Over the years, we have written quite a bit about AGM batteries. That’s for several reasons: 1.) AGM batteries often require different service routines than traditional flooded lead acid batteries, especially when it comes to testing and charging, two topics that are near and dear to our hearts; 2.) there is quite a bit of confusion and misinformation out there related to this battery type, which we try to do our part to set straight; and 3.) AGM batteries have seen rapid growth in the North American car parc in the past 10-15 years, which means that our audience is encountering these batteries more and more, whether they’re a professional technician or a vehicle owner.
To provide a sense of just how AGM batteries are growing in popularity, here’s a quick excerpt from US AGM Batteries for Car Market, a December 2025 research report from Emergen Research. “The growing prevalence of start-stop systems in modern vehicles is a primary driver of the AGM battery market… According to the US Department of Transportation, the adoption of start-stop technology has increased by over 30% in new vehicles since 2020. This trend is expected to continue, with manufacturers increasingly incorporating AGM batteries to support the energy demands of these systems.”
So, if you’re servicing vehicles in a shop or dealership, you are definitely encountering a significant increase in the number of AGM-equipped vehicles in your bays. If you are a vehicle owner, it is just a matter of time before AGM batteries are part of your life, if you haven’t run into these batteries already.
So, what is it that you should know about these batteries? That’s the focus of this month’s article.
What is an AGM Battery and How is it Different?
If you talk to six people and ask what AGM stands for, you’re likely to get 6 different answers, especially when it comes to what the “A” stands for. We prefer the term Absorbent Glass Mat. Here’s a quick definition from Lifeline Batteries, Inc.: “AGM batteries function through a sophisticated design that sets them apart from traditional lead-acid batteries… In AGM batteries, a specially designed glass mat separator absorbs and immobilizes the electrolyte solution, allowing oxygen to recombine with hydrogen during charging, creating a maintenance-free sealed battery.”
Some of the advantages of AGM batteries vs flooded lead acid batteries are that they are maintenance-free, vibration resistant, provide better low temperature performance, are spill-proof and have a lower self-discharge rate. Despite this last advantage, we still caution you to charge your AGM battery every 90 days during periods of non-use. AGM batteries come in a wide variety of sizes and shapes and include traditionally shaped AGM batteries, Spiral Wound AGM batteries, Start-Stop AGM batteries and Deep Cycle AGM batteries, just to name a few. The good news is that battery manufacturers are doing a much better job of identifying these batteries as AGM construction, which helps to remove the guesswork, as in, “What type of lead acid battery is this?”
Stop Me If You’ve Heard This One Before – You Need an AGM-Optimized Charger
We’ll get this one out of the way first, since, if you been with us for any length of time, you are likely sick of hearing this mantra from us. It is very important, though.
Any time you are servicing (charging or maintaining) an AGM battery, it is in your best interest to use a quality charger with an AGM-specific charge profile built into it. AGM batteries are very sensitive to voltage – deploying a flooded battery charge profile on one will raise the internal voltage above the recommended limit, which will cause damage to the battery. This is especially true when charging an AGM battery using a flooded profile at high amperages (+20A) or for the long duration charging that happens when maintenance charging seasonal use vehicles (even at low amperage).
Testing AGM Batteries – Same Story (sort of)
If you are testing AGM batteries using an electronic (conductance-style) battery tester, it’s the same story as charging. The electronic tester should have AGM-specific testing regimens. This is because AGM batteries have lower resistance than flooded batteries and will react to the electronic pulse of a digital tester differently as a result. In fact, our electronic battery testers feature three different AGM testing regimens – standard AGM, Spiral Wound and Start-Stop AGM. Each of these AGM battery types are different enough that, if you want an accurate assessment of battery health, they need their own testing regimens.
If, on the other hand, you are testing AGM batteries using a traditional invasive load tester (carbon pile or fixed load), there isn’t really a way to modify or adjust the testing regimen based on the battery type. Proponents of this testing style would say, “Good. I just want to know if the battery can hold a load.” This makes perfect sense, but we would caution that AGM battery “end of life” doesn’t look the same as that of a flooded battery. So, using a digital testing process can sometimes spot a lurking problem in an AGM battery when an invasive load test would indicate that the battery still has the required capacity. In fact, many shops use a combination of digital testing plus carbon pile testing to get the most accurate assessment and deliver high customer satisfaction (customer is told the battery is good, but it later turns out to be bad, and vice versa).
