The first and most likely indication of a low battery would be a hard
starting problem caused by slow cranking. If the battery seems weak or fails to
crank your engine normally, it may be low. To find out, you need to check the
battery's "state of charge."
A battery is nothing more than a chemical storage device for holding
electrons until they're needed to crank the engine or run the lights or other
electrical accessories on your vehicle. Checking the battery's state of charge
will tell you how much juice the battery has available for such purposes.
If your battery is low, it needs to be recharged, not only to restore full
power, but also to prevent possible damage to the battery. Ordinary automotive
lead-acid storage batteries must be kept at or near full charge to keep the cell
plates from becoming "sulfated" (a condition that occurs if the battery is run
down and left in a discharged condition for more than a few days). As sulfate
builds up, it reduces the battery's ability to hold a charge and supply voltage.
Eventually the battery becomes useless and must be replaced.
Checking The State Of Charge
The charge level depends on the concentration of acid inside the battery. The
stronger the concentration of acid in the water, the higher the specific gravity
of the solution, and the higher the state of charge.
On batteries with removable caps, state of charge can be checked with a
"hydrometer." Some hydrometers have a calibrated float to measure the specific
gravity of the acid solution while others simply have a number of colored balls.
On the kind with a calibrated float, a hydrometer reading of 1.265 (corrected
for temperature) indicates a fully charged battery, 1.230 indicates a 75%
charge, 1.200 indicates a 50% charge, 1.170 indicates a 25% charge, and 1.140 or
less indicates a discharged battery. On the kind that use floating balls, the
number of balls that float tells you the approximate level of charge. All balls
floating would indicate a fully charged battery, no balls floating would
indicate a dead or fully discharged battery.
Some sealed-top batteries have a built-in hydrometer to indicate charge. The
charge indicator only reads one cell, but usually shows the average charge for
all battery cells. A green dot means the battery is 75% or more charged and is
okay for use or further testing. No dot (a dark indicator) means the battery is
low and should be recharged before it is returned to service or tested further.
A clear or yellow indicator means the level of electrolyte inside has dropped
too low, and the battery should be replaced.
On sealed-top batteries that do not have a built-in charge indicator, the
state of charge can be determined by checking the battery's base or open circuit
voltage with a digital voltmeter or multimeter. This is done by touching the
meter leads to the positive and negative battery terminals while the ignition
key is off.
A reading of 12.66 volts indicates a fully charged battery; 12.45 volts is
75% charged, 12.24 volts is 50% charged, and 12.06 volts is 25% charged.
Recharging The Battery
CAUTION: Do not attempt to recharge a battery with low (or frozen)
electrolyte! Doing so risks blowing up the battery if the hydrogen gas inside is
ignited by a spark.
Your charging system should be capable of recharging the battery if it is not
fully discharged. Thirty minutes or so of normal driving should be enough.
If your battery is completely dead or extremely low, it should be recharged
with a fast or slow charger. This will reduce the risk of overtaxing and
damaging your vehicle's charging system. One or both battery cables should be
disconnected from the battery prior to charging it with a charger. This will
eliminate any risk of damage to your vehicle's electrical system or its onboard
electronics.
0 comments:
Post a Comment