Vol.7 (2017) No. 4 ISSN: 2088-5334 Lifetime Prediction of Lead-Acid Batteries in Base-Transceiver Station Unggul Wibawa #1 , Bobby Pratama #2 , Rini Nur Hasanah #3 # Electrical Engineering Department, Faculty of Engineering, Brawijaya University, Jl. MT Haryono 167 Malang 65145 Indonesia E-mail: 1 unggul@ub.ac.id; 2 bxpratama@yahoo.com; 3 rini.hasanah@ub.ac.id Abstract— The battery is an essential component in providing continuous electricity supply using renewable energy sources. It can be found in many daily applications, such as in the telecommunication system, radio microwave system, emergency lighting, the backup system of power plants, even in a photovoltaic system. It is often used as the backup source in case of a failure in the main supply system. The duration of how long the battery can still supply energy to loads without being charged is defined as the battery autonomy day. If during its daily utilization the battery often exceeds its autonomy day, it can result in the deterioration of the battery lifetime. It produces the deviation of the battery lifetime specification which has been previously determined by the manufacturer. This paper presents the results of battery lifetime prediction at a base-transceiver station (BTS) of Telkomsel Company in Indonesia. It has two main purposes which are to evaluate the policy of autonomy day and to predict the remaining lifetime of the battery before reaching its time limit. The obtained results show that there have been some alterations from the batteries’ former policy of autonomy day, from 72 hours to 43.03 hours and 43.26 hours for both existing batteries respectively with considered depth-of-discharge (DOD) of 20%. By using a linear data curve fitting, the results of calculation and analysis indicate that the remaining useful lifetime of both batteries were 5.72 years and 5.77 years. Another approach using an exponential data curve fitting resulted in the remaining lifetime of 7.12 years and 7.16 years for both batteries respectively. Keywords— autonomy day; battery lifetime; lead-acid battery. I. INTRODUCTION Electricity is one of the daily necessities which rises exponentially from year to year as a result of the expanding technology and the complex human needs. The sources of electricity are nowadays still dominated by the fossil energy, which is widely known to become the main cause of environmental pollution and global warming. The energy demand has been continuously increasing from time to time, but the energy supply has been decreasing in the last three decades [1]. As many types of research have proven, this problem demands a very serious concern because during the recent hundred years the average global temperature has been rising within the range of 0.74 ± 0.18 0 C [2]. One of the wise solutions to this problem is the use of renewable energy sources. Indonesia is a tropical country which is endowed with various choices of alternative energy resources. There is a great potential to harness energy from the sun radiation. This is a good opportunity for many enterprises and companies to turn into the use of more eco-friendly energy supply system, as the Indonesian government has also the commitment and even provides some interesting incentives to support such type of initiatives. Telkomsel is the most important telecommunication company in Indonesia. It possesses many base-transceiver stations (BTS) in various locations to support their operation services around the country. In a telecommunication system, a BTS is an equipment to facilitate the wireless communication between the user equipment and the telecommunication network. In general, the BTS is supplied using the power provided by the state electricity company, using a diesel-generator set, and/or using a photovoltaic (PV) system. The main limit of the PV systems is the low conversion efficiency of the PV panels, which is strongly influenced by their operating temperatures [3]. A combination of supply systems is normally adopted to provide a power back-up during a failure of the main supply system. In the case of a PV system, the battery utilization must consider the duration of how long it can still support the loads without being charged, which is defined as its ‘autonomy day’. The autonomy day has also a close connection to the lifetime of a battery. These two variables must be controlled simultaneously, as a part of the energy management system [4]. 1361