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- Sep 7, 2013
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First, a quick primer on AGM technology:
AGM stands for Absorbed Glass Mat. There is a mat made of fine woven fiberglass fibers in each cell, and the acid is absorbed (technically adsorbed) in the mat and then wrung out 5% so that it is left at 95%. This is important because it gives the electrolyte some room to expand. Then the glass mats are sandwiched between the plates and compressed and then soldered in place. Because things are tightly compacted, AGM batteries are almost immune to vibration.
The internal resistance in an AGM battery is much lower than a flooded cell. One benefit of this is that an AGM battery can be charged much faster than a flooded cell battery. It allows a higher discharge rate, which translates into more cold cranking amps in automotive batteries.
Compared to flooded cell batteries, AGM batteries can operate at much lower temperature, are not spill prone (even if case is broken), can be operated in any position, even upside down, and have virtually zero emissions, making them completely safe to use indoors, even in confined spaces. Because they are not spill prone, they can be shipped without HazMat fees, somewhat mitigating the higher cost.
Although there are still deep cycle and non-deep cycle AGM batteries, some AGM automotive batteries (such as the Die Hard Gold) are listed as a deep cycle batteries, yet still have slightly more cold cranking amps than the flooded cell batteries of the same size (775 vs 750 in the case of the Die Hard Gold AGM vs the flooded cell Die Hard Gold of the same size))
And significantly for backup systems, AGM batteries have a much lower self discharge rate than flooded cell batteries, so they can be stored without a float charge much longer without damage. It is still recommended to maintain them with a float charge, but you need a maintainer that has an AGM mode because the voltage at 100% charge is lower than with a flooded cell battery, and overcharging will damage them.
OK end of primer...
I thought I was having battery problems with my car and while looking for a new battery I ran across this at Sears:
http://www.sears.com/diehard-advanc...SellerId=Sears&prdNo=1&blockNo=1&blockType=G1
This is a Die Hard Gold automotive AGM battery, it is also listed as a deep cycle battery. The battery is rated at 75 AH.
Here is the flooded cell Die Hard Gold of the same size:
http://www.sears.com/diehard-gold-automotive-battery-group-size-65-price/p-02850965000P?rrec=true
The price difference is about 20%.
Due to the research I did when looking for batteries for my backup power system at home (6KW Inverter, 2 125 AH VMax AGM batteries), I was familiar with AGM technology. Comparing the cost per AH, this battery (which was on sale for under $120 at the time) was far more economical than any other AGM battery I could find. Even at the current price ($132.74) it is still very economical.
After buying the battery, I discovered my problem wasn't the battery! Fortunately, I had taken an ancient dead battery in for the core charge, so I still had my old battery. I decided to put the original battery back in the car and use the Die Hard in a secondary backup system using a 2 KW pure sine wave inverter for those things that had problems with the modified sine wave of my main inverter (I had been using a conventional flooded cell marine deep cycle battery).
I then went back to Sears and bought another. I told them I was using it for an inverter, so there wasn't a battery that I was replacing, and they graciously waved the core charge!
To get the online price, you have to order online....DUH! Actually the first one I bought was on sale at the store too, but with the second one, I had to use my phone to order the battery (with store pickup), and then wait a few minutes for the order to come through.
AGM stands for Absorbed Glass Mat. There is a mat made of fine woven fiberglass fibers in each cell, and the acid is absorbed (technically adsorbed) in the mat and then wrung out 5% so that it is left at 95%. This is important because it gives the electrolyte some room to expand. Then the glass mats are sandwiched between the plates and compressed and then soldered in place. Because things are tightly compacted, AGM batteries are almost immune to vibration.
The internal resistance in an AGM battery is much lower than a flooded cell. One benefit of this is that an AGM battery can be charged much faster than a flooded cell battery. It allows a higher discharge rate, which translates into more cold cranking amps in automotive batteries.
Compared to flooded cell batteries, AGM batteries can operate at much lower temperature, are not spill prone (even if case is broken), can be operated in any position, even upside down, and have virtually zero emissions, making them completely safe to use indoors, even in confined spaces. Because they are not spill prone, they can be shipped without HazMat fees, somewhat mitigating the higher cost.
Although there are still deep cycle and non-deep cycle AGM batteries, some AGM automotive batteries (such as the Die Hard Gold) are listed as a deep cycle batteries, yet still have slightly more cold cranking amps than the flooded cell batteries of the same size (775 vs 750 in the case of the Die Hard Gold AGM vs the flooded cell Die Hard Gold of the same size))
And significantly for backup systems, AGM batteries have a much lower self discharge rate than flooded cell batteries, so they can be stored without a float charge much longer without damage. It is still recommended to maintain them with a float charge, but you need a maintainer that has an AGM mode because the voltage at 100% charge is lower than with a flooded cell battery, and overcharging will damage them.
OK end of primer...
I thought I was having battery problems with my car and while looking for a new battery I ran across this at Sears:
http://www.sears.com/diehard-advanc...SellerId=Sears&prdNo=1&blockNo=1&blockType=G1
This is a Die Hard Gold automotive AGM battery, it is also listed as a deep cycle battery. The battery is rated at 75 AH.
Here is the flooded cell Die Hard Gold of the same size:
http://www.sears.com/diehard-gold-automotive-battery-group-size-65-price/p-02850965000P?rrec=true
The price difference is about 20%.
Due to the research I did when looking for batteries for my backup power system at home (6KW Inverter, 2 125 AH VMax AGM batteries), I was familiar with AGM technology. Comparing the cost per AH, this battery (which was on sale for under $120 at the time) was far more economical than any other AGM battery I could find. Even at the current price ($132.74) it is still very economical.
After buying the battery, I discovered my problem wasn't the battery! Fortunately, I had taken an ancient dead battery in for the core charge, so I still had my old battery. I decided to put the original battery back in the car and use the Die Hard in a secondary backup system using a 2 KW pure sine wave inverter for those things that had problems with the modified sine wave of my main inverter (I had been using a conventional flooded cell marine deep cycle battery).
I then went back to Sears and bought another. I told them I was using it for an inverter, so there wasn't a battery that I was replacing, and they graciously waved the core charge!
To get the online price, you have to order online....DUH! Actually the first one I bought was on sale at the store too, but with the second one, I had to use my phone to order the battery (with store pickup), and then wait a few minutes for the order to come through.
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