Data Sheet

#33 A guide to leisure batteries

#33 #33 A guide to leisure batteries

Leisure battery construction and care

Whether you camp on a Club site with full electric hook-up or attend rallies with no mains electric supply a battery in your unit is an essential addition. This data sheet explains the construction and provides some guidance to buying and maintaining a leisure battery to enable a stress free holiday. Get free help and advice when you join the Club.

Not all leisure batteries are made equal

Not all leisure batteries are made equal

The 12V equipment in a caravan or motorhome relies on a leisure battery. This important item is not normally supplied with a new caravan whereas most new motorhomes have one as standard. Batteries that are designed to start a vehicle are made differently from batteries specifically intended to run caravanning appliances. This is because their operating requirements are different. For instance a vehicle battery has to provide a high current surge to start an engine, but once that has been achieved, a vehicle’s alternator immediately replenishes the power it provided.

In contrast, a leisure battery has to provide a steady flow of current over a prolonged period and seldom gets replenished until the user recognises that its voltage level has substantially fallen. That’s when a re-charge is duly provided. If left long in a discharged state, a battery will generally not regain its former condition. Furthermore, manufacturers often recommend that re-charging is commenced when a battery drops to 50 per cent of its full condition.

To achieve the required performance, a leisure battery should be constructed in a way that copes better with a life of repeated significant discharging followed by re-charging. This is referred to as ‘deep cycling’ and other products that perform in this manner include ‘semi-traction’ and ‘traction batteries’, these are used on golf buggies, disability wheelchairs, and several types of warehouse vehicles. There's also 'uninteruptable power supplies' (UPS) batteries, capable of very deep cycling and withstanding a continuous charge too, these are found supporting servers, security systems and emergency medical facilities.

This Data Sheet focuses on lead-acid batteries which are manufactured for particular tasks but in recent years we've seen an increase in the availability of lithium batteries so they're now worth a mention. They also get classified using various names.

Types of conventional lead-acid batteries:

  • Standard starter batteries (sometimes referred to as calcium batteries, cranking batteries, lead-acid batteries, wet batteries).
  • Standard leisure batteries (also referred to as auxiliary batteries, deep-cycling batteries, lead-acid batteries, wet batteries).
  • Semi traction and traction batteries (also referred to as deep cycling batteries, lead-acid batteries, wet batteries).

Products made differently such as gel, lead-crystal, lithium and AGM batteries are mentioned later in this Data Sheet.

Battery versatility

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To resist distortion from repeated deep cycling, leisure battery lead oxide paste grids need to be sturdy.

Not surprisingly, batteries are made to be ‘job specific’. For instance, a conventional car battery seldom lasts long when asked to provide a 12V supply in a caravan or motorhome. This is partly because its lead plates are thinner and its separators (described later) are different, too.

In consequence, it cannot cope with repeated heavy discharge and recharge cycles. Conversely, a standard ‘wet’ leisure battery doesn’t perform well as a starter battery either.

So bear in mind that conventional lead-acid batteries are not able to perform both starting functions and accessory supply functions with equal effectiveness. However, products called AGM batteries, described later, are better at performing both operations.

Leisure batteries’ two-fold tasks

Although a key function of a leisure battery is to run 12V appliances, it also performs a second important function. Bearing in mind that it is permanently linked to a caravan or motorhome’s built-in charger, a leisure battery is also able to smooth out any irregularities in the supply received from this device.

This is why a caravan’s 12V accessories should not be run directly from a charger – i.e. without a battery installed in the supply system.