3 Tips You Need to Know for Filling & Charging an AGM Powersports Battery. Acdelco battery add water

Tips You Need to Know for Filling Charging an AGM Powersports Battery

Absorbent Glass Mat (AGM) batteries are commonplace in powersports applications nowadays.

There’s a big reason why: These AGM batteries are virtually maintenance free. Back in the day, a flooded lead acid battery needed to be routinely checked and filled to ensure it could maintain a charge. On the other hand, AGM batteries are pretty much hands off—provided you follow the proper steps to prepare them for the initial charge, that is.

That’s why we’re writing this quick article. If you buy your AGM battery from a walk-in store or dealership, there’s a good chance it’s already been properly charged and is ready to drop into your motorcycle, snow mobile, lawn mower, or whatever.

But if you buy your powersports batteries online, you’ll probably have to set up your AGM battery yourself. And this initial prep and charging process is critical; if you don’t follow the instructions, you risk permanently damaging your battery.

And while your battery will likely come with its own instructions, we wanted to emphasize three tips to ensure your battery has a long service life.

AGM Battery Initial Prep Charging Tips

Fill Your Battery with the Right Amount of Electrolyte (Not Water!)

First off, electrolyte is essentially a fancy word for battery acid. It’s corrosive and can burn the skin, etch surfaces, and dissolve paint—so make sure you take the appropriate precautions when handling and filling your battery, and dispose of excess electrolyte properly.

It’s vitally important to realize that electrolyte isn’t water. Yes, unlike AGM batteries, flooded lead acid batteries get topped-off with distilled water as part of their regular maintenance process, but not before being filled with acid first.

importantly, don’t confuse traditional lead acid battery maintenance procedures with any of the steps involved with prepping an AGM battery prior to its initial charge. No water, distilled or otherwise, is involved in an AGM battery’s filling process. You need to use electrolyte, AKA battery acid.

In all of our initial battery charging experiences, the AGM battery manufacturer has included the electrolyte with the battery purchase. But if yours didn’t, you can buy your battery acid separately.

Either way, you want to make sure you fill your battery to the proper levels.

After Filling the Battery, Wait for the Acid to be Fully Absorbed

This is probably the step that’s overlooked the most. After the electrolyte has drained into the battery…wait! This allows the acid time to absorb into the glass mat. Remember, it’s exactly what the “A” is in AGM, after all.

If you immediately throw the battery on the charger, it could damage the battery and shorten its lifespan. You may not notice it at first but over time, the battery could develop issues like weak starting performance and a Rapid discharge rate.

How long you should wait depends on the battery manufacturer, but in our experience it’s about an hour or two. After the wait, you’re now ready to hook it up to a battery charger.

Use the Proper Current (Amperage) to Charge Your Battery

Here’s another simple aspect of battery prep that folks can overlook.

If you read our earlier story on EV Battery Life, you already know that batteries don’t always like being charged at high current levels. And that’s especially true for new AGM batteries getting an initial charge. While a lot of battery charger models have selectable current levels in excess of six amps, in our experience, many initial charging instructions call for a lower current rate, more like two amps.

Slamming too much amperage into a new battery can fry the acid inside, which again, could significantly reduce its usable life and cause other performance issues. While there’s no universal current rating for every battery, each battery manufacturer will spec the particular battery’s preferred initial charge amperage in the instructions.

In addition to charging current, your battery manufacturer will also indicate how long you should leave the battery on the charger for its initial charge. It’ll usually vary between five to 10 hours, again at a low amp rating.

Follow Your Battery’s Charging Instructions

While these three tips are important, consider them a supplement to your original battery manufacturer’s instructions. You should always read your particular battery’s initial changing and maintenance manual thoroughly before beginning, to ensure you’re hitting all the proper steps.

All told, it’s not difficult to prep and charge an AGM battery for the first time, it’s just critical that you follow all the instructions precisely. Doing so will ensure your battery has a long, happy service life.

