RECHARGING A DISCHARGED BATTERY

(also see our page on “ALTERNATOR, VOLTAGE REGULATOR, BATTERY…  HOW IT WORKS”)

The battery behaves like a storage tank for electrical power.  When the storage tank is empty, it will accept a large volume of electrical current flow before it tops off and builds pressure.  When the storage tank is full it will only accept small amount of current and pressure will be high.

AMPS = The electrical measure of current flow.

VOLTS = The electrical measure of pressure. 

          When a powerful model of battery has become discharged, it will accept a large amount of current flow (AMPS) for a considerable time before it tops off and builds the normal amount of electrical pressure (VOLTS).  And this assumes that the battery is not defective, but is discharged.  (Defective batteries behave quite differently than discharged batteries.) 

          In photos, we will show what to expect when recharging a battery that was discharged.  The battery used for this demonstration is a normal, functional, Group 24 size battery.  A reputable battery company (GNB) manufactured this particular battery.  We partially discharged the battery at a reasonably slow rate using headlights.  And now we will show photos of re-charging.  Both a small charger and a large workshop model battery charger will be photographed as the battery is recharged.

          Also, our measurements are about what we would find when testing an alternator-regulator-battery system with use of a SUN model VAT 40, or other professional diagnostic equipment.  We hope that readers will find our demonstration informative, with regard to observing how a discharged battery will behave when being recharged. 

          The photo above shows a typical, small battery charger, the same type that many people would keep in the garage.   

          (Plugged in and charging now.)  This charger is only rated at 6AMPs, when switched to the highest 12volt charge rate.  As we are beginning to recharge the battery, the AMP gauge built into the charger is indicating a little more than a 4 AMP charge rate.  Also notice that a percentage of battery charge scale is at the left of the gauge, and it is indicating under a 50% state of charge. 

          With the battery in a partially discharged condition, it is accepting about 70% of the maximum amperage output from the little 6 AMP charger, and voltage (electrical pressure) measured at the battery is low. 

          In the above photo, we have removed the 6 AMP charger, and a large output workshop type battery charger is connected.  (Shown in this photo at its lowest 12volt setting.) 

          The large battery charger has a charge rate selector switch with three different rates for recharging 12volt batteries.  In the photo above the switch is set to 12V LOW.

          The AMP meter shown in the above photo is built into the large battery charger.  This gauge will show the amount of current flowing into the battery during recharging. 

          With the charge rate selector switched to Medium, the partially discharged battery is accepting 30amps current flow, and battery voltage remains low at only 13.4volts 

click here to see the rest of the story, and we will show readings as the battery reaches a fully charged condition.