I always wondering which leading battery brand actually lasts longer. Duracell or Energizer? Or perhaps another brand?

Do batteries actually regain some power when they're put into a freezer for a certain amount of time?

Are rechargeable batteries as efficient as the non rechargeable ones?

Is keeping a rechargeable battery plugged although it is fully charged bad?

1. Depends on the application. Some battery brands do better with heavy loads, others last longer with light loads. To get a true picture, you would almost have to rate each battery manufacturer and battery type in the specific object you want to power with that battery. And then it would only be a reliable reference if you always used that object in the same way and the same duty cycle. In other works, the best answer is "it depends".

2. No. Keeping a battery cold will reduce it's rate of self-discharge, but it will in no way actually add anything to the batteries charge.

3. Efficient? In what way? For a given battery size, (D, C, AA, AAA) a single use battery will normally have a greater capacity than a rechargable equivalent. But the rechargable can be used and then recharged a number of times. So again, depending on the application, a rechargable may or may not be most cost effective.

4. A good charger will control it's output so as to not overcharge the connected battery. A cheap charger can kill a battery in short order.

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4. A good charger will control it's output so as to not overcharge the connected battery. A cheap charger can kill a battery in short order.

This is true in all appliances. That's what the transformer is for. Sometimes it's a big box in the middle of the cable (i.e. macbooks, this ps2's) and sometimes it's right at the end of the cable where you plug it in the wall (the big, boxy-looking plugins) or sometimes it's right in the equipment itself. Most electronics are safe from this happening, but if you buy a chargeable flashlight from a major store for 3 dollars and the instructions say 'don't charge for more than 5 hours' then please, don't. lol

Slightly related, I've heard that a 6 volt battery is just 6 1 volt batterys with a wrapper over it and is cheaper than buying 6 1 volts.

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Canped wrote:
Slightly related, I've heard that a 6 volt battery is just 6 1 volt batterys with a wrapper over it and is cheaper than buying 6 1 volts.

Depends on the manufacturer, but basically, yes.

Technically, small “batteries” like AAA, AA, C and D are really “cells”, and a true battery is a collection of such cells.