Can You Overcharge A Motorcycle Battery?

I. Introduction


The battery is an important part of your motorcycle and modern motorcycles depend on the current supplied by the battery for many of its functions including the starting of the motorcycle. Charging your motorcycle battery is a part of battery maintenance.

The question of this article is ‘can you overcharge a motorcycle battery?’. The answer is yes, it is possible to overcharge a motorcycle battery if you use a higher ampere rated charger to charge it. And, if you are not careful you may ruin the battery completely and make it useless.

This article discusses this issue in detail along with other subtopics like

  • what happens if you overcharge a motorcycle battery,
  • is there any method to know the motorcycle battery is completely charged,
  • how can I avoid overcharging my motorcycle battery,
  • and answers a few frequently asked questions on the topic.

II. Can you overcharge a motorcycle battery?

The answer is yes, you can overcharge a motorcycle battery if you use a higher-rated battery charger (like a charger used for charging the battery of your SUV or mini truck) to charge your motorcycle battery and also forgot to keep a check on it.

The thumb rule of charging a motorcycle battery is the amperage should be around 10% of its amp hours (Ah rating).  So, ideally, a 14 Ah motorcycle battery should be charged at 1.4 amps (for 10 hours) or as recommended by the battery manufacturer.

Due to the advancement in technology, many batteries are designed for charging at a current higher than 10% of its Ah rating.

Suppose your motorcycle battery is completely discharged and you do not have a smart battery charger. You have an old battery charger used for charging the battery of your family SUV or pickup truck. You may think ‘why I should not use this charger to charge my motorcycle battery after all both are 12-volt batteries?

Sorry, you are wrong!

Your motorcycle battery and the SUV battery may have the same voltage (12 volts), but the Ah rating of the motorcycle battery is around 14 and the Ah rating of the SUV battery will be 35 or more. Accordingly, the charging current of an SUV battery will be much higher than that of a motorcycle battery.

The charging current supplied to a motorcycle battery should match its natural or designed rate of absorption, and this normally may not exceed 3 amperes (it can be charged at a higher current if specified by the battery manufacturer).

If you use an SUV battery charger (the charging current can be 5 amperes or more) for charging your motorcycle battery, the battery will be overcharged and if you keep it for more time the battery will become useless and in extreme cases, an accident may happen.

Overcharging of the battery by the motorcycle charging system

Overcharging of the motorcycle battery can happen if the rectifier/regulator unit of the motorcycle charging system is malfunctioning. When the rectifier/regulator unit is not functioning correctly the motorcycle electrical system may allow charging at higher than the recommended voltage and this damages the battery permanently.

The charging voltage can go up to 20 volts or beyond instead of the normal 13/14 volts. So, if your motorcycle battery becomes dead prematurely, it will be wise to get the rectifier/regulator unit checked.

III. What happens if you overcharge a motorcycle battery?

If you connect your motorcycle battery to a high-ampere rated charger, overcharging can happen due to the higher charging current. You can save the battery from complete damage if the charger is disconnected as soon as the battery is charged. But, if the charging is continued, the battery will undergo overcharging.

The first indication of overcharging is the battery becomes hotter than normal. When a fully charged battery continues to receive the current, the current is converted into heat.

As the battery becomes hotter, it receives more current. This phenomenon is technically called a ‘thermal runaway’ and it can destroy the battery in a few hours.

Overcharging a battery will dry up its electrolyte, the more you overcharge, the more the loss of electrolyte. Since the battery is sealed you cannot repair the battery by adding water or water and acid. Also, the heat produced during overcharging can warp the lead plates and make the battery unserviceable.

Small brief about motorcycle batteries

The modern motorcycles are fitted with sealed and maintenance-free batteries like an AGM (absorbed glass mat) battery [also referred to as VRLA (valve regulated lead acid) or SLA (sealed lead acid) batteries], or a GEL battery or it can be Lithium-ion battery if it is a high-end motorcycle.

The working of a sealed AGM or Gel battery is similar to a standard lead acid battery; except that the electrolyte does not spill even if the battery is mounted on its side.

The battery stores chemical energy that is converted into electrical energy due to chemical reactions. The chemical reactions are between the dilute sulfuric acid (electrolyte), cathode (lead dioxide (PbO2)), and anode (sponge lead).

A fully charged battery can release electric current due to chemical reactions till it gets discharged. A discharged battery can be recharged by passing the rated charging current into it for the specified time.

IV. Is there any method to know if the motorcycle battery is completely charged?

Yes, you can ensure the battery is completely charged by checking the voltage across the battery terminals.

Disconnect the battery from the charger, and allow it to cool down. Take out your multi-meter and connect the negative terminal of the multi-meter to the negative terminal of the battery and same way connect the positive terminals. Put on your multimeter and check the voltage across the battery terminals.

A fully charged 12 volts motorcycle battery should show a voltage between 12.7 to 13.2 volts. If the voltage reading is more than 12 volts but less than 12.5 volts, it means the battery is not fully charged.

If the battery shows 12 volts or less, it indicates the battery may have lost its life. You can charge it once again, if it still shows less than 12 volts, please consult a battery technician.

V. How can I avoid overcharging my motorcycle battery?

The best way to avoid overcharging your motorcycle battery is to use a smart charger. A smart charger ensures there is no overcharging and stops charging automatically when the battery is fully charged. Also, the digital display on the charger shows you the status of charging, battery status, charge voltage, charge current, etc.

The charger has protection features against reverse polarity, overcharging, and many other issues. The smart charger comes with two alligator clamps for easy connection.

VI. Frequently asked questions (FAQ)

1 What is the charging voltage for a motorcycle battery?
The charging voltage of a motorcycle battery charger will be more than the battery voltage (12 volts). The voltage of a 12 volts motorcycle battery charger should be between 13 and 14 volts.
2 Is there any way I can know if my motorcycle battery is charging or not?
Yes, use a smart charger to charge your motorcycle battery, and it digitally displays all the data you ask for viz. status of charging, battery status, charge voltage, and charge current.
3 How can I know if my motorcycle battery is fully charged or not?
Disconnect the battery from the charger and check the voltage across the battery terminals using a multimeter. A fully charged battery should give a voltage reading of 12.7 to 13.2 volts.
4 How long does it take to charge a motorcycle battery at 10 amps?
The time taken to charge a motorcycle battery depends on the capacity of the battery (Ah or ampere-hours) and the charging current.

So theoretically a motorcycle battery of 14 Ah can be charged in 1.4 hours at a charging current of 10 amperes.

However, 10 amperes charging current is too high for a motorcycle battery, and should not be used unless it is explicitly mentioned by the battery manufacturer.

5 If I keep my motorcycle running idle, does it help charge the battery?
No, the idling rpm of the engine is not sufficient for the motorcycle stator to produce enough current for the battery charging. Instead, taking a ride of 30 minutes will help charge the battery at least partially.

VII. Conclusion

Charging your motorcycle battery is part of maintaining the battery. But, you should be careful about using the correct charger since the wrong chargers can take the life out of the battery. It will be best if you purchase a smart charger since it takes care of the charging and you can be worry-less.

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