Datasheets assume 25 degrees Celsius. Coastal Lagos, humid Accra, and tropical Douala are not 25 degrees. They are 30 to 35 degrees ambient, with humidity that pushes effective heat index higher. That difference matters for lithium battery life.
The rule of thumb we use: for every 10 degrees Celsius above 25, lithium battery degradation roughly doubles. A battery rated for 6,000 cycles at 25 degrees will give you closer to 3,000 cycles at 35 degrees, all else equal. So if you size for 10 years of daily cycling at the datasheet rating, you will get closer to 5 years in the field.
The fix is two things: oversize the battery, and ventilate the enclosure. We oversize by 25 to 30 percent for hot, humid installs. A 10 kWh nominal bank becomes a 13 kWh nominal bank, which gives us 10 kWh usable after derating. The cost is real, but it is smaller than replacing the bank two years early.
Humidity is the underrated one. Coastal salt air corrodes battery terminals and BMS boards. We spec conformal-coated BMS boards for any coastal install, plus IP65 enclosures for outdoor cabinets. The cost difference is small. The warranty difference is not.
A worked example: a clinic in Tema, Ghana, 50 km from the coast. Daily load 8 kWh. We spec a 15 kWh nominal LiFePO4 bank (12 kWh usable after derating), 5 kW hybrid inverter, and 4.5 kW of panels. The system has been running for 18 months with no degradation reported. That is what good sizing buys you.