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SA4x4 Clinic got a technical query

Trickle Charging


Qusetion by: Obie Oberholzer Answer by: Chris SmithI’d like to know if one needs to keep a deep-cycle battery on continuous charge (trickle charge), or can one charge it every two to three months? I only use the battery once or twice a year when on holiday – the rest of the time it’s left in storage.
Obie Oberholzer

Fundamentally, a deep-cycle battery is chemically no different to a cranking battery; they both work on the principle of lead and sulphuric acid reacting with one another.
That said, the danger of continuous trickle charging occurs when the battery’s voltage – electrical pressure – is raised to an equal voltage to that of the charger, at which point the current ceases to flow between the two. When this takes place the convection effect of the charging ceases and the battery becomes stagnant, causing the denser acid to settle within the water.
Once this happens, the localised acid is at a high concentration level so it eats at the lead plate – causing crystallisation – while the diluted water damages the lead plate at the top / surface.
For these reasons, trickle charging isn’t recommended. The easiest way to manage an unused battery is to employ an automatic charger, capable of turning itself on and off, and sensing the battery’s voltage.
If a manual charger is used, one needs to mimic an automatic charger by switching the charger off and on to allow the battery voltage to drop and then climb back up again. This can be done every few days or so.
How long the charger should be switched off and on for will depend on the charger’s capabilities, the condition of the battery and the environment in which the battery is stored.
Lastly, remember the general rules of battery storage: it must be kept clean, warm and dry.

Chris Smith
Batman Batteries
Battery Centre Mowbray
(021) 448 7033