Car batteries are not an option either, despite their inexpensive nature. The main reason is that the geometry of car battery electrodes is designed for short current bursts such as cranking a car engine. The batteries are very sensitive to being low-discharged as it would be natural design criteria in common power-out scenarios in Africa: A car battery only once low-discharged will suffer irreversible damage.
The option we thoroughly tested and use ourselves for IT purposes is lead crystal batteries. Heavy like car batteries, however unimportant due to their stationary use case, they contain no liquid or harmful acid. Such batteries are safe and even approved to be carried by plane. Their life-cycle in a normal use scenario in Africa is about 15 years. Quick-charge, high-current, and low-discharge qualities add to their benefits.
Due to their reliable, safe, and inexpensive nature, lead crystal batteries are widely used in telecommunications, IT, solar, train, military, hospital or airport use cases.
Configurations are easily made by (a) defining customers’ needs (i.e. three servers with 2000 W power consumption to be run in “grid power-out” conditions for i.e. 1 hour, 5 hours, 1 day, 1 week, 1 month) and (b) plugging together 12V to 220V inverters and BMCs (battery management systems) at the desired quality and price point.