Installation, Testing and Maintenance

Installation, Testing and Maintenance of Motorcycle and Powersport Batteries

Battery Installation

In most applications, batteries should be installed in an upright position. If there is any question regarding a particular vehicle/battery/installation please contact us for our specific recommendations before installation.

Points to note

• The Yuasa Online battery Finder or Motorcycle & Powersport Battery Applications and Specifications Guide are the best sources for battery applications information
• When replacing a battery that uses an original equipment sensor, always replace the sensor
• Conventional and YuMicron batteries should never be installed in any position other than upright as their liquid electrolyte will leak from the battery case causing damage to the vehicle
• For any position other than upright (off the shelf orientation) a “non-spillable” “Factory Activated” battery is recommended

Inspecting a Battery

Battery testing should begin with an inspection of the battery using the following steps:

1. Make sure the battery case is clean and dry. Grime on top of the case can provide a path for current to flow, causing the battery to discharge. Use a soft brush and water and soap or a solution of baking soda and water to clean the battery case or terminals. On a Conventional battery, make sure filler cap plugs are finger tight.
2. Inspect battery terminals, screws, clamps and cables for problems including: breakage, corrosion or loose connections. Clean the terminals and clamps with a wire brush. Once battery cables are installed, dielectric grease (available at most motor factors) can be applied to the terminals to prevent oxygen from causing corrosion.
3. Inspect the battery case for obvious damage such as cracks or leaks; look for discoloration, warping or a raised battery case top, which may indicate that battery has overheated or been overcharged.
4. If equipped, check the battery vent tube. Make sure it’s not kinked, pinched or otherwise obstructed. It should exit away from the drive chain and from below the swing arm. Small cuts in the tube near the battery vent are OK; they form an emergency escape for trapped gas in case the vent tube becomes obstructed.

Battery Testing


Because Conventional batteries have filler caps their state of-charge can be checked using a hydrometer by measuring specific gravity. If after charging, the battery’s specific gravity does not increase to indicate a full charge, the battery should be replaced. A hydrometer measures the ratio of sulphuric acid to water, or the specific gravity (SG) of the electrolyte. The SG for pure water is 1.000 and sulphuric acid has an SG of 1.835. Combined, their SG is between 1.265-1.280. In general, an SG reading between 1.265-1.280 indicates a fully charged battery. A reading of 1.230 to 1.260 indicates the battery should be charged before testing. Ideally, readings should be taken at 25°C.


Unlike Conventional batteries, AGM types cannot be tested using a hydrometer because they are sealed. Instead a voltmeter can be used to perform an open circuit voltage test. The test can be used for both Conventional and AGM batteries. The test is used to determine the following: battery state-of charge, ability to hold a charge and shorted or open battery cells. Before performing an open circuit voltage test the battery must be fully charged.

Charging a battery using the vehicle’s charging system or a battery charger creates a “surface” charge across the battery’s cells. The surface charge needs to be removed before an accurate test can be performed. To remove surface charge, turn on the ignition for about three minutes then turn it off. Let the battery sit for about 10 minutes before completing a test.

Open circuit Voltage indicates what percent of charge the battery has reached after charging. Open circuit voltage for a fully, 100% charged AGM battery is 12.8 to 13.0 Volts. AGM batteries that are 75% to 100% charged will measure 12.5 to 12.8 volts. Conventional batteries have slightly lower open circuit Voltages: 12.6 volts (12.8 volts with Sulfate Stop) for 100% charge and 12.4 for 75% charge.

If after charging the open circuit voltage indicates that the battery is less than 75% charged, the battery is probably no good and should be replaced. Before the battery is condemned, try charging it again. If the battery is still not close to 100% charged it needs to be replaced. The open circuit voltage test is not conclusive. It is possible to have a 100% charged battery as indicated by the open circuit voltage test that will not start a powersport vehicle reliably. In such cases a load tester is recommended.

Digital Conductance Tester

Due to the increasing number of sealed maintenance free batteries in the market place, acid specific gravity (SG) readings cannot always be taken, therefore a test with a digital conductance tester is recommended.

Find out more about the MDX 117

Charging System Quick Check

A quick check of a powersport vehicle’s charging system can be performed using a digital voltmeter. Connect the voltmeter leads directly to the battery (red to positive and black to the negative terminals). Read the open circuit voltage and start the engine. Operate the engine between 3000 to 4000 rpm while watching the reading on the voltmeter. If the vehicle’s charging system maintains voltage between 13.0 and 14.5 volts, the charging system is probably working properly. If the voltage is the same as thr open circuit voltage (usually less than 13 volts) the charging system is not working and further diagnosis will have to be performed.

Battery Maintenance

AGM Batteries. AGM batteries do not have to be checked as often as Conventional batteries—about every three months, or three months from the date of battery activation at the factory if stored at room temperature. Higher storage temperatures cause faster self-discharge and require that batteries be checked more often. The battery will last longer if it is 100% charged most of the time. The single most important aspect to maintaining an AGM battery is to not let it sit discharged for long periods of time—keep it fully charged for peak performance.

Conventional Batteries. Conventional batteries should be checked for state of-charge about once per month if not used on a regular basis. Recharging may be required if the vehicle is not used for more than two weeks or if the starter turns slower than usual when starting the engine. A Conventional battery requires the periodic addition of distilled water when the electrolyte level becomes low. Water loss is normal in these batteries through the process of electrolysis and evaporation. Low electrolyte levels that expose the lead plates to the air will result in permanent damage to the battery.

Battery Storage

If the vehicle is in storage or used infrequently, disconnect the battery cable to eliminate current drain from electrical equipment. Check the battery every month (for Conventional types) and every three months for AGM batteries. If open circuit voltage indicates a low state-of-charge, charge the battery. Temperatures below 15°C or above 25°C may require more frequent inspections and/or charging.

Sulphation and Freezing

Sulphation and freezing are the most common causes of damage to batteries. These are not a problem if the battery is properly charged, and if the water level is maintained (Conventional types). Battery sulphation takes place due to continuous discharging or low electrolyte levels.

When a battery discharges the chemical reaction between the sulphuric acid in the electrolyte solution and the plate active material results in the production of lead sulphate. This is actually a crystal which grows larger when the discharge is continuous and uninterrupted. In a Conventional battery, low electrolyte levels expose the cell plates to air causing the lead material to oxidise and form sulphates. In either case it doesn’t take long before the battery won’t hold a charge. Low electrolyte levels cause another problem because the acid in the electrolyte becomes more concentrated, causing the active material to corrode and fall to the bottom of the battery case. If this condition takes place over a long enough time period the process will in an internal short circuit and battery failure.

Freezing is not a problem with a fully charged battery. However if the battery becomes discharged (and the acid in the electrolyte turns into mostly water) the electrolyte will freeze.

Freezing can cause a condition called “mossing” which is indicated by small red lines on the battery plates. Freezing can also crack the battery case and buckle the plates permanently damaging the battery.

For added protection, YUASA’s YuMicron and AGM batteries are treated with a special chemical formula called “Sulphate Stop.” This dramatically reduces sulphate crystal build-up on cell plates resulting in longer battery life.