What About Jump Starting?
Jump starting is very different than battery charging and maintaining. When jump starting, you are essentially augmenting the vehicle’s starting battery, adding capacity to overcome its low energy condition. In this sense, when jump starting, you aren’t really “pushing” energy to the vehicle’s battery, like a charger does. So, you can use an AGM (SLA) jump starter to jump start a vehicle with a flooded, AGM or lithium starting battery. Similarly, you can also use a lithium jump starter to jump start a vehicle with a flooded, AGM or lithium starting battery.
Of course, we have to mention safety whenever we’re talking about jump starting.
! Always wear safety goggles when working around vehicle batteries.
! Always inspect your jump starting equipment to be sure it isn’t compromised by damaged components, such as frayed output cables or problematic clamps.
! Always make sure that your jump starter’s operating voltage matches that of the vehicle under service.
! Lastly, always be sure to connect the negative lead to a good engine or chassis ground, not the vehicle battery’s negative battery terminal.
All of these safety tips apply to charging events as well, including “negative goes to ground.”
What Should I Know About Replacing the Battery in My Vehicle?
Generally speaking, the consensus is to always replace your vehicle battery with a like battery: size group size, battery type, power capacity, etc. Specific to the AGM question, vehicle manufacturers and battery suppliers both caution against downgrading from an AGM battery to a standard flooded battery when choosing a replacement. This is because an AGM has different properties, especially when it comes to managing vehicle loads and deeper discharge conditions, particularly in vehicles with Start-Stop systems. So, if the original battery is an AGM, is always best to replace it with an AGM.
Going the other way is slightly more complicated. We have seen many references that say it’s OK to upgrade from a standard flooded battery to an AGM when the time comes for replacement. This is definitely safer than downgrading, but it is not a simple answer. Many older vehicles have charging systems that reach higher voltage levels than what an AGM battery should be exposed to. Our suggestion is to do your homework before making this switch. In many cases, you will be fine. But, in some cases, the AGM will be exposed to excessive voltage (for it), which will reduce the useful life of the battery. So, it might not turn out to be the upgrade you thought you were getting.
When it Comes to Managing AGM Batteries, We’ve Got You Covered
At Clore Automotive, we have been delivering best-in-class AGM battery service equipment for 20+ years. We know AGM batteries, what they need and how best to interact with them. That means our solutions offer the precision needed to properly assess and service AGM batteries, effectively, efficiently beneficially and safely. Here’s a quick list of our products designed to help you execute optimal AGM service applications:
Do you encounter tons of vehicles equipped with AGM batteries in your shop? Have you seen the prevalence of AGM batteries in your customers’ vehicles increase in the last 6-10 years? Do you have any tips or tricks you would like to share with your fellow readers? We (and they) would love to hear about them in the comments below.
15 Responses
I was confused as to why this article you didn’t mention the Truck Pac Power Source Power Supply, especially the ES6000 unit that I have.
William – Thanks for your comment. You make a great point. Sometimes, we emphasize JNC and sometimes emphasize Booster PAC. In this case, since JNC has both AGM-battery jump starters and lithium-battery jump starters, we chose to focus on it. The Booster PAC / Truck PAC models are equally effective as a jump starter for vehicles equipped with flooded, AGM or lithium starting batteries. The ES6000 is a monster unit and we recommend it to customers regularly. Thanks again, Jim from Clore Automotive
if I never use auto stop start , can I use a regular battery?
Ron – It is not recommended. If your vehicle’s system is designed for use with an AGM battery, it will likely have operational aspects that would be detrimental to a standard flooded battery. Thanks, Jim from Clore Automotive
This article wasn’t about your jump starter or any jump starters specifically. The topic is battery types and they’re differences
Don – Thanks for your comment. That’s correct. This article was intended to inform our audience about the current state of AGM batteries, their service implications and the details we feel that our audience needs to know. Thanks again, Jim from Clore Automotive
Great AGM info thanks for article
You say “AGM battery “end of life” doesn’t look the same as that of a flooded battery”. What does it look like?
