Vehicle Battery & Alternator Diagnostics

Why should an AGM (Absorbent Glass Mat) battery never be charged with an old high-voltage manual taper charger exceeding 14.8V?

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 Correct IncorrectExcessive voltage causes recombination valves to vent gas, drying out the fiberglass mats permanently. AGM batteries are sealed and cannot have distilled water added back.

Why should an AGM (Absorbent Glass Mat) battery never be charged with an old high-voltage manual taper charger exceeding 14.8V?

• The battery will turn into a lithium cell
• High charging voltage vents gas through pressure valves, drying out electrolyte in sealed cells permanently
• The fiberglass mats will dissolve into paper
• The positive post will turn negative