Filter
Top Products
8
Sears 211 - Sch 510 9/14/95
Calculating charge timeCalculating charge time
Calculating charge timeCalculating charge time
Calculating charge time
The Chart MethodThe Chart Method
The Chart MethodThe Chart Method
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 — motorcycles, garden tractors, etc.
— are usually rated in Ampere Hours (AH). For
example; 6 to 12 AH, or 12 to 32 AH.
• Batteries in cars and smaller trucks are usually
rated in Reserve Capacity (RC), Cold-Cranking
Amps (CCA), or both.
• Marine, or deep-cycle batteries are usually rated in
Reserve Capacity (RC).
• NR means that the charger setting is NOT
RECOMMENED.
Find your battery’s 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 se-
verely discharged batteries.
CHARGE RATE/CHARGING TIME - HOURS
6-12AH
12 -32 AH
40 -60 RC
60 - 85 RC
85 -190 RC
80 RC
140 RC
160 RC
180 RC
BATTERY SIZE/RATING
SMALL
BATTERIES
CAR/TRUCKS
MARINE/DEEP CYCLE
200 - 315 CCA
315 - 550 CCA
550 - 1000 CCA
Motorcycle, garden
tractor, etc.
The Hydrometer or ElectronicThe Hydrometer or Electronic
The Hydrometer or ElectronicThe Hydrometer or Electronic
The Hydrometer or Electronic
MethodMethod
MethodMethod
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 PERCENT PERCENT OF
GRAVITY OF CHARGE 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:
Amp Hours = Reserve Capacity + 16
2
To calculate time needed for a charge:
• Find the percent of charge needed. (A battery at
50 percent charge that will be charged to 100
percent needs another 50 percent (.50).
• Multiply the Amp Hour rating by the charge
needed (.50) and divide by the charger setting
(2 or 10 amps).
• Multiply the result by 1.25 and you’ll have the
approximate time needed, in hours, to bring the
battery to full charge.
• Add one additional hour for a deep-cycle battery.
Example:
Amp Hour Rating x charge needed x 1.25 = hours
Charger Setting of
charge
100 (AH Rating) x .50 (charge needed) x 1.25 = 6.25
10 (Charger Setting) hours
100 x .50 = 5 x 1.25 = 6.25
10
You would need to charge your 100-Ampere Hour Bat-
tery for approximately 6¼ hours at the 10-Amp charge
rate using the above example.
2 AMP
2 - 4
4 - 10
11 - 14
14 -18
18 - 35
18
27
30
33
10 AMP
NR
NR
2 - 2
7
/8
2
7
/8 - 3
3
/4
3
3
/4 - 7
3
1
/2
5
1
/2
6
7