Trickle charging is a method of charging a fully charged battery at a rate equal to its self-discharge rate, which allows the battery to remain at its fully charged level. This method is used almost exclusively when the battery is not loaded, as trickle charging will not keep a battery charged if current is being drawn by a load. Trickle charging is used to maintain the batterys charge level over a long period of time, and it is often used for vehicles that are not used all the time or are stored away for the winter or summer.

Trickle charging is different from regular charging in that it delivers a very low voltage, which means that the battery will be charged slowly over a period of time. A trickle charger removes the need to recharge periodically, as it feeds a constant low charge to the battery without the pronounced risk of overcharging. It is important to note that a trickle charger and a maintenance charger are not the same things. A trickle charger will deliver a charge that is equal to the batterys rate of self-discharge and should be disconnected once a full charge has been established to avoid overcharging.

Trickle charging is commonly used for lead-acid batteries under no load float charging, such as in SLI batteries. In such cases, the trickle charging equals the energy expended by the lead-acid battery splitting the water in the electrolyte into hydrogen and oxygen gases. However, other battery chemistries, such as lithium-ion battery technology, cannot be safely trickle charged. In that case, supervisory circuits adjust electrical conditions during charging to match the requirements of the battery chemistry. Failure to accommodate the limitations of the chemistry and electro-chemistry of a cell, with regard to trickle charging after reaching a fully charged state, can lead to overheating and possibly to fire or explosion.

In summary, trickle charging is a method of charging a fully charged battery at a rate equal to its self-discharge rate, which allows the battery to remain at its fully charged level. It is commonly used for vehicles that are not used all the time or are stored away for the winter or summer. Trickle charging is different from regular charging in that it delivers a very low voltage, which means that the battery will be charged slowly over a period of time. It is important to note that a trickle charger and a maintenance charger are not the same things.