Motorcycle Battery Draining Overnight (Causes, Troubleshooting & Solutions)

June 24, 2020

Inspecting the dead motorcycle battery in the morning.

Have you ever had the unfortunate experience of starting your bike, and it refuses to come on? You made some inspection and then discovered that the battery is dead. A motorcycle that worked perfectly fine on the previous day. How did this happen? An answer to your question might be a battery drain. Some factors are responsible for a battery drain, and treated below are those factors as well as possible ways of fixing them. 

Causes of Motorcycle Battery Draining Overnight

1) Circuit Leakage

Circuits that are considered leaky drain your battery until it is dead. They come from accessories that come with the bike or the ones installed by you. Examples are GPS, alarms, different types of lights, especially high beam lights, among others. The best way to inspect for leaky circuits is to install a multimeter between your battery’s negative cable and the negative terminal of the battery. Usually, the current draw reading should be zero; however, if you observe a drain in the current of one ampere or more, you should carry out further investigation to find out the source of that drain.

The type of drain that occurs when the motorcycle is meant to be off is regarded as a Parasitic power loss. The source of such a drain could be an electrical part, such as an amplifier, light in the glovebox. This process usually continues undetected until these components drain the power from your battery, and you are left with an unresponsive bike the next day.

2) Faulty Voltage Regulator

A faulty voltage regulator spells doom for your motorcycle’s battery. This issue usually occurs in bikes that have relatively high mileage. Therefore, it is important to regularly check and ensure that the connections that join the regulator to the alternators are in perfect condition. Furthermore, you should note the resistance of both components. 

It is essential to note that your bike regulator and the alternator will not last forever. That is why you have to inspect them regularly and repair or replace them and one you find faulty. 

3) Poor Ground Connection

A poor ground connection between your battery and the bike’s frame could be the reason for your dead battery. It is a common problem and can stop your battery from charging normally. That is why it is important to carry out regular checks on your bike, especially this area. You should ensure that the ground connection is in good condition. In some cases, you may need to clean the connections using light sandpaper or similar material. 

It is important to double-check after this and inspect other parts of the connection while ensuring everything is connected correctly. 

Possible causes of issues that arise in relation to grounding are rusting and corrosion and when the ground straps are loose or not properly connected. However, it might not be the best place to visit as a result of the wiring, and other components find there, but it is important to find out if the issue is coming from there.

4) You Forgot To Turn the Key Off Last Night

Don’t beat yourself too much, this happens to most riders, especially when you thought you switched it off while not knowing that you did not switch it off properly. However, this can lead to your battery draining before the day breaks. 

You can still remove the key from the ignition in some motorcycles before turning them off or on. This can give riders the wrong impression as they may feel they have switched off the ignition all to wake up and find a different story. 

Therefore, it is essential not to be in a hurry to switch off your bike. Ensure that you have switched it off properly before leaving. 

5) A Short In The Electrical System

A short in the electrical system can drain your battery in a hurry.

This problem will give you a dead battery faster than you can imagine. To make matters worse, it is not easy to fix even for the most experienced mechanic. This is because of the design of most motorcycles being manufactured nowadays, as well as the tweaks individuals add to their bikes. However, it is fixable. 

When you detect a short in the electrical system of your bike, the first thing is to visit an experienced mechanic to get it sorted out. The faster, the better. 

Although, there a few things you can do for yourself before rushing to the mechanic’s place. Knowledge of how to test load your bike’s battery will be helpful and should give you a head start on what the problem is.  

6) Faulty Voltage Regulator/Rectifier

The primary function of a rectifier is to convert alternating current (AC) to direct current (DC). It is part of the electrical system of a motorcycle. However, the design of the regulator/rectifier in more recent bikes is different from the ones in older bikes. In newer bikes, both the regulator and the rectifier come as one unit while in older bikes, they come as separate units. 

