The FT-897D is a very flexible radio with different options to suit differing requirements, one of which is portability.
The radio itself is bulkier than its smaller brother (FT-857D) even though they contain the same circuit boards. The bulk comes in the form of a robust case, better control panel and large carrying handle. An empty area at the base of the radio is kept free for options such as the internal PSU (FP-30) and the internal batteries (FNB-78)
These all produce extra weight and bulk but DO provide a much more robust radio.
The FNB-78 Batteries are sold in single form and generally you would need two of them, these are known as A and B battery. They both fit internal under the cover on the base of the radio and are attached to the circuit board using a simple molex style connector. On the rear of the battery is the charging point and this extend out through the back of the radio to allow the charger to be connected, whilst leaving the batteries in situ.
The FNB-78 is a Japanese made NiMH battery, rated at 4500mAh at 13.2 Volts Charged, 11 Volts Discharged the recommend charger current is 1400mA. I mention that it is Japanese made because they make batteries far better than the other cheap rubbish made in places like China. The same applies to the CD-24 and the PA-26 they are all made in Japan.