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Eye On Electronics
The recycling of just about anything that can be is widely
accepted to be a good thing. But a large number of batteries
may be getting recycled much sooner than is necessary.
Mike
Dale
hicles, shop tools and even cell phones. With
some help from that website and a few others,
we can dig into this “refurbished” thing, to see
what it really means.
The trade group Battery Council International estimates that 98 million vehicle batteries are replaced in the U.S. each year; worldwide the number is more than 225 million.
The primary function for most of these batteries was to run the starter motor and to act as
reserve storage to supplement the alternator
for short-term peak loads.
But not all of the batteries replaced were
actually defective. Battery University (BU)
says that a leading German battery maker recently checked 400 starter motor batteries
that had been returned and found that nothing was wrong with 200 of them. Another European battery manufacturer says that genuine failures for warranty returns is
in the range of 5% to 7%.
What this must mean is
that there are a lot of discarded batteries that could
be returned to useful service. Even some of the defective batteries could possibly be revived back to
some level of performance.
This is a business opportunity that some companies
have been taking advantage
of. This refers not only to
starter motor batteries but
to cell phone batteries,
nickel-cadmium (Ni-cad)
batteries and both lithiumion (Li-ion) and nickel
metal-hydride (NiMH)
electric car batteries. Franchises are springing up all
This container of batteries—a rather large load of toxic
over to rework these diswaste, actually—is ready for recycling. The question is, are
carded batteries.
there good ones in that pile that could be made useful again?
There are at least three
Photo courtesy Mack’s Recycling
[email protected]
T
he local parts store here has the
usual display of new car batteries.
Two things are remarkable: One
is that most of the new batteries
are pushing well past the $100
mark, up sharply from just a few
years ago. The other is the small sign that says
the parts house also offers refurbished batteries
for about $40.
Refurbished? What does that mean? What
really has been done to those batteries? What
will the customers who buy them be getting
for their money?
A great website for information on batteries
is www.BatteryUniversity.com, which offers a
broad range of technical information on batteries and how they work. It covers car batteries, of course, but also batteries for electric ve-
continued on page 20
18
May 2014
Eye On Electronics
challenges in the refurbishment business. The first is testing. Somehow,
those enormous piles of so-called bad
batteries have to be combed through,
tested and evaluated. The good ones
can be cleaned up and prepared for resale. This testing is not simple; it takes
equipment and training and can still
leave gray areas of uncertainty.
The second challenge is finding
those batteries whose performance is
truly not up to snuff. There are some
techniques that can be used to bring
them back to a reasonable level of
performance. These batteries will
need even more investment in terms
of time, effort and technology than
those that were never truly bad in the
first place. In fact, you could make
the point that there are more than
enough still-good batteries out there
to satisfy the market for lower cost
refurbished batteries, so why bother
trying to fix the others at all?
The third challenge to refurbishment will be those batteries that are
genuinely bad and unrepairable. This
includes batteries with mechanical
problems such as cracked cases, broken
terminals and internal opens or shorts.
This group includes the end-of-life batteries that are simply used up. These
batteries are recycled.
For recycling, batteries are disassembled and the metals salvaged. Doing this correctly is not without risk.
Lead is toxic and battery acid is corrosive. A number of former locations for
battery recycling plants (Haina in the
Dominican Republic is one example)
are well-known environmental hot
spots. Problems include lead contamination in the soil, air and water. In
Haina, they found that one-third of
the soil in the area of the former battery plant was actually lead.
So, how did all these good batteries
get condemned in the first place? The
BU website says that low charge and
acid stratification are the most common
causes of apparent battery failure. The
low-charge circumstance is well illustrated by the typical use pattern for
cars in Japan. Motorists there drive an
average of 8 miles a day in congested
cities. At typical low speeds, the batteries just never really get fully recharged.
Poorly charged batteries are also a
problem in large luxury vehicles.
Electric power steering, electrically
controlled suspension systems, HVAC
systems and so on add loads to the
battery. If the alternator does not spin
fast enough and long enough to generate the needed power, then the battery has to supply that power. Depending on how a motorist uses his
vehicle, the battery may be in a constant state of undercharge.
The direct result of leaving a battery in a chronic undercharge state is
sulfation. Sulfation is a phenomenon
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that occurs when small sulfate crystals form. By themselves, they’re
harmless. However, during prolonged
low-charge circumstances, the amorphous lead sulphate converts to a stable crystalline form that then accumulates on a battery’s negative plates.
This leads to the development of
large crystals that can block the active
area of the plates. Sulfation lowers
the rate at which a battery will accept
a charge by effectively increasing the
battery’s internal resistance.
The website goes on to say that
there are two kinds of sulfation—reversible and nonreversible. Soft sulfation can be reversed by applying an
overcharge to a fully charged battery.
The overcharge is on the order of 15
to 16V, controlled to a current of
200mA. It can take up to 24 hours to
accomplish the desulfation, but it can
restore capacity to the battery. This is
one meaning of the term refurbished.
The BU website shows a lot of respect for long, slow, careful charging
of the battery. Fast charging can generate heat and, through electrolysis,
cause gas to form in the battery. It
can also cause water loss, plate
warpage and other evils that may actually damage the battery.
