AGM or Absorbent Glass Mat battery technology is an advanced lead-acid battery that provides superior power to support the higher electrical demands of today’s vehicles and start-stop applications.
AGM and gel batteries are often considered to be one and the same. This is because they have a similar core of attributes. Both are unspillable. Both offer deep cycles and they can both be mounted anywhere, so they’re flexible.
In AGM batteries, the positive and negative plates are separated by an absorbent glass mat that absorbs and holds the battery’s acid and prevents it from flowing freely inside the battery.
The plates are in tight compression with each cell and held under pressure in the rigid battery case. The internal compression limits the shedding of plate material caused by cycling and allows for a significantly longer life. Thus, AGM battery can resist vibration, recharges faster, cycles more, and lasts longer in demanding applications.
The concept of AGM battery is similar to that of gel battery but this time, it’s more advanced. This product offers the same resistances and the same sealed and spill-proof case as a gel, but now the flexibility and high performance distinguish AGM from gel battery.
AGM battery has many advantages over other types of battery. AGM has the lowest internal resistance of any commercial battery. This is one of the reasons why AGM battery is the preferred choice in many applications.
Here are some of the Advantages of AGM battery:
- AGM batteries have much better internal resistance to vibration and shock due to their construction than other batteries.
- The glass mats used in AGM battery are not totally saturated and the liquid does not expand to cause plate and case damage. Thus AGM batteries can withstand harsh climates and demanding conditions like freezing.
- AGM battery has a fast reaction between acid and plate material. This is because the glass mat absorbs and immobilizes the acid while still keeping the acid available to the plates. The result? Even if the battery is broken, no electrolyte will spill out.
AGM Battery is Also:
- Up to 2x longer life than standard flooded batteries
- Handles high electrical loads
- Quickly recharges and extends cycle life
- Ideal for start-stop application
- Nonspillable and maintenance-free
- Greater mounting flexibility
AGM battery is most times maintenance free. so if you want to learn about maintenance and how to check the health of your battery, I recommend you read: How to check the health of solar battery in the previous posts.
GENERAL BATTERY TERMS AND TERMINOLOGY
STATE OF CHARGE
The percentage of capacity that your battery is at. Typically this can be worked out by measuring battery voltage when there are no loads or draws on the battery.
Example: AGM Battery at approx. 12.7 volts is 100% fully charged (AKA 100% state of charge), while an AGM battery at 10.5 volts is entirely discharged at 0%.
DEPTH OF DISCHARGE (DOD)
Depth of Discharge (often abbreviated to DOD or D.O.D) is the percentage amount of a deep cycle battery’s capacity that you drain, before charging it back up again.
To understand DoB in a practical sense, let’s take a quick example. When you buy a solar battery which holds 13.5 kilowatt-hours (kWh) of electricity, and you discharge 13 kWh, then the DoD is approximately 96 percent.
So when purchasing a solar battery or AGM battery make sure the DoB is 100%. DoB is expressed in percentage.
SELF DISCHARGE RATE
All batteries slowly lose power over time, even when they are not in use. The self-discharge rate is the percentage of capacity that the battery will lose when it is in storage.
Typically batteries like AGM or Tubular Gel will only lose a couple of percent capacity per month, while other batteries can lose over 10%. This is important when working out how often you need to provide a maintenance charge on batteries when they aren’t in use.
A cycle is a process of discharging a deep cycle battery or AGM battery and then recharging it to full. One cycle means that the battery is discharged and then recharged once. Deep cycle batteries or AGM batteries rate to a certain number of cycles at a depth of discharge.
Example: If a battery is to perform 1650 cycles at 30% depth of discharge rate. This means that the battery should withstand being discharged 30% and then recharged to full 1650 times.
Round-trip efficiency is the useful energy we get back after storing energy. This term usually applies to home solar batteries which are design to be “stackable,”
This means that you can include multiple batteries to your solar storage system to get extra capacity. I know that this isn’t a common term we are using, but let’s look at it this way.
If you store (5kWh) of electricity into your battery bank and can only get (4kWh) of useful electricity back. Then the battery has 80 percent round-trip efficiency (4 kWh / 5 kWh = 80%).
Note that the higher the round-trip efficiency, the less energy you lose due to storage, and the more efficiency of the system as a whole.
Internal resistance is how much a battery “resists” energy flow. Lower is better, allowing charging and discharging at more efficient rates. Most of the loss in charging and discharging batteries is due to internal resistance, and the lost energy then converts to heat (which is why batteries get hot when they are charging). Many factors can affect internal resistance such as battery age and sulfation.
BATTERY CAPACITY, AMP HOURS (AH)
Battery capacity is measured in Amp Hours (AH). Using this capacity, you can roughly work out how long your battery will last by finding out the Amp Hour draw of whatever you are going to run off the battery.
Example: a 100AH Deep Cycle Battery running a fridge with a 5AH draw would last about 100/5 = 20 hours before going completely flat. However, it is recommended not to drain the battery that low.
CAPACITY Hr RATE, HOUR RATE, C RATING
While battery capacity is in AH, it is also rated at a certain hourly rate. This is because the capacity of battery changes depending on how quick you are discharging it.
Example: Discharging a battery with a steady 5 amps/hr draw, the battery lasts 20 hours. This means that the battery is rated to 5×20 = 100AH at a 20hr rate.
Using the same battery or AGM battery with a higher draw of 8.5 amps/hr, the battery only lasts 10 hours. This means that the battery is rated to 8.5×10 = 85AH at a 10hr rate.
To accurately compare capacities of battery they must measure at the same hour rating. Most deep cycle batteries follow a standard 20hr rate (sometimes shown as C/20), or a 100hr rate for off-grid scenarios.
Simply means “named” voltage, and is basically an easy way to categorize any batteries within a standard voltage range. This is because the voltage of deep cycle battery actually fluctuates depending on its construction and use.
Example: A 12V Nominal voltage battery could actually measures at 11V, 12.2V, 14V, etc. But to easily categorize them, we just call all of them 12V.
This is the recommended voltage to charge the battery at. Different batteries charge at different rates, such as flooded batteries charging at a higher voltage than AGM.
It is important not to charge a battery above its charge voltage, as this will overcharge the battery and cause damage.
The discharge rate of a battery is the amount of power you are draining at any one time (usually measured in amps). If you have a particularly high amount of power you are trying to draw in a short amount of time, it’s important to make sure that the battery you are using can support this rate.
CCA (Cold Cranking Amps), MCA, CA
Cold-cranking amps are the maximum amount of amps that a battery is able to release on a cold start. This is typically for starting engines in vehicles, as the engine will draw a high rate of amps over a short period of time to start the vehicle.
Since I have discussed deep cycle battery in my previous post, I recommend you read it also. my next post is a comparison between AGM battery and other sealed batteries. So subscribe to our newsletter to be the first to get the post once I release it.
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