However, it uses Cadmium, a toxic, heavy metal. They are also very expensive and replacement cells are not widely available. This can result from charging power cells before they have been completely drained. The bubbles reduce the amount of surface area available needed to produce elecricity. Therefore, make sure that this type of power cell is completely drained before recharging .
Batteries are electro-chemical devices.
The chemistry has a useful life and begins, as all energetic chemical compounds do, to lose potency immediately after the manufacturing process. Make sure that any power cell that you purchase comes with some type of warranty and that you have the right to return the item if it doesn't perform as advertised. This type of charger is somewhat expensive and may not be economical for individual users. I can't find a replacement battery for my system. In many cases, the power cell can be rebuilt.