There are a number of chemicals,
pills and even electronic equipment
on the market devoted to removing
sulfation. BU offers a method for using Epsom salts to accomplish it.
There are a number of battery chargers that use AC currents to try to
break up the sulfation.
If a battery is left in an uncharged
or partially charged condition for
weeks or months, the sulfation can
harden to the point where no form of
restoration is possible.
Acid stratification affects the electrolyte in the battery. For the typical
car battery, the electrolyte is a mix of
distilled water and sulfuric acid. In an
undercharged battery, the heavier
sulfuric acid concentrates at the bottom of the battery. This happens
when the battery stays below 80%
charge, never receives a full charge
and has shallow discharges.
With acid stratification, the electrolyte at the top of the battery limits
plate activation because it doesn’t have
enough acid. This promotes internal
corrosion and reduces performance.
The concentration of acid at the bottom makes the battery test as being
more charged than it is. It also raises
the open circuit voltage of the cells. Because there’s an uneven charge across
the surface of the plate, the effective
cold cranking amps (CCA) performance of the battery is reduced. The
concentration of acid at the bottom of
the battery also leads to sulfation on the
lower half of the plates.
Acid stratification cannot always be
continued on page 62
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Eye On Electronics
continued from page 21
avoided. The BU website cautions that during winter months,
the starter motor batteries of most passenger cars dwell at
75% of a full charge level. If the driving routine for the vehicle
cannot be altered, it may be necessary to do some external
recharging. Stratification can also be broken up through a controlled overcharging process (up to 16V for one or two hours,
not more). Tipping or shaking the battery is another way to redistribute the electrolyte.
Note that the solution for acid stratification again involves a
careful, controlled plan for charging the battery. Refurbishment really means restoring a battery’s storage capacity to an
acceptable level. It does not mean taking the battery apart and
replacing bits and pieces of it.
Other problems can shorten the life of a battery. Internal
mechanical problems include shedding, corrosion and internal
shorts. Inside the cells of a battery are positive and negative
grids that have been pasted with active materials. Over a battery’s life there’s a natural shedding of these materials, which
then fall into the spaces at the bottom of the battery. As this lost
material builds up, it eventually can form a bridge that shorts
out the plates. Shedding can be limited by reducing the depth
of discharge of the battery and the number of starter motor cycles. (The new start-stop systems can be hard on batteries.)
Internal corrosion of a battery can be reduced by controlling its temperature and by choosing the right alloys of lead for
62
May 2014
the grids and straps. Batteries used in hot climates generally
have a much shorter life than those used in moderate climates.
Overcharging a battery can cause the water to split into hydrogen and oxygen (electrolysis) that can then escape the battery. This uses up water and can shorten the life of the insulators inside the battery if the water is not replenished.
Probably the most difficult and technical aspect of the refurbishment business is battery testing. The Battery University
website says that the leading health indicator for a battery is its
capacity. Measured in amp-hours, capacity is the number of
minutes a battery can supply a 25A load. Put another way, capacity is the amount of energy the battery can store. Cold
cranking amps is a different measurement that refers to the
power delivery rate the battery is capable of.
BU says that the large number of warranty returns of stillgood batteries is partly to blame on the lack of reliable testers.
Most testers read only CCA; the capacity is not measured and
therefore not known. This means that resistive measurements
are unreliable as a state-of-health indicator or end-of-life indicator. This leads to wrong diagnostics in which a good battery
is replaced in error while one with low capacity is passed, only
to fail on the road.
The health of a battery cannot be exactly measured, only estimated, says BU. They say that there’s no one single tester today that’s fully capable of assessing the state of health of a battery in a single measurement.
The most common battery test method uses a large resistor
to put a load on the battery. The voltage output of the battery
is monitored during this test. The problem with this method is
that it cannot spot a poorly charged battery, or one with high
internal resistance (sulfation) or lost capacity. Another problem is that the load resistor gets really hot and the test further
drains the battery.
As an alternative approach, various AC conductance testers
are now on the market. These devices inject a sine wave or
square wave pulse into the battery. Different makers use different frequencies and pulse rates. The idea is to measure the
impedance of the battery as a way to gauge how well current
can move in and out. This still doesn’t measure battery capacity, but it’s better than the load resistor method.
Cadex, a company associated with Battery University, says
there’s a method called electrochemical impedance spectroscopy (EIS) that would work to measure battery capacity.
The problem with EIS is that it’s a complicated method that’s
more appropriate to a research lab than a refurbishment operation. The equipment is expensive and it takes skilled operators to decipher the data. Cadex says it has built a hand-held,
field-usable version of this they call “Multi-Model electrochemical impedance spectroscopy,” or “Spectro” tester, for
short. It’s capable of measuring CCA to ±5% accuracy and capacity to ±20% accuracy.
For starter motor applications, the evidence shows that
there are literally tens of millions of batteries every year that
are being recycled before their time. There’s money to be
made from that pile. How good any refurbished batteries
might be depends on technical quality of the charging and
testing methods used to refurbish them.