Capsulating Energy Systems for Small Submersibles
Authors: Anderson A.G. , Wright C.P. , Newman J.P. 
Published: October 2008

ABSTRACT
The primary purpose of the paper is to present operating and design experience which Perry Oceanographic has had so that it may be recorded for the technical community.
Underwater power application imposes constraints which require unique design solutions to problem so-f power sources. This paper will discuss experiences with different power sources designed to go to various depths. Submersible battery pod designs will be discussed in some detail.
A diesel pod design used directly with a small submersible will be reviewed. The experiences of encapsulating a fuel cell and operating it in conjunction with an underwater lab will be reported. Implications of these power sources on the future will be discussed.

INTRODUCTION
It is the intention of this paper to outline some of the practical problems faced in attempts to use power sources such as batteries or fuel cells in, an underwater application. The experience at Perry Submarine Builders has been unique.

BATTERY PODS
Many submersibles with batteries in different locations have been built. These can be divided into two basic systems: The volume compensation system where the cells are in lightweight containers surrounded with a special oil; and so-called hard system, where the batteries are capsulated in a pressure vessel to withstand sea pressure. References l, 2 and 3 discuss the pros and cons of the volume compensation system. The hard system used by Perry Submarine Builders in the design of its submersibles, will be covered on the following pages.
The techniques for the encapsulation of lead-acid storage batteries, for use as small submersible power supply systems, have evolved from the requirements of a series of these vehicles by Perry Submarine Builders. The first Cubmarine, the PC3X fitted its batteries into available spaces within the pressure hull. The PC3A and PC3B series of Cubmarines were next and the batteries were emplaced in an isolated, sealed battery compartment located within-the-pressure hull. Figure 1 is a photograph of one of the earlier submersibles with internal battery compartments.
As the size and power requirements of the submarine increased, the internal battery compartment became less practical. The PCSC submarine (Figure Z) had its battery compartment structurally integral with the pressure hull, but otherwise isolated in a completely pressure tight compartment.
The next generation submarine PLC4, had the battery pod completely separate and was made droppable for emergency deballasting. The original design concept for the PLC4 Series battery pod allowed for the changing of pods to shorten turn-around time between dives. As operating experience was gained with these submarines, it became evident that the logistics of at-sea quick changes of the battery pod were too complex for reliable safe operation. Instead, it is easier to change batteries by having them mounted on trays. Figure 3 shows the PLC4B with its droppable battery pod.
The design, manufacturing and operating experiences of the PC3X, PC3A, PC3B, PLC4, and PCS series submarines were prime factors in the design of the battery pods for the PC9C submarine shown in Figure 4, which is now under construction for Brown & Root.