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How to Resuscitate a Deeply Discharged AGM Battery

Resuscitate a Deeply Discharged AGM Battery
How to Resuscitate a Deeply Discharged AGM Battery

In this article, we discuss how to resuscitate a deeply discharged AGM battery that won’t take a charge from a smart battery charger or car’s alternator. Follow our guide and the steps below to bring it back to life.

The challenge with an AGM battery is that if you let it discharge deeply, you may never get it to pick up the charge again. It’s challenging to do for a long-discharged AGM battery. However, we’ve found you a solution to this problem. Follow this, and you might get your AGM battery to pick up a charge again.

How to Resuscitate a Deeply Discharged AGM Battery – The Steps

The complete rejuvenation of a deeply discharged or dead battery is discussed here and shown below.

This process tricks the battery charger into assuming it’s charging a good battery, while the real thing is it’s charging a dead battery through a good battery.

Tools and Equipment You’ll Need

  1. A 12 and half+(plus) Volt working-Battery (AGM or Wet Cell battery will do)
  2. Your car’s dead AGM Battery
  3. Battery Tester
  4. Smart Battery Charger
  5. Jumper Cables
  6. A Handwatch or Timer
Resuscitate a Deeply Discharged AGM Battery

Step 1: In step one, put on your rubber gloves and put your battery tester on the deeply discharged battery to see the battery’s condition. Showing low means there is not enough charge in the charger to kick in and start charging the battery.

Step 2: After determining the battery is too low on power, take a well-working battery at least 12 ½ + volt. You may take it from another car, or any spare battery will do the job. 

Step 3: Double-check the working battery with the tester to ensure the voltage is on point. It should be good to go if it shows more than twelve point half!

Step 4: Now, you’ll have to connect the batteries parallelly. But before that, unhook the AGM battery you have in the car. You need to unhook the negative or the ground strap first. Keep the charger disconnected when you connect the batteries.

Step 5: Use a set of jumper cables and put the black clamp first on the negative side of the working battery, and do not connect the positive end until you hook the dead battery. Now, connect the black wire of the opposite side to the negative side first on the dead battery, then the red wire to the positive side of the same battery.

When you’ve connected both sides of the dead battery with the jumper cable, get back to the working battery and connect the red wire to the positive pole. Ensure all the terminals are tight enough or positive to positive and negative to negative.

Resuscitating process of a Deeply Discharged Battery

Step 6: Now that both batteries are connected to each other through a jumper wire, the next step is to hook the smart battery charger up to the working battery before you plug it in. Follow the positive to positive and negative to negative procedure first, and connect the positive one. Now plug the charger in. The charger will come to life. In short, connect the leads to the terminals of the working battery.

Step 7: In this step, you’ll have to go through the battery charger settings for your dead car battery. Set the charger for a medium-sized battery. You may have options of 2, 10, and 15 Amps. Set it to 10 amps or what suits your car’s AGM battery. Next, you should see Standard, AGM, or Gel cell settings. We are choosing the AGM battery setting, of course.

Step 8: The charger will notice the voltage of the working battery and charge it. It will show the energy flow in volt and the percentage of charge it currently has on its little red monitor. If the battery is not kicking back, let it sit for an hour and get back later.

Step 9: Turn off the charger and disconnect it from both batteries. Then, put the tester on and measure the volt of the rejuvenated battery.

  • Repeat all previous steps if the tester shows a volt less than 10.5.
  • If it has a 10.5+ volt, charge your AGM battery as usual.


***It is OK if the battery is warm at the charging point. But if it gets too hot to touch, or if you hear a hissing, STOP CHARGING RIGHT NOW! Overheating or hissing noise indicates there might be something wrong with the battery. Let the professionals handle it.

Safety Precautions

*Use rubber gloves.

*Wear eye protection.

*Be careful while handling positive and negative wires.

How to Resuscitate a Deeply Discharged AGM Battery FAQs

What is an AGM Battery?

AGM or Absorbent Glass Material batteries are sealed Lead-Acid, spill-proof, and more reliable than typical Lead-Acid batteries. These batteries are lighter than the traditional ones and hazard-free.

How Do You Recognize an AGM Battery?

You can tell if a battery is an AGM battery by looking at the label, of course. AGM batteries are usually labeled “AGM” or “Absorbed Glass Mat.” They may also be labeled as “sealed regulated valve,” “dry cell,” “non-spillable,” or “valve regulated.”

However, if you don’t see AGM written anywhere on the label, you can look for the model number of the battery and check for its information online or contact the manufacturer and ask for it.

What’s a Trickle Charger?

Trickle chargers charge a battery slowly, preventing it from overcharging. When you store a battery for a long period, investing in a trickle charger is worth investing in to prevent the battery from deep discharge damage.

How to Resuscitate a Deeply Discharged AGM Battery – Conclusion

May this article have helped you to resuscitate a deeply discharged or dead AGM battery. Make sure to follow all the safety protocols to handle the dead car battery and recharge it. However, you can always call for professional help in an emergency. So, don’t delay when you need help.