How to Fill the Dry Battery of your Electric Fence Energizer

One integral part of maintaining your electric fence is, of course, the maintenance of the associated battery. Before we explain how acid batteries are filled, let us briefly review the different terms of battery types.

The terms “wet battery”, “gel battery”, “dry battery” and “dry charged battery” are somewhat confusing as the classification of “dry” and “wet” is not technically correct. So-called “dry batteries” contain sulfuric acid, but it is bound in an absorbent medium and sealed. For this reason you should not try to refill it yourself.

Electric Fence Battery AKKU 12V.jpeg

This article deals with the dry charged batteries, thus refillable lead acid batteries. These are particularly suitable for electric fences, since they have a nearly unlimited shelf life prior to being filled with acid and have a very low self-discharge during use. Pre-charged batteries are also referred to as lead or wet batteries.

They should be filled with great care — as described below in the following safety notes.



Read the safety instructions before filling dry charged batteries. These are always indicated with symbols on the battery. Incorrect handling of batteries can lead to severe burns, therefore protective goggles and rubber gloves are recommended. Children should be kept away from the batteries. In each case, follow the instructions for operating the battery and the fence energizer, and do not allow anyone to smoke in the vicinity. If skin or eyes are exposed to the acid, wash it with plenty of water for a few minutes. Drink plenty of water, but do not provoke nausea. A doctor should be consulted if the eyes are affected. Acid sprays on clothing should be immediately washed out with soapy water. To avoid electrostatic sparks, antistatic cloths and insulated tools are recommended for the installation of the battery.


How to fill dry charged batteries:

  1. First, remove all caps and any plugs from the decarburization notches and place them in a clean, dry place.
  2. Use a suitable filler such as a carboy stand to fill the battery. Only use accumulator acid 1.28. Ensure that there is sufficient ventilation in the room and keep away from any ignition sources, like cigarettes or grinding tools. Never exceed the maximum filling mark!
  3. After filling the battery, wait 20 – 30 minutes and check the level once more. If the maximum mark is not yet reached, add a little more acid. If the filling level is correct, screw the plugs back in. The openings for degasification must not be closed except by suitable hoses.
  4. Check the voltage with a voltmeter suitable for 12V batteries.
  5. In case the voltage is below 12.65V, connect the battery to a suitable charger. The use of a conventional charger with automatic shutoff is NOT recommended, because the battery must be monitored during charging.
  6. The battery cannot be used until it is fully charged.


How to connect and disconnect the battery:

  • Always wear protective clothing and ensure adequate ventilation.
  • Connect the positive terminal first, then the negative terminal.
  • Switch on the charger.
  • Switch off the charger prior to disconnecting the battery; then disconnect the negative terminal first, then the positive terminal.
  • After charging, allow the battery to stand still for at least one hour and avoid any ignition sources (such as sparks) near the battery, as flammable gases are generated during charging.

Important Note: The battery contains lead and therefore must not be disposed of in household waste under any circumstances. It is considered hazardous material and must be taken to a proper reprocessing facility. There is, however,  a good argument for the use of lead-acid batteries, because lead-batteries are almost 100% recyclable. There are companies which can handle the recycling, as well as collection of the battery.

One example is „One Call Collection“, the first Europe-wide, manufacturer-independent network for the collection of lead-acid and other batteries. A disposal inquiry can be placed directly here: