ABSTRACT: In this paper a capacity fade and cycle-life estimation of lithium iron phosphate (LiFePO4) battery based on a two year measured field data is reported. The testing was done to complement the tests made by research institutes in a laboratory by cycling charge/discharge profiles that represent solar home systems scenario. The battery testing laboratory at further training institute (FTI) laboratory ofAdama science & Technology University, Ethiopia is used for testing.Five Pico systems consistingof LiFePO4 (LFP), 18650 type batteries with a nominal capacity of 4200mAh were distributed in a neighboring village. Capacity fade and Cycle-life estimation analysis was done on the data collected over the course of two yearswhere measurements were taken every month. Using the data collected, the capacity fade and the cycle-life of these batteries have been calculated, accordingly the result showed average capacity fade of 8% of the initial measured capacity and average cycle-life of about 6.5Years. These results exceed well above even that of what the manufacturers give as specification, which is in most cases is estimated to be 2000 cycles (5.5 years).The resulting conclusion is that the LiFePO4 battery could be the best alternative to solve one of the prominent pitfalls of solar home systems (SHS),specifically reliability and running cost. Therefore it is recommended to deploy this battery more oftenin new designs. In addition to that the result obtained from this work can be used as an input for further studies in the area of SHS.
In order to achieve hundreds of cycles with minimal capacity loss a cell must cycle at well over 99.9% ef ﬁ ciency. The cell in Fig. 1f has a maximum cycle ef ﬁ ciency of ~99.8%, which continues to decrease as a function of cycle number. There is more going on in the ef ﬁ ciency data than is obvious at ﬁ rst glance. Consider the rise in cathode voltage as a function of cycle number in Fig. 1d. As the end of charge voltage at the cathode rises, more Li will be liberated from the cathode. This will increase cell ef ﬁ ciency (Fig. 1f), as ‘ new ’ Li is being added to the system. Although Li inventory is constantly being consumed due to irreversible processes (e.g. ef ﬁ ciency < 1.00 in Fig. 1f), some of the lost Li is being replenished due to the increased charge voltage at the cathode. This arti ﬁ cially increases cell ef ﬁ ciency. In fact, Fig. 1f shows that ef ﬁ ciency rises during the ﬁ rst ~50 cycles. This rise in ef ﬁ ciency tracks well with the rise in end of charge voltage in Fig. 1d, corresponding to new Li being liberated on each cycle. However, when cathode materials are cycled to high voltages ( > 4.2 V), cycle ef ﬁ ciency will drop; the higher the voltage, the lower the ef ﬁ ciency, the faster the capacity fade.
A pseudo two-dimensional (P2D) electro-chemical lithium-ion battery model is presented in this paper to study the capacity fade under cyclic charge-discharge conditions. The Newman model [1, 2] has been modified to include a continuous solvent reduction reaction responsible for the capacity fade and power fade. The temperature variation inside the cell is accurately predicted using a distributed thermal model coupled with the internal chemical heat generation. The model is further improved by linking the porosity variation with the electrolyte partial molar concentration, thereby proving a stronger coupling between the battery performance and the chemical properties of electrolyte. The solid electrolyte interface (SEI) layer growth is estimated for different cut-off voltages and charging current rates. The results show that the convective heat transfer coefficient as well as the porosity variation influences the SEI layer growth and the battery life significantly. The choice of an electrolyte decides the conductivity and partial molar concentration, which is found to have a strong influence on the capacity fade of the battery. The present battery model integrates all essential electro-chemical processes inside a lithium-ion battery under a strong implicit algorithm, proving a useful tool for computationally fast battery monitoring system.
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In agreement with previous studies, we find that capacity fade reduced by 2.2 % and 2.4 % with the application of 5 psi and 15 psi compressive loads respectively. Unlike previous studies, however, this paper also considered the effect of compressive loads on power fade. The pulse power results show that at every timescale the resistance rise was lowest for atmospheric pressure and highest for 5psi. The average resistance rise (averaged across time scales) was 7.5 %, 39 % and 18 % respectively for 0 psi, 5 psi and 15 psi conditions. This contrast with the capacity fade results. From analysis of the origin of resistance, using EIS, it was found that the pure Ohmic resistance, associated with ion transport resistance of the separator, mainly contributes to this resistance rise. It was also found that, due to a contrasting mechanism, increased pressure with cycling improved the wettability and thus increased the double layer capacitance and reduced ion transfer resistance – which compensates, to some extent, the degradation of double layer due to cycling. This increase of resistance which contrast with capacity fade results, must be carefully considered by engineers in their respected fields of application. This study can contribute to determining the optimal external pressure for a particular cell type and application.
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type of anode can detect easily the dissolution of iron because the passivation layer of graphite anode is ionic conductor and electronically insulator; so the dissolution of iron from the cathode side to the anode increases the electronic conductivity of passivation layer of graphite that results on the capacity fade of the cell. LTO has been used because is passivation layer free and zero strain material. The anode has 0% excess to the cathode that gives the high stability of the cycling and also prevents side reactions or reduction of electrolyte to the potential of LTO (1.5 V vs Li + /Li 0 ).
Ageing stress factors lead to the activation or enhancement of var- ious degradation modes and mechanism [19,21]. The resulting physical e ﬀ ects are typically quanti ﬁ ed by energy storage systems engineers using two metrics: capacity fade that aﬀects the amount of capacity a battery can hold and power fade, which is the increase in the internal resistance or impedance of the cell and limits the power capability of the system and decreases the eﬃciency of the battery. To quantify ca- pacity fade, a retained capacity measurement at a temperature of 25 °C for a constant discharge current of 1 C is undertaken. To estimate re- sistance rise, power pulse tests were employed, where the voltage re- sponse of each cell is measured for a 10 s current pulse at 20%, 40%, 60%, 80% and 100% of the manufacturers recommended maximum continuous charge and discharge current. Pulses are applied to each cell when preconditioned to a SOC of 90%, 50% and 20% respectively, with all tests conducted at an ambient temperature of 25 °C.
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road transport mode to conventional internal combustion engine (ICE) based vehicles due to their high energy ef ﬁ ciency and low tail pipe emissions. Vehicle battery systems are typically equipped with a high number of cells connected electrically in parallel and series to meet the requirements of energy and power. During battery life, the available energy and power that may be extracted from the battery is known to reduce due to degradation. Degradation of lithium-ion batteries (LIBs) is an extremely complex process that depends on a variety of ageing mechanisms caused by different intrinsic and extrinsic factors [1,2]. Intrinsic factors include in- consistencies in manufacturing processes and in the materials used. Intrinsic factors are currently mitigated by improving quality con- trol, manufacturing processes and battery designs. Extrinsic factors include those due to the inhomogeneous operating conditions that a LIB may be subject to, e.g. non-uniform current or temperature distribution within the complete battery pack. In order to reduce battery degradation, the Battery Management System (BMS) miti- gates the impact of extrinsic factors by setting a number of vari- ables that include, but are not constrained to: the level of charge or discharge power, the temperature range that the battery operates over and the allowable depth of discharge (DoD) of the battery. State of Health (SoH) is typically the parameter used by the BMS to quantify battery degradation with respect to its nominal state and it is often quanti ﬁ ed based on two measures: capacity fade (CF) and power fade (PF) . These metrics are directly related to available driving range and power, respectively. However, the de ﬁ nition of SoH within a BMS does not currently include an indication of the underpinning ageing mechanisms causing the degradation.
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FTL-097 is a rigid material having a non-asbestos base. It is grey in color and incorporates a blend of selected friction modifying agents. This complex matrix of ingredients is consolidated with a specially developed binder system. FL- 097 has a high friction coefficient which is combined with an excellent resistance to fade and wear. Its high performance characteristics are particularly suited to severe duty applications. This material although not intended to operate in oil is not physically damaged by moderate oil contamination. Material is certified to non-sparking. It has excellent resistance to fade and wear.
A new and generalized statistical model, called Málaga or simply M distribution, has been derived recently to characterize the irradiance fluctuations of an unbounded optical wavefront propagating through a turbulent medium under all irradiance fluctuation conditions. The aforementioned model extends and unifies in a simple analytical closed-form expression most of the proposed statistical models for free-space optical (FSO) communications widely employed until now in the scientific literature. Based on that M model, we have studied some important features associated to its fade statistics and expressed in terms of the expected number of fades per second. The derived expressions become relevant for many aspects in a FSO system, especially those ones related to determine the optimum threshold in a receiver based on a direct detection scheme employing a fixed detection threshold.
Abstract—The X-band satellite communication (satcom) has been conventionally set aside for military and government organizations. It is also commonly known as the military band. The attributes of an X-band satcom hardware are expected to be designed specifically for military operations and they are expected to differ very much to those of commercial frequencies. The satcom will be likely to be exclusively designed to support smaller, low powered, tactical terminals deployed across various theatres of operation. In addition, X-band link is also anticipated to offer a more substantial increased of system capacity due to its higher frequencies compared to the forerunner S-band and C-band. The X-band satcom technology is drawing growing interest from military users including of the Malaysian authorities. However, there are many aspects of X-band that are harder to realize than of those of at lower frequencies. X-band frequencies certainly have higher atmospheric propagation losses, higher RF losses, and certainly much severe signal degradation due to rain. It is would be in the best interest of the satellite designers and engineers alike to accurately appraise the challenges of an X-band satcom link especially in the case of tropical regions where heavy rains are copious whilst the required technological advancements are in pursuit.
Satellite communications developed to a tremendous global success in the field of analog and then digital audio/TV broadcasting by exploiting the inherent wide-area coverage for the distribution of content. It appeared a “natural” con- sequence to extend the satellite services for point-to-point multimedia applications, by taking advantage of the ability of satellite to eﬃciently distribute multimedia information over very large geographical areas and of the existing/potential large available bandwidth in the Ku/Ka band. Particularly in Europe, due to the successful introduction of digital video broadcasting via satellite (DVB-S) , a promising techni- cal fundament has been laid for the development of satel- lite communications into these new market opportunities using the second generation of DVB-S , commonly re- ferred to as DVB-S2, as well as return channel via satellite (DVB-RCS)  standards. Thus, for satellite systems cur- rently under development and being designed to support mainly multimedia services, the application of the DVB-S2, for the high-capacity gateway-to-user (forward) links and of DVB-RCS for the user-to-gateway (return) links, is widely accepted.
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There are several fade mitigation techniques. One obvious solution is to employ two antenna system transmitting the same signal. One antenna is mounted on the top of fuselage, while the second antenna is mounted on the bottom of the fuselage. Whenever the line-of-sight (LOS) propagation from the bottom antenna to the ground station is blocked, link is maintained by the LOS propagation from the top antenna. As the two antennas are transmitting the same signal and these two antennas are separated in space, the two signal received at the ground control station have difference in their phases, which causes constructive as well as destructive interference resulting in undesirable gain pattern.
WMNs are employed for military applications where protected routing of information is the major need. The FADE mechanism utilizes both multidimensional assessment and monitoring techniques to determine the colluding attackers within the network. Apart from only determination of attacker in the routing path, this mechanism also re-sends the packets in a new path removing the attacker from the data forwarding route. This mechanism is very efficient in determining the attacker within the network, thus a secure routing concept may be followed in resolving and
In this work, the values of point refractivity gradient obtained has been used to figure out the geo-climatic factor, K in Ibadan, South western, Nigeria. The results obtained shows monthly and seasonal radio refractivity gradient and geo-climatic factor K and the results affirmed that the geo-climatic factor K is region based. The percentage of time at a given fade depth was exceeded for a single frequency, as it increases rapidly with increasing path length. Based on the effective earth radius and geo- climatic factor obtained, the work proposes a general model power1 multipath fading adapted to a link distance
Anecdotal reports suggest that MEP responses degrade or undergo anesthetic fade during surgery despite un- changed anesthetic levels and other physiologic variables . MEP tends to exhibit gradually rising thresholds dur- ing the hours of surgery. Sedative-hypnotics (e.g., propofol) cause unconsciousness by producing corticocortical inhib- ition, possibly by GABA-mediated inhibitory interneuron activity within the cerebral cortex  with minimal de- pression of spinal alpha motor neurons . Propofol, like halogenated agents, produces a dose-dependent depression of MEP responses [17, 18]. The influence of propofol is also suggested in this study.
