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wrote in
ups.com:

The article
stated that the flodded type have the same problems as AGMs with
sulfation on the plates. But dosent follow up that equilizing is a
common method of maintaining the floded type, but the manufacturer only
recently recommends it on the Lifeline AGMs. If you follow the article,
the batteries should be sold with a big warning lable and a good set of
instructions. I was told that they were bullet proof, could take abuse
and all the amp hours you can through at them. The article makes it
sound like if you are .1 volt off and don't fully recharge, you are
tosting the batteries. That was not what was sold to me.

Price is not an indication of quality in all things. Look inside one.
Very thin (they have to wrap them around a post you know)lead plates
separated by a gauze like mat soaked in sulphuric acid that, once used up
in an area, cannot MOVE like a LIQUID electrolyte can to cool the plates
with convection and mix with the rest of the electrolyte in the cell. All
this reminds one of gelcells with the jelly acid that doesn't move either
and when it "shrinks" away from the plate, that place is dead as there is
no contact.

Bulletproof it's not.

I'm concerned about the heat insulating qualities of this glass mat. We
use fiberglass to insulate our homes. How hot does this rolled up battery
get INSIDE when it is charged or discharged? How can you cool something
efficiently rolled up so tightly? At what temperature does the glass mat
and little rolled up plates warp? boil into steam? God the red starting
AGM in my stepvan just melted when one cell shorted out!

Let's ask some embarrassing questions about "sulphation". Lead is turned
into lead sulphate to make free electrons. As long as the lead sulphate
doesn't get too concentrated, it stays in solution in the electrolyte so we
can force it to revert back to sulphuric acid and elemental lead at the
surface of the plates. That's how it works, right? If we kill it too
dead, lead sulphate crystals form on the plates, insulating the lead plates
from the electrolyte. The cell is "dead" because the sulphuric acid is
used up, converted into lead sulphate crystals and we can't recover it
because the electrolyte now becomes almost an insulator, distilled water.

In a wetcell, lead sulphate crystals can and do fall off the lead plates,
exposing more lead as the crystals fall to the space at the bottom of the
container under the plates made just for this purpose. Life goes on, the
cell now has less "capacity" to charge because there is less acid in the
cell to use up as it discharges.

How do lead sulphate crystals precipitate out of a rolled up, acid soaked
guaze battery where nothing can move? Nothing can move anywhere in the AGM
(or gelcell) battery all squeezed inside that cylinder case, can it? I
can't adjust the specific gravity to make up for some of the acid loss
because it's all sealed. Balancing the cells adjusting acid concentrations
is impossible. What you get, you get.

No thanks. I think AGM batteries were invented to simplify battery
manufacture and the marketing mongers saw a great opportunity to create
market hype of a "new" and "extraordinary" new product we can sell at
exhorbitant profits. I'll keep my temperature-compensated hydrometer and
little distilled water filler monitoring what is really going on in the
cells.

Running my ham station is a set of "Edison Cells" given to me by a friend
who used to be a Holiday Inn innkeeper back in the 1960's. These cells use
Nickel and Iron for plates, making them an environmental disaster of nickel
pollution if you dump them, which you never need to do. The electrolyte is
potassium hydroxide, a base, not an acid. The date on the cells reads
1947, except on one cell that reads 1949. Nickel-Iron batteries last
virtually forever, of course making them a target to get rid of them by
battery manufacturers. These cells ran an old Holiday Inn telephone
exchange that required a live operator running a plugboard manually. The
cells are near 2V each. I have 7 in series charging them with a modified
simple SCR charger since the 1970s. Fork lift trucks used to all be
nickel-iron batteries you just charged and put distilled water into as it
is used up.

Too bad we can't put Ni-Fe batteries in a boat and replace them every 80
years or so....(c; Those are great batteries!

I found a website "expert" who says they are awful. I disagree:

"NiFe (Nickel Iron)

Energy storage density = 55 watts per kilogram
Alkaline-type electric cells using potassium hydroxide as the electrolyte
and anodes of steel wool substrate with active iron material and cathodes
of nickel plated steel wool substrate with active nickel material. This is
the original "Edison Cell". Very long life.

...."Our experience with customers using alkaline batteries in stand alone
AE systems suggests that they may have as many drawbacks as advantages when
compared to lead-acid type batteries. We suggest that potential alkaline
users evaluate the economics and performance claims carefully to determine
the suitability of any battery being considered..."
Christopher Freitas Trace Engineering
Downsides:

1. Low efficiency - may be as low as 50%, typically 60-65%.
2. very high rate of self-discharge
3. high gassing/water consumption
4. high internal resistance means you can get large voltage drops across
series cells.
5. high specific weight/volume

This also means that the output voltage varies with load and charge much
more than other batteries. If you are using an inverter, the inverter needs
to be designed with these voltage swings in mind. You may not be able to
use NiFe's if your system depends on a stable voltage, for example if you
are running certain common DC appliances such as a refrigerator directly
off the batteries. Also when using NiFe's to power DC lighting, you will
notice the light intensity fluctuates. One could always use a voltage
regulator to feed those appliances that need it, but that would decrease
the efficiency even more.

Currently, it appears that the only source for new NiFe batteries is from
Hungary, and we have heard mixed reports on them. In short, we do not
recommend them unless they are nearly free. The high losses in charging and
discharging will add an extra 25-40% to the size of the solar panels you
will need for the same energy usage.
In short, despite some hype about long life and thousands of cycles, we
feel that overall these batteries are a poor choice for nearly all solar
applications."

It's a moot point as you can no longer buy them......Did I mention you can
discharge them DEAD and they charge right back up to FULL capacity for
DECADES?......Of course, this guy saying this SELLS LEAD-ACID BATTERIES!!