Rechargeable batteries have been hailed as more environmentally friendly and economical than their disposable equivalents, but do their accolades live up to the test? With the number of gadgets we use rapidly increasing, from smartphones to laptops and cameras to cordless DIY tools, rechargeable batteries are becoming far more common. And with affordable electricity prices in the UK being hard, but not impossible to find, consumers are factoring the cost of charging their gadgets into their energy usage calculations. images (57) Rechargeable batteries produce current in just the same way as disposable batteries. They contain a negative terminal, the anode, and a positive terminal, the cathode. They also contain a solution called the electrolyte. Electricity is produced via a series of reactions between the three components, with electrons produced in the anode and accepted in the cathode. Electricity is produced until reactions stop at either terminal. In a rechargeable battery, these reactions can be reversed. When recharging, the anode becomes the positive terminal and accepts current, and this ability for reversibility allows current to be restored. Rechargeable batteries come in various forms, from small cells to large systems, and use different chemicals, including lithium ion (LiOn), nickel metal hydride (NiMH) and nickel cadmium (NiCd). Alkaline batteries use a reaction between zinc and manganese dioxide. All very well and good, but how do they compare with conventional batteries for use in different appliances? With regards to initial outlay, rechargeable batteries are typically more expensive. However, the fact that they can be used numerous times gives them an obvious selling point. Rechargeable batteries can be easily found in various sizes, including AA, AAA, C and D. They are rated in milliamps hour (mAh), an important point to note as this gives the clearest indication of battery strength or capacity. NiCd batteries, previously widely used, have been gradually phased out due to the unfortunate problem of quickly losing capacity if not fully discharged with each usage. NiMH batteries do not suffer this issue and are widely available in AA and AAA sizes and digital cameras. LiON batteries are smaller and hold a charge better than NiMH equivalents; they are widely utilised in gadgets, but are expensive to produce and not found in standard sizes. Alkaline batteries come in various sizes and are commonly used. On a like for like basis, rechargeable AA alkaline batteries were found to show savings after just five uses (FrequencyCast). This was based on using 25 packs of standard AA 1.5V alkaline batteries at 2200 mAh, costing £87.50 in total, compared with four rechargeable AA 1.2V alkaline batteries at 1800 mAh, costing £15 including the charger. The cost per recharge was just £0.002, making the total cost of five charges £15.01 and 10 charges £15.02. Compared with standard batteries costing £17.50 for five packs of new batteries and £35.50 for ten packs, rechargeables seem to be a clear winner on economical grounds. The cost of recharging phones also appears to be negligible. FrequencyCast estimated the cost of charging a Nokia 6033 at £3.80 a year and an iPhone 3G at £1.90 a year. Meanwhile, the Inquirer reported that charging an Apple iPad costs just £0.87 a year – charging an average laptop came in rather more expensive at £5.32 a year, still a very small amount when spread throughout the year. So it seems that you can go ahead and charge up your gadgets without worrying too much about the effect on your electricity bill.

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Gadget watch: how much electricity are you spending just to recharge batteries?
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