How To Recondition AGM (Absorbent Glass Mat) & SLA (Sealed Lead-Acid) Batteries

Supplementary Guide: How To Recondition AGM (Absorbent Glass Mat) and SLA (Sealed Lead-Acid) Batteries version 2.5

“Learn how to bring AGM and SLA batteries back to life again.”

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Table of Contents Copyright ................................................................................................ 2 EZbatteryReconditioning.com Terms & Legal Disclaimer ........................ 3 Don’t Throw Out Your AGMs or SLAs – Recondition Them! .................... 7 Why Do AGM & SLA Batteries Die? ......................................................... 9 Two Additional Ways To Bring an AGM and SLA back to Life: ............... 10 Method One: ...................................................................................... 11 Method Two: ...................................................................................... 18 Conclusion: ........................................................................................... 19

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Don’t Throw Out Your AGMs or SLAs – Recondition Them!

It’s amazing how many good AGM (Absorbent Glass Mat) and SLA (Sealed Lead-Acid) batteries get thrown out because people think they’re dead and can’t be reconditioned.

About 85% of the AGM and SLA batteries we see can be brought back to life with pretty simple reconditioning methods, which we’ll teach you in this guide.

AGMs and SLAs are pretty expensive so using the information in this guide will save you a significant amount of money. You’ll also have better performing AGM and SLA batteries that last much longer than they otherwise would. And the good news is, you can continue to reuse this information every time one of your AGM or SLA batteries gets old or dies!

So if you’re ready to recondition your AGM and SLA batteries, let’s get started!...

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*To Recondition Sealed Lead-Acid (SLA) batteries: SLAs are lead-acid batteries so use the main “EZ Battery Reconditioning Lead-Acid Guide” in conjunction with this guide.

The “EZ Lead-Acid Battery Reconditioning Guide” goes into more depth about SLAs and how to recondition them. However, this guide provides more details about how to do certain things we mention in that guide: like opening up an SLA battery and recharging it with a technique unique to SLA and AGM batteries.

*To Recondition Absorbent Glass Mat (AGM) batteries: This is the main guide you should use to reconditioning AGMs. However, some of the methods and technical terms we discuss in this guide are shown in detail in the “EZ Battery Reconditioning Lead-Acid Guide”. So please use both guides when reconditioning your AGMs also.

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Why Do AGM & SLA Batteries Die? There are a number of reasons this happens. AGM and SLA batteries are lead-acid batteries so the same problems we discuss in our main lead-acid battery reconditioning guide also affect AGM and SLA batteries. So if you haven’t read our main lead-acid battery reconditioning guide yet, we recommend you do so now before you read this guide because we talk in depth about why lead-acid batteries die.

Basically it boils down to a few issues typically. First, cells of AGM and SLA batteries dry out. Not many people realize this because they figure this doesn’t happen in sealed lead-acid batteries – but it does.

Additionally, AGM and SLA batteries deal with sulfation issues, just like the other lead-acid batteries discussed in our main lead-acid battery reconditioning guide. This can be fixed by re-dissolving the sulfate crystals in the electrolyte. To learn how to do this, please use our main lead-acid battery reconditioning guide because we won’t go over it again in this guide.

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Two Additional Ways To Bring an AGM and SLA back to Life: In addition to the methods we teach in our main lead-acid battery reconditioning guide, AGMs and SLAs can be reconditioned with two additional methods. The issues that absorbent glass mat and sealed lead-acid batteries have (that we previously described in this guide) can be remedied with one or both methods typically.

Method One in this guide will bring your AGM/SLA batteries back to life most of the time. But you can always try Method Two if you’re still having trouble with your battery after finishing Method One’s steps.

So to get started, get out your old SLA or AGM batteries and let’s begin.

Also, be sure to use the safety precautions we talk about in our main lead-acid battery reconditioning guide when working with these batteries (especially when we open them up).

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Method One: Like previously mentioned, the cells of an SLA or AGM battery dry out and this causes several issues. Luckily, there is a way to fix this.

