How to Troubleshoot a Battery Charger

Electric toothbrushes, cordless shavers, cordless drills, cellular and portable phones, and a whole mess of kitchen appliances rely on rechargeable batteries to keep them running. What do you do if they won't charge?

Difficulty: Moderate

Instructions

Things You'll Need:

• 12-V Battery Chargers
• Battery Chargers
• Laptop Battery Chargers
• Cotton Swabs
• Nail Files
• Cotton Swabs
• Voltmeters

1. Make sure the charger cord is plugged in and the outlet is getting power.

2. Look closely at the battery pack. Is there corrosion or leakage? If so, replace the battery immediately.

3. Test the charger. For DC chargers, set a voltmeter to 25 VDC and touch the contacts with the probes. The meter should read about 1 V more than the charger's rating. If the reading is zero, switch the probes.

4. Test an AC charger by setting a voltmeter to 25 VAC. Touch the contacts with the probes. The transformer in the charger is bad if you get no reading at all.

5. Check the contacts. These are metal strips or points located on the appliance and in the charging base. With the charger unplugged, wipe them with a cotton swab. Use a fine emery board to remove visible corrosion.

Tips & Warnings

• If you've noticed that the appliance has been holding a charge for shorter periods, suspect the battery, not the charger.
• A charger's rated output is usually located on a label on the bottom of the unit.
• Avoid testing AC chargers rated higher than 25 V.
• Be careful with leaky batteries. The highly corrosive contents can damage just about anything they touch.

on 4/1/2006 A few switch mode battery chargers(such as used on some wheel chairs) may not show any voltage on the output unless they sense the presence of a minimal acceptable battery voltage level. This is a safety feature to prevent attempted and potentially damaging charges on bad batteries. Always check with a known good set of batteries first to see if the voltage goes at least 1 volt higher than the initial measured battery voltage. If you read the voltage that existed prior to plugging in the charger, then there is a good chance that it is the charger or connection between ac mains to charger or charger to battery. Bear in mind that some chargers perform a slow start that can take anywhere from 3 seconds to a couple of minutes before you see any voltage increase. If your charger has LEDs that give a particular pattern when the unit is properly charging, then become familiar with this pattern when you get the charger (aka READ THE MANUAL)so that you can quickly spot unusual behavior and take it to the dealer for service.
Switch mode battery chargers contain lethal voltages (300 to 700 vdc or more) that can kill. Refer servicing of such chargers to authorized qualified personnel.