Snap-On BATTERY CHARGER PLUS - CALCULATING CHARGE TIMES; Charge Time Estimation Methods

• 11 •
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 ts into the chart.
Small batteries – motorcycle, garden tractors, etc. – are •
usually rated in Ampere Hours (AH). For example: 6, 12,
32 AH etc.
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 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 nd 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 Capacity + 16
2
NOTE: The reserve Capacity can be obtained from the
battery specication sheet or the owner’s manual.
To calculate time needed for a charge:
Find the percent charge needed. (A battery at 50% •
charge that will be charged to 100% needs another 50%
(.50)).
Multiply the Amp Hour rating by the charge needed (.50) •
and divide by the charger setting (4, 15, or 60 amps).
Multiply the results by 1.25 and you will have the total •
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 % 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.