36 37
RECOMMENDED CHARGING PROCEDURES
DETERMINING STATE-OF-CHARGE
The simplest method to determine the state-of-charge
of a battery is to read the battery “rested” open-circuit
voltage (OCV) with a digital voltmeter� Consider these
facts:
– Rested OCV indicates an undisturbed battery
with no charging or discharging for at least eight
hours or more�
– The use of a hydrometer to read the cell-specic
gravities is encouraged since this complementary
value will aid in battery diagnostics�
– At activation (rst dry-charged battery acid ll), the
OCV is fairly close to the true rested OCV, and no
wait is necessary to determine true state-of-charge�
BATTERY-CHARGING THEORY
The best way to understand how a charger works is to
make the analogy of two tanks connected at the
bottom by a pipe. The tank lled with water represents
the charger, while the empty tank represents the
battery� As the full tank discharges into the empty
tank, its level rises (voltage), while the water ow
through the pipe into the empty tank decreases
(amperage)� The amount of charging amperes (A)
multiplied by time (hours) will provide the battery
capacity in ampere-hours of charge�
During charging, the battery will self-regulate the
charge ow according to the charger output voltage,
which is just as important as the amperage that is
forced into the battery� The voltage must be controlled
and used according to the operator’s needs to avoid
battery damage�
The various voltage levels for batteries and a variety
of chargers are described in the chart at right�
HOW THE CHARGING CURRENT WILL
BEHAVE DURING RECHARGE
The current (amperes) owing into the battery will be
dictated by the battery’s state-of-charge,
temperature, and charging voltage (kept fairly constant
by the charger)�
The current prole will almost invariably follow the
pattern shown at right, according to the state-of-
charge of the battery�
13.5V
12.6V
12.4V
12.2V
16.5V
15.0V
13.0V
12.8V
TYPICAL FULLY CHARGED BATTERY
OPEN-CIRCUIT VOLTAGE (OCV)
TYPICAL DISCHARGED BATTERY
OPEN-CIRCUIT VOLTAGE (OCV)
TYPICAL “FLOAT/TRICKLE-CHARGE”
CHARGER VOLTAGE SETTING
(Used for unattended trickle charging)
TYPICAL “MEDIUM-CHARGE”
CHARGER VOLTAGE SETTING
(Used for NORMAL charging)
TYPICAL “HIGH-CHARGE”
CHARGER VOLTAGE SETTING
(Used for START or short
BOOSTING only)
12.0V
11.7V
25% SOC
0% SOC
100% SOC
50% SOC
75% SOC
(TYPICAL 14V
ALTERNATOR
VOLTAGE)
AMPS
CHARGE
TIME (HOURS)
Normally Discharged
Battery, OCV~12V
Charged
Battery
OCV~12.7V
Deeply Discharged Battery, OCV~Less than 8V
*Rested 8 hours or more OCV (use 1 ⁄2 OCV for 6-volt batteries).
**Based on the 20-hour (ampere hour) capacity�
†
Based on “low-voltage” charger setting
(13�5- to 14-volt charger output)�
The appropriate state-of-charge and approximate time to
complete full charging at 80°F can be determined from the
following table�
BATTERY-CHARGING SCENARIOS
Boost-charging a recently discharged battery
A battery discharged in the past three days can be easily
charged since the materials will respond to charging by
readily converting to their original chemical state� The table
on the previous page may be used as a guideline with
medium settings� High/start-voltage or boost-voltage
settings will accelerate charging, requiring close supervision
to ensure that batteries are not overheating or gassing
excessively� High/start and boost settings must be done in
two-hour intervals until voltage rises to specications.
Boost-charging a rundown (at) battery
Batteries with little or no voltage have little chance for
recuperation, especially if they have remained in this state
for a long period of time�
To charge a battery in this condition, the operator must use
the lowest setting on the charger (low/trickle/oat) and
allow the battery to charge over a 24-hour period�
If the battery resists charge, a high-boost charge may be
attempted for 30 to 60 minutes until the battery begins to
accept charge� After this limited time period, the setting
must be switched to low to avoid excessive overheating�
The operator must make sure the battery is still accepting
charge by watching the needle move above the zero mark�
Once charging is completed, the battery must be tested to
determine its condition�
Use the Battery Replacement Data Book as a complete
source for nding the right battery quickly�
The Battery Council International Battery
Replacement Data Book makes it easy
to nd the correct BCI group (size) for
a specic application. The book is an
invaluable resource packed with useful
information, and it is easy to use:
– Dene the manufacturer, model,
and year of the vehicle or machine�
– Identify the BCI group and OE (Original
Equipment) cold cranking amps�
– Turn to the book’s battery data
section� Then, cross-reference
the John Deere part number to
the BCI group identied.
Best-t estimate — Some equipment manufac turers
do not provide complete replacement battery
information� Estimates are provided for replacement
battery size to give some guidance to the Battery
Replacement Data Book user� However, use caution
— the size stated is only an estimate� You should always
try to obtain the specic battery replacement size
information from the equipment manufacturer�
More valuable information — The BCI Data Book also
includes explanations on battery terminal types,
terminal placement, use of booster cables, safety
precautions, a BCI/DIN/EN reference chart, cell
layouts, and more� Use the BCI Data Book to your
advantage — it’s a great reference tool! Also,
information on the Battery Council International
organization can be found at http://www�
batterycouncil�org�
California Proposition 65 — The posters shown below
have been posted in John Deere California dealerships
according to California’s Proposition 65 requirements�
Noncompliance with California Proposition 65 could
cause dealerships to be liable and lose protection from
such claims under the terms of a battery
manufacturer’s settlement�
12.60 (or higher) 1.265 (or higher) 100% 3 (or less)
12.40–12.60 1.22 75% 4–6
12.20–12.40 1.16 50% 12
12.00–12.20 1.1 25% 22
11.70–12.00 1.04 0% 24
OCV*
Avg. Cell-Specic
Gravity
Approx.
SOC**
Approx.
Charging
Hours
†