your battery discharges when you store your motorcycle for longer. So, if you’re storing your motorcycle for winter, don’t forget to disconnect the battery terminals.

How To Check If Your Battery Is Being Drained?

You can check your motorcycle battery voltage with the help of a multimeter. Set the multimeter knob to 20V DC and connect the red wire with the battery’s positive terminal and black with the negative.

When the motorcycle engine is turned off, there should be more than 12V reading on the multimeter. If it’s less than 12V, recharge the battery with a charger or jumpstart with another vehicle.

What Are The Sign Of A Bad Motorcycle Battery?

The average life of a motorcycle battery is 2 to 3 years. If your motorcycle is not cranking or the battery doesn’t hold a charge, it’s the first sign of a bad battery, and you need to replace it.

Apart from this, some physical signs like broken terminals, a crack or bulge in the plastic casing, and any leaking fluid or discoloration are common signs of a bad battery.

Can A Dead Motorcycle Battery Be Recharged?

Yes, a dead motorcycle battery can be recharged with a 12V DC charger. However, if your battery is more than two years old, it will create a problem with cranking.

Why Does My Motorcycle Battery Dies After 3 Days?

If your motorcycle battery dies after 3 days, it means the charging system isn’t functioning properly. It could be due to a faulty regulator-rectifier, terminal corrosion, loose connections, or a bad battery.

Why Does My Motorcycle Battery Dies After A Week?

If your motorcycle battery dies after a week, it means some electrical accessories are constantly draining the power or the battery is faulty. It’s better to inspect your regulator-rectifier and replace it if it’s faulty.

Conclusion

A motorcycle battery drains overnight due to a faulty ignition switch, short-in electrical wiring, a faulty regulator-rectifier, etc. It is important to diagnose the root cause by following the steps in this guide to fix this issue.