This problem is usually common in bikes with high mileage. A bad regulator left unfixed will affect your battery negatively. 

7) Corroded Connections

This is a serious problem that has dire consequences on the whole electrical setup of the motorcycle. 

Nowadays, motorcycles have more wirings compared to older ones. They have their purpose, but it can’t be fun finding a corroded connection. 

It won’t be easy for a mechanic, but it doesn’t mean it is not traceable and fixable. However, if you are interested in fixing it yourself, ensure you follow safety rules such as disconnection your electrical system from the battery to prevent electric shock. 

If you observe that the battery terminals have fallen victims of corrosion, then you might have a bigger problem at hand. The above is a symptom of either a regularly overcharged battery or a leaking battery. It could be more. 

Ensure you are carrying out safety procedures while cleaning battery terminals such as wearing gloves and preventing contact with the chemicals in your battery. You should note there are different ways of cleaning corroded battery terminals.

8) Heat & Vibration

Some motorcycle batteries cannot take on heat and vibrations. Even when you take good care of the motorcycle battery, heat or vibrations can still reduce the lifespan. It severely damages some internal components of the batteries. AGM and gel cell batteries take on a higher amount of heat or vibrations. They often last longer than the common wet lead-acid battery types.

When it comes to tolerance of heat and vibrations, there are different degrees different motorcycle batteries can take. Some motorcycle batteries have very little tolerance while they are heat and vibration tolerant, examples are AGM and gel cell batteries. They have longer lifespans than lead-acid batteries. But it is important to know that heat and vibration will generally reduce the lifespan of any battery. 

Regardless of how well you take care of your battery, if it cannot tolerate heat and vibration, it will fail prematurely when subjected to those conditions.

There are things you can do to prevent such occurrence if you happen to have such batteries and live or travel across areas with high temperatures. You can wrap the battery on a Thermo-heat shield. This should help increase the lifespan of your battery. 

9) Weak and Bad Battery Condition

Your battery is refusing to start maybe as a result of it being in a weak state as a result of previous damage done to it. The source of the damage can be heat and vibration or the battery draining out on one occasion or more.

This observation is based on experience. I notice that anytime I use my battery till it got drained totally. After recharge, it never performs like before again and usually spells the beginning of the end for the battery. 


1) Check Your Accessories

We like adding some stuff to our bikes, some are necessary, but most are not needed. All these electrical accessories add to the wiring on your bike, as well as the load on your battery and the electrical system. In some cases, it overloads the system and drains the battery very fast. 

Over time, the battery of your motorcycle weakens as a result of too much work and, in the end, leads to premature failure.

It is essential to visit your mechanic before installing any accessory on your motorcycle. Also, if you are interested in adding more accessories to your bike, you should consider investing in a distribution box and a multimeter to monitor the amount of current they drain. 

Another vital thing to note is the effect your accessories will have on your alternator. In some cases, you might need to upgrade it to put up with the new load.

Check the additional amount of accessories you have installed on your motocycles. Adding too many accessories on your motorcycle tends to cost you much apart from the effect it has on your battery. If there is a fault, the accessories have to be removed to solve the problem leading to more cost. 

The more accessories you put on your bike, the higher the chances of experiencing a battery-related issue. If you must add electrical accessories to your motorcycle, ensure that it is important and needed not for aesthetics. Also, ensure you keep the number very low. 

2) Checking for Faulty Wiring

Battery – Your battery is likely not the one at fault if you detect that you have a short in your electrical system.

Check Your Main Fuse – A faulty main fuse will shut down all the electrical components of your bike. It can lead to confusion about where the source of the problem is. Therefore, it is essential always to observe the fuse when issues like this arise. It is also essential to have at least a spare of this stuff wherever you go to with your bike. 

Look for Bad or Broken Wiring – observe the wiring in your motorcycle. Be on the lookout for unprotected wires, bad connections, or exposed cables as they may be responsible for the short in your bike’s electrical system.