So follow these steps: Step 1) Typically AGMs and SLAs have a plastic cover over the top of the battery. Slip a blade in between the cover’s edge and the battery top and gently drag the blade all around the edge of the cover to help break the seal of the cover. If you have a box cutter, these work great for this step.

Description: Gently breaking the seal between the battery cover and casing with a small blade

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Step 2) Pop off the top of the battery with a screwdriver or icepick. You can slip the edge of a slot/flat screwdriver under the plastic cover we just broke the seal to and pop it off like in the following example: *Note: Once you pop the top off, each individual cell will most likely have a little battery cap as well. Pop these off also to expose the inside of each battery cell.

Description: Popping off the top of an SLA or AGM battery

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Step 3) Refill the cells with distilled water. Please note that it’s important to only use distilled water for this step. Tap water will damage your battery.

We also find it very helpful to use a syringe to fill each cell but you can also just pour the distilled water into each cell if you don’t have a syringe.

We recommend filling each cell so the plates are covered with a 1/4” to 1/2” inch of distilled water.

Also, during this step you can also optionally add Epsom salt to each cell to help with the reconditioning process. We show how to do this in our main lead-acid battery guide - so please reference that.

Description: Filling each cell with distilled water using a syringe

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Step 4) Once the cells are full again, leave the cover of the battery off (and the cell caps off), and charge the battery with a charger. A standard 4 stage charger works great for this.

Description: Charging the battery with the top and cell caps off

During this step, excess water may start to run out over the battery when it's bubbling (like in the following example). Be sure to monitor this and soak it up.

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Description: Water from the cells may bubble up onto the battery during charging. Be sure to clean this up.

This is important: Do not reseal the battery during this step. We want to ensure each cell is full of distilled water once charging is done (and in the next step we will continue refilling the cells as the water bubbles out – and the top must be off to do this).

Safety precaution: During this process the water will eventually start to boil. Please use the precautions discussed in our main lead-acid battery reconditioning guide.

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Step 5) During the charging process the cells will start to get low again because water will bubble and gas out like we discussed in the last step.

So continue refilling the cells with distilled water while it's charging.

To do this, we recommend using a syringe to squeeze the water into each cell in a controlled manner. The distilled water should be 1/4" to 1/2" inch above each cell.

Description: The water level in each cell will start to get low again during charging. When you see this, continue to refill the cells while still charging.

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Step 6) Once the battery is charged again, soak up any excess distilled water and reseal the battery.

At this point, the battery should be working great again! This process fixes most of the major issues AGM and SLA batteries experience. So you can now put your battery back into use or test it with a multimeter to check on its status (*Note: we show how to do this in the main leadacid battery reconditioning guide).

Also, remember to always keep the battery in an upright position.

Description: The battery is now reconditioned so you can reseal it and put it back into use!

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Method Two: At least one vendor makes a product (BatteryMinder) which can desulfate SLAs and AGMs. It does this by using a pulsed charge at RF frequencies.

This is supposed to keep the charging power low while maintaining a high enough voltage. Lead sulfate cells resonate in the RF region and break up into smaller pieces. This helps them dissolve more quickly.

So if you want to use a device to recondition your SLAs or AGMs, we recommend trying out the BatteryMinder.

We have one in our shop and it works great. But the manual reconditioning method (Method One) should be attempted first.

Method One works most of the time and you may not need a pulsed charger (like the BatteryMinder).

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Conclusion: About 85% of the SLAs or AGMs we get in our shop can be reconditioned with these methods. Many people throw away perfectly good batteries because they don’t know they can easily recondition them like we just showed you.

Please also remember to always use proper safety precautions when working with SLAs and AGMs. Wear protective eye glasses, gloves, and every other precaution we discuss in the 12v guide when following our reconditioning steps.

We hope you enjoy your “like new” SLAs and AGMs! These are expensive batteries so reconditioning and reusing these batteries will save you a lot of money! Especially when you consider that you can use this information every time one of your batteries gets old or dies. Learn this information once and benefit from it the rest of your life!

Thank you for reading our guide. And thank you for making us your trusted battery reconditioning experts.

Happy Battery Reconditioning, Tom Ericson and the EZbatteryReconditioning.com team

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