Data Sheet

#36 Charging a leisure battery

#36 #36 Charging a leisure battery

Charging a Leisure Battery

The service life of a leisure battery depends on how frequently it is discharged, how deeply it is discharged and how soon it is recharged. A battery kept in a good state of charge will last much longer than one left standing for weeks or months on end with a low state of charge. 

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Good connections are important to maximise current flow and allow the charger to sense the battery

The chargers generally fitted in caravans and motorhomes are not really battery chargers but power supplies designed to run the 12V equipment on board. As such they are not ideal for fully charging a leisure battery although the so called ‘intelligent chargers’ introduced in the last few years are much better in this respect.

Removing your leisure battery and periodically and charging it with a good leisure-battery charger will help keep it in tip top condition. The important thing with any rechargeable battery is to know when to recharge it, how fast to do so and for how long.

Most leisure batteries use lead acid technology very similar to that used for car batteries. In time we may see the emergence of lithium-based batteries for this role but they are beyond the scope of this Data Sheet.

It is also worth noting that lead acid batteries discharge through internal leakage, even when no load is applied. Some types are more resistant than others to this phenomenon but, as a rule of thumb, batteries in storage and not in circuit should be charged every three months or so.

A lead acid battery will not perform well if it is completely discharged. Indeed to do this is likely to result in irreversible damage in the form of reduced capacity and in the battery’s ability to hold on to a charge. Some types of lead acid battery (notably gel types) stand up better than others to this type of treatment but, as a rule of thumb, 50 per cent should be seen as the maximum level of discharge before recharging. In practice this means when the battery voltage level has fallen to about 12.4V as measured at the terminals with no load applied.

Sulphation

As a lead acid battery discharges lead sulphate forms on the plates. If a long time (i.e. many weeks or months) elapses before recharging the lead sulphate can begin to crystallise. This is bad news as it is difficult to reverse and can lead to a permanent reduction in the capacity of the battery. The effect is known as sulphation.

Leisure batteries are designed to provide low currents for long periods of time and then to be recharged relatively slowly. This is the opposite of a car battery which has to provide a very high current to start the car and then is very quickly recharged by the car’s alternator.