This paper presents the cumulative rainfall data collected for 140 years from six different regions of India. The long-term annual rainfall data has been converted to rain intensity data by using Chebil conversion model. The rain intensity proposed by International Telecommunication Union (ITU-R) and converted data are used to predict the rain fade for satellite-to- earth at C, X and Ku-Bands. In this paper rain attenuation calculated theoretically as well as experimentally using ITU-R model for Ku, Ka bands and instrumental for developing a new model.
The study is carried out in Imo state, Nigeria where multipath fading and rain fading are the two major fade mechanisms mostly considered in wireless network design. Furthermore, mutual exclusive relationship exists among multipath fading, and rain fading . As such, in practice, the fade mechanism with higher fade depth is considered as the effective fade mechanism for the communication link. In addition, in locations where only multipath and rain fade mechanisms are considered, for frequencies above 10 GHz, rain fading dominates whereas; the multipath fading dominates at the lower frequencies [29,30,31]. In addition, according to , when multipath fading dominates, the optimal path length can be determined using a close-form solution. However, when rain fading dominates, the resulting mathematical expression leads to a product log function that does not have a closed-form solution. As such, a numerical method or the Lambert W function approach can be used to determine the optimal path length . In this paper, a modified bisection numerical method is used. The study focused on the frequencies above 10 GHz where the rain fading is the dominant fade mechanism for the case study area.
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In satellite communication links, rain attenuation is the dom- inant impairment especially for frequency above 10 GHz par- ticularly in tropical and equatorial regions. Precipitation causes attenuation due to scattering and absorption of the electromagnetic energy and it leads to significant perfor- mance degradation. Consequently, Ku-band broadcasting services are affected by link outage especially during time- critical transmission such as real-time news and sport events. The probable duration of rain fade, the time of day when it is likely to occur, and how frequently it happens are all impor- tant aspects for the design of satellite services .
from binder degradation causing complete delamination along this central track, further suggesting that 6 C-rates for this specific cell cannot be used for accelerated lifetime testing. The impact that temperature and SoC have was also studied. Cells subjected to higher temperatures had a higher resistance and capacity loss. However, the capacity and resistance of these NMC / graphite cells did not increase linearly. At 45 o C the capacity and resistance is the highest but this was followed by low temperatures (10 O C) and then at 25 O C. For resistance, the increase can be associated with typical temperature trends, highest being worst, lowest being best. SoC showed a strong electrical relationship to both capacity and resistance with the highest SoC consistently the worst performer. Post-mortem analysis shows that the chemical composition of the film is continually changing from low to high temperatures and SoC. However, based on the two primary patterns of chemical changes seen an accelerated testing profile could contain a high SoC / low temperature study and a high temperature / high SoC condition to replicate the same chemical nature of the surface film in an accelerated period of time.
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, 115 mAh/g at C/10  and a controversially exceeding capacity of 140 mAh/g by Li et al.  are available in the literature. Recently Martha et al. have reported on the importance of nanosized material and conductive carbon coating to realize much improved specific capacity values , which is quite similar to the reported views of Goodenough et al. . On the other hand, Yamada [6-10] and Molenda et al. [14, 15] have forecasted an alternative approach of preparing the solid solutions of LiMnPO 4 , as a means of addressing the critical issues related to the electrochemical properties of
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