This is a vibration noise which occurs when electric current flows through a transformer or a winding wire inside a component part. However, the charger may still be used without any concern as there is no need to worry from a safety point of view.

Turn off the device and remove the battery immediately. Remove the remaining leakage using a cotton swab. Avoid skin contact at all times.

The results of a voltmeter vary depending on the type of voltmeter used. For a more accurate result, be sure to use a voltmeter with more than 1 megaohm input resistance for alkaline buttons batteries or a 10+ megaohm for lithium batteries.

If service time has reduced to half of its initial capacity or if charging time never seems to complete, it’s probably time to replace the battery.

A hot battery could have several causes: from wrong storage to short circuiting. Some warmth is okay but keep an eye out for unusual heat.

The capacity of batteries is indicated as XXXX mAh (milliampere/hour). If you insert this battery into an appliance which consumes 100 milliampere current continuously, the operating time of the appliance will be around 20 hours mathematically.

Never use Ni-MH rechargeable batteries for waterproof appliances, appliances specifically designed for alkaline batteries, or in appliances with battery indicators.

Mixing batteries causes an imbalance in the energy flow. Some batteries will overcompensate this by discharging faster than usual - greatly reducing their lifespan.

Make sure you measure the correct way: connect the poles to their corresponding measuring ends.

As new energy flows into your battery, some heat is perfectly fine. If you notice the battery or charger becomes too hot to touch, cease the charging process immediately.