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11
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EEBc500-int-Z
cALcuLAtinG cHArGE tiMES
the chart Method
Use the following table to more accurately determine the
time it will take to bring a battery to full charge. First, identify
where your battery fits into the chart.
Small batteries – motorcycle, garden tractors, etc. – are
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usually rated in Ampere Hours (AH). For example: 6, 12,
32 AH etc.
Batteries in cars and smaller trucks are usually rated in
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Reserve Capacity (RC), Cold-Cranking Amps (CCA), or
both.
Marine or deep-cycle batteries are usually rated in
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Reserve Capacity (RC).
NR means that the charger setting is NOT
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RECOMMENDED.
Find your battery rating on the chart below and note the
charge time given for each charger setting. The times
given are for batteries with a 50-percent charge prior to
recharging. Add more time for severely discharged batteries.
BAttErY SiZE/rAtinG
cHArGE rAtE/cHArGinG tiME in HourS
(unless otherwise stated)
4 AMP
15 AMP
60 AMP
SMALL
BATTERIES Motorcycle, garden tractor, etc.
6 - 12 AH
2 - 4
NR
NR
12 - 32 AH
4 - 10
NR
NR
CAR/
TRUCKS
200 - 315 CCA
40 - 60 RC
11 - 14
60 - 90 min.
20 - 30 min.
315 - 550 CCA
60 - 85 RC
14 - 18
90 - 120 min.
30 - 40 min.
550 - 1000 CCA
85 - 190 RC
18 - 35
2 - 3.5
45 - 60 min.
MARINE/DEEP CYCLE
80 RC
18
105 min.
NR
140 RC
27
2 hrs, 45 min.
NR
160 RC
30
3
NR
180 RC
33
3.5
NR
the Hydrometer or Electronic Method
To find the time needed to fully charge your battery,
determine the battery’s charge level with a hydrometer or
electronic Percent-of-Charge Tester. The following table will
help you convert hydrometer readings to percent of charge
values.
SPEciFic
GrAVitY
PErcEnt oF
cHArGE
PErcEnt oF cHArGE
nEEdEd
1.265
100%
0%
1.225
75%
25%
1.155
25%
75%
1.120
0%
100%
When you know the percent of charge and the Amp
Hour (AH) rating of your battery, you can calculate the
approximate time needed to bring your battery to a full
charge.
To convert Reserve Capacity to Amp Hours, divide Reserve
Capacity by 2, and add 16:
Example:
Amp Hour Rating = Reserve Ca 16
2
notE:
The reserve Capacity can be obtained from the
battery specification sheet or the owner’s manual.
To calculate time needed for a charge:
Find the percent charge needed. (A battery at 50%
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charge that will be charged to 100% needs another 50%
(.50)).
Multiply the Amp Hour rating by the charge needed (.50)
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and divide by the charger setting (4, 15, or 60 amps).
Multiply the results by 1.25 and you will have the total
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time needed, in hours, to bring the battery to full charge.
Add one additional hour for a deep-cycle battery.
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Example:
Amp Hour Rating x % of charge needed x 1.25 = hours of charge
Charger Setting
100 (AH Rating) x .50 (charge needed) x 1.25 = 3.125 hours
20 (Charger Setting)
100 x .50 x1.25 = 3.125
20
You would need to charge your 100-Ampere Hour Battery
for a little more than three hours at the 20-Amp charge rate
using the above example.
