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Battery rechargers use printed circuit boards to control an electrical transformer.
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Batteries offer portable power. Dozens of things in everyone's home run on batteries. Some household batteries are use-and-toss while others use a recharger to replenish their stored electricity. They include household battery rechargers (AA, AAA, C, D batteries) as well as all the new shop tools (drills, saws, vacuums, etc.) that run on special rechargeable batteries. Let's visit the Fix-It Club to find out how to keep all those batteries charging.
Batteries produce electric current from the chemical reaction between two electrodes and an electrolyte. Battery rechargers convert 120V alternating current (AC) into small-voltage direct current (DC). The voltage ranges from 1.2V to 24V or more, depending on the battery and the charger.
Many cordless appliances are powered by a rechargeable nickel-cadmium (nicad) battery or battery pack consisting of as many as 20 cells. Each cell provides direct current at about 1.2 volts. Batter packs slip directly into the appliance or tool or have snap-on terminals. Some battery packs have built-in batteries that cannot be removed; they must be charged in the unit.
Restore full electrical contact:
- Unplug the recharger from the electrical receptacle.
- Use a small file, emery paper, or electrical contact cleaner to clean the contacts between the power handle and the charger.
- Move the power unit in and out of the charger several times to be sure it makes full contact.
Test a DC output charger:
- Set a multimeter to the 25 DCV (direct current volts) scale.
- Plug in the recharger to the electrical receptacle (outlet).
- Touch the two multimeter probes to the appropriate charger contacts (+ and -). If the meter reads zero volts, reverse the probes.
- The DCV output should be at or slightly above the charger's rated output. That is, a 9VDC charger should give a reading of about 10VDC.
Test an AC output charger:
- Set a multimeter to the 25 ACV scale.
- Touch the two multimeter probes to the two charger contacts. If there is no reading, the transformer is faulty. Check an electrical supplier for a transformer of the same rating and size.
Test a battery pack:
- Completely charge the battery pack.
- Set a multimeter on the DCV scale larger than the battery pack's rated output.
- Touch the red multimeter probe to the pack's + terminal and the black probe to the - terminal.
- Replace the battery pack if the reading is more than 1 volt below the rated output (8VDC for a 9VDC pack).
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