How to Resuscitate A Deeply Discharged AGM Battery?

Knowing draining a battery fully is a bad thing, I am assuming you have discharged your AGM battery accidentally. Knowing how to resuscitate a deeply discharged AGM battery may give it a second chance.

Either using an AGM-compatible charger or applying a common DIY trick, you can start charging a fully discharged AGM battery. Below, I have described all possible ways briefly.

Before you begin applying these methods, let me warn you that your battery may not survive after 100% discharge. So, don’t have high hopes, and let’s get started.

How to Resuscitate A Deeply Discharged AGM Battery?

The first way of making a dead AGM battery alive is by tricking the battery charger.

Those who don’t have the time or patience to try my first method can apply the second one which simply uses a charger.

And, if none of them work, you will have to take the battery to a professional for a thorough inspection.

1. A DIY Solution

The main purpose of this trick is to let the charger think that it is charging a good battery while you try to save the dead one.

For this method, you have to arrange a good AGM battery with 12V or more, a battery tester, a smart battery charger, jumper cables, and a timer.

First of all, put on rubber gloves so that you don’t accidentally electrify yourself.

Then, you can use the battery tester to evaluate the condition of the deeply discharged battery.

Once you have confirmed that the battery power is too low to operate, take the 12V+ working battery, and connect them parallelly.

Use the set of jumper cables I have told you to arrange earlier for the connection. Here is a video showing how to connect two batteries parallelly.

Before connecting them, you must use the tester once again to confirm the required voltage level of the good AGM battery.

Pro Tip: One should keep the charger disconnected while connecting the good and bad batteries in parallel.

Now, connect the charger’s cable to the terminals of the good working battery, and turn the charger on.

Here, a traditional charger will think that it is charging a good battery. Keep it charging for at least one hour, and use the timer to keep track of time.

After that, turn off the charger, disconnect all components in this setup, and see whether the dead one is warm.

If the warmth is tolerable, it will be a good sign. Otherwise, you have to assume that the method has failed.

Important: Noticing too much heat or hearing hissing sound is alarming. You have to stop charging immediately after any of the symptoms occur.

Finally, check the voltage of the dead battery again.

Assuming everything has gone according to the plan, your dead AGM battery should show some voltage in the readings of the tester.

In case it is less than 12 volts, you have to repeat the whole process. After a second or third try, hopefully, the battery will be in working condition again.

2. Ready-made Solution Using a Charger

Smart AGM chargers are all-rounder devices with lots of features and capabilities.

They can initiate the de-sulfation process to regain the lost power. Also, they work as a battery maintainer and trickle charger.

For the best results, I recommend NOCO GENIUS5. Indeed, there are lots of other models and brands to choose from.

If you find a better charger in this price range, please share it with us so that we can take advantage too.

3. Reviving 90-95% Discharged AGM Battery

When your AGM battery is not fully discharged but has reached to level of no return (in the normal sense), you can try this method.

Here, using a smart all-in-one battery charger like NOCO Genius 5 is recommended.

Do not try to fast charge or trickle charge the battery in the beginning. Use the charger to normally recharge it up to 80%.

Once you have confirmed that the voltage level is at an acceptable level, you can treat the previously dead AGM battery like a good one.

Also, don’t forget to run a de-sulfation process every two or three charging cycles.

That is how you can revive a deeply discharged AGM battery. Optima has made a great video on this topic that has helped thousands. Check it out.

Frequently Asked Questions (FAQs)

u003cstrongu003eHow do you revive a dead AGM battery?u003c/strongu003e

Revive and resuscitate mean the same thing. So, the method I have described above answers the question here.

u003cstrongu003eWhat happens if you drain an AGM battery?u003c/strongu003e

After completely draining an AGM battery, you have to revive it using special methods. Only then, you can reuse the battery.

u003cstrongu003eHow long does it take to charge a completely dead AGM battery?u003c/strongu003e

I have gone through several videos charging a completely discharged AGM battery and seen that it takes about 2 hours for charging a dead AGM battery. However, the time limit can change depending on several other factors. You can u003ca href=u0022 target=u0022_blanku0022 rel=u0022noreferrer noopener nofollowu0022u003eu003cstrongu003echeck out this articleu003c/strongu003eu003c/au003e to find out the charging time.

u003cstrongu003eCan you completely discharge AGM batteries?u003c/strongu003e

Yes, you can completely drain an AGM battery but you must not do it because it shortens the battery’s life drastically. Experts recommend owners to not discharge the battery less than 12.2V.

u003cstrongu003eHow deep can I discharge an AGM battery?u003c/strongu003e

The DoD or Depth of Discharge rate in AGM batteries is 80% which is great compared to the cheap flooded batteries. They are limited only to 50% of their capacity.


I hope that you have got the answer to the question, how to resuscitate a deeply discharged AGM battery.

But you should know that the method I have described above may or may not work as some AGM batteries have more than one life and some don’t.

You can read this thread and know more about it. All you can do is try. If it does not come back to life, you should get a new one.

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