pressure hull. Each approach has its own 

 advantages and disadvantages. 



In-Hull Placement 



Placing the battery within the pressure 

 hull reduces circuit complexity, eases main- 

 tenance and minimizes the possibility of the 

 cells coming in contact with seawater. Con- 

 versely, this option increases the hull weight 

 (and decreases payload), takes up internal 

 space which could be used for equipment or 

 personnel and presents a potential safety 

 hazard to occupants. The first two of these 

 disadvantages are fairly obvious; the safety 

 aspects should be explained. On a short dura- 

 tion dive (8-12 hr) hydrogen gas from dis- 

 charging batteries, as discussed previously, 

 is not sufficient to harm the human occu- 

 pants, nor should it reach a concentration 

 (4%) whereby explosion in the event of 

 sparking could occur. Indeed, employment of 

 Hydrocaps should negate either of these pos- 

 sibilities. The first area of concern lies with 

 spillage of the lead-acid electrolyte at high 

 pitch or roll angles. In this case the electro- 

 lyte could come in contact with the occu- 

 pants and cause acid burns or, even worse, it 

 could combine with seawater in the hull and 

 release toxic chlorine gas. It also could dam- 

 age the submersible structure and equip- 

 ment therein. Work (14) cautions that a vig- 



orous short circuit can boil out the electro- 

 lyte in silver-zinc batteries and vaporize the 

 mercury within them to further endanger 

 the occupants. Undoubtedly, the most signif- 

 icant hazard arises during battery charg- 

 ing — and this may occur regardless of bat- 

 tery location — where overcharging might 

 cause electrolyte spillage into the Hydrocap 

 and cause it to cease functioning. In this 

 case hydrogen might build up to dangerous 

 concentration. Anderson et al. (15) cites a 

 further consideration in reliance on Hydro- 

 caps; this resides in the possibility that in 

 enclosed spaces insufficient oxygen may be 

 present to recombine with the hydrogen. It 

 should be noted that their discussion relates 

 to the situation where batteries are carried 

 within an external pod, not in the pressure 

 hull where a far greater volume of air is 

 available. 



Placement of the battery within the hull 

 has been approached in two ways: The first 

 is to simply install the battery securely in 

 some convenient spot, e.g., SEA OTTER, All 

 Ocean Industries, and the second is to seal 

 off a portion of the hull, generally low in the 

 hull, and place the battery there (Fig. 7.8). 

 The latter procedure further protects the 

 occupants, and if the sealed area is also 

 pressure resistant it offers additional safety 

 advantages. The in-hull procedure has been 



AFT 



TRIM 



AND V BT 



FORWARD 



TRIM AND 



VARIABLE 



BALLAST 



TANK 



SONAR 



MOTOR 

 ROOM 



CMPT. 



FWD. 

 FOOT 

 WELL 



Fig. 7.8 In-hull battery location in the PC-3A. (Perry Submarine Builders) 



326 



