Battery Recharger Repair

Some household batteries are use-and-toss while others need a recharger to replenish their stored electricity. Those include household battery rechargers (AA, AAA, C, D batteries) and shop tool rechargers. This Fix-It Guide on battery recharger repair tells how a battery recharger works, what often goes wrong, how to identify a battery charger problem, and what parts and tools you will need for battery recharger repair. It then gives simple step-by-step instructions for how to restore full electrical contact, how to test a DC output battery charger, how to test an AC output battery charger, and how to test a battery pack. This guide also refers to electrical cord repair.

How Does a Battery Recharger Work?

 Battery Recharger Repair

Household battery chargers include a transformer and a circuit board–not much to work on unless you’re an electrical technician.

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.

What Can Go Wrong with a Battery Charger?

Lots of things can happen to rechargeable batteries, none of them unsolvable. Rechargeable batteries lose their power. Electrical contacts may not be making full contact. The charger may be defective. Batteries wear out or become defective.

Fix-It Tip

How long will rechargeable batteries last? As many as 1,000 recharges. To get the most from rechargeable batteries, read and follow the instructions that come with the recharger unit.

How Can I Identify a Battery Charger Problem?

  • If a cordless device (with built-in rechargeable battery) doesn’t work, lacks power, or does not run long enough, make sure power is on at the outlet and that the outlet is not wired into a wall switch that has been turned off. Also check the electrical cord and replace it if it is defective. Test the recharger unit (see below) and replace as necessary.
  • If a cordless device or rechargeable batteries run for shorter and shorter periods between rechargings, the nicad batteries are probably worn out. Inspect them for damage or leaks and replace as needed. Test the recharger unit (see below) and replace if not working.
  • If there is no leakage visible, test the battery pack and replace if necessary.

Fix-It Tip

Batteries, too, have Senior Moments as they begin to lose energy, and memory becomes a problem. Read instructions that come with the recharger and batteries. Many nicad batteries require a full discharge before a recharge. Otherwise, the battery gets a smaller recharge each time until it cannot retain a charge. Fortunately, battery discharge units are relatively inexpensive. Camera stores have them for video camera batteries. Electronic stores offer them for other rechargeable batteries.

What Do I Need for Battery Charger Repair?

There really aren’t any replacement parts available for battery rechargers–except the rechargeable batteries themselves. You can open up the rechargers and check for obvious damage, such as a disconnected electrical cord , and clean internal contacts, but that’s about all. Here are the tools you’ll need:

  • Screwdrivers
  • Small file
  • Electrical contact cleaner
  • Multimeter

What Are the Steps to Battery Charger Repair?

Restore full electrical contact to battery charger:

  1. Unplug the recharger from the electrical receptacle.
  2. Use a small file, emery paper, or electrical contact cleaner to clean the contacts between the power handle and the charger.
  3. Move the power unit in and out of the charger several times to be sure it makes full contact.

Test a DC output battery charger:

  1. Set a multimeter to the 25 DCV (direct current volts) scale.
  2. Plug in the recharger to the electrical receptacle (outlet).
  3. Touch the two multimeter probes to the appropriate charger contacts (+ and -). If the meter reads zero volts, reverse the probes.
  4. 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 battery charger:

  1. Set a multimeter to the 25 ACV scale.
  2. 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:

  1. Completely charge the battery pack.
  2. Set a multimeter on the DCV scale larger than the battery pack’s rated output.
  3. Touch the red multimeter probe to the pack’s + terminal and the black probe to the – terminal.
  4. Replace the battery pack if the reading is more than 1 volt below the rated output (8VDC for a 9VDC pack).

Fix-It Tip

Need to get rid of some old rechargeable batteries? Call your local solid waste management service for specifics because some locations don’t allow rechargeable batteries to be included with household trash. The store from which you purchase the replacement batteries may know about local regulations.