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A lead acid battery will naturally self-discharge at a rate of 0.2-1.0% per day - and that's before the constant drain of an alarm, immobiliser or other accessory.
For the longest effective working life, a battery should be kept at full or near full charge capacity. This can be obtained with the use of an intelligent charger.
A trickle charger (or smart charger) is so called because once the battery is detected as fully charged, it will reduce the power (to a 'trickle' ) to recover a battery's self-discharge without allowing it to overcharge.
Conventional lead-acid batteries are constructed of a number of lead plates submerged in the electrolyte. Motorcycle and scooter batteries are capable of a large power-to-weight ratio compared to other types of battery, by utilizing a large number of thin lead plates, maximising the surface area for electrolysis. The downside is that these plates are fragile and easily damaged by deep discharge.
Automotive lead-acid batteries are not designed to be deeply discharged, as in most circumstances they will be kept in full or near full charge by the charging system on the bike or scooter.
Deep cycling is when the battery is nearly or fully discharged. The repeated charging and discharging causes additional mechanical stress to the thin lead plates, which can substantially reduce the life of a battery.
On vehicles with an alarm or immobiliser, the battery can reach deep discharge within a few days.
It is particularly important to keep a battery on a trickle charger if it is connected to accessories that continuously drain power from the battery.
Sulphation build up can occur when the charge descends below 75% of full capacity. Sulphur molecules from the electrolyte (acid) react with the lead plates, forming lead sulphate. This both weakens the acid and prevents current from flowing effectively between the plates.
When recently formed, lead sulphate is soft and can be separated into lead and acid again by the regular charging process. However, if not immediately recharged, the lead sulphate will form crystals that cannot be dissolved by a standard charge.
Depending on the state of this desulphation, a battery may be recovered by an intelligent charger with a desulphation cycle.
Equalisation serves two purposes:
Cell Balancing: Lead-acid batteries contain a number of cells. Due to the tolerances used in the manufacture of lead-acid batteries, in addition to exterior factors such as uneven temperature, some cells may hold a different amount of charge to another in the same battery. This can result in some cells being overcharged while the rest of the cells are still charging.
By keeping the cells balanced, the failure of individual cells (which requires replacement of the entire battery) can be minimised.
Preventing Electrolyte Stratification: If a battery is undercharged (for example, by a failing alternator) or not used for a long period of time, it is possible for the acid and water in the electrolyte to separate. This can significantly reduce the battery performance.
See our Battery Care Guide and Battery Installation Guide for more information about the care of different types of lead acid battery.
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