Batteries/Lead-acid/Valve Regulated 051108
The quest for the perfect battery continues. The state-of-health in VRLA batteries can be determined by a full discharge, but methods for nondestructive testing of every cell in a battery installation would be ideal both for time efficiency and completeness of investigation. FIAMM, as a manufacturer, has a challenge to initially build a battery with known state-of- health characteristics. The company realized the conditions which lead to variations in measurements and have applied AC resistance methods to guarantee initial quality. Over a three year period, the AC resistance at 1 kHz has been applied. to newly manufactured batteries; the batteries now provide a large scale data base to show the baseline quality. Teardown of the failures which accounted for about 1% showed significant correlation to the measurements and this data will lead to an improvement in the process. Despite the positive outcome, it is stated that AC resistance alone is not an absolute criterion for battery integrity.
Batteries International, January 2005, pp. 56-61
For anyone considering the implementation or management of a battery backup system, this information is critical. Based on the goal of achieving a specific reliability goal, many analysis use only such critical factors as interrupt sense and transfer time but must include battery characteristics. For economic reasons of initial cost and maintenance, 5-10 year VRLA batteries are often chosen over 20 year flooded (vented) Lead-acid batteries. Far from simple, the total effects on the VRLA battery system have dramatic impact on the system reliability. Topics considered are Voltage history, typical Ohmic value, Ohmic history, temperature history (for every 15 0F above 77 0F, battery life is halved), replacement percentage, parallel string interaction, individual battery interaction and discharge data. Reference is made to the new IEEE Battery Monitoring Standard.
Batteries International, January 2005, pp. 70-75
Question – I am making a VRLA battery using an AGM separator; the design change is to increase the battery’s acid specific gravity. I was wondering whether the separator would have an influence?
ANSWER: One of the big issues with a VRLA battery is that the headspace does not contain acid, limiting the supply of sulfate during the discharge, as compared to a flooded battery. In an attempt to overcome this limitation, battery designs for VRLA tend to use a higher specific gravity than what a typical design may use in a flooded battery. Many designs use 1.3 and above for the final acid specific gravity (s.g.). Higher specific gravity does give higher battery capacity but may also result in other battery performance issues such as diminished cycle life. (See additional reading.)
An all glass or hybrid separator will be influenced by the battery acid’s specific gravity, concerning how quickly the separator would wick the acid.There is a much slower wicking rate of a separator as the acid concentration increases. Data suggest that acid specific gravity could impact battery filling performance and/or time, and high rate performance.
1: D. Pavlov, A. Kirchev, M. Stoycheva, B. Monahov, Lead-Acid Batteries Department, Institute of Electrochemistry and Energy Systems (former CLEPS), “Influence of H2S04 concentration on the mechanism of the processes and on the electrochemical activity of the Pb/Pb02/PbS04 electrode,” Journal of Power Sources 137 (2004) 288-308.
2:X Muneret, “Practical Influence of Float and Charge Voltage Adjustment on the Service Life of AGM VRLA Batteries Depending on the Conditions of Use,” 2004 Intellec, 0-7803-8458-X/04/$20.00, C2004 IEEE
(April 2004) EaglePicher enters commercial marketplace in India. EaglePicher is working with SAR Silicon Pvt. Ltd. in New Delhi to market batteries under the Luminous EaglePicher brand. These batteries include automotive batteries as well as VRLA (Valve Regulated Lead Acid) batteries for use in Uninterruptible Power Sources (UPS.) The companies intend to add batteries for back-up power and inverters in the near future.