AGM (absorbed glass mat) technology first became popular in the 1980s as they reduce battery weight and improve reliability. Since then they have become more common as they are able to provide a high current at relatively low costs. Moreover, as all of the electrolyte (acid) is absorbed into the fine fibreglass mat, they cannot spill, even if damaged. This means that they are great for off road batteries, so you could jump your truck all over the place and still have a battery that works.
The ability of AGMs to withstand plenty of abuse and their durability gives them the advantage over gelled batteries, whilst their low self-discharge of between just 1-3% also means they can remain in storage for long periods without charging, vastly better than standard batteries.
Despite these benefits, along with all sealed and gelled units, AGM batteries are particularly sensitive to overcharging, meaning that most chargers are likely to overcharge them. To avoid this it is best to use chargers which are micro-processor controlled with specific AGM settings. Five of the best AGM battery chargers are outlined below.
Best AGM battery charger for your RV battery
Optima Digital 1200 12V AGM Battery Charger Review
If you are looking for an AGM battery charger that is able to bring deeply discharged batteries back to life then look no further than the Optima Digital 1200 12V Performance Battery Charger and Maintainer. Whereas other 12V AGM battery chargers will be unable to charge a battery that has depleted to 10.5 volts, this charger can bring back to life batteries that have reached as low as 1.25 VDC.
The charger will charge car, marine, motorcycle and other AGM batteries faster than competitive chargers with up to two times the output. It also has a 5 Watt USB charging port so can also charge smartphones, tablets and cameras with this charger.
In addition to being able to charge your vehicle’s battery when it is flat, this AGM battery charger comes with an additional battery maintainer port and cable so that the AGM battery is automatically maintained if your vehicle is in storage.
This charger is user friendly, with an easy to read backlit LCG gauge displaying battery charging, fill rate, mode setting and fault messages. It also has an inbuilt safety mechanism so the battery will not overcharge. As you can see, this AGM battery charger is an all rounder and an essential item for your garage for both reviving disused or discharged RV batteries, and maintaining battery charge.
Q&A: Is there a float feature to keep batteries charged during the winter?
A: Yes, the Optima Digital 1200 comes with this functionality.
Best for use with Gel Batteries
Battery Minder 128CEC1 Gel Battery Charger Review
The Battery Minder 128CEC1: 12V 2/4/8 AMP Battery Charger is similar to the Optima Digital charger above, however, this charger is the best battery charger for use with a Gel battery. This is another battery charger that is able to revive neglected and abused batteries and works with both AMP and Gel batteries. As this charger caters to different battery types the output voltages will vary depending on the battery type selected, and different amp power can be selected depending on the size of your battery and how fast you want to charge it.
As one of the more advanced battery chargers on the market, this clever device is able to diagnose the batteries condition and can predict failing batteries before they give up. It promises to extend both the performance and life span of all types of 12V batteries by maintaining your batteries to 100% capacity when they are not being used – an economical choice as you are less likely to need to replace batteries that have given up the ghost.
This is a great choice for maintaining cars, motorcycles or trucks that you are keeping off-road for the winter as it can maintain a whopping 8 batteries at one time when connected in parallel (this requires the purchase of Y-Connectors 210AY which are sold separately).
You can also rest assured that your batteries will not be overcharged or undercharged as this is guaranteed by the Auto-Temp Compensation Sensor which is installed in this battery charger.
Environmentally, this product also delivers. Its high efficiency and low power consumption means it meets the strict energy efficiency guidelines of the US Environmental Protection Agency and the Department of Energy.
Q&A: What amp charges are available for a regular seal lead acid battery?
A: You can select from 2, 4 and 8 amp charge settings.
Best tender for AGM batteries (great for off-road vehicles)
Battery Tender 021-0123 Battery Tender Review
If you are looking for the best battery tender for AGM batteries then look no further than the Battery Tender 021-0123 Junior 12V, 0.75A Battery Charger. At the cheaper end of the market than the AGM battery chargers reviewed above this is ideal if you are just wanting to maintain the AGM batteries in off-road vehicles, and are not needing to rescue dead batteries.
The Battery Tender keeps both AGM and Gel batteries fully charged and then maintains the battery charge so that the vehicle or battery-operated equipment you are wanting to maintain is ready to use when you need it. It is designed to switch its output voltage to a safe storage level so that you don’t need to worry about overcharging the battery and, then, if the voltage drops the charge cycle resumes and ensures the battery resumes the correct charge level. Perfect!
Equipped with alligator clips and ring terminals this product is designed to be easy to attach to your device, and its compact size means it can fit in small spaces. The solid state two color LED also allows you to see what stage the charger is at – perfect for ease of use.
