Charging an AGM Battery

Discussion in 'Dodge Challenger General Maintenance' started by SRT-Tom, Dec 19, 2019.

  1. SRT-Tom

    SRT-Tom Well-Known Member Super Moderator Article Writer

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    Here's a word to the wise on using a trickle charge with an AGM (Absorbant Glass Mat) battery.

    Late model Challengers come with an AGM battery. AGM batteries cannot be maintained with conventional battery chargers. You must use a charger/maintainer that is specifically designed for AGM batteries. If you connect a conventional battery charger to an AGM battery, the charging indicator will light but never turn off. It will simply keep charging the battery until it is overcharged and, if left on too long, will damage or shorten the life of the battery. AGM batteries require chargers with microprocessors that regulate the charge rate and have the correct logic to turn off when the battery is fully charged.
     
  2. 2010RT

    2010RT Full Access Member

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    I use a Battery Tender brand that I better check to make sure is ok for AGM’s. It does show the green light indicating it has and maintaining the charge.
     
  3. KEVIN DONOVAN

    KEVIN DONOVAN Full Access Member

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    Sorry Tom but that is not true. You DO NOT need a special charger/maintainer for AGM batteries. Unless deeply discharged (below 10.5 v) AGM batteries can be charged with pretty much any automatic charger. Below that voltage, an AGM battery may trick your charger into thinking it's bad and the charger may not even come on. This is mainly due to the unusually low internal resistance of AGM batteries. You can however trick your old charger to charge the deeply discharged AGM battery by grabbing a set of jumper cables and hooking up another known good battery in parallel with the deeply discharged AGM battery and then hooking the charger to the good battery. Charge both for about an hour and then you can disconnect the good battery and hook the charger directly to the originally discharged AGM battery. If the charger comes on and charges, you're all set. If not, chances are the originally discharged battery truly is bad and you should consult a professional to further diagnose or dispose of the battery.
     
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  4. SRT-Tom

    SRT-Tom Well-Known Member Super Moderator Article Writer

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    I am corrected. You can use a standard battery tender with an AGM battery, if you use it on the lowest and slowest setting. Still, the battery must be closely monitored since it can get over-charged.

    That is why even though you technically don’t have to have an AGM tender for an AGM battery, it is a good idea to have one.

    For more details, see this website:

    https://autofthings.com/agm-vs-standard-battery-charging/
     
    Last edited: Dec 20, 2019