PB Mother earth News December 2016/January 2017
plications. This is the increasing
shift to sealed, absorbed glass mat
(AGM) batteries from the more
traditional flooded lead-acid. The
transition is still under the radar
in much of the industry. Sealed
batteries are capable of supplying
acceptable performance and cycle
life in the deep-cycle demands of
many off-grid applications. This is
a relatively new shift without years
of experience from which to draw
conclusions and predict perfor-
mance. The expectations of some
experienced installers are that
high-quality, maintenance-free
AGM batteries may be expected to
last for eight or more years of full-
time, off-grid use with good care.
Sealed batteries offer some
substantial benefits over flooded
batteries. They require no main-
tenance beyond proper charging.
Because the electrolyte is either gelled or
absorbed, these batteries don’t release gas
during normal charging, and they don’t
need a sealed enclosure with controlled
ventilation to the outdoors. They can
tolerate smaller arrays and lower charge
rates as long as they’re fully recharged
regularly. They don’t leak and won’t con-
taminate battery storage areas or attract
corrosion on terminals. AGM batter-
ies can be shipped via common ground
freight with no hazardous-material costs.
Because access to the cell tops to add wa-
ter isn’t necessary, they can be mounted in
any orientation without harm. They may
occupy less floor space when stacked than
flooded batteries do.
Sealed batteries aren’t without their
drawbacks. They’re substantially more
expensive and more susceptible to dam-
age from overcharging. They’re well-
suited to homeowners who don’t want
to perform their own battery mainte-
nance, as the charge for professional ser-
vice several times each year adds up. This
group might include many newcomers
to off-grid living, who value the benefits
but don’t desire the DIY involvement of
earlier generations. They want (and can
afford) a professionally designed and in-
stalled system and can live well within its
limitations, but they prefer not to be in-volved with maintenance. Sealed batteries
are also well-suited to homes used season-
ally and maintained more infrequently,
and for weekend cabins in which small
arrays and larger banks provide energy for
weekend-only use.
My advice on current battery tech-
nology for homestead use is to stick
with tried-and-true lead-acid batteries
for now, whether flooded or sealed. For
most homesteaders, I advise against us-
ing any of the new technologies at this
time. Tremendous advances in battery
technology are happening now, and bat-
tery choices will look very different in five
to 10 years. Homesteaders may want to
consider waiting through one more set
of batteries before trying lithium or other
emerging technologies. Superior technol-
ogies are coming, and prices will drop as
PV module prices have dropped in recent
years, but we’re not there quite yet.This well-boxed L16 battery bank gave new life to an
older off-grid system.Circle #36; see card pg 97Allan Sindelar has been designing,
installing, servicing, and teaching about
off-grid PV systems since 1988. He’s a
licensed electrician with dual NABCEP
certifications. He’s the retired founder
of Positive Energy Solar and has lived
off-grid for most of the last 25 years.p 61-64 Battery Power.indd 64 10/13/16 3:09 PM