HOW TO TROUBLESHOOT YOUR MOTORCYCLE BATTERY

A motorcycle battery is a key component in your charging system. It is important to monitor the condition of your battery and charging system to ensure you don’t have any issues down the road. Being able to identify whether the issue is with your battery or another component in the system is key to getting to the root of the problem quickly and efficiently.

TESTING THE BATTERY VOLTAGE

Measuring Static Voltage

Before measuring the voltage of the battery, ensure it is fully charged. Using a multimeter set to 20v DC, check the voltage of your battery. With the engine off, touch the negative probe to the negative terminal of the battery and the positive probe to the positive terminal . Anything above 12.4v should be enough to start your bike. The ideal range for a battery is 12.6-14.4 volts. Anything below 12 volts is likely to be beyond saving.

If your voltage measures around 10 volts, there is an issue with one of the cells of the battery. Modern motorcycle batteries consist of 6 cells, each with a voltage of around 2.1 volts (2.1 x 6 = 12.6v). If your reading shows 10 volts, it is a clear indicator that one of the cells is damaged. This can happen due to vibration over time, or overcharging amongst other things. If this is the case you’ll need a new battery.

Running Voltage

Take the same measurement once you have started your bike. If the charging system is working properly, you should read at least 13.8 volts, with a maximum of around 15 volts – any lower than 13.8 will point to potential issues with the charging system. It is worth referring to a workshop manual for your bike to confirm the acceptable voltage range given by the manufacturer.

If you get a reading over 15 volts with your engine running, your reg/rec is likely faulty. Equally, a swollen battery is a big indicator that your reg/rec isn’t regulating the amount of voltage it’s sending to your battery.

Causes of Low Voltage When Running

If your battery reading is below 13.8 volts, there might be a break in the system somewhere, a poor ground connection, a blown fuse, or your alternator or reg/rec are not working. It is worth checking all connections are secure before any further troubleshooting. A loose connection can cause chaos. It is worth noting, even if you find one element of the system that isn’t working, check everything. You might be incredibly unlucky and have a bad stator, reg/rec and battery all at once…

If your readings are outside of any of the given values, you’ll need to do some further digging.

WHAT TYPES OF MOTORCYCLE BATTERY ARE THERE?

Here is an outline of the types of motorcycle battery available on the market.

Lead Acid

This is the most basic type of battery. You need to fill these with electrolyte (acid) before use and can only be mounted in one orientation – upright. On the plus side, they are the cheapest you can buy. On the downside, you need to keep an eye on the electrolyte level to make sure it doesn’t drop below the minimum level. This type of battery isn’t really widely available these days. Due to government laws around battery acid, it is no longer possible to purchase these along with a separate acid bottle. They are also the most susceptible to vibration and tend not to last as long as the other available options.

Common use: vintage motorcycles and scooters

VRLA (Valve Regulated Lead Acid)

Valve regulated batteries are also known as sealed batteries. The general construction is similar to a standard lead acid battery, except that it features an internal valve system to manage gas venting. The battery is completely sealed. The discharge rate of lead acid batteries is higher than gel or AGM due to the construction of the plates. They are more susceptible to vibration damage than gel or AGM batteries and can only be mounted upright. 

Common use: Most motorcycles and scooters

Gel

Similar in construction to a lead acid battery, they have had silica added to the acid in order to form a gel. They are more stable than lead acid (as there isn’t acid sloshing about inside) and are also fairly cheap. They are fairly resistant to vibration. You can mount these on their side.

Common use: Most motorcycles and scooters

AGM (Absorbed Glass Mat)

AGM batteries tend to be the best all round option for most motorcycles. The acid is absorbed into glass fibre which is wrapped around the terminals of the battery. This results in a battery that tends to have higher cranking amps and is less susceptible to vibration and discharge. They tend to be more expensive than gel or lead acid, and heavier too. You can mount these on their side.

Common use: Adventure bikes and large capacity motorcycles

Lithium

Generally the most expensive option, lithium batteries are also the lightest, most powerful and the most resistant to discharge. If left for an extended period of time, they might need to ‘wake up’ first by turning your lights on for a minute before starting. You can mount these in any orientation. The downside is that they require a dedicated lithium charger and are expensive to buy.

Common use: Racing/track bikes

THE BATTERY CHARGING/DISCHARGING CYCLE

Understanding the basics of how a battery works can help you to understand the issues you may experience with it. This video does a good job of explaining how it works.

A battery is constructed of cells featuring a positive lead dioxide (PbO2) plate and a negative sponge lead (Pb) plate, separated by dividers and submerged in electrolyte. The electrolyte is a sulfuric acid solution.

Discharge Cycle

When the battery discharges, sulfate from the sulfuric acid combines with lead on the negative plate to create lead sulfate and simultaneously releases two electrons. These electrons are transported to the cathode around the electrical circuit, being used in the system for the various components that need power. The sulfate also combines with the lead oxide on the anode, which in turn produces water in the electrolyte. This weakens the solution.

Charge Cycle

Charging the battery reverses this process. The power generated by the alternator supplies new electrons to the anode (negative terminal), which combine with the lead sulfate particles, releasing the sulfate back into the electrolyte, once again strengthening the acid solution.

You can see that if a battery is left to discharge, you’ll end up with a layer of lead sulfate on the plates and watered down electrolyte. Without the charging process to reverse this, your battery can become permanently damaged. The longer it is left, the worse it will get – hence why batteries tend to die over winter if uncared for. If you have a low voltage reading on a battery after it has been fully charged, odds are that it is sulfated. The quickest and easiest solution to this would be replacing the battery.

MOUNTING A BATTERY

You might find when you buy a battery that the terminals are in a different orientation to your original. If you have an AGM, lithium or gel battery, you can mount your battery on it’s side in order to fit the terminals correctly. If you look at the diagram below, you can see how one of these batteries can be mounted differently in order to change the orientation of the terminals. When purchasing a battery, it is worth paying attention to the terminal layout – this will make up part of the battery code.

CONCLUSION

Hopefully that clarifies some of the issues you may experience with your battery and gives you an idea of the next type of battery you might want to get for your bike.