All crimp-type lugs are rated to fit a specific conductor size, so matching the lug to the conductor is required. High-quality battery/inverter cables are made of fine-strand copper conductors with a flexible insulation covering and a cross section ranging from 35mm² - 75mm². In the present case the cable lugs were mounted by tapping them with a hammer.

The used cable is not rated and permitted as battery cable!

Internal construction of the junction box of solar modules  found in a poor performing system in Africa.
Cable terminals or cage clamps are absent! Bare copper stranded wires were wrapped around the conductors in the junction boxes of each solar panel, which leads to very poor conductivity. Low contact quality results in high contact resistances causing dissipation losses, hence heating of the conductors in the junction boxes.
The arrangement of the so called bypass diodes makes clear, that the supplier did not really care about the effect of bypass diodes.

Battery bank arranged in a series-parallel connection of 20 batteries. Such an arrangement does not make much sense from a technical point of view, because it is nearly impossible to ensure even and distributed charging of the entire bank. Although battery connectors with crimp-type lugs were applied and the cross section of the wiring is adequate, interconnects with different lengths were used. The measurement of the batteries indicated a huge deviation of the individual battery voltages. While some battteries were overcharged, others were found in state of deep discharge. If batteries are overcharged they can, in the worst case, overheat, melt and even short circuit explosively. 

Good quality solar products are often hard to find in Africa. Some unscrupulous producers take advantage of this situation and offer copies of well-known brands locally. The  picture shows such a fake product,  a copy of the Steca PR 10-30 series of charge controllers.

It is highly improbable that such copies meet the technical specifications of the original.