Clarification on AGM battery

[frankz66]

Hello everyone, I have 110 amp 12v agm batteries

Some time ago in the forum I was provided with a link for how much the batteries. Among the various readings I wanted to understand what is described in the site:

The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life

I have always been told that lead-acid batteries must be discharged at a maximum of 50% of the DOD, but being AGM and according to what the technical guide writes, it seems that I could advance the discharge by up to 80%. Considering that I normally have available with 50% DOD about 2576 Kw if I had to apply the indications of the guide, I could get to 4224 Kw with 20% DOD. Did I misinter interpret what was written? Thank you

BU-201a: Absorbent Glass Mat (AGM)

Learn what differentiates Absorbent Glass Mat (AGM) batteries from other lead acid battery types

batteryuniversity.com

 

[mikefitz]

it seems that I could advance the discharge by up to 80%.

There are many statements on the internet that are not entirely correct and are also misleading.
Example this statement ,
' The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life.

Real life testing shows that, regardless of charge current specification of the charger, it takes a minimum of 5 hours to charge a flooded or AGM battery from 50% SOC to 100%.
Both AGM and flooded quality batteries have similar cycle performance,


'

Note the mid range, red flooded, blue GEL, purple AGM are similar, with flooded being the better performer by a small amount. In Europe these Trojan and similar true deep cycle batteries cost 3 times the cost of the batteries on ebay and Amazon.

Most of the low cost branded 'deep cycle' batteries sold on the European leasure market, ebay and Amazon, are actually starter batteries and will not have the performance of true deep cycle batteries. The cycle performance with depth of discharge will be not as good as the the Trojan test results.
Testing on batteries, similar to your Electronicx AGM, show a cycle life of around 50 cycles, where the batteries were fully discharged. Discharging to 80% improved the useful cycles to around 250 . ( useful life is where the battery capacity dropped to 0.8 of rated capacity)
I expect your batteries, at best, to have a performance similar to the Signature line shown on the Trojan chart

From the chart the AGM battery has 500 cycles to 80% and 1000 cycles to 50%.
Assume you have 400 Ah of battery.
Useful storage total capacity discharging 50%, 200 Ah x 1000 cycles = 200,000 cycle Ah
Useful storage total capacity discharging 80%, 320 Ah x 500 cycles = 160, 000 cycle Ah
Discharging only 20%, in this case the total storage capacity is 80 Ah ' 2800 cycles = 224, 000 cycle Ah

What this seems to show is that the battery has a useful number of Cycle Ah, in this case around 200,000 cycle Ah, and the depth of discharge is not as damaging as expected.

Mike

 

[frankz66]

There are many statements on the internet that are not entirely correct and are also misleading.
Example this statement ,
' The leading advantages of AGM are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life.

Real life testing shows that, regardless of charge current specification of the charger, it takes a minimum of 5 hours to charge a flooded or AGM battery from 50% SOC to 100%.
Both AGM and flooded quality batteries have similar cycle performance,


'View attachment 177225

Note the mid range, red flooded, blue GEL, purple AGM are similar, with flooded being the better performer by a small amount. In Europe these Trojan and similar true deep cycle batteries cost 3 times the cost of the batteries on ebay and Amazon.

Most of the low cost branded 'deep cycle' batteries sold on the European leasure market, ebay and Amazon, are actually starter batteries and will not have the performance of true deep cycle batteries. The cycle performance with depth of discharge will be not as good as the the Trojan test results.
Testing on batteries, similar to your Electronicx AGM, show a cycle life of around 50 cycles, where the batteries were fully discharged. Discharging to 80% improved the useful cycles to around 250 . ( useful life is where the battery capacity dropped to 0.8 of rated capacity)
I expect your batteries, at best, to have a performance similar to the Signature line shown on the Trojan chart

From the chart the AGM battery has 500 cycles to 80% and 1000 cycles to 50%.
Assume you have 400 Ah of battery.
Useful storage total capacity discharging 50%, 200 Ah x 1000 cycles = 200,000 cycle Ah
Useful storage total capacity discharging 80%, 320 Ah x 500 cycles = 160, 000 cycle Ah
Discharging only 20%, in this case the total storage capacity is 80 Ah ' 2800 cycles = 224, 000 cycle Ah

What this seems to show is that the battery has a useful number of Cycle Ah, in this case around 200,000 cycle Ah, and the depth of discharge is not as damaging as expected.

Mike

Thank you, clearly more than in real life I would affirm the quality of the battery. Probably what I read (the link provided by diysolar) probably wants to express that 80% discharged AGM batteries can have a life similar to a 50% free acid battery. I agree and firmly convinced that quality makes a lot of difference, so as a beginner I reflected that in my accumulation now at 48v 110 amps if I reach a DOD of 65% or 70% at most you do not think you are doing any harm. Thank you for your opinion, which I hold in high regard.