1. Inspect the cell for damage, Read Warning Label On Cell Before Proceeding.
  2. Remove vent caps, fill each cell above the top of the splash guard (protection mat covering separators) with approved 1.265 specific gravity battery grade electrolyte.
  3. Keep sparks and flames away from battery at all times. Allow electrolyte to saturate plates and separators for 30 minutes. Temperature of electrolyte will rise and specific gravity will drop. Add electrolyte if not visible. Check for correct polarity with a voltmeter.
  4. Place on charge at the finishing rate (5% of the 8 or 20 hour rate). The rate may be increased if the battery does not begin to gas. Do not let the cell temperature exceed 115° F (46° C) If the temperature becomes excessive or the cells begin to gas vigorously, reduce the rate of charge. Continue charging until the cell (or cells) reach within .005 points of the specific gravity of the filling electrolyte corrected for 77° F (25° C)
  5. Top up or remove electrolyte as necessary for proper level. Never add electrolyte (only approved water) after activation.
  6. Replace vent caps and remove any spillage of electrolyte. If necessary clean with bicarbonate of soda and water ( 100 grams of soda to one liter of water) Rinse with water and wipe dry. Verify that soda solution does not get into cells.

Shelf life of a dry charge battery will vary, but may be kept for several years under ideal conditions.  Store in a cool dry area. The positive plate has an unlimited shelf life. The negative plate will revert to lead oxide when in the presence of water and oxygen. If this should happen, the battery is not ruined, but activation will take considerably longer.

The electrolyte temperature will rise dramatically during activation. Do not place on charge until the temperature drops below 115° F. Activation may take several days.

Before installing the batteries, clean the contact surfaces of the lead terminal post and battery terminals with a wire brush. Apply a thin coat of Vaseline to all contact points and connector bolts. After all connections have been securely tightened, they should be gone over and tightened a second time.


Preventive Maintenance (for more information see Preventative Maintenance of Deep Cycle Batteries)

  1. Check the height of the electrolyte twice a month. If necessary replace with approved water only. Many times domestic water is satisfactory. Water with a high mineral content is not satisfactory.
  2. Do not use water that is difficult to create a lather when washing your hands with soap and water.
  3. Never fill the cells above the bottom of the vent well. Over filling will cause loss of electrolyte and reduce the battery capacity.
  4. Never add acid to the battery. (Only during activation)
  5. Avoid over discharging of the battery as the useful life will be reduced. The rule of thumb is not to exceed 80 percent of the capacity of the battery. On a 12 volt system this would be approximately 11 volts. Remember over discharging or low voltage will also reduce the life of most electrical equipment.
  6. Battery capacity is based on each cell having an electrolyte temperature of 77° F (25° C). Temperatures below 77° F reduce the battery's effective capacity and lengthen the time to restore to full capacity. Temperatures above 77° F will slightly increase capacity, but will also increase self discharge and shorten battery life.

The state of charge of a battery can be measured with a hydrometer. The chart below shows the approximate "percent of charge" corrected for temperature at various specific gravity values.

ChargedSpecific GravityOpen Circuit Voltage

Determining state of charge by voltage is more difficult as there must be no load or surface voltage present.

When taking specific gravity measurements, it is important to correct for temperature to get a true reading. As a rule of thumb, specific gravity will change by 0.003 for each ten degrees Fahrenheit change in temperature above or below 77° F (25° C). Below 77° F subtract from readings and above 77° F add to the readings. As an example a reading of 1.250 at 67° F corrected for temperature would be 1.247 and a reading of 1.250 at 87° F corrected for temperature would be 1.253.

It is recommended that fully charged gravity and voltage readings be taken of each cell every month and compared with readings from the preceding period. The readings will indicate any marked difference in battery condition as well as differences between cells. A good rule of thumb is if there is 0.025 points or less between the high and low cell the battery is not defective. Low readings would indicate the battery being discharged.

The charging system can have a profound effect on the life of the battery. A high voltage setting can cause excessive gassing and water loss. Eventual damage to the battery system will take place. A low setting will leave the batteries in an under charged condition resulting in a loss of capacity and eventually the battery system may not take a charge. A proper setting will result in a minimum of water consumption and still able to maintain the batteries at full charge.

For more information, please refer to the Rolls Battery User Manual