Car Batteries: Than Just Wet Lead

Working on car electrical systems used to be easy. The battery simply provided power for the car’s starter motor when starting or to run the small number of accessories when the engine wasn’t running. The rest of the time, the alternator charged the battery and provided power for the rest of the vehicle and the ignition system. While very early cars didn’t have batteries, and some old cars had 6 V positive ground systems, most of us have lived our entire lives where car batteries come in several sizes (controlled by Battery Council International) and cars have a 12 V, negative ground system.

Times have changed. Cars don’t have distributors anymore, they have computers. They also have lots of gadgets from GPS to backup cameras and cellphone chargers. Batteries have had to get beefier and the modern trend is to also require less maintenance So, today, you’ll find that there isn’t just one kind of car battery. But how do these other batteries work and what was wrong with the good old lead acid wet cell?

For the purposes of this post, I’m not talking about electric car batteries which is a whole different topic — and most of them have a regular car battery, too.

In the Realm of the Practical

Back to reality, you don’t need to pay 800 for a car battery, but there are a number of choices. The traditional battery we all grew up with is a flooded-cell lead-acid battery. These batteries have a number of desirable characteristics. They stay charged for a long time. They can handle large surges like the ones that occur when you crank the starter motor. They can survive being lightly discharged and recharged many times. In fact, most of these batteries don’t like being totally discharged and recharged.

These batteries are simple enough. Each cell has a grid with a lead-based alloy for the cathodes and lead oxide anodes sitting in sulfuric acid. A typical battery has six cells to get to 12.6V, and there was a cap that allowed the user to add water — preferably, distilled water — when needed and also would vent out hydrogen gas generated during charging.

Evaporation and Shedding

The scourge of all this is evaporation of the electrolyte battery. With old batteries, you could actually spill the contents. Battery operation also removes water. Heat can evaporate liquid. Less liquid means less surface area exposed to electrolyte which reduces the battery’s capabilities. It also can lead to sulfation, where the electrodes are coated with lead sulfate which weakens the battery and requires careful recharging.

However, the primary wear on this type of battery is how part of the material sheds lead sulfate during operation, which sinks to the bottom of the battery. Deep cycle batteries will have thicker plates and more room at the bottom for waste to accumulate. Eventually, if enough waste material accumulates at the bottom, the battery will fail.


In the day when you had to check the water in the battery like checking the air in tires, there were additives like VX-6 that you could dump into the battery cells that used cadmium sulfate to prevent sulfation. At least, that was the claim that some disputed.

But clearly, you would like to have a battery that lasts forever and doesn’t require any maintenance. You can’t have everything, of course, but you can try. New alloys reduced the amount of water decomposed, so batteries can have enough liquid in them to last over their useful service life. That’s why most batteries today are sealed and only have vents for gas to escape during charging.

Enhanced flooded batteries were another innovation and managed to largely supplant conventional batteries. These use a polymer separator that is porous to electrolyte but prevents the plates from shorting together. These batteries last much longer than conventional batteries and have far greater tolerance to deep discharge.

Glass Tacks

The major battery today, however, is the AGM or absorbent glass mat battery. These are also known as valve-regulated lead-acid or VRLA batteries or sealed lead-acid batteries. Technically, VRLA or sealed lead acid can also refer to gel cells, but in automotive applications, you usually see AGM batteries due to the fast charging and long service life they provide.

The key innovation to AGM batteries is that the electrolyte isn’t a liquid. Instead, it is held in a fiberglass mat woven from very thin glass fibers. During manufacturing, the mats are soaked in acid, wrung out to remove excess liquid, and then installed in the battery where they keep sufficient acid in contact with the electrodes for the life of the battery.

AGM batteries require little maintenance and, unlike liquid batteries, can operate in any orientation. This is especially important in all-terrain vehicles and motorcycles where the battery may be tipped or flipped. They also emit less hydrogen gas which makes them safer. They do not require any periodic maintenance, but they may or may not last longer than a properly maintained conventional battery. Note, though, that if you don’t maintain the normal battery properly, all bets are off. Then again, overcharging is harder on AGMs.

