Battery Maintenance

Trojan Battery Company has been manufacturing deep-cycle, flooded batteries for more than three generations.

While reviewing our battery maintenance tips, please keep in mind that all battery systems are unique. Battery type, charger technology, equipment loads, cable size, climate, and other factors can all vary. Slight or significant, these differences will require battery maintenance to be adjusted accordingly. These are only guidelines to follow for proper battery care. Each particular system will always require a degree of customized attention.


There are many tools that may help in properly caring for and maintaining batteries. Below is a list of basic items that Trojan recommends for this task:

CAUTION: Always wear protective clothing, gloves and goggles, when handling batteries, electrolyte, and charging your battery.

Batteries should be carefully inspected on a regular basis in order to detect and correct potential problems before they can do harm. It is a great idea to start this routine when you first receive the batteries.

Inspection Guidelines

1.  Examine the outside appearance of the battery.

  • Look for cracks in the container.
  • The top of the battery, posts, and connections should be clean, free of dirt, fluids, and corrosion. If batteries are dirty, refer to the Cleaning section for the proper cleaning procedure.
  • Repair or replace any damaged batteries.

2.  Any fluids on or around the battery may be an indication that electrolyte is spilling, leaching, or leaking out.

  • Leaking batteries must be repaired or replaced.

3.  Check all battery cables and their connections.

  • Look closely for loose or damaged parts.
  • Battery cables should be intact; broken or frayed cables can be extremely hazardous.
  • Replace any cable that looks suspicious.



Water should always be added after fully charging the battery. Prior to charging, there should be enough water to cover the plates.


Important Things to Remember

  1. Do not let the plates get exposed to air. This will damage (corrode) the plates.
  2. Do not fill the water level in the filling well to the cap. This most likely will cause the battery to overflow acid, consequently losing capacity and causing a corrosive mess.
  3. Do not use water with a high mineral content. Use distilled or deionized water only.

CAUTION: The electrolyte is a solution of acid and water so skin contact should be avoided.

Step-By-Step Watering Procedure

  1. Open the vent caps and look inside the fill wells.
  2. Check electrolyte level; the minimum level is at the top of the plates.
  3. If necessary add just enough water to cover the plates at this time.
  4. Put batteries on a complete charge before adding any additional water (refer to the Charging section).
  5. Once charging is completed, open the vent caps and look inside the fill wells.
  6. Add water until the electrolyte level is 1/8″ below the bottom of the fill well.
  7. A piece of rubber can be used safely as a dipstick to help determine this level.
  8. Clean, replace, and tighten all vent caps.

WARNING: Never add acid to a battery.

Watering Diagram


Flooded batteries need water.

But more importantly, watering must be done at the right time and in the right amount or the battery’s performance and longevity suffers.

General Watering Instructions:

  • Add water, never acid, to cells (distilled water recommended)
  • For fully charged standard deep-cycle batteries, add water to the level of 1/8 below bottom of vent well (see diagram A below)
  • For fully charged Plus Series batteries, add water to the maximum water level indicator (see diagram B below)
  • If the batteries are discharged, only add water if the plates are exposed. Add just enough water to cover the plates, then charge the batteries. Once fully charged, add water to the proper level indicated above
  • After watering, secure vent caps on batteries


Batteries seem to attract dust, dirt, and grime. Keeping them clean will help spot signs of trouble when they appear and avoid problems associated with grime.

  1. Check that all vent caps are tightly in place.
  2. Clean the battery top with a cloth or brush and a solution of baking soda and water.

•  When cleaning, do not allow any cleaning solution or other foreign matter to get inside the battery.
  1. Rinse with water and dry with a clean cloth.
  2. Clean battery terminals and the inside of cable clamps using a post and clamp cleaner.

•  Clean terminals will have a bright metallic shine.
  1. Reconnect the clamps to the terminals and thinly coat them with an anti-corrosive spray or silicone gel.
  2. Keep the area around batteries clean and dry.


Charging batteries properly requires administering the right amount of current at the right voltage.

  1. Become familiar with and follow the instructions issued by the charger manufacturer.
  2. Batteries should be charged after each period of use.
  3. Lead acid batteries do not develop a memory and do need not be fully discharged before recharging.
  4. Charge only in well-ventilated areas. Keep sparks or flames away from a charging battery.
  5. Verify charger voltage settings are correct (Table 2).
  6. Correct the charging voltage to compensate for temperatures above and below 80° F (26.6°C). (Add .028 volt per cell for every 10° below 80° F (26.6°C) and subtract 0.028 volt per cell for every 10° F (12.2°C) above 80° F (26.6° C))
  7. Check water level (see the Watering section).
  8. Tighten all vent caps before charging.
  9. Prevent overcharging the batteries. Overcharging causes excessive gassing (water breakdown), heat buildup, and battery aging.

10.  Prevent undercharging the batteries. Undercharging causes stratification which can lead to premature battery failure.

11.  Do not charge a frozen battery.

12.  Avoid charging at temperatures above 120° F (48.8° C).