Lead-acid batteries: choice of the technology

Car batteries

Notice that though often used in small solar installations in holiday's houses or developing countries, the car batteries (often called "starting" batteries), are not best suited for a solar installation running conditions. Designed for staying charged most of the time, and to produce a big starting current, they are not able to be cycled (some hundreds of cycles), have an important self-discharge, and their lifetime is limited to about 4-5 years. Their use is only economically justified in low-use installations (holiday houses or caravans).

Solar batteries

For more professional uses, the special solar batteries (with grids or tubular, open or sealed without maintenance), are more expensive at buying time. But due to their lifetime the real stored energy cost is often lower. You should consider the real cost of a battery as a function of the total energy you will store in this battery along its life (price of the kWh = price of the battery / total energy stored).

In warm countries, where the overcharging and evaporation risks are important, the open batteries may be preferred to the sealed maintenance free models, so that the user can always complete the electrolyte by distilled water. However if the maintenance staff is not very competent, sealed batteries without maintenance should be used (with precautions concerning the overcharging).

Another key point is that the (big) batteries are often delivered without electrolyte, so that they should be filled with the acid on site. This requires some expertise and represents a danger. In some countries of for some transporters, the acid itself is considered as a dangerous good, which requires specific precautions, regulations, custom taxes, etc.

Market evolution

Due to the evolution of the technology and prices of Li-Ion batteries, the Lead-acid batteries are less and less used.

Remember that their lifetime is very sensitive to the temperature: it is commonly accepted that above 25°C, the lifetime diminishes by a factor of two every 10°C increase. In hot conditions like in subtropical climates, this may be catastrophic.

Industrial and grid-connected systems don't use lead-acid batteries. They are always based on the Li-Ion technology.