Many electric fences are powered by a 12 volt battery for many quite viable reasons. They are portable and do not need a power source close by. They may also be connected to a solar panel for permanent energy removing the requirement of charging them every so often.

It is quite possible to use ANY type of 12 volt battery BUT – like everything – there are poorer and better options that may be utilised. All batteries stores energy in a chemical form and converts this into electrical energy by utilising a process where chemicals interact with each other to complete the process in to energy that may be used.

There are two principal types of 12 volt battery. A CAR battery or a LEISURE battery, both supply 12 volts but they are very different in their construction.

CAR BATTERY.

A car battery is designed to give an instance jolt of big power to start an engine followed by an immediate recharge. They are constructed by a series of positive and negative plates (originally lead oxide but now a range of alloys are being used – Lithium, Cobalt etc.) immersed in an electrolyte solution - usually sulphuric acid (H2SO4) and distilled water. The more plates that a cell contains, and therefore form a larger surface, the larger the cold start power (CCA) that the battery can deliver. The plates are thinner and perforated to offer a larger surface for the chemical reaction to supply that surge of power required when starting a car but at the cost of cyclic stability so the unit suffers when it is discharged below acceptable limits (as happens on an electric fence) and the re-charge cycles are reduced hence affecting the life of the battery. The larger the surface area of the plates the faster the chemical reaction will occur supplying a stronger surge of energy.

Early batteries had screw plugs which enabled them to be topped up with distilled water. Modern batteries are completely maintenance-free. Water does not need to be - and must not be topped up. When a car Battery stands for a length of time these thin, perforated plates are affected by  a build-up of sulphates and have a reduced effectiveness so are not conducive to periodic recharging.

LEISURE, DEEP DRAW-DOWN or DEEP CYCLE BATTERY.

All names refer to the same type of battery. Generally used in boats and caravans.

The basic construction is essentially the same except with a difference in the manner in which the plates are made. These plates are thicker and not perforated. This means that the battery is designed for a slower release of energy with a higher charge throughput – the continual charging and discharging process. Hence these batteries are also known as “Deep Draw-down batteries” These thicker plates release their energy slower because of their smaller surface area and rarely lose 'too many' electrons and will not suffer the same level of destruction via sulphate build-up. This means that a leisure battery can stand being discharged and recharged periodically. They will ultimately power your Electric Fence for a good deal longer than a car battery before needing replacing.

Everyone likes a bargain, if you can get cheap car batteries from a source then there is nothing wrong with using them.

When should a 12 volt battery be recharged?

All energisers are transformers and will convert the 12 volt input energy to 6000 volts output energy. If your battery loses 20% of its energy then your fence will lose 20% of its energy. Most energisers will continue to operate until about 9 volts when it will cut off. Battery Manufactures will recommend recharging at 11 volts. How long this will be depends on the capacity (measured in AmpHours) of the battery and the consumption of the energiser (measures in milliAmps). Divide the energiser consumption into the battery capacity will give you an approximate length of operation. (180 milliAmps consumption energiser connected to a 100 AmpHour capacity Leisure battery may last 550 hours)

The cost of batteries is directly correlated to the increasing ampHour capacity. In most cases a 60 to 80 ampHour battery is adequate.

When should an electric fence battery be recharged

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2 comments

  • Thanks for the information and the illustrations, very helpful thank you.

  • Very simple explanation of the difference. Easy to understand.

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