Filter
Top Products
VEC088VEC088
1111
APPENDIX A APPENDIX A — CHARGING TIMESCHARGING TIMES
To calculate the approximate charging time required to fully charge a battery, it is necessary to
determine the specific gravity (or, percent of battery charge) using a hydrometer. Use this technique if
battery vent caps can be removed. Check each cell. if there is one cell with a very low specific gravity
compared to the other cells, there is probably a shorted cell in the battery. Replace the battery.
The following chart converts hydrometer readings into percent of charge values.
SPECIFIC GRAVITYSPECIFIC GRAVITY PERCENT OF CHARGE PERCENT OF CHARGE NEEDEDPERCENT OF CHARGE PERCENT OF CHARGE NEEDED
(HYDROMETER READING)(HYDROMETER READING) IN BATTERYIN BATTERY BY BATTERYBY BATTERY
1.265 100% 0%0%
1.225 75% 25%
1.190 50% 50%
1.155 25% 75%
1.120 0% 100%
Refer to the chart below for approximate charging times.
PERCENT OF CHARGEPERCENT OF CHARGE 75%75% 50%50% 25%25% 0%0%
2 AMPS 7 HRS 13 HRS N.R* N.R*
6 AMPS 2.5 HRS 5 HRS 7 HRS 9 HRS
12 AMPS 1.2 HRS 2.5 HRS 3.2 HRS 4.6 HRS
* Not Recommended because over 18 hrs charging time.
The times shown in the chart above are approximate and refer to an average automotive battery. For
smaller batteries, the charge time should be adjusted using the formula shown below and adding 1 hour
to the time calculated.
To estimate charging time for a discharged battery, divide the AH rating of the battery by the charge rate
selected. This is the number of hours required to recharge the battery. For example, a 50 AH (12 volt)
battery is discharged (10 volts). How long should it be charged at the 12 Amp rate. Divide the 50 AH by
12. The answer is approximately 4.2 hours. Always round up the charge time by 10% to ensure full
charge. In most cases, battery recharge times will vary depending on the age and condition of the
battery. Smaller batteries should be charged at a lower rate (2 Amps) and add an extra hour to charge
time.