Sears 200.71440 - Manual (Page 11)

Calculating charge time
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
RECOMMENDED.
Find your battery’s rating on the following chart and
note the charge time given for each charger setting.
The times given are for batteries with a 50-percent
charge. Add more time for totally discharged batteries.
BATTERY SIZE/RATING
CHARGE RATE/CHARGING TIME - HOURS
2 AMP 40 AMP
SMALL
BATTERIES
Motorcycle, garden
tractor, etc.
6-12AH 2-4 NR
12-32 AH 4-10 NR
CAR^RUCKS
200-315 CCA 40 - 60 RC 11-14 1/2-3/4
315-550 CCA 60 - 85 RC 14- 18 3/4-1
550 - 1000 CCA 85-190RC 18-35 1 -2
MARINE/DEEP CYCLE
80 RC 18 NR
140 RC 27 NR
160 RC 30 NR
180 RC 33 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 PERCENT PERCENT OF
GRAVITY OF CHARGE CHARGE NEEDED
1.265 100% 0%
1.225 75% 25%
1.155 25% 75%
1.120 0% 100%
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 ratirig by the charge
needed (.50) and divide by the charger setting (2
or 40 amps),
• Multiply the result by 1.25 and you’ll have the time
need, in hours, to bring the battery to full charge.
• Add one more hour for a deep-cycle battery.
Example:
Amp Hour Rating x % of charge needed x 1.25 = hours
Charger Setting of
charge
needed
When you know the percent of charge and the Amp
Hour (AH) rating of your battery, you can calculate the
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
100 (AH Rating) x .50 (charge needed’! x 1.25 = 1.5625
40 (Charger Setting) hours
IOOx.50 = 1.25 X 1.25 - 1.5625
40
You would need to charge your 100-Ampere Hour Bat­
tery for a little more than 1.5 hours at the 40-Amp charge
rate using the above example.
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