Your prospects are not good.
Prolonged storage of lead-acid batteries tends to destroy them due to
self-discharge and resultant sulfation; deep cycle batteries are more
resistant to this but are still susceptible to this. Storage on wood
generally doesn't make much, if any, difference. High temperatures
during storage accelerate the process.
Someone may have practical experience that will help, but the only
prospect that I see is that the water has not fully mixed with the
sulfuric acid electrolyte. Have you measured the specific gravity of
the electrolyte at the top and bottom (if that is physically possible)
with a hydrometer? NOTE: I presume that you are familiar with the
strongly corrosive properties of sulfuric acid - it can cause
blindness if it gets in the eye, facial scarring, and can eat through
clothing - how strong it has to be to do this I don't know, but I
wouldn't take chances without adequate protection. I also presume that
you are familiar with the usual warnings about the possibility of
explosions due to hydrogen gas.
Here is some information from research:
* The Power Battery site seems to be under development and have only a home page:
http://www.powbat.com/index.html
* From a site on deep cycle batteries
http://www.windsun.com/Batteries/Battery_FAQ.htm#Lifespan%20of%20Batteries
"Lifespan of Batteries
The lifespan of a battery will vary considerably with how it is used,
how it is maintained and charged, temperature, and other factors. In
extreme cases, it can vary to extremes - we have seen L-16's killed in
less than a year by severe overcharging, and we have a large set of
surplus telephone batteries that sees only occasional (5-10 times per
year) heavy service that are now over 25 years old. We have seen
gelled cells destroyed in one day when overcharged with a large
automotive charger. We have seen golf cart batteries destroyed without
ever being used in less than a year because they were left sitting in
a hot garage without being charged. Even the so-called "dry charged"
(where you add acid when you need them) have a shelf life of at most
18 months, as they are not totally dry (actually, a few are, but hard
to find, the vast majority are shipped with damp plates)."
...
"Most industrial deep-cycle batteries use Lead-Antimony plates rather
than the Lead-Calcium used in AGM or gelled deep-cycle batteries. The
Antimony increases plate life and strength, but increases gassing and
water loss. This is why most industrial batteries have to be checked
often for water level if you do not have Hydrocaps. The self discharge
of batteries with Lead-Antimony plates can be high - as much as 1% per
day on an older battery. A new AGM typically self-discharges at about
1-2% per month, while an old one may be as much as 2% per week."
...
"All Lead-Acid batteries supply about 2.14 volts per cell (12.6 to
12.8 for a 12 volt battery) when fully charged. Batteries that are
stored for long periods will eventually lose all their charge. This
"leakage" or self discharge varies considerably with battery type,
age, & temperature. It can range from about 1% to 15% per month.
Generally, new AGM batteries have the lowest, and old industrial
(Lead-Antimony plates) are the highest. In systems that are
continually connected to some type charging source, whether it is
solar, wind, or an AC powered charger this is seldom a problem.
However, one of the biggest killers of batteries is sitting stored in
a partly discharged state for a few months. A "float" charge should be
maintained on the batteries even if they are not used (or, especially
if they are not used). Even most "dry charged" batteries (those sold
without electrolyte so they can be shipped more easily, with acid
added later) will deteriorate over time. Max storage life on those is
about 2-3 years.
...
Batteries self-discharge faster at higher temperatures. Lifespan can
also be seriously reduced at higher temperatures - most manufacturers
state this as a 50% loss in life for every 15 degrees F over a 77
degree cell temperature. Lifespan is increased at the same rate if
below 77 degrees, but capacity is reduced. This tends to even out in
most systems - they will spend part of their life at higher
temperatures, and part at lower.
Myth: The old myth about not storing batteries on concrete floors is
just that - a myth. This old story has been around for 100 years, and
originated back when battery cases were made up of wood and asphalt.
The acid would leak from them, and form a slow-discharging circuit
through the now acid-soaked and conductive floor.
State of Charge
State of charge, or conversely, the depth of discharge (DOD) can be
determined by measuring the voltage and/or the specific gravity of the
acid with a hydrometer. This will NOT tell you how good (capacity in
AH) the battery condition is - only a sustained load test can do that.
Voltage on a fully charged battery will read 2.12 to 2.15 volts per
cell, or 12.7 volts for a 12 volt battery. At 50% the reading will be
2.03 VPC (Volts Per Cell), and at 0% will be 1.75 VPC or less.
Specific gravity will be about 1.265 for a fully charged cell, and
1.13 or less for a totally discharged cell. This can vary with battery
types and brands somewhat - when you buy new batteries you should
charge them up and let them sit for a while, then take a reference
measurement. Many batteries are sealed, and hydrometer reading cannot
be taken, so you must rely on voltage. Hydrometer readings may not
tell the whole story, as it takes a while for the acid to get mixed up
in wet cells. If measured right after charging, you might see 1.27 at
the top of the cell, even though it is much less at the bottom. This
does not apply to gelled or AGM batteries."
