approached by the makers of large lead-acid traction batteries
for powering the locos on the railway system in Hong Kong,
to investigate a fire which had occurred in one of the batteries.
The base of the battery (Plate 1) showed a large hole with
a brittle crack running through the middle (Optical Micro Plate
The hole was surrounded by burnt
plastic. SEM was crucial in determining the cause of the
fire, by using EDX analysis. Plate 3 shows the SEM image
taken of the section, and Figure
1 and Figure
2 the EDX analysis of the surface in the hole. In addition
to lead and sulphur peaks, there were also two peaks from
aluminium and silicon.
Since the latter peaks only occurred
in the hole, and not elsewhere, we were able to infer that
the battery had landed on an aluminium stud already on the
floor of the holder where the battery sat normally. The stud
had impacted the base, cracked the case, and created a short
circuit with the internal battery plates (Fig
3). The cause of the fire was not the battery manufacturer,
but rather the installer of the battery who had not checked
that the floor of the holder was clear of debris.