Objectives and problems to be solved:
The objective of this project is to develop a small Valve Regulated Lead-acid (VRLA) battery with very high power density (>1500 W/dm3), high specific power (>600 W/kg) and higher reliability for UPS applications. Nowadays UPS manufacturers demand batteries with very high specific power and relatively low specific energy, because most of main failures can be defined as "micro-failures", usually of the order of seconds. Due to this fact, it is not necessary to provide energy but power. The aim of this project is therefore to develop a new battery with weight and volume substantially reduced, as well as a substantial improvement in its reliability. These aspects can provide the achievement of a more efficient, safe and economic energy supply.
Description of work:
Battery specific power is practically related to electrode area, then its increase appears essential to achieve the project objective. Within this project, the use of new materials that are now being developed, and that would allow a substantial electrode thickness reduction, from about 1 mm (present values) to around 0.5 mm, are studied. In this way, very thin lead strips of about 0.35 mm thickness are under testing with a proper grid alloy to decrease electrode corrosion and thus to avoid a reduction of the battery life. Furthermore, it is necessary to achieve a similar reduction in the conventional glass micro-fibre separator, resulting in a total thickness of around 0.4 mm. But such thin material makes the battery more prone to develop short circuits across the separator. In order to avoid this problem, a new micro-porous polyethylene membrane is tested, due to its promising mechanical properties, high porosity and low pore size. For these reasons, the final separator configuration includes a combination of both materials, improved glass micro-fibre non-woven and the polyethylene membrane. Batteries are designed and assembled by S.E. Acumulador Tudor S.A. as battery manufacturer and tested in real conditions by MGE UPS Systems as end user. The separator manufacturers, DARAMIC for the membrane and Bernard Dumas for the glass micro-fibre mat, develop and supply the adequate materials in order to improve its mechanical resistance and conductivity; while the Inorganic Chemistry Department of Córdoba University carries out the fundamental studies on very thin electrodes.
Expected results and exploitation plans: It is expected that the new high power VRLA batteries designed would reach the following minimum performances:
- Specific power > 600 W/kg (20C discharge at 70% SOC)
- Power density > 1500 W/dm3- Life on float: 3-5 years
- Cycle life > 600 cycles at 60% DOD (IEC 896-2)
- Cost < 100 Euro/kWh.
The battery under development is mainly focused to UPS market, in order to be able to use such equipment in portable applications as well as in telecommunication cabinets. The improved performance of this new battery has also application in 42 V automotive systems.
Funding SchemeCSC - Cost-sharing contracts
38334 Saint Ismier