All hybrid batteries will heat up upon charging much like every other battery. Cooling is provided for by the above fans.
Honda Fit hybrid/ Honda insight Intelligent power unit(ipu) hybrid cooling fans. The above special fan uses a pwm signal from the hybrid control unit to vary the speed of rotation hence the intensity and of air drawn to cool the hybrid battery.
part number available: IJ810-REO-0031
IJ810-RTW-0031