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How to Charge a Dead AGM Battery: Step by Step

How to charge a dead AGM battery
How to charge a dead AGM battery

Batteries, generally speaking, can fail in time, including AGM batteries. Many cases consider these batteries to be dead, where they are deeply discharged. Here lies a problem with most battery charging devices they come with built-in features of safety that prevent recharging faulty batteries, although they just may be deeply discharged. Keep reading, as we explain below, how to charge a dead AGM battery step by step.

The charger cannot detect it is not faulty but that the minimum voltage may have merely slid below the charger threshold. So, the charger cannot understand the ways to treat the battery to turn it on, so it selects doing nothing.

The low internal resistance in AGM batteries allows output at a very high amperage for the battery to power accessories for a longer period compared to a mainstream battery. However this remarkable feature also simultaneously discharging it deeply.

How to Charge a Dead AGM Battery – The Steps

You can bring back a deeply-discharged AGM battery once more to its peak functional performance if you go through these options.

1. Avoid using a standard battery charger

The usually preferred system is to purchase a developed-technology charger with AGM-specific settings for recharging a deeply-drained AGM battery. It also guides the battery through the de-sulfation process for achieving recondition and recovery of deeply-discharged AGM batteries.

This modern Battery Charger tends to fit the lead-acid batteries quite well while being double for vehicle storage as a battery upholder. A few of them are designed with additional leads (ring terminals) for charging with the remote access of your battery. Hooking up gets easier this way when you store your RV, boat, or another vehicle.

2. Trick the traditional battery charger

This method (known as a recovery process) uses available equipment concerning the do-it-yourselfers. This option allows you to deceive your mainstream charger and it charges the deeply-discharged AGM battery. You can use what you have in your garage and the list includes the seemingly dead deeply-drained AGM battery as well as:

  • Jumper cables
  • Battery charger below 15 amps
  • A good >12.2 volts AGM/ flooded/ Wet battery
  • A voltmeter
  • A watch/timer

>>Check this out: 10 Best AGM Batteries Review<<

The walk-through of the process:

Link the deeply-drained AGM battery with the working battery using the jumper cables in parallel- connect positives with positives and negatives with negatives accordingly. There is no requirement for a charger connection yet or turning it on at this point.

After that, connect the charger leads (ring terminals) to the terminals on the working battery and turn it on. Once the battery voltage (in parallel line) is sensed, the charging will begin in the parallel line. After an hour, turn off and disconnect from the good battery. Also, dispatch the jumper cables that link up both batteries.

After being charged for about 1-hour, the AGM battery should feel slightly warm/hot when you touch. While the charger getting warm when charging is considered okay, excessive heat indicates battery faults. You must immediately discontinue charging when the battery feels hot if you touch.

You must also lay off the charging process in case of a hissing sound of the battery, called gassing and safety-valves makes the noise. So ensure the charging is disconnected when the battery hisses or when it gets hot because the battery is overheating on the inside.

If you are not facing a hot or hissing battery, then follow through the next steps. Now you need to make a voltmeter assessment to find out the voltage of the battery. Repeat the process up to the measurement until you reach 10.5 volts and above.

When the voltmeter shows 10.5 volts or more, the charger should be disconnected and then the working battery must be removed from it. Now, it is the turn for only the deeply-drained AGM battery to plug into the charger and turn it on. Continue charging until a full charge cycle of the AGM battery, or completion of the charging process through an automatic charger. The AGM battery, hence in most scenarios, should be recovered this way.

3. Enlist/seek professional help

This option validates when there is no battery charger or investment or when you do not want to experiment. Take the drained battery to an AGM battery specialist. For a low fee, most of them will follow through a procedure named, charge and check.

Typically, auto parts stores are not always capable of determining the condition of an AGM battery accurately. Most of them use conductivity-testers with incorrect readings. However, battery specialists/distributors are such experts for determining battery recovering possibility of your drained battery.

1 thought on “How to Charge a Dead AGM Battery: Step by Step”

  1. can i use a lead acid storage battery instead of “A good 12.2 volts AGM/ flooded/ Wet battery”?

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