temperatures as low as   -65°F. without freezing. An acceptable hydrometer reading of 1.210  - 1.220 at 80°F will be obtained from a fully charged battery (2.0-2.2 volts dc per  cell). c.  Battery  Preparation WARNING Do not smoke or use an open flame in the  vicinity  when  servicing  batteries. Batteries  generate  hydrogen  during charging, a highly explosive gas. A severe bum   will   result   when electrolyte  is  spilled  on  the  skin  or clothing. Use   extreme   care   in handling  while  filling  batteries. (1) Remove cell caps and fill battery cells with electrolyte to 38 inches above the plates. (2) Make sure vent holes in cell caps are open and install  caps. TM   5-6115-545-12 TO-35C2-3-444-l NAVFAC   P-8-626-12 TM-00038G-12 3-83. Battery Tray Replacement To replace the battery tray, remove batteries as described in paragraph  3-82a.  Remove  screws  (9,  fig.  3-4)  and lockwashers (10) which secures battery tray (11) in position, and install new battery tray. 3-84.  Slave  Receptacle  Replacement. To  replace  the  slave  receptacle,  see  figure  3-4  and  proceed as follows: a. Disconnect battery negative cable (1). b.  Remove  six  screws  (12)  which  secure  receptacle box (13) to housing and tilt box forward to gain access to wiring  connections. Disconnect wiring  connections, clamps, harness ties and tag for ease of Installation. c. Remove four screws (IS) and nuts (16) which secure  slave  receptacle  (I”),  and  remove  receptacle. d.  (Deleted) e. install receptacle in reverse order of removal. Section X. MUFFLER AND EXHAUST PIPES AND BREATHER SYSTEM 3.85.  General. Thin  section  contains  information  on  the  muffler  and exhaust pipes and breather system of the engine generator set. The muffler and exhaust pipes provide a method for expelling  exhaust  gases  from  the  engine  generator  set.  The exhaust pipe allows the exhaust gases from the engine to he discharged from an opening above the grille. The discharge opening is covered by a cap that is opened by exhaust pressure when the engine generator set is running. The breather system provides a method for returning oil to the crankcase and improving the atmosphere around the engine generator  set.  Accumulated  oil  residue  and  gases  in  the  valve cover  pass  through  an  oil  separator  which  separates  the  oil and the gases. The oil is returned to the crankcase and the gases exhaust into the air cleaner inlet. The breather system is  removed  as  outlined  in  paragraph  3-87. 3-86. Muffler and Exhaust Pipe Replacement. To replace the exhaust pipe, see figure 3-12 and proceed as follows cap (3). WARNING Allow exhaust pipe to cool if engine has been  running. Loosen nut (1) from screw (2) and remove weather b. Loosen nuts (4) which secure 0-bolt (6) and bracket (7) to nozzle (8) and muffler (9) pipes, and slide 0-bolt (6) and bracket (7) toward muffler. Remove screws (10) which secure nozzle (8) to housing. Place 0-bolt (6) on muffler (9) pipe and remove nozzle (8). d. Loosen nuts (11) which secure 0-bolt (13) and bracket (14) to muffler (9) and exhaust pipe (15). Place 0-bolt (13) with bracket (14) on muffler pipe and remove muffler  and  both  0-bolt  assemblies. e. Disconnect exhaust pipe (15) from engine and remove  exhaust  pipe. f. Install new exhaust pipe in reverse order of removal. 3-87.  Breather  System  Replacement. To replace the breather system. see figure 3-12.1 and proceed as follows: Loosen  clamps  (1)  and  disconnect  hose  (2)  from  oil separator (4) and elbow (3). b. Loosen clamps (5) and disconnect hose (6) from oil separator  (4)  and  valve  cover  crankcase  breather. c. Loosen clamps (7) and disconnect hose (8) from oil separator (4) and air cleaner inlet (9). d. Loosen clamp (10) and slide out oil separator (4) Remove nuts (1 1). camp and bracket (10), nuts (12), and screws (13). f. Install breather system in reverse order of removal. Change 17 3-31