13. HOW CAN I STORE BATTERIES?
Last Updated on July 11, 2004
INDEX:
13.1. How Do I Prevent Permanent Sulfation?
13.2. So How Do I Store My Battery?
People kill more deep cycle batteries
with bad charging and maintenance practices, than
die of old age!
All lead-acid batteries are perishable. During
the normal discharge process, soft lead sulfate crystals
are formed in the pores and on the surfaces of the
positive and negative plates inside a lead-acid battery.
When a battery is left in a discharged condition, is
continually undercharged, excessive temperatures or
the electrolyte level is below the top of the plates,
some of the soft lead sulfate re-crystallize into hard
lead sulfate. It cannot be reconverted during subsequent
recharging. This creation of hard crystals is commonly
called permanent "sulfation". It is the leading
cause and accounts for approximately 85% of
the premature deep cycle lead-acid battery failures.
The longer sulfation occurs, the larger and harder
the lead sulfate crystals become. The positive plates
will turn a light brown and the negative plates will be dull,
off white. These permanent crystals lessen a battery's
capacity and ability to be recharged. Deep cycle batteries
that are typically used for short periods and then
are stored for long periods where they slowly self
discharge. A car or motorcycle starting battery is
normally used several times a month, so permanent sulfation
rarely becomes a problem unless it is unused or stored
for long periods.
While a battery is in storage or not
being used, the discharge is a consequence of parasitic
load or natural self discharge. Parasitic load is
the constant electrical load present on a battery while
it is installed in a vehicle even when the ignition
key is turned off. The load is from the continuous
operation of electrical appliances, such as an emissions
computer, clock, security system, maintenance of radio
station presets, etc. While disconnecting the negative
battery cable will eliminate the parasitic load, it
has no affect on the natural self discharge of battery.
Thus, permanent sulfation can be a huge problem for
lead-acid batteries while sitting for long periods
on a dealer's shelf, in a basement, cellar, barn or
garage, or in a parked vehicle, especially in hot temperatures.
13.1. How Do I Prevent
Permanent Sulfation?
The best way to prevent sulfation
is to keep a lead-acid battery fully charged because
lead sulfate is not formed. This can be accomplished
three ways. Based on the battery type you are using,
the best solution is to use a charger that is capable
of delivering a continuous "float" charge at the battery manufacturer's recommended
float or maintenance voltage for a fully charged
battery. 12-volt batteries, depending on the battery
type, usually have fixed float voltages between 13.1
VDC and 13.6 VDC, measured at 80° F (26.7° C)
with an accurate (.5% or better) digital voltmeter.
(For a six-volt battery, measured voltages are one
half of those for a 12-volt battery.) This can best
be accomplished by continuously charging using a
three stage for AGM or Gel Cell batteries or four
stage for wet batteries, "smart" microprocessor controlled charger. If
you already have a two stage charger, then use a
voltage-regulated "float" charger, set at the correct float
voltage to "float" or maintain a fully charged battery. If
you need Web addresses or telephone numbers of the
charger manufacturers, please see the Chargers and
Float Chargers and Battery Maintainers sections of Battery
Information Links List. A cheap, unregulated "trickle" or a manual two stage charger can overcharge a
battery and destroy it.
A second and less desirable method
is to periodically recharge the battery when the State-of-Charge
drops to 80% or below. Maintaining a high State-of-Charge
tends to prevent irreversible permanent sulfation.
The frequency of recharging depends on the parasitic
load, temperature, battery's condition, and battery
type. Temperature matters! Lower temperatures
slow down electro chemical reactions and higher temperatures
will significantly increase them. A battery stored
at 95° F (35° C) will self discharge twice
as fast than one stored at 75° F (23.9° C).
Standard (Sb/Sb) batteries have a very high self discharge
rate; whereas, AGM batteries have a very slow rate.
There are trade-offs between the
economics of continuous "float" charging,
where self discharge and resulting sulfation does not
occur, and periodic charging with the increased potential
for a shorter battery life due to permanent sulfation.
If you decide to periodically recharging the batteries
while in storage, increased recharging frequency and
storing them in colder temperatures will impede the
self discharge and reduce the possibility for permanent
sulfation, but reduce the total number of life cycles.
A third technique is to use a
voltage regulated solar panel designed to "float" charge batteries. This is a popular solution
when AC power is unavailable for charging.
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13.2. So How Do I Store
My Battery?
Batteries naturally self discharge
1% to 60% per month (depending on the battery type
and temperature) while not in use and sulfation will
begin occurring when the State-of-Charge (SoC) drops below
100%. Please see Section 16 for more information on sulfation. Cold will
slow the process down and heat will
increase it up. Storing batteries under 250 AH on concrete
floors will not cause them to naturally self discharge
faster. Please see Section 14.1 for more information on this myth.
Below are six simple steps while your batteries are
not in use to protect them from permanent sulfation
and premature failure.
13.2.1. Physically inspect for damaged
cases, remove any corrosion, and clean and dry the
tops of the batteries to remove possible discharge
paths from dried battery electrolyte. If the battery
is in a vehicle, remove the negative connection from
the battery to eliminate the additional parasitic (key
off) discharge.
13.2.2. If the battery has filler caps,
check the electrolyte (battery acid) level in each cell. If required, add only distilled,
deionized or demineralized water to the recommended
level, but do not overfill, clean and the top
of the battery to remove any discharge paths caused
by dried or wet battery electrolyte and clean the posts
and terminals.
13.2.3. Fully charge and equalize wet
(flooded) batteries, if required, using the procedures
in Section 9.
13.2.4. Store in a cold dry
place, but not so that it will freeze where it can
be easily recharged. The freezing point of a battery
is determined by the SoC and the higher it is, the
lower the freezing temperature. (Please see the State-of-Charge Table in Section 4.) Based on the battery type you are
using, connect a "smart", microprocessor based three
stage or four stage charger or a voltage regulated float charger to continuously "float" charge your
battery. Do not use a cheap, unregulated "trickle" charger or a manual two stage charger
which was not designed for "float" charging or you will overcharge your battery.
A less desirable alternative to float charging would
be to periodically test the State-of-Charge using the
procedure in Section 4. When it is 80% or below, recharge using the procedures
in Section 9. The frequency of testing and recharging will depend
on the ambient storage temperature.
FLOAT CHARGING VOLTAGE
TEMPERATURE IN DEGREES C (F)
[Source: Concorde]
13.2.5. Periodically test the State-of-Charge
(SoC) and ensure that the electrolyte is at the proper
levels.
13.2.6. When you remove the batteries
from storage, charge and equalize, if required, using
the battery manufacturer's recommended procedures or,
if not available, the one in Section 9.
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