Charging AGM Batteries Properly To Maintain Battery Health
Charging AGM batteries properly is a very important step in ensuring a long service life. AGM batteries are used for a wide range of applications. For example, they are used in powering your electronic devices, providing backup power to your UPS, powering your car and storing renewable energy for future use. In order to ensure your AGM battery lives for years, it is critical that it is charged properly. If you charge your AGM batteries in the wrong way, they will face premature aging. Meaning, your batteries will die our much faster than they are designed to. In fact, improperly charging your AGM battery may cause the cells to preheat, damaging the battery and causing it to die within a matter of hours. In order to make the battery live for years, follow the 4 tips below for charging your AGM battery:
1. Buy The Recommended Charger
Battery chargers are not designed to as a one-size fit all. Some chargers are designed to provide small amounts of power, while others are designed to provide a lot of power. Generally speaking, the larger the battery, the bigger the charger you’ll need. The opposite is also true. The smaller a battery is, the smaller charger you’ll need. When we’re talking about the “size” of the battery or the “size” of the charger, we’re not talking about the physical dimensions. In fact, we are talking about capacity, which is annotated in amperes (Ah). To learn more about how to select an AGM battery charger.
2. Understand How Charges Affect Different Batteries
Many people believe that charging AGM batteries is similar to charging their laptop battery, but of course this is not true. In fact, the batteries used in laptops are a completely different technology. Laptop batteries are lithium while AGM batteries are lead acid. For this reason, charging AGM batteries is different and requires special charging procedures. For example, lithium batteries may be partially charged for a while without significantly harming the batteries. Charging AGM batteries requires you to fully recharge the battery. In fact, you’re supposed to slightly over-charge the batteries to give them a “top up”. Smart AGM chargers does that all for you, so you don’t need to worry if you’ve got one of those. If you repeatedly only partially recharge an AGM battery, let’s say up to 70% every time, the battery may actually lose it’s ability to fully recharge to 100% in the long term. This means the AGM battery would only be able to recharge up to 70%.
3. Charge AGM Batteries In The Right Temperature
AGM batteries have a certain charge temperature range. This means if the temperature falls outside of this range, you should not be charging AGM batteries. For all types of lead acid batteries, you should avoid charging if the temperature raises above 40 degrees Celsius or 104 degrees Fahrenheit. Cold weather also affects charging AGM batteries. You should avoid charging your batteries if the temperature falls below 0 degrees Celsius or 32 degrees Fahrenheit. Ensuring the temperature is within the range of 0 and 40 degree Celsius is important while charging, in order to ensure the battery lives as long as it is designed to.
4. Don’t Worry If Battery Warms Up
Toward the end of charging AGM batteries, the cells may feel warm. This warmth is normal for lead acid batteries. In fact, you can still use the battery in your electronic devices while it’s warm. Please be careful and note that we are only referring to AGM batteries when claiming it’s fine to use them while they’re warm. This does not apply to small AA and AAA rechargeable batteries, which you may have picked up from your local grocery store. Furthermore, when referring to a warm AGM battery, we are not saying hot. If the battery is too hot, you definitely should not use it. However, if you place you hand on the battery and feel a bit of warmth, then it is normal. If you feel your AGM battery is getting too warm during the charging stage, you may give it a break by disconnecting the battery. Once the battery cools back down, then you can reconnect the charger to continue charging.
Bonus Tips!
The table provides charging tips for three types of batteries:
- Lead Acid
- Nickel-based
- Lithium-ion
Please remember that the 4 tips mentioned above are for charging AGM batteries. The tips do not apply to Nickel-based or to Lithium-ion. However, this table was provided to you in order to note that there are many different types of batteries. It is also important to note that each battery type requires different charging specifications. Click here for the source of this table.
EXCELLENT INFORMATIONAL ARTICLE! MAY WANT TO ADD–Longer service life can be gained by never discharging AGM style batteries more than %50 if possible.
Hi, I have a 90Ah main battery with a 14Ah stop/start. I took it to a battery shop that tested the big one at 11.8v and said it needed a charge as it should be closer to 13v(?). I have charged it for 48hrs at 8A but it’s still not showing fully charged on the charger although it is now showing over 12v on my simple voltmeter. I’ve just put it back in the car and I am still seeing the “battery not charging” warning so I have just taken off the small one to charge it. They are both AGM and off a 7-year-old Jaguar XF Sportbrake which I have had from new and I’ve never charged either battery. Any ideas or do I just have to accept the batteries are old and buy replacements? TIA for advice
It sounds like your 90Ah battery reached the end of its life and requires a replacement.
Because you have already tested it by charging 3 to 4 times its capacity and the voltage is still only 12V, then it is a clear indication that one cell in your battery is gone (internally short circuit). You have to replace the battery now. 7 years of use is good enough for the battery. I can say this because of my more than 40 years of teaching experience in electrical and electronics engineering and the practical use of various types of batteries.
Prof. C.K. Dwivedi
Hi, I have four AGM batteries on a boat. what is the best solution to charge these batteries when the boat is near the main power on shore? two is of varta LA70 Ah and two is BANNER 12V 80Ah
I was very impressed with the design of the Canbat 12v 100ah AGM Battery: Compact and sturdy construction, adaptable to different circumstances, Canbat’s Batteries minimize any possible acid spill without no need to check acid and water level frequently, it can generate 24V or 48V ranges without any problem. The choice of materials used in the design of this 12V 100Ah battery gives it exceptional durability. It features a heavy-duty and top-notch calcium-alloy mesh known for its excellent and long-lasting performance.
Great tips! I especially found the advice on adjusting the charging voltage for AGM batteries really helpful. I never realized the importance of that detail. Looking forward to trying these out!