Cool batteries charge best
Accessories manufacturer, Hähnel Industries, has joined the select band of battery brands to offer a rechargeable NiMH AA cell rated to the dizzying heights of 2350mAh. To date, the highest capacity NiMH batteries generally available have been rated at between 2000 and 2300 mAh. But that's not all - bundling a four-pack of batteries with a new fan-cooled charger.
According to Hähnel, rechargeable NiMH batteries should not exceed 50 degrees centigrade when being charged. The problem is that if you need to charged batteries fast, the increased current required will heat the cells significantly. Excessive heat will damage the cells. The higher the capacity is of a battery the longer it takes to charge, which is why fast chargers are now more popular than ever.
Above is a graph that demonstrates the temperatures generated by both a standard fast charger (red) and the Hähnel PowerStation HSC–104 fan-cooled charger over a typical 3 hour charge cycle using 2000mAh cells.
The highest temperature recorded for the conventional charger is 57 degrees centigrade and for the Hähnel PowerStation HSC-104 just 34 degrees. These measurements are based on an ambient temperature of 20ºC. If ambient temperature is increased to 30 degress, during summer time, for example, the maximum temperature will increase by the same amount, resulting in 67 degrees for the conventional charger but just 44 degrees, comfortably under the critical 50 degree level, for the Hähnel PowerStation HSC–104.
The idea of a fan-cooled fast charger is not new, but Hähnel is bundling a set of four 2350mAh NiMH batteries with its charger and the total expected selling price is expected to be in the region of £30, which competes well with some ordinary fast chargers without any bundled batteries.