It can also be used on a variety of devices including cars, motorcycles, ATVs, personal watercraft, RVs, boats, airplanes, golf carts and back-up generator systems. The 5 year warranty also adds to the attraction of this product.
Q&A: What do the flashing lights mean?
A: If the lights are alternating red and green, this means the 72 hours safety timer has been activated or the battery is defective.
Best Tender For Charging Multiple Agm Batteries
Battery Tender 022-0148-DL-WH AGM Battery Charger Review
If you are a keen collector of recreational vehicles such as cars, motorbikes, and marine vehicles you will no doubt have experienced sitting down to drive your favourite vehicle, starting the ignition and then…nothing. With the Battery Tender 022-0148-DL-WH 12-Volt 4-Bank Battery Management System you don’t need to worry, it can fully charge up to four 12V batteries at the same time and then maintain them at their storage voltage.
This charger uses a 4-step charging program (initialization, bulk charge, absorption mode and float mode), and is simple to use – just connect the charger to up to four batteries (they can be either in or out of the vehicle) and then leave them until you are ready to use. With inbuilt advanced microprocessor technology, you can also rest assured that your batteries will not overcharge but will be kept at the optimum charge voltage – so no need to check on them.
It also comes with a mounting system so can easily be stored and easily accessed, and despite its capacity is compact in size so won’t take up much space. Alligator clips (4 sets) and Ring Terminals (4 sets) are included so you can get charging immediately.
The perfect option for those keeping multiple vehicles in storage over the winter.
Best all rounder
NOCO Genius G7200 AGM Battery Charger Review
If you are looking for a great all-rounder, from a brand you can trust, then the NoCo Genius G7200 battery charger is for you. It is possible to use this to charge any kind of deep cycle or starting battery that you have (for both 12V and 24V lead-acid and lithium-ion batteries) and impressively doubles the charging speed for AGM deep cycle batteries in comparison to a normal charger.
This great value device is incredibly lightweight at under 3lbs, extremely portable and, thanks to its use of the latest battery charging technology, is able to minimize energy consumption whilst in use. This device will also maintain battery life for longer, using advanced technology to monitor battery health and repairing discharged and sulfated batteries with its excellent “repair” mode.
It is also fitted with spark-proof technology, reverse polarity, overcharge protection and a 5 year warranty, so you can feel confident that this is one of the safest chargers on the market.
Q&A: Will this work on two 12V batteries at the same time?
A: Yes, but they will need to be identical batteries of the same age.
Why do I need a specific AGM battery tender?
Basic battery chargers or ‘trickle chargers’ constantly apply a charge irrespective of whether a battery is fully charged or not. As AGM’s are highly sensitive to overcharging it is vital to use an AGM battery tender which only begins charging when it senses voltage has dropped below a given level. This means a battery tender can be left attached indefinitely, without the risk of battery damage, and there is no need for you to check on the battery.
As AGM batteries are often found in vehicles reserved for seasonal use, it is vital for battery maintenance that appropriate charge is given, especially if you don’t want to be stuck on the driveway come holiday season.
How do I know what type of AGM battery charger I need?
The key thing to remember with AGM batteries, as with any lead battery, is that low and slow charging is the best. This means you should choose a low amp charger of between one-to-12 amps, which will amply keep a RV or Motorhome charged over the off season.
If you do need to quickly restore a battery with no charge, you may need a more powerful charger. However, just remember that the quicker an AGM battery is charged, the more heat will be generated, reducing battery-life.
As AGM’s are lead acid batteries you should also ensure your charger has a desulfation mode (to help prevent the formation of lead sulfate crystals on discharge). This will help to condition your battery and maintain its efficiency.
Look out for chargers that have microprocessors, as this is what you will need. Just make sure it has an appropriate setting for AGM batteries
Do AGM batteries and gel batteries need to be charged differently?
AGM and gel technology each have their own specific charging requirements, so you should always select a charger that offers the appropriate mode for your battery. If you do have a charger for a gel battery, it is possible to use gel settings to charge your AGM battery. However, be warned, it won’t charge fully and will likely lead to damage to the AGM battery itself in the long run.
As mentioned above, chargers with microprocessors are best for AGM charging. Moreover, they are designed specifically to charge AGM 12-volt batteries and are fully automatic, helping you to keep your battery maintained at the push of a button thanks to one-touch technology.
The key thing to remember about charging AGM batteries is that, if you want your battery life to last, you will need to buy a specific AGM charger. As AGM batteries are at risk of overcharging, if you just use a normal charger, To ensure the device is safe, make sure you buy a charger that has a micro-processor. This will also come with the added benefit of quicker charging times and, if you choose appropriately, additional useful settings such as battery repair functionality – just be sure to check the charger you buy has a desulfation mode!