...
"Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.
Bulk Charge - The first stage of 3-stage battery charging. Current is
sent to batteries at the maximum safe rate they will accept until
voltage rises to near (80-90%) full charge level. Voltages at this
stage typically range from 10.5 volts to 15 volts. There is no
"correct" voltage for bulk charging, but there may be limits on the
maximum current that the battery and/or wiring can take.
Absorption Charge: The 2nd stage of 3-stage battery charging. Voltage
remains constant and current gradually tapers off as internal
resistance increases during charging. It is during this stage that the
charger puts out maximum voltage. Voltages at this stage are typically
around 14.2 to 15.5 volts.
Float Charge: The 3rd stage of 3-stage battery charging. After
batteries reach full charge, charging voltage is reduced to a lower
level (typically 12.8 to 13.2) to reduce gassing and prolong battery
life. This is often referred to as a maintenance or trickle charge,
since it's main purpose is to keep an already charged battery from
discharging. PWM, or "pulse width modulation" accomplishes the same
thing. In PWM, the controller or charger senses tiny voltage drops in
the battery and sends very short charging cycles (pulses) to the
battery. This may occur several hundred times per minute. It is called
"pulse width" because the width of the pulses may vary from a few
microseconds to several seconds. Note that for long term float
service, such as backup power systems that are seldom discharged, the
float voltage should be around 13.02 to 13.20 volts.
Chargers: Most garage and consumer (automotive) type battery chargers
are bulk charge only, and have little (if any) voltage regulation.
They are fine for a quick boost to low batteries, but not to leave on
for long periods. Among the regulated chargers, there are the voltage
regulated ones, such as Iota Engineering and Todd, which keep a
constant regulated voltage on the batteries. If these are set to the
correct voltages for your batteries, they will keep the batteries
charged without damage. These are sometimes called "taper charge" - as
if that is a selling point. What taper charge really means is that as
the battery gets charged up, the voltage goes up, so the amps out of
the charger goes down. They charge OK, but a charger rated at 20 amps
may only be supplying 5 amps when the batteries are 80% charged. To
get around this, Statpower (and maybe others?) have come out with
"smart", or multi-stage chargers. These use a variable voltage to keep
the charging amps much more constant for faster charging."
...
"Batteries should be watered after charging unless the plates are
exposed, then add just enough water to cover the plates. After a full
charge, the water level should be even in all cells and usually 1/4"
to 1/2" below the bottom of the fill well in the cell (depends on
battery size and type).
...The vent caps on flooded batteries should remain on the battery
while charging. This prevents a lot of the water loss and splashing
that may occur when they are bubbling.
...When using a small solar panel to keep a float (maintenance) charge
on a battery (without using a charge controller), choose a panel that
will give a maximum output of about 1/300th to 1/1000th of the
amp-hour capacity. For a pair of golf cart batteries, that would be
about a 1 to 5 watt panel - the smaller panel if you get 5 or more
hours of sun per day, the larger one for those long cloudy winter days
in the Northeast.
Lead-Acid batteries do NOT have a memory, and the rumor that they
should be fully discharged to avoid this "memory" is totally false and
will lead to early battery failure.
Inactivity can be extremely harmful to a battery. It is a VERY poor
idea to buy new batteries and "save" them for later. Either buy them
when you need them, or keep them on a continual trickle charge. The
best thing - if you buy them, use them."
* From another site (regarding the effects of prolonged storage)
http://www.powerstream.com/Storage.htm
"Flooded Lead Acid Battery Storage
Trojan: Periods of inactivity can be extremely harmful to lead acid
batteries. When placing a battery into storage, follow the
recommendations below to insure that the battery remains healthy and
ready for use.
NOTE: Storing, charging or operating batteries on concrete is
perfectly OK. The most important things to avoid:
Freezing. Avoid locations where freezing temperature is expected.
Keeping battery at a high state of charge will also prevent freezing.
Freezing results in irreparable damage to battery's plates and
container. [Freezing can happen between -19 F (40% charge) and -98 F
(fully charged)]
Heat. Avoid direct exposure to heat sources, such as radiators or
space heaters. Temperatures above 80° F accelerate the battery's
self-discharge characteristics.
