The Motorcycle Battery







Some common facts concerning batteries.

Cell Numbers:

12 volt models have 6 cells generating approximately 2.14 volts per cell. 6 volt batteries have half that amount.

Battery Type: Wet Standard

Removable caps. Prone to leak/spill acid. High maintenance. If treated well mayhave a life expectancy of 5-8 years.

Battery Type: Wet (Maintenance Free)

Caps sealed with built in obsolescence. These batteries are not completely 'sealed' as they need to let small amounts of gas escape if charged. If these batteries have too many charges they can loose too much of their acid/water mix and fail prematurely.

Note: Both Standard and Maintenance Free Types suffer from Plate build up when old. Conductive residue (from the + plate) falls to the bottom of the battery, and eventually shorts out the plates at the base. This can cause catastrophic failure with strong aroma of sulphur, killing batteries instantly. Batteries can be washed out (with care) but generally this will only extend the life by 1 year approx. if the positive plates are still intact.
If treated well mayhave a life expectancy of 5 years.

Battery Type: Gel (Maintenance Free)

Non spillage. Low maintenance (ideal for Motorcycles). Acid is 'gelled' with Silica Gel. Some Gel batteries have windows through which the state or colour of the Gel can be inspected. This should be Phosphorus Green (in the example we viewed.) Typically may last 5 years +.

Battery Type: AGM (Absorbed Glass Mat) (Maintenance Free)

These new batteries have the advantage of very slow discharge (1% to 3% a month.) Most AGM batteries are "recombinant" combining Oxygen and Hydrogen inside so as to prevent water/acid loss through electrolysis. These batteries are 2-3x more expensive.
Filled with an extremely fine fibre of Boron Silicate glass mat which is 95% soaked in Sulfuric acid, these batteries are as safe as the Gel filled equivalent but can be charged far more vigorously as the internal mat is far more stable. (See Charging Batteries below).

Charging Batteries:

Normally charge 12 volt battery at 13.8 volts. 6 volt battery at 6.9 volts.

Fast charge (not Gel Filled) 12 volt battery at 14.4 volts. 6 volt battery at 7.2 volts.
(Note: Fast charge a Gel battery and you run the risk of bubbling the Gel to the point where the spaces created limits the performance leading to failure.)

On Completion of Charging:

When fully charged, current will fall to .5-1 Amp approx for 12 volt battery depending on age. 6 volt batteries from .25-.5

Dangers of Charging:

Generally speaking, battery plates are liable to buckle if overcharged or discharged quickly. Rapid charge or discharge will heat the plates to the point where they buckle and short out.

Always be aware that charging causes batteries to give off explosive hydrogen gas! Do your charging in a well ventilated area.


Concerning acid build up on +Ve terminal. A negatively charged chassis is less likely deteriorate over a positively charged one. The build up seen on + ve battery terminals will appear throughout positively charged chassis.

Construction: Terminals are usually Lead. Plate material is usually Zinc and Copper. Originally the plates were Lead, hence the name 'Lead Acid'. At this time the batteries were also known as 'Accumulators.' Newer batteries, such as AGM, use Lead and Calcium for increased life. These advanced materials mean that modern batteries have a slightly better Power to Weigh Ratio.

The cranking current of a Diesel Engine is higher due to the increased compression. On start up, Petrol engines draw current for the ignition whereas Diesels may need to power glow plugs. Modern Direct Injection (DI) Diesels do not use glow plugs but need to generate higher pressures for the (common rail) fuel Injection system.

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