Charging an Absorbed Glass Mat (AGM) Battery

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These are all-important factors to consider when maintaining an absorbent glass-mat (AGM) battery.

  • Alternators are NOT chargers
  • Do not rely on the vehicle alternator to do the work of a charger
  • An alternator is meant to maintain a vehicle battery, not charge it
  • Newer chargers incorporate newer battery technology
  • Many newer battery chargers, or Smart Chargers, have microprocessors that collect information from the battery and adjust the current and voltage accordingly
  • Some have different settings for charging traditional wet cell (flooded), gel and AGM batteries. − Sulfation limits battery performance
  • All lead-acid batteries can experience sulfation, the formation of lead sulfate crystals upon discharge
  • Look for a charger with a de-sulfation mode to help condition the battery and keep it performing at its best
  • All batteries eventually die - Batteries are a consumable product; no battery will last forever. The goal is to consistently maintain your battery to get the highest performance and most life out of it

Charging Considerations for AGM Batteries

Different chargers have different capabilities - Although under normal conditions most 12-volt automatic battery chargers will work on an AGM battery, the battery will only charge to about 80 percent of its full capacity. Many newer battery chargers have settings specifically for AGM batteries. Remember the technology of an AGM battery is not the same as a gel battery, which has its own charging requirements. If the charger offers different modes, select the correct one for your battery. Using the gel setting to charge an AGM battery will not fully charge and over time will actually damage your AGM battery.

Lower is better - A low amp charger (1 to 10 amps) is always the best choice for charging any lead acid battery. It is faster to charge at higher amperage, but it generates a lot of heat, which reduces the life of a battery.

Charging an AGM at 10.5 volts or greater: No problem - Under normal starting conditions.