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How to Select a 12V Battery Charger

One important fact is that all batteries, regardless of their chemistry, will self-discharge.

May 26, 2016

If you’re a fleet manager looking to recover underperforming batteries or you need to keep batteries “factory fresh” over months of storage, there are several factors to consider.

One important fact is that all batteries, regardless of their chemistry, will self-discharge.

“The rate of self-discharge for lead-acid batteries depends on the storage or operating temperature,” says Rick Miller, sales manager with PulseTech Products, Southlake, Texas. “At a temperature of 80 degrees Fahrenheit, a lead-acid battery will self-discharge at a rate of approximately 4 percent a week. A battery with a 125-amp hour [AH] rating would self-discharge at a rate of approximately five amps per week.”

Storing a 125 AH battery for four months over winter without charging will cause it to lose 80 amps of its 125-amp capacity. It will also suffer from severe sulfation.

Sulfation is a buildup of lead sulfate crystals that inhibits the plates from accepting and distributing a charge, and is a common cause of early failures in lead-acid and sealed AGM batteries, or batteries with wet cell-filler caps (flooded).

“When looking for maintenance battery chargers, for example, managers should understand the term ‘pulsing,’ which may or may not be reflective of the chargers’ ability to remove lead sulfate buildup on the battery plates—the No. 1 reason for battery failure,” Miller says.

A charger may deliver a pulse charge; however, that doesn’t mean the pulse is cleaning the battery plates of sulfates and restoring the battery’s ability to fully recharge, according to Miller.

“Some ‘smart’ chargers not only feature LEDs to indicate the battery’s state of charge, but also are capable of switching from a bulk charge to a float maintenance charge depending on the battery’s state of charge,” Miller says. “Plug-and-play smart chargers will not turn on unless connected properly and will not arc. Also, look for a charger that is capable of equalizing the cells within a single battery with all batteries in a parallel battery bank.”

Miller recommends answering these questions before selecting a charger:

  • What are you using the battery charger for?
  • Where are you going to put the charger?
  • What voltage is the battery being charged?
  • What size charger do you need?
  • Are you looking for one battery charger that will evaluate and test all types of 12V batteries, including AGM, gel-cell and VRLA?
  • Are you looking for a battery charger system that will maintain and charge as many as 8 batteries automatically in a cycle rotation?

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