Lead-acid batteries: choice of the technology

Car batteries

Although commonly used in small solar installations for isolated homes or in developing countries, car batteries (often called "starting" batteries) are poorly suited to solar system operating conditions. Designed to remain charged and deliver large starting currents, they cannot withstand cycling (only a few hundred cycles), have high self-discharge rates, and their lifetime is limited to about 4-5 years. Their use is economically justified only in low-use installations such as holiday homes or caravans.

Solar batteries

For professional applications, specialized solar batteries (with grid or tubular plates, open or sealed/maintenance-free) are more expensive initially. However, due to longer lifetime, the actual energy storage cost is often lower. Consider the true cost of a battery as a function of total stored energy over its life (cost per kWh = battery price / total lifetime energy stored).

In warm climates where overcharging and evaporation risks are significant, open batteries may be preferred to sealed maintenance-free models, allowing users to replenish electrolyte with distilled water as needed. However, if maintenance staff lacks expertise, sealed maintenance-free batteries should be used with careful overcharge control.

Another key consideration is that large batteries are often delivered without electrolyte and must be filled with acid on-site. This requires expertise and presents a hazard. In some countries and for some transporters, the acid itself is classified as a dangerous good, requiring specific precautions, regulatory compliance, and customs duties.

Market evolution

Due to advances in li-ion technology and cost reductions, lead-acid batteries are increasingly less common.

Recall that their lifetime is highly temperature-sensitive: above 25°C, lifetime decreases by a factor of two for every 10°C increase. In hot climates such as subtropical regions, this can be catastrophic.

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