Step by step storage procedure: 1. Completely charge the battery
before storing. 2. Store the battery in a cool, dry location,
protected from the elements. 3. During storage, monitor the specific
gravity (flooded) or voltage. Batteries in storage should be given a
boost charge when they show a 70% charge or less. Completely charge
the battery before re-activating.
For optimum performance, equalize the batteries (flooded) before
putting them back into service. Refer to the Equalizing section for
this procedure.
Continental Battery Storage:
Q: Will a battery rapidly self discharge if placed on concrete?
A: No, placing a battery on concrete will not cause it to discharge
any faster than any other surface.
Q: Can I store a battery indefinitely?
A: No, a battery will self-discharge slowly over time. Allowing a
battery to sit in a discharged state will ultimately lead to severe
positive grid corrosion and battery failure. An unused battery should
never be allowed to sit over 6 months without a recharge. "
* The following is from a site the sells the particular type of
charger they recommend and so may have a conflict of interest. I
believe that they are talking about regular lead-acid batteries here.
http://www.batterystuff.com/tutorial_battery.html
"Battery Charging - Remember you must put back the energy you use
immediately. If you don't the battery sulfates and that affects
performance and longevity. The alternator is a battery charger. It
works well if the battery is not deeply discharged. The alternator
tends to overcharge batteries that are very low and the overcharge can
damage batteries. In fact an engine starting battery on average has
only about 10 deep cycles available when recharged by an alternator.
Batteries like to be charged in a certain way, especially when they
have been deeply discharged. This type of charging is called 3 step
regulated charging. Please note that only special SMART CHARGERS using
computer technology can perform 3 step charging techniques. You don't
find these types of chargers in parts stores and Wal-Marts. The first
step is bulk charging where up to 80% of the battery energy capacity
is replaced by the charger at the maximum voltage and current amp
rating of the charger. When the battery voltage reaches 14.4 volts
this begins the absorption charge step. This is where the voltage is
held at a constant 14.4 volts and the current (amps) declines until
the battery is 98% charged. Next comes the Float Step. This is a
regulated voltage of not more than 13.4 volts and usually less than 1
amp of current. This in time will bring the battery to 100% charged or
close to it. The float charge will not boil or heat batteries but will
maintain the batteries at 100% readiness and prevent cycling during
long term inactivity. Some gel cell and AGM batteries may require
special settings or chargers."
* Here is another site indicating that prolonged storage tends to
destroy batteries:
http://pweb.uunet.de/william.darden/carfaq13.htm
"All lead-acid batteries are perishable. If not used weekly, people
kill more deep cycle and power sport batteries with bad charging and
maintenance practices, than die of old age!
When a lead-acid battery is discharged, soft lead sulfate crystals are
formed in the pores and on the surfaces of the positive and negative
plates. When left in a discharged condition or excessive high
temperatures, is continually undercharged, or the electrolyte level is
below the top of the plates or stratified, some of the soft lead
sulfate re-crystallize into hard lead sulfate. These crystals 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 failures of
lead-acid batteries not used on weekly basis. 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 or hold a charge. Sulfation
primarily occurs in deep cycle and power sport batteries that are
typically used for short periods and then are stored for long periods
where they slowly self-discharge. Whereas, 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
result 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."
And from another part of this site
http://www.uuhome.de/william.darden//carfaq16.htm
"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 an external charger in a well ventilated area
that is capable of delivering a continuous, temperature compensated
"float" charge at the battery manufacturer's recommended float or
maintenance voltage for a fully charged battery. For 12-volt
batteries, depending on the battery type, usually have fixed float
voltages between 13.1 VDC and 13.9 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 VRLA (AGM or Gel Cell) batteries or four stage for
wet (flooded) batteries, "smart" microprocessor controlled charger. If
you already have a two stage charger, then use a voltage-regulated
"float" charger or battery "maintainer", set at the correct
temperature compensated 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 by drying out the electrolyte.
A second 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. Lower temperatures slow down
electrochemical 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 and Gel
Cell VRLA batteries have very low rates. Please see Section 7.1 for
more information on battery types.
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, disconnecting any parasitic load, or storing them in colder
temperatures will impede the self-discharge and reduce the possibility
for permanent sulfation, but will also reduce the total number of life
cycles.
A third technique is to use a solar panel or wind or water generator
designed to "float" charge batteries. This is a popular solution when
AC power is unavailable for charging. The size of a solar panel or
wind or water generator required will depend on the average amount of
available natural resource, battery capacity and temperature. Normally
a five watt or larger panel is required for an average car battery. A
charge controller (voltage regulator) is required when the peak
current output exceeds 1.5% of the amp hour capacity of the battery." |
