Looking at these(not necessarily form this source but they are the lowest price so far) https://www.walmart.com/ip/12V-100Ah-AGM-Sealed-Lead-Acid-Battery-UB121000-Group-27/172904380 Universal Power Group...
I find its an issue if the batteries being sold are actually AGM, ie, are they really
ABSORBENT GLASS MATT I have had AGM batteries for over 10 years, using them continually with a 1300ah battery bank. Most of them are Used and from Mobile phone transmitter masts where they ticked over giving a UPS to the transmitter/receiver. I would normally get them at their end of service life of about 4 years from new.
So for the last 10 years I have had many sizes and types of 12v AGMs but nothing under 100ah, ie about 28kg about 60lbs each.
As one or two of you may know that I have examined several different types of real AGM batteries and those that are not AGM.
By examine I mean that I have disassembled.
But please! please! do not do this your self unless you have chemical clean room, chemical fume extraction sealed chambers etc, and know how to deal with hazardous materials. The interior of a true AGM 12v is lead based plates with absorbent matts in between the plates. the matts are damp with acid,
there is NO liquid acid. There is a also a separate sealed expansion chamber normally covering the complete top of the AGM battery.
After time the cell, normally 6 cells per 12v battery, expands and buckles and the plates are buckled upwards and touch the main lead buz/buss bars that have the main battery terminals attached, normally about a 5 to 10mm clearance, and then that cell is dead.
I find that a dead cell with a 12v AGM will give a holding voltage of about 11v after a 12 hour rest, ie a holding voltage.
I normally become suspicious of a 12v AGM when the holding voltage is below 13v. and then that particular AGM will require observation and less arduous duties, but with a bit of care you may get a few more years.
In Conclusion.
I have had well over 60 different size and types of AGM's and for my use AGM's are not really feasible. I put up with them as they were cost effective solution for battery storage. But they were a lot of work swapping them into matching strings etc.
However, like everything, things change and the Mobile masts have changed, and I can no longer get AGM's that have a known history life.
I have also tested and used SLA for the last 7 years and had good results, and 5 years ago moved to a SLA, sealed lead acid, 12v batteries that are Marine use, and phasing out my AGMs as they fail. I now have only one string of 110ah 12v AGM's operating as they should.
Middle men have got involved with Used AGMs so their used price is about $90 each for a 12v 110ah and no history.
My SLA Marine deep cycle 12v 110ah, New are about $110 each when I get 12.