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|Radiosonde battery still in protective wrapper|
|Deformed Nopopo battery 1st generation||Leaking and de-forming NoPoPo battery 1st and 2nd generation|
Typically, a large variety of aqueous solutions can be used in place of plain water. This battery type is specifically designed to be moreenvironmentally friendly due to an absence of heavy metals. Water-activated batteries are used most commonly found in radiosondeswhich cannot contain heavy metals because they regularly fall to the ground or ocean surface and remain there indefinitely.
A carbon-magnesium battery, named NoPoPo, coming in AA size, was released in Japan in 2007. The batteries came with a syringe to inject water or electrolyte, such as juice. However these batteries have failed to make an impact due to their extreme low power output, very short active life-span and high cost. Moreover, due to the chemical reaction involving magnesium, these batteries are known to deform and cause damage to products used with these batteries. A water activated consumer battery called Aquacell is a carbon zinc battery with most heavy metals deleted from the cell. The battery weighs 12 grams and provides 1000 mAh on low drain applications. The overall environmental impact of the Aquacell life cycle is expected to be 4 - 5 x less than a standard alkaline battery.
Kits using copper-magnesium cells activated by water or the liquid sample itself are also in development. Another water-activated battery had been invented by Susume Suzuki of Total System Conductor. Aluminium anodes are used on many water-activated batteries designed for use with salt water such as seawater. The HydroPak uses water-activated disposable fuel cartridges as an alternative to lead acid battery packs and portable generators. It uses water added to sodium borohydride which releases hydrogen fuel for a proton exchange membrane fuel cell. It can be re-charged simply by replacing the fuel cartridge rather than the lengthy recharging that other batteries require, however the cartridges cost $20 each.