please type e-mail and submit         ok     cancel		:: The Unique Features of the "Squirrel" Design :: :: Comparison with Other Vanadium Batteries :: :: Comparison with Lead-Acid Batteries :: :: Preparation of the Electrolyte :: Comparison with Lead-Acid Batteries Although a variety of different rechargeable electrical batteries exist the only types commercially available in a wide range of sizes are nickel-cadmium and lead-acid batteries. Nickel-cadmium batteries are reliable but expensive, so lead-acid batteries are more common. The lead-acid battery has lead plates immersed in sulfuric acid with a coating of lead oxide on the positive plates. When electricity is drawn from the battery lead sulfate accumulates on both plates causing the coatings to expand. When the battery is recharged the coatings contract. This expansion and contraction causes the coatings to deteriorate after repeated charging and discharging and makes the lifetime of lead-acid batteries short. Vanadium fuel cells have many advantages over lead-acid batteries. A comparison between the two types is given in Table 1. Table 1. Comparison between Deep Cycle Lead-Acid Batteries and Vanadium Fuel Cells Deep Cycle Lead-Acid Batteries Vanadium Fuel Cells     Storage efficiency 70-80% depending     on age.     Storage efficiency 75-98% depending     on the designed power rating.     Storage capacity and power rating are     interrelated by chemical storage in the     electrodes.     Non-participating electrodes allow     storage capacity and power rating to      be designed independently.     Easily damaged by complete     discharge or overcharging.     No damage from complete discharge,     but overcharging must be prevented.     Damaged by rapid discharging.     Not damaged by rapid discharging.     Recharging must be slow.     Recharging can be at any rate. Instant     recharging is possible by replacing     the electrolytes.     Lifetime reduced by charge/discharge     microcycles as in solar and wind     applications.     Not affected by charge/discharge     microcycles.     Requires regular maintenance.     Very low maintenance expected.     Normal lifetime rarely exceeds five     years.     Lifetime expected to significantly     exceed 20 years.     Cost and size of battery per kilowatt is     constant as storage capacity increases.     Cost per kilowatt decreases as storage     capacity increases and size is smaller     than lead-acid battery.     Slow self-discharge occurs by chemical     reactions in the cells.     Separation of the electrolytes prevents     self-discharge, but electrolyte tanks     must be airtight.     Bulky external rectifiers and inverters     are needed for AC input and output.     AC input and output are possible with     compact built-in Cellennium circuitry.     Discarding of old batteries is a potential     environmental hazard.     Limited environmental impact.     An old mature technology. No more     major advances are possible.     A young technology with potential for a     variety of new major advances.

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