nickel-cadmium cells used in the battery consist of two basic types–vented and sealed cells. Most naval aircraft nickel-cadmium  storage  batteries  employ  rectangular vented-type cells. Sealed cells have limited applications   and   come   in   both   the   rectangular   and cylindrical types. BATTERY SAFETY PRECAUTIONS The   principal   hazard   in   working   with   lead-acid batteries   is   acid   burns   when   you   are   refilling   or handling   them.   You   can   prevent   getting   burned   by wearing eyeshields, rubber gloves, rubber aprons, and rubber   boots   with   nonslip   soles.   Rubber   boots   and aprons are only needed when you are refilling batteries. You should wear eyeshields whenever you are working around batteries. Eyeshields will prevent acid burns to your  eyes.  Wood  slat  floorboards,  in  good  condition, will help prevent slips and falls. Additionally, electric shock from the high-voltage side of charging equipment is reduced. Another  hazard  of  working  with  batteries  is  the chance    of    an    explosion.    Hydrogen    gas,    a    high explosive, collects while batteries are charging and can cause  an  explosion  during  battery  charging.  This  is especially  true  when  using  the  accelerated  charging method. The charging rate should be held to a point that prevents the rapid release of hydrogen gas. Follow the manufacturers'    recommendations    for    the    charging rates. Be careful to prevent short circuits while batteries are being charged, tested, or handled.   A spark from a shorted circuit could easily ignite the explosive gases. This   danger   is   also   true   for   personnel   performing aircraft  maintenance  near  batteries.  Open  flames  or smoking are not permitted in the battery charging room. Use a shop exhaust system to remove the gases. Use  extreme  caution  when  you  are  installing  or removing  an  aircraft  battery.  Batteries  are  heavy  for their size and awkward to handle. These characteristics require the use of proper safety precautions. Aircraft batteries may overheat because of internal shorting    or    thermal    runaway.    In    either    case,    an overheated battery causes a hazardous condition. When an overheated battery is detected, crash crew personnel should open the battery compartment and check for the following conditions: !    Flame—If present, use CO₂ extinguisher. !    No  flame—If  smoke,  fumes,  or  electrolyte  is coming  from  the  battery  or  vent  tubes,  spray the  battery  with  low-velocity  water  fog.  This will lower the battery temperature. WARNING CO₂  is  a  good  fire-extinguishing  agent  once  a fire has started. Never spray CO₂ from a portable fire extinguisher into a battery compartment for cooling or to displace explosive gases. The static electricity generated by the discharge of the extinguisher could explode the gases trapped in the battery compartment. Following    a    visual    check,    allow    crash    crew personnel  to  remove  the  battery.  If  additional  battery cooling is required, use low-velocity water fog. You may use the above procedures on all types of aircraft batteries installed in all types of aircraft. CAUTION If  acid  or  electrolyte  from  a  lead-acid  battery touches  your  skin  or  eyes,  flush  the  affected  area with     large     quantities     of     fresh     water.     Report immediately for medical examination and treatment. CAUTION If     the     electrolyte     from     a     nickel-cadmium (NICAD) battery touches your skin or eyes, flush the affected   area   thoroughly   with   large   quantities   of fresh   water.   Neutralize   with   vinegar   or   a   weak solution (3%) of boric acid. Report immediately for medical examination and treatment. Q7-1. What     are     the     two     primary     sources     of electrical energy for an aircraft? Q7-2. During     normal     aircraft     operation,     what component maintains the battery in a charged state? Q7-3. What  are  the  principal  hazards  of  working with batteries? Q7-4. What can cause aircraft batteries to overheat? Q7-5. What should you do if acid or electrolyte from a lead acid battery comes in contact with your skin? Q7-6. What are the two ways to neutralize electrolyte  from  a  nickel-cadmium  (NICAD) battery if it contacts your skin? 7-2