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While a mat seems to imply a flat pad-like structure, AGM mats can be rolled or put in other configurations depending on the battery. For example, below you can see a comparison of a conventional battery and a spiral AGM battery. Another option for semi-solid electrolytes is the gel cell, but you don’t see these often in automotive applications because the gelled sulphuric acid doesn’t perform well at colder temperatures.

There are ways to fix some types of problems in unsealed batteries, some of which involve big voltage spikes. Thomas Edison liked using nickel-iron batteries in his electric car, and there may be a bit of a revival of this technology in some cases, too.

Posted in Battery Hacks, car hacks, Hackaday Columns, Slider Tagged AGM battery, car battery, lead acid battery

The Most Important Facts (And Myths) About Your Car Battery

We’ve also got a few tips on how you can take care of and recharge your car’s battery.

By Alex Leanse Published: Aug 11, 2021

Even if you’re driving a gas guzzling SUV, electricity remains crucial to driving a car. Thanks to modern-day electric batteries, drivers no longer have to turn an engine over by hand. It now all happens with the turn of a key or a press of a button.

➡ You love cars. So do we. Let’s nerd out over them together.

But beyond that initial ignition, the battery continues playing a vital role in all of your vehicle’s electric systems, but some myths have circulated about this electric heart pulsating in all our autos. Here’s a thorough examination of those myths and some some cold, hard facts to replace them.

Battery Life (and Death)

A car battery should last about six years, but like most car parts, that all depends on how you treat it. Multiple discharge/recharge cycles shorten any battery’s life, and using electronics in the car while the engine is off is the quickest route to a dead battery. Of course, a battery can maintain a charge while the engine is on, but once it’s off, electronics draw directly from the battery.

To avoid this recurring auto nightmare, always turn the headlights and interior lights off when you’re done driving. Remember that leaving electronics like GPS or cell phones plugged into a car charger can drain the battery, too.

Take Charge: Car Battery Recommendations

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No matter how well you take care of it, eventually your battery will die and you’ll need a replacement. Failing batteries usually display obvious symptoms that let you know it’s on its way out. Slow cranking on startup indicates that the battery may not be able to provide enough power to fire up the engine, and an illuminated Battery Warning Light on the dashboard is clear indicator it needs attention. If vehicle electronics like remote locks or interior lights randomly stop working, a dying or dead battery could be why.

Also, batteries—alive or dead—are full of chemicals, so do nature a favor and dispose of dead ones properly. Don’t just toss it in the trash because chances are your local mobile mechanic or auto supply store can recycle it for you.

Weather Matters

Ambient temperature has a significant impact on battery life and performance. Most car batteries use a liquid electrolyte solution to hold a charge, which is affected by hot or cold weather. While it takes extremely low temperatures to freeze a battery, cold reduces the solution’s ability to transfer full power (which is why it can be hard to start a car in winter). There’s a misconception that buying a battery with a higher CCA (cold cranking amp) rating will remedy this, but since vehicle computers regulate the amperage required for startup, it actually won’t make any difference. Use a battery heater instead – it’s like a toasty jacket that will keep your battery warm and reliable all winter.

Keep Your Car in Mint Condition

On the flip side, hot weather can cause the battery solution to evaporate, limiting its ability to hold a charge. You may notice a rotten egg smell from the sulfur in the solution if this happens. A common myth is that you can simply refill it with tap water to make up for evaporation, but tap water contains minerals and impurities that can damage battery cells. Use deionized or demineralized water instead, but if you have to do this it’s probably a sign that you need a replacement soon. Keeping your car garaged helps the battery cope with temperature extremes so it lasts longer and works more reliably.

Jumpstarting Made Easy

Almost every driver has to deal with a dead battery, and jumpstarting is usually the easiest way to get it recharged. Before jumpstarting your car, read the owner’s manual. The process is similar for most cars, but there may be special considerations for your specific vehicle.

First, to jumpstart a car, you will need a set of jumper cables, rubber work gloves, a pair of safety goggles and another vehicle with a fully charged batter of the same voltage of the car being jumped. Check out some of our favorite tools below:

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