What is an AGM battery?

Deep cycle or deep discharge solar battery is designed to cope with the demands of continuous charging and discharging processes. They supply moderately high electricity loads continuously for several hours. In general, deep-cycle batteries, at their maximum state of charge, can supply electricity for 20 continuous hours.- an AGM battery

The time it takes for a rechargeable battery to discharge to its minimum charge limits and then recharge to 100% capacity is known as “cycling”. A deep-cycle battery is designed to be able to discharge, as the name implies, “deep” – up to 80% of its full charge capacity. They are intended for small solar panel installations where the price-performance ratio has to be balanced. 

A complete Off-grid Solar Kit includes solar panel, solar battery, solar inverter, charge controller, cables and connections and everything necessary to begin generating clean energy. Agm battery is one of solar batteries for off grid solar system, we will encounter this question, what is agm battery? AGM is the abbreviation of Absorption Glass Mat, a modern technology in battery manufacturing where the acid is absorbed better and faster by the lead plates of the battery. A thin glass fiber blanket immobilizes the acid between them. Absorbent fiberglass-based separators are used, a material that has the consistency similar to muleton. When the battery is assembled and the liquid electrolyte is added, it is absorbed by the AGM fiber, which acts like a sponge.

Like the gel battery, AGM batteries will not leak liquid in case of rupture, this technology also has the advantage that the battery can be installed lying down.

Main characteristics of AGM batteries

Higher active mass efficiency due to better absorption of acid

Longer service life due to minimal shedding of active material due to battery design

Higher cold start values

Maintenance-free: zero water consumption

Spill and leak proof

Designed to meet the latest vehicle demands as required by the original manufacturer

Compatible with sensitive electronic equipment

Today, AGM technology comes standard with many high-end vehicles and vehicles with the “Stop-Start” system where the high performance of AGM batteries is required.

Differences between the liquid acid battery and the AGM acid battery

Under normal operating conditions, the interior design of AGM batteries ensures that gas recombination takes place and ensures that there is no water leakage, thus avoiding the need for electrolyte reserves and relieving the user from maintenance.

The one-way venting system provides partial pressure in each cell, ensuring total tightness and safe handling.

The absorption of acid from the glass fiber means that the battery packs can operate at higher pressures than liquid electrolyte batteries, which offers advantages, such as significantly extending the battery’s cycling endurance by reducing slurry disposal.

Increased AGM battery pack pressures increase the vibration resistance of the batteries.

The larger reaction surface ensures a higher starting capacity in the same size as conventional liquid electrolyte batteries.

In a nutshell:

Maintenance-free AGM batteries

Higher efficiency 

Higher efficiency

Better cold starting

Spill and leak proof

Can be laid flat

Compatible with sensitive electronic equipment

High performance in vehicles with Start-Stop system

Can I store my AGM battery in the garage during the winter or will it freeze?

As with liquid electrolyte batteries, as long as the batteries are stored charged, they can be stored without fear of freezing. Many people think that if batteries are placed on concrete the power “leaks out”. The truth is that you can place any modern battery on concrete without fear of damage or accelerated self-discharge.

This myth has its origins in the days of old wood or glass cased batteries, where moisture in the ground caused water to penetrate the outer wooden casings, causing the wood to swell. In fact, modern batteries made with hard plastic casings, concrete is an excellent surface on which to keep a battery. The key issue is that the floor should be free of sharp objects, which could damage the battery casing, but there are no other electrochemical reasons. Besides, AGM batteries doesn’t have a memory, this function belongs to the nickel alkaline battery system, such as nickel-cadmium.

What are the differences between GEL and AGM batteries?

Both are recombinant batteries (i.e. under normal operating conditions they recombine the gases released during charging to form water) and both are classified as valve regulated batteries.

The main difference is that in AGM, the electrolyte is totally immersed in a special absorbent fiberglass separator that immobilizes the acid, whereas in GEL battery, the acid is mixed with silicon to form a GEL that also immobilizes the acid. The benefits of AGM batteries over GEL batteries are that, by using the absorbent glass fiber, the battery pack can operate at a higher working pressure thus improving cyclic durability. In GEL batteries, you don’t get the same pack pressure so typically durability is provided with increased paste density, which is good for service life but not so good for the high rated cranking capacity performance required by automotive applications.

Why is charging voltage so important for both GEL and AGM applications?

Charge voltage is important for these types of batteries because they are both recombinant batteries. This means that the oxygen normally produced in the positive plate of all lead-acid batteries is recombined with the hydrogen released from the negative plate. The recombination of hydrogen and oxygen produces water, which is recycled in the battery acid, so the battery does not need maintenance or topping up.

The sealing orifice used in the design ensures that a positive internal pressure is maintained to ensure that gas recombination takes place and that the cell does not dry out and fail.

In addition, the valve must safely release excess pressure that may occur during overload (e.g. alternator rectifier failure), otherwise the cell may be irreversibly damaged. The excess pressure released by the valve is both hydrogen and oxygen that cannot recombine in the battery, so the cycle is broken and the result will be that the battery may dry out.

It should be noted that AGM batteries should not be opened after leaving the factory, as the plates may sulfate leading to an irreversible loss of performance. It is more difficult to correct the charge of Gel batteries, since overcharging could cause the gel to be irreversibly damaged. AGM batteries are not exposed to this type of failure, which makes them more suitable for automotive use. if you’d like to know more information about AGM and Gel battery, or want to see the AGM batteries or other lithium batteries for sale, just contact Renogy Team, Our Renogy solar power kits include every one of the equipment called for to construct an off-grid solar power system. We bring a wide selection of off-grid solar panel system kits, our solar kits provide an easy way to start with your off-grid solar system.

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