Duracell Supreme HR06 - Battery 4 x AA type NiMH 2650 mAh

...charge a brand new battery. Duracell on their packaging only specify this forming charge.

'''And the Duracells?'''

They are well presented, and look to be well constructed. In short they have a quality feel. Instructions on use are more than adequate. Note that they only specify the forming charge, and not the higher charging rates typical of most battery chargers.

The batteries are marked as being 2650 mAh ...
...this is the maximum possible under ideal conditions. I have a charger that is able to deliver a forming charge - it's a long and slow process. My Duracells achieved around 2580 after a forming charge. A tad shy of the advertised capacity.

They have been in use now for nearly 12 months, have been recharged on a weekly basis and are essentially trouble free. 2 weeks ago I tested the batteries and capacity had fallen to 2450 mAh, which ... more

Why Rechargeable?

There are 3 main technologies that you may encounter - (1) Nickel Cadmium (NiCd) outlawed in the EU; their big downside was the "memory" effect and high toxicity. (2) Nickel Metal Hydride (NiMH) has replaced NiCd batteries, and this is the type you will find on sale in supermarkets and the like. NiMH have no memory effect, but lose charge over time. (3) Li-ion, more expensive than NiMH, have a greater energy density, and hold their charge for longer. Li-ion technology is still young and is likely to supersede NiMH as the rechargeable battery of choice.

Rechargeables have come to the fore in recent years largely because of their green credentials. However they do make economic sense when utilised in high current drain devices. Their higher initial cost is offset by the fact that they can be recharged multiple times, meaning they can save money in the long run. They are not so useful in low current drain devices such as remote controls, where slow discharge is a serious disadvantage, and an alkaline battery may last 2-3 years anyway. I use my rechargeables in bicycle lights - when the light is on full power, batteries can last as little as 3 hours.

What's all the milliamp hours malarky?

Batteries are typically rated in milliamp hours (mAh). This is a measure of the amount of charge they hold. For instance a battery rated at 2400 mAh could in theory sustain a 2.4A current for one hour, or a 1.2A current for 2 hours. In practice though a rechargeable is better able to sustain low currents - the mAh rating typically refers to a discharge rate at 20% of the batteries capacity. Sometimes you may see "C" referred to when talking about charging or discharging rates. C refers to the capacity of the battery. Applying a current of 1C would completely charge a battery in 1 hour. Typically a NiMH battery is charged at a maximum of 0.3C, however many manufacturers will specify a much lower current than this. What is known as a forming charge - a very low charge designed to fully charge a brand new battery. Duracell on their packaging only specify this forming charge.

And the Duracells?

They are well presented, and look to be well constructed. In short they have a quality feel. Instructions on use are more than adequate. Note that they only specify the forming charge, and not the higher charging rates typical of most battery chargers.

The batteries are marked as being 2650 mAh batteries. What you need to bear in mind is that this is the maximum possible under ideal conditions. I have a charger that is able to deliver a forming charge - it's a long and slow process. My Duracells achieved around 2580 after a forming charge. A tad shy of the advertised capacity.

They have been in use now for nearly 12 months, have been recharged on a weekly basis and are essentially trouble free. 2 weeks ago I tested the batteries and capacity had fallen to 2450 mAh, which I feel is pretty good for powering a high power drain device. Note that they have been recharged overnight at 0.1C; battery performance may degrade faster using a higher charging current.

The only slight caveat is that constantly taking the batteries in and out has started to damage the plastic cover exposing the metal battery casing below, which could increase the risk of a short. Other than that they have performed well.

So they might be tad more expensive than other brands, but they achieve a capacity close to that advertised, and perform very reliably.  

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