Battery Equivalents and Replacements

How Many Volts Is A Motorcycle Battery?

Most motorcycles have 12V electrical systems, although some oldtimers still operate at 6V, but they are rather rare.

Motorcycle batteries are tasked with starting the motorcycle's internal combustion engine and powering lights and a few more electric systems while the engine is turned off.

By using simple multimeters, one can check the voltage of the battery in various situations and find out the actual battery condition.

Published: October 17, 2022.

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Motorcycle Batteries Chemistries

Motorcycle batteries can be starting lead-acid and lithium batteries.

Flooded/Wet Lead-Acid batteries have been in use for a long time. They must be operated in an upright position since they are not spill-proof batteries.

Also, occasionally one has to add distilled water since they lose water over time, especially during hot days.

Gel-Cell Lead-Acid batteries are spill-proof, maintenance-free batteries that operate in any position except upside down.

Gel-cell batteries feature electrolytes suspended in silica in the form of gel - hence the name.

Gel-cell batteries are resistant to vibrations and feature a very low self-discharge rate.

Absorbent Glass Mat (AGM) Lead-Acid batteries are another type of spill-proof, maintenance-free battery that can operate in any position except upside down.

AGM batteries are a very popular choice for people looking for a lead-acid motorcycle battery due to their mechanical robustness and good electrical features.

Lithium motorcycle batteries are based mostly on Lithium Iron Phosphate (LiFePO4) chemistry (stable chemistry, good performances), although some manufacturers even offer Lithium Polymer batteries (fantastic performances, but not the most stable battery chemistry; IMHO, not recommended).

Lithium motorcycle batteries MUST feature a built-in Battery Management System to protect the battery from unwanted events like overcharging, over-discharging and similar - even LiFePO4 batteries must have BMS.

Most motorcycles still use lead-acid batteries, but lithium batteries are gaining in popularity. After all, they offer improved starting features, some weight savings, and a few more features not available with lead-acid batteries.

Lead-Acid Battery Voltages

Using a voltmeter, one can easily check the voltage of the motorcycle battery in various situations.

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When the motorcycle is completely Off (ignition key out), the lead-acid battery voltages are (measured at 77°F/25°C):

Type 100% SoC 75% SoC 50% SoC 25% SoC 0% SoC
Flooded/Wet 12.65 volts 12.45 volts 12.24 volts 12.06 volts 11.89 volts
AGM 12.80 volts 12.60 volts 12.40 volts 12.00 volts 11.80 volts
Cranking Possible Yes Yes Probably Yes Probably No No

Note: these are average values since some batteries may have slightly different values, depending on the type (Calcium Enhanced AGM, Enhanced Flooded, and similar). Gel-cell batteries have voltages between Flooded and AGM, but this is also model dependent - check the documentation that came with the battery for exact voltages, although they are not always provided.

But, if the battery reads above 12.7V while the motorcycle is Off completely, the battery is (almost) fully charged and ready to go.

If the battery reads ~12.3V, there is a good chance that the newish battery will be able to crank the engine, but...

In order to prolong the lifetime of the lead-acid batteries, it is recommended to keep them charged in the 80-100% SOC range.

Lithium Battery Voltages

Most motorcycle lithium batteries feature a nominal voltage of 12.8V.

Since lithium batteries feature BMS that monitors the battery voltage/charge, if the voltage drops below a certain level, the BMS disconnects the battery in order to protect it from the over-discharge condition.

The actual cutoff voltage depends on the battery model and must be found in the battery's documentation - it usually ranges between 10.0-11.5 volts.

Lithium Battery Reset Button

Some lithium motorcycle batteries come with a reset button - when the actual voltage drops below a certain level, BMS cutoffs the battery.

However, the battery still holds enough charge for one or a few possible cranking attempts - the user has to press the reset button, after which BMS connects the battery for one (or more) final cranking attempts.

And when the engine starts, the motorcycle alternator, in combination with the charge controller, recharges the battery.

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Battery Voltages With The Engine On

When the engine is On but idle, the charging current is low, if any. To verify that everything is alright with the charging system, rev up the engine to 2000+ RPM and check the voltage.

If the voltage is between 13.5 and 14.5 volts, the battery is being properly charged.

If the cranking was slow and lazy, and the voltage is nonetheless in the 14+ volts range (at 2000+ RPM), that means that the charging system is able to increase the voltage, but the battery is not able to accept charge well.

If the battery successfully started the engine, but the voltage is around or slightly below 12.5V even when the engine is at 2000+ RPM, the motorcycle's charging system is not working as it should.

How To Charge The Motorcycle Battery

If the motorcycle battery is discharged, for various reasons, it may be recharged by riding a bike for at least 60-120 minutes or by using an advanced battery charger.

Such battery chargers analyze the battery first and only then charge it according to its condition.

Lead-acid batteries should be charged with currents in the 0.10-0.15C range, while lithium batteries can be recharged using stronger currents, usually around 0.5C.

This means that most lead-acid motorcycle batteries can be recharged using 1-3 Amps smart lead-acid battery chargers, while lithium motorcycle batteries can be recharged using 3-10 Amps smart lithium battery chargers.

Long Story Short: By monitoring the voltage of the motorcycle battery, one can tell the condition of the battery and the condition of the motorcycle charging system.

A good AGM motorcycle battery can easily last 2-4 years, while a good lithium motorcycle battery can last around 5-7 years.

The biggest killers of properly maintained motorcycle batteries are extreme temperatures and mechanical impacts and vibrations.

So, park the motorcycle in the garage during winter and summer and ride safely ...