PHOTON International The Photovoltaic Magazine

Nickel-cadmium batteries from Saft requiring lower maintenance

In July, the French company Saft S.A. announced the launch of a new generation of its Sunica rechargeable nickel-cadmium (Ni-Cd) battery.

© Saft S.A.

Low maintenance: The new generation of Ni-Cd batteries from Saft requires less upkeep than preceding models.

The Sunica.plus is available in models with capacities from 45 to 1,110 Ah for a discharge over 120 h. It has a float life of 20 years, and at 15 percent depth of discharge reaches about 8,000 cycles.

The main improvement compared to the old Sunica models, which will be taken from the market by the end of the year, is in its strongly increased maintenance intervals. A new construction forces the gases that are set free on the electrodes to recombine to water, thereby strongly reducing the need for water replenishment. At a constant charge voltage of 1.5 V and a temperature of 20 °C, water replenishment is due only after about four years, compared to one and a half years in the earlier devices.

© Saft S.A.

Long life: Ni-Cd batteries achieve much higher lifetimes compared to lead-acid batteries, and thus are especially suited for remote applications.

While Ni-Cd batteries in general are too expensive for most PV applications, they are a good alternative to the cheaper lead-acid accumulators in cases requiring very long operation life in either cyclic or standby use, excellent reliability, or a high energy to weight ratio, and for very extreme temperatures. The Sunica.plus batteries operate between -20 °C and +50 °C, but can tolerate -50 °C to +70 °C without risk of freezing electrolyte. A typical loss of lifetime for Ni-Cd batteries on float duty is 20 percent for every 9 °C rise in temperature above 25 °C. Lead-acid batteries can freeze below about -10 °C, and rarely reach lifetimes above five years.

The housing of the Sunica.plus is 405 mm high and 195 mm wide. Length per block is between 88 and 352 mm, and weight ranges from 3.2 kg per cell for the Sun 45, with 45 Ah at C120, to 46 kg per cell for the Sun 1,100, the largest in this product line. The batteries are sold in 6 or 12 V units. Saft provides a service to collect and dispose the used batteries at the end of their service life. The accumulators are compatible with all current PV charge controllers and are distributed worldwide. Saft failed to provide prices or delivery times.

Saft S.A.
12, rue Sadi Carnot
93170 Bagnolet, France
phone +33/1/4993-1769, fax -1964
ibg.info@saftbatteries.com
www.saftbatteries.com