Page 64 - North American Clean Energy July August 2015

energy storage

How to Select

the Right AGM

Battery

By John Connell

-- providing
FINDING THE IDEAL BATTERY FOR A SYSTEM DOESN’T HAVE TO BE DIFFICULT
one knows what to look for. On the surface, many batteries share almost identical specs
and boast bold promises. But glossy brochures and spec sheets only tell part of the story.
Materials, manufacturing methods, and quality control procedures in a battery

profoundly impact performance, maintenance, and lifespan. Some manufacturers use
subpar materials and out-dated manual assembly that compromise performance and
lifespan, resulting in “bargain” batteries that fail early, require additional maintenance,
and cost more over time. Other manufacturers use technologies which will keep their

batteries running longer and better, from more lead and heavier grids, to computerized
pasting, robotic assembly, and vision systems. Learning to identify the diferences
between batteries and asking the right questions of manufacturers is important to
inding the right solution for each application.

Finding the right solution
Renewable energy (RE) systems require electricity for long time periods and constantly
charge and discharge, which means they require deep-cycle batteries. hat means

many common battery types are poorly suited to this environment. Commercial and
automotive lead-acid starter batteries only provide short bursts of power, making them a
poor it. Uninterruptible power supply (UPS) batteries can’t handle constant cycling. And
lithium-ion batteries are maintenance-free but have a high cost per ampere-hour (aH),

sufer from ire and thermal runaway risks, and degrade at high temperatures. Lithium-
ion batteries also can’t be fully recycled.
For most people, lead-acid batteries are the best it. heir reliability and safety have
been proven for over 100 years, and they’re 97% recyclable. hese batteries come in two

primary types: looded, and absorbent glass mat (AGM). Flooded batteries are afordable,
easy to maintain, long-lasting, and reliable.
Originally developed for military aircraft and vehicles to boost reliability, AGM
batteries are sealed, spill-proof, safe, and no-maintenance. hey ofer low internal he next step is applying active lead material to plates (“pasting”), a process with

resistance, long service life, and high current delivery. hey can charge up to ive times dozens of variables that can bolster or compromise battery performance. Conventional
faster than their deep-cycle counterparts. AGM batteries have higher manufacturing manufacturing relies on manual variable adjustment, so quality depends on whether
costs and a slightly lower energy storage capacity, but because of their features, they the operator is skilled and at peak performance. In contrast, computerized paste mixing
often save time and money in maintenance.
instantaneously adjusts key variables for greater control.

After pasting, grids are dried in precision “curing ovens” at an ideal temperature and
What makes a better battery?
humidity to bond active lead to the grid -- and improve capacity and service life. In
AGM batteries generate electrical current by converting stored chemical energy into some plants, this process is adjusted manually every hour or so. In others, the battery’s

electrical energy, in a process that starts in their lead. Because almost all North American plates are prepared in computerized curing ovens that instantly optimize humidity,
battery manufacturers use recycled lead, diferences in longevity and performance
temperature, and other variables during the entire curing cycle.
come from quality controls, additive formulation, and lead oxide production methods. Once plates are cured, they’re stacked into groups and fused together with a lead strap
Computerized lead oxide production can be considered the most reliable method of that creates a parallel circuit. Much of the global lead-acid battery industry still uses

production.
manual strap assembly techniques from the 1950s to cut costs. Workers attach lead lugs
An AGM battery’s lead, or potential energy, is stored in metal grids. Lesser grids are to a strap, then burn them together one at a time with a torch and lead stick. Manual
stamped using expanded metal, a process that’s cheaper but embeds impurities and welding can lack temperature control which results in weaker connection points.
porosity into grid wires, and cuts lifespan. Better battery grids are made using gravity A newer process referred to as Inline Cast-on-Strap Assembly (COS), uses robotics

casting, a process that eliminates impurities, results in near-zero porosity, and improves to fuse battery plates together simultaneously at their ideal temperature. COS allows
reliability and battery life.
for 4,000 adjustments versus only 40 for hand welding. Robotic COS assembly also
Heavier, thicker plates ofer improved corrosion resistance and material for chemical eliminates common failures in manually assembled batteries, such as “lead run-down”
reactions, bolstering lifespan. But raw lead prices have almost doubled since 2006, and between plates.

lead makes up 60-80% of a battery’s cost. his has led some manufacturers to reduce Despite the beneits of COS assembly; strengthened connections, reduced corrosion
battery lead content, which shortens battery life. More reputable manufacturers never and maintenance, and increased current and lifespan, the process can be time-consuming
scrimp on vital materials such as lead; instead, they boost active lead utilization and and expensive to set up. Some battery manufacturers will have invested the time to ine-
manufacturing eiciency to keep long-lasting batteries afordable.
tune their COS system and guarantee that 100% of their batteries are made using COS.

64 JULY/AUGUST 2015 nacleanenergy.com