User Manual

11
deposits on the plates is the reason that a battery can’t supply
energy indefi nitely. For example, lights left on for several days
or extensive cranking of the starter motor.
In fact, prolonged
discharge causes harmful sulfation and the battery may
not recover no matter how long it’s charged.
Besides not being able to produce enough current to start an
engine, a dead battery is also prone to freezing in cold
temperatures because the battery’s electrolyte is mostly
water instead of acid. When temperatures drop below freezing
the electrolyte may freeze and permanently damage the
battery. A charged battery won’t freeze until the temperature
drops well below
-75° F. The suggested operating temperature
range for all Yuasa Batteries is
14° F to 140° F (-10° C to 60° C).
Battery Self-Discharge. It’s a fact that a battery’s ability to
produce electricity will decrease from just sitting around. Self-
discharge is always taking place even if the battery is not connected
to anything. How rapidly batteries self-discharge depends on
ambient temperature and battery type. At temperatures above
130° F self-discharge is even more rapid. These temperatures
can be reached if the battery is stored in a garage or shed in hot
weather.
Speaking of discharging, a common misconception about
battery storage is that if one is left on a concrete fl oor it will
self-discharge rapidly. This was true over thirty-fi ve years ago,
when battery cases were made of hard rubber—the moisture
from concrete caused this type of battery to discharge directly
into the concrete fl oor. However, modern battery cases are
made of polypropylene plastic and can be stored on concrete
without any concern for excessive self-discharge.
Reasons for Self-Discharge
Short Charging Time. Low state-of-charge can be caused by
short trips that aren’t long enough for the vehicle’s charging
system to recharge the battery. Engine operation of less than
15
or
20 miles and occasional use of a vehicle only a couple of times
Battery Discharging
One of two chemical processes is always occurring inside a
battery at any given time—discharging or charging. Here is how
the discharge process works. The electrolyte solution contains
charged atomic particles called ions, made up of sulfate and
hydrogen. The sulfate ions are negatively charged, while the
hydrogen ions have a positive charge. When an electrical load
is placed across a battery’s terminals (starter motor, headlight,
horn, etc.) the sulfate ions travel to the negative plates and
give up their negative charge, causing the battery to discharge
or produce electrical energy. This excess electron fl ow out of
the negative side of the battery, through the electrical device,
and back to the positive side of the battery is what creates DC
current. Once the electrons arrive back at the positive battery
terminal, they travel back into the cells and re-attach themselves
to the positive plates. The discharge process continues until the
battery is dead and there is no more chemical energy left.
Discharge Chemistry. In addition to the electron fl ow within
the battery as it discharges, the ratio of sulfuric acid to water
in the electrolyte solution is also changing to more water and
less acid. A chemical byproduct of this process is lead sulfate
that coats the battery plates within each cell reducing its surface
area. With less area available on the cells to produce electrical
energy, the production of amperage, or current is also reduced.
If the discharge process continues, even more lead sulfate is
deposited on the cell plates and eventually the chemical process
that produces current is no longer possible. The lead sulfate
Battery Discharging and Charging 3
100
Remaining Capacity (percent)
80
90
60
70
40
50
012
Storage Period (month)
34567
32°F (0°C)
32°F (0°C)
77°F (25°C)
77°F (25°C)
104°F (40°C)104°F (40°C)
AGM
Conventional
Current Drain (Y50-N18L-A)
Discharging
Ampere
Days From
100% Charged to
50% Discharged
Days From
100% Charged to
100% Discharged
7 mA
10 mA
15 mA
20 mA
30 mA
60 Days
42 Days
28 Days
21 Days
14 Days
119 Days
83 Days
56 Days
42 Days
28 Days
This chart illustrates how temperature and type of battery effects
battery capacity. Colder storage temperatures are best for long-term
storage. For example, an AGM battery stored at 32ºF holds 90% of its
capacity for about 6 months. The same battery stored at 104ºF loses
50% of its capacity in 4 months. These temperatures can be reached
if the battery is stored in garage or shed in hot weather.
On-board computers, clocks and other accessories can drain a
battery over time. This chart shows the amperage draw in milliamps
and the number of days until the battery is 50% to 100% discharged.