Ron – Thanks for your question. When many of us learned to drive (years ago), we learned the telltale signs that our flooded lead acid battery was on its last legs. Often, we’d experience extremely long cranking or the need to attempt the start multiple times. Maybe the vehicle’s lights weren’t as bright as normal. For many AGM batteries, they do not show those signs because their decline is steep and sudden, vs the gradual decline of the traditional flooded lead acid battery. Often, an AGM-equipped vehicle starts the car perfectly fine on Tuesday and is totally dead on Thursday. Electronic testers could provide more early warning to this coming “fall of the cliff” than traditional carbon pile testing. That’s what I was referring to. I hope this better explains it. Thanks again, Jim for Clore Automotive
great informative article on AGM batteries. I am actually dealing with an AGM issue on my tow car at the present. I thought I “knew” about AGM but learned more here, like definitely do not use STD 12v charging on an AGM.
My recent experience has tough me more than what is in this article though it has more to do with vehicle energy demand the the battery itself. I have a 2023 Equinox RS with most of the modern conveniences. It came with an AGM. At 23 months I had to have it towed to the dealer for replacement under warranty. After the replacement I started to watch electricity usage by this car and was very surprised by the result. These modern cars are energy hogs. As soon as you unlock the door the interior and exterior lights energize. The infotainment system will also turn on as well as many sensors. If you car came with Auto start this too energizes by defalt, even if you turned it off before. If you are going in and out of your car, such as making multiple trips from the car to the house with groceries, the car goes through this process every time you lock and unlock the car. All this draws energy. If you are a daily commuter of 30 miles or more this generally has limited effect but if you are an urban dweller, making several short trips to the grocery, post office and general shopping during the week with runs of only a few miles between each stop you can significantly draw down the battery as the alternator doesn’t operate long enough to recharge the battery. Auto start puts even a greater drain on the battery. In addition my car has an alarm system that is armed when the car is turned off.
I found that going from a full charge of 12.8 to 13.0 for a resting battery, in the course of a typical week’s driving my battery SOC drops to 11.8- 12.0. if I go 10 days with minimal use the battery voltage can drop to 11.5. Running the running the engine at idle for 15-20 minutes will only add about .5v (12.0 to 12.5). As a result I have to put the battery on a charger about once per week to fully charge.
In my case our toad is also our daily driver although when at home we only drive a few times a week. YMMV.
Many modern cars do not come with a standard alternator gauge but the battery status may be found via your infotainment system. BTW – the dealership has been of no assistance in finding a solution to this other than to advise driving more often for longer periods.
Nolaguy – Thanks for your comment. You make some great points. Yes, this is a very real problem for those who use their vehicle only sporadically and then for short trips when they do use it. Our friend Bill, the creator of batteryfaq.org, has address this very situation in our blog comments over the years and via a Clore Story from several years ago. As you point out, the electrical/electronic load demand on modern vehicles is very significant, and without regular longish use, the strain placed on the battery can be significant. They way Bill addresses this in his life is to regularly charge his vehicle batteries using a quality charger/maintainer (in his case, PRO-LOGIX chargers) to keep the fully charged despite this usage situation. Thanks again, Jim from Clore Automotive
I had the same issue on my 2015 Subaru outback (second hand car). Finally traced it to the computer turning the alternator “off” unless a large load was activated – A/C, Lights, High fan setting, etc. I used a cigarette lighter combo power spliter/usb ports/digital volt meter, all in one device.
Sure enough, my battery voltage started around 12.6 or lower, and I could watch it go down steadily to under 12 volts while I was driving around down or on the highway, as long as I had no “large” power draw active. Battery voltage at the meter immediately jumped to 14.4 as soon as I activated lights, high fan speed, etc. More research exposed the culprit – Subaru wanted to save a slight amount of gas by turning off the alternator when it was “needed”. There are numerous blogs about this – lookup 2015-2018 Subaru outback for more. My solution is to turn on the running lights when I drive in daytime. Only problem is that I need to remember to switch to “Automatic” at night time. Good luck
Fred – Thanks for sharing your experience. Jim from Clore Automotive
I’ve been using Solar jump starters for probably almost 20 years. A couple of years back I bought the Solar charger/maintainer and replaced my original jump box with the lithium 345 jump pack.
I enjoy reading the newsletters as I always learn something.. technology and batteries always change.
Is company is one that I can trust with their information.
Don – Thanks for your comment. We appreciate your long standing support of our products. We are glad that our articles are helpful to you. Thanks again, Jim from Clore Automotive