First of all, what is a leisure battery!


There are two main types of lead acid battery:-

1. Standard car battery

2. Leisure battery for marine, caravan or such things as solar power

Although it is not impossible to use either battery in any of the above situations, the leisure battery has been designed to supply power over a long period of time, whereas the standard car battery is designed to produce a high power over a very short time.

The leisure battery also has the greater ability to constantly discharge and recharge compared to the standard car battery. This is known as deep cycling, although the battery shapes are similar they should not be interchanged on a permanent basis.


Battery Construction

The two battery types are similar in construction, they mainly have six cells filled with sulphuric acid which is topped up with distilled water. The main construction material is Polypropylene for the casing. The cells each have a set of lead plates and during the recharging and discharging process each plate expands and contracts. Unlike the car battery has good cell separation which helps contain the active materials and prolongs the battery life.

Sulphuric acid fills the voids in each of the cells and is used as a conductor between the cell plates. As the cells discharge the density of the acid decreases reducing the ability of the plates to produce electricity. Obviously the recharging process reverses the condition.


Battery Life

The predicted life of a battery very much depends on it's use, by regularly inspecting for electrolyte levels (top up with distilled water if not a maintenance free type) and state of charge. It is also worth cleaning the battery around the terminals and ensuring that the area is grease free, clean any white deposits from the terminals with warm water and coat the terminals with a petroleum jelly such as Vaseline or a better product specifically for the purpose. ALWAYS WEAR PROTECTIVE CLOTHING - BATTERIES CONTAIN ACID AND ANY SPILLAGE WILL DAMAGE YOUR CLOTHES AND BURN YOUR SKIN. Never totally discharge a battery as it is unlikely you will be able to recharge it back to it's original state. In practice it is best not to let the battery discharge to less than 85% of it's capacity. Using a direct current voltmeter check the state of charge. 12.7 volts or above indicates a fully charged 12v battery, 12.3 volts means it is approximately half charged and anything less than 11 volts means it is very flat and may not ever recover. There is much talk about and dispute about this minimum voltage, of course it can vary from battery to battery. You can chat on this subject in the Solar Chat Plus Forum http://groups.google.co.uk/group/solar-plus .

Another way of checking the battery condition is to test the electrolyte in the cells using a hydrometer. A reading of less than 1.1 indicates a discharged battery, at 1.28 the battery is fully charged. During a long lay up period store the battery in a dry place (not on the garage concrete floor) but on a strong suitable bench and charge up at least once a month.


Safety and Care Check List

Avoid naked lights or electric sparks when inspecting or topping up

Remove the negative terminal first

Ensure the battery is securely fixed

Use gloves, protective clothing and goggles when cleaning and topping up

Never smoke near a battery or when maintaining

Turn off battery charger and disconnect mains electricity before moving battery

Always use proper clamping clips on battery terminals

Ensure battery venting is clear and properly positioned if a pipe is supplied


A Rough Guide To Battery power

Calculations are based upon amount used per day, therefore for example purposes only, a 75Ah battery would last for approximately four days and be fully discharged, you should never run down a battery like this. It is inadvisable to take a battery below 11.6 volts as it can cause permanent damage to the cells and may never recover properly. With the above example, adding a solar panel and regulator could maintain a charge on the battery covering any daily usage. See also Battery Care and Solar Panels for further examples and charging.

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