Newsletter Archive

Filling Batteries

Maintaining Electrolyte Levels in Batteries with a Battery Filler

It is important to check the electrolyte level in your batteries on a monthly basis (assuming your regulator is working correctly). The electrolyte level gradually becomes lower due to the electrolysis of the water into oxygen and hydrogen. This is a normal and necessary process in charging a lead acid battery.

The lead plates inside the battery must always be kept below the level of the electrolyte, otherwise the battery will be irreparably damaged. Many batteries have some sort of indicators for the minimum and maximum electrolyte levels. Generally this will be 1 to 2 centimetres over the plates. Do not overfill your battery or the electrolyte may splatter out when charging.

Be aware that when approaching full charge, the volume of the electrolyte will expand due to little bubbles of gas (hydrogen and oxygen) moving to the surface throughout the electrolyte (some get trapped under and between the plates. Speaking of gas, this is a very explosive mixture if ignited by a spark or flame. Never smoke near a battery or use a match to help you see inside the battery! Turn on any torch some distance away from the battery vents, in case the switching action creates a spark.

You should also be aware that the water, which you add, will tend to initially float on the surface of the heavier electrolyte (sulphuric acid). This will give you a pessimistic reading on your hydrometer. It is suggested that you top up your batteries when they are being charged, as the bubbling action will help stir up and mix the electrolyte.

We strongly recommend that you only use distilled or demineralised water, which is sold in automotive and department stores. Do NOT use bottled drinking water, tap water, tank water or water from a creek or river or lake, or collected off a tin roof.

The electrolyte is a strong acid and it is recommended that you wear goggles while you top up the battery. If you do get acid on you, wash it off immediately with large amounts of fresh water for several minutes.

Demineralised water is usually sold in 4-5 litre plastic containers. Pouring it into the battery from the container can be an awkward task - it is easy to get acid splashing up, or to miss the hole and wash contamination on the outside surface of the battery into the acid reservoir. This can easily contaminate your battery causing severe damage.

We now sell a very useful and economical battery filler. This is like a large hydrometer allowing you to suck up some demineralised water and then to safely insert it in your battery.

A few minutes of attention to your battery each month can greatly prolong its life.

For a picture of the battery filler see the Battery Accessory section.