Calculating charge time – Sears 200.71210 User Manual

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Sears 210 - Sch 50911/13/95

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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

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 severely
discharged batteries.

CHARGE RATE/CHARGING TIME - HOURS

6 - 12 AH

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 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%

1.225

75%

25%

1.155

25%

75%

1.120

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

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.

10 AMP

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