The really useful magazine - now part of Motor Cycle Monthly

Battery Care

MAINTENANCE-FREE BATTERY

With this type of battery the only regular maintenance requirement is to check that the battery terminals are clean and tight.

To assess the state of charge, measure the voltage across the battery terminals. This can be done with the battery on the bike as shown, but with the ignition off. Use a multimeter set to the DC volts range and connect its positive probe to the battery positive (+) terminal, and the negative (–) probe to the battery negative (–) terminal (see illustration 1). When fully charged there should be around 13 volts present. If the voltage falls below 12.3 volts, remove the battery and recharge it as described below.

If the machine is not in regular use the clock and alarm, and on-board electronics on some bikes, will very gradually discharge the battery. Check battery condition every four weeks and recharge if necessary. A trickle charger can be connected to the battery to maintain its condition and state of charge, or alternatively, disconnect the battery and charge it from an external source as described below.

Make sure the ignition is switched OFF before you disconnect the battery. Unscrew the negative (–) terminal bolt and disconnect the lead from the battery, then lift up the insulating cover to access the positive (+) terminal bolt and disconnect the lead
(see illustration 2).

Free the battery retainer; the battery will be held in its box by a rubber strap or metal bracket, then lift out the battery – noting which way round it is installed – it will be quite heavy (see illustrations 3 and 4).

Before installing the battery, ensure that its terminals and the lead ends are clean; use emery paper to clean up the lead ends. Install the battery so that the positive (+) and negative (–) terminals align with the appropriate leads, then fit the retainer bracket or rubber strap.

Reconnect the leads, connecting the positive (+) terminal first. Note that you can spray battery terminal grease or smear petroleum jelly (Vaseline) over the terminals after the leads have been connected. This will prevent a build up of corrosion occurring. DO NOT use a mineral based grease.

STANDARD BATTERY (with filler caps)

Standard batteries require a little more attention than MF batteries. In addition to periodic checks of the terminal condition as described above for MF types, you’ll need to check the fluid (electrolyte) level and top up if necessary.

The electrolyte level is visible through the translucent battery case – with the bike upright it should be between the UPPER and LOWER level marks (see illustration 5).

If the level is low in any cell it will require topping up with deionised water – don’t use tap water for this.

Make sure the ignition is switched OFF. Unscrew the negative (–) terminal bolt first and disconnect the lead from the battery (see illustration 6). Lift up the insulating cover to access the positive (+) terminal, then unscrew the bolt and disconnect the lead.

Pull the vent tube off its stub on the side of the battery (see illustration 7). Release the battery strap or bracket and lift or draw the battery out, noting that it is quite heavy (see illustration 8).

Remove the cell caps (they will either be a plug type which pulls out when gripped with pliers, or will unscrew). Top up any cells which are low with deionised water (see illustrations 9 and 10). Do not overfill. Fit the cell caps.

Terminal voltage is measured by connecting a voltmeter across the battery terminals as described above for the MF battery (see illustration 11).

The condition of the battery can be assessed by measuring the specific gravity of the electrolyte. To do this an hydrometer is needed. Remove the cell caps from the battery. Insert the hydrometer nozzle into each cell in turn and squeeze the hydrometer pump to draw some electrolyte from the cell. Check the reading on the float at the level of the electrolyte – it should be between 1.26 and 1.28. Charge the battery if the specific gravity is low.

Fit the battery back into its holder, pushing the vent tube back onto its stub. Retain the battery with its bracket or rubber strap.

Check the battery terminals and leads for corrosion. If corrosion is evident, clean the terminals and lead ends with emery paper, then reconnect the positive lead to the positive terminal and slip the terminal cover back into place. Reconnect the negative lead. Note that you can spray battery terminal grease or smear petroleum jelly (Vaseline) over the terminals after the leads have been connected. This will prevent a build up of corrosion occurring. DO NOT use a mineral based grease.

BATTERY CHARGING

The bike’s charging system should maintain the battery in a good state of charge. If, however, the battery frequently becomes flat through lack of use, it will need to be charged from an external source.

The battery charge rate is usually marked on the battery case. A dedicated motorcycle battery charger, or battery optimiser as they are often called, is the best choice of charger. They are suitable for 6v and 12v batteries and their complex circuitry prevents overcharging or an excessively high charge rate being applied (see illustration 12).

If a normal domestic charger is used, i.e. as sold for car battery use, check that after a possible initial peak, the charge rate falls to a safe level (see illustration 13). If the battery becomes hot during charging STOP. Further charging will cause damage to the battery.

Caution: Be extremely careful when handling or working around the battery. The electrolyte is very caustic and an explosive gas (hydrogen) is given off when the battery is charging.

BUYING A NEW BATTERY

Make sure you buy the correct battery for the bike. The battery specification on the case will determine its electrical capacity (Ah Amp hours), physical size and terminal type. It is important to get this right, not only so that it will fit, but also to suit the charging system’s output rate. If in doubt buy and fit the OE (original equipment) battery supplied by the bike manufacturer.

Bear in mind that if you buy the battery from a bike dealer, you receive it ready filled and charged, and you’ll simply have to fit it on the bike. If you buy a battery mail-order, you’ll have to fill it yourself. Beware that the sulphuric acid in battery electrolyte is very corrosive and the instructions must be followed carefully.