Demineralised Water in a Car Battery | Our Advice

If you want to prolong the life of your car battery you should top up regularly with distilled or even purer, demineralised water. Here’s why;

Most car batteries use lead-antimony plates which require regular watering to replace water lost due to electrolysis on each charging cycle. By changing the alloying element to calcium, more recent designs have lower water loss, unless overcharged.

Modern car batteries have reduced maintenance requirements, and may not provide caps for addition of water to the cells. Such batteries include extra electrolyte above the plates to allow for losses during the battery life.

If the battery has easily detachable caps then a top-up with distilled or demineralised water may be required from time to time. Prolonged overcharging or charging at excessively high voltage causes some of the water in the electrolyte to be broken up into hydrogen and oxygen gases, which escape from the cells; this is called gassing.

If the electrolyte liquid level drops too low, the plates are exposed to air, lose capacity, and are damaged. Impurities or additives in the water will reduce the life and performance of the battery.

It is for this reason that manufacturers recommend  the use of demineralized or distilled water, since even potable tap water can contain high levels of minerals.

Please see The Distilled Water Company website for more information on our demineralised water and distilled water.