TRUCK SERVICE MANUAL TM 5-4210-230-14&P-1 TABLE 5 Ambient Temperature 21° C 16°  C 10° C 4° C -1°  C -7°  C -12° C -18° C (70° F)& (60° F) (50°  F) (40°  F) (30° F) (20° F) (10° F) (0° F) above 12 Volt Battery 9.6 9.5 9.4 9.3 9.1 8.9 8.7 8.5 6 Volt Battery 4.8 4.75 4.7 4.6 4.5 4.4 4.3 4.2 Minimum Permissible Voltage CHARGING CAUTION Before  attempting  to  charge  a  battery,  be  aware  of  all  safety precautions   to   be   followed   during   the   charging   operation. Refer    to    Battery    Charging    Precautions    under    SAFETY PRECAUTIONS. Always follow battery charger manufacturer's instructions. When   possible,   use   a   battery   charger   with   alternator   or polarity    protection    that    prevents    charging    the    battery    in reverse polarity. Two   methods   of   recharging   a   battery,   the   Slow   Charge Method and the Fast Charge Method, are described below. The  charge  a  battery  receives  is  equal  to  the  charge  rate  in amperes multiplied by the time in hours.  Thus a five ampere rate applied to a battery for ten hours would be a 50 ampere- hour  charge  to  the  battery.    To  fully  recharge  a  battery,  you must  replace  the  ampere-hours  or  ampere-minutes  removed from it, plus an extra 20% charge.  This is due to the fact that batteries are not 100% efficient on recharging. The    Battery    Charging    Guides,    Tables    6    and    7,    show approximately  how  much  recharge  a  fully  discharged  battery requires.        For    partially    discharged    batteries,    reduce    the charging current or charging time (ampere-hours) accordingly. For example:  If the battery is 25% charged (75% discharged), reduce  charging  current  or  time  by  one-fourth  (1/4).    If  the battery  is  50%  charged,  reduce  charging  current  or  time  by one-half (1/2). If  time  is  available,  the  lower  charging  rates  in  amperes  are recommended. While   battery   is   being   charged,   periodically   measure   the temperature  of  the  electrolyte.    If  the  temperature  exceeds 51.6°C (125°F).  Or if violent gassing or spewing of electrolyte occurs,   the   charging   rate   must   be   reduced   or   temporarily halted.  This must be done to avoid damage to the battery. IMPORTANT DO  NOT  OVERCHARGE  batteries,  particularly  maintenance free   type   batteries.      Overcharging   causes   excessive   and needless loss of water from the electrolyte. Fig. 14  Charging Battery CTS-2771  Page 13 PRINTED IN UNITED STATES OF AMERICA