1970-1979 Ski-Doo Snowmobiles Service Manual, Page 124Get this manual
ELECTRICAL SYSTEM
Take reading at eye level
chargedPerform periodic specific gravity tests with hydrometer to determine the level of charge and how long charge stays up before it starts to deteriorateBattery Specific Gravity Test Determine the state of charge of the battery with hydrometerTo use this instrument, place the suction tube (Figure 12) into the filler opening and draw in just enough electrolyte to lift the floatHold the instrument in vertical position and take the reading at eye levelSpecific gravity of electrolyte varies with temperature, so it is necessary to apply temperature correction to the reading you obtainFor each 10 that the battery temperature exceeds 80F, add 0.004 to the indicated specific gravitySubtract 0.004 from the indicated value for each 10 that the battery temperature is below 80FWARNING Do not smoke or permit any open flame in any area where batteries are being chargedHighly explosive hydrogen gas isformed during the chargingprocess
Do not suck in too much electrolyte