Advanced materials for next generation NiMH portable, HEV and EVbatteries

While Ovonic NiMH batteries are already in high volume commercial production for portable applications, advances in materials technology have enabled performance improvements in specific energy (100 Wh/kg), specific power (600-1000 W/kg), high temperature operation, charge retention, and voltage stability. Concurrent with technology advances, Ovonic NiMH batteries have established performance and commercial milestones in electric vehicles, hybrid electric vehicles, as well as scooter, motorcycle and bicycle applications. As important as these advances, significant manufacturing cost reductions have also occurred which allow continued growth of NiMH technology. In this paper, advances in performance, applications and cost reduction are discussed with particular emphasis on the improved proprietary metal hydride and nickel hydroxide materials that make such advances possible     

Hubble performance on-orbit

A summary of the Hubble Space Telescope (HST) nickel-hydrogen (NiH/sub 2/) battery performance from launch to the present. Over the life of HST vehicle configuration, charge system degradation and failures, together with thermal design limitations, have had a significant effect on the capacity of HST batteries. Changes made to the charge system configuration to protect against power system failures and to maintain battery thermal stability resulted in undercharging of the batteries. This undercharging resulted in decreased usable battery capacity as well as battery cell voltage/capacity divergence. This cell divergence was made evident during on-orbit battery capacity measurements by a relatively shallow slope of the discharge curve following the discharge knee. Early efforts to improve battery performance have been successful. On-orbit capacity measurement data indicates increases in the usable battery capacity of all six batteries as well as improvements in the battery cell voltage/capacity divergence. Additional measures have been implemented to improve battery performance, however, failures within the HST Power Control Unit (PCU) have prevented verification of battery status.     

Advanced lithium ion battery charger

A lithium ion battery charger has been developed for four and eight cell batteries or multiples thereof. This charger has the advantage over those using commercial lithium ion charging chips in that the individual cells are allowed to be taper charged at their upper charging voltage rather than be cutoff when all cells of the string have reached the upper charging voltage limit. Since 30-60% of the capacity of lithium ion cells may be restored during the taper charge, this charger has a distinct benefit of fully charging lithium ion batteries by restoring all of the available capacity to all of its cells     

Charge equalization for series-connected batteries

A novel nondissipative charge equalization circuit is proposed for charge equalization control of series-connected batteries. Each battery associates with a subcircuit, which is essentially a buck-boost converter acting as a current diverter to redistribute the excessive energy from more affluent batteries to the hungry ones. By dynamically redistributing the charging current, charge equalization can be achieved more quickly and efficiently. The applicability of this approach is confirmed by experiments.     

Selective buck-boost equalizer for series battery packs

To maximize the capacity and reliability of a series connected battery pack, a new selective equalizer developed from the earlier ramp equalizer is proposed. A set of bipolar junction transistors (BJTs) controlled by a microcontroller is used to route equalization current to the lowest voltage batteries. Since only the lowest voltage batteries are connected to the equalizer, the need for uniform transformer leakage inductance is avoided, and a lower power level can be used since no excess current flows to the other batteries. An equalization experiment has shown that a 37 W selective equalizer had a slightly better effect on a 24-battery pack than a 63 W ramp equalizer     

Battery management considerations for multichemistry systems

The performance advantage of Li-ion batteries versus NiCd and NiMH technology has created a worldwide demand for Li-ion cells that is much greater than current manufacturing capacity. This is keeping prices high and supplies scarce-a situation expected to continue for at least several more years. Multichemistry chargers, while challenging to design, keep price-performance points flexible and guard against interruptions in supply. This paper surveys the design issues in implementing chargers that handle NiCd, NiMH, or Li-ion cells interchangeably     

Hubble Space Telescope at twelve years of age

The Hubble Space Telescope was deployed from the Space Shuttle Discovery into a 380-mile high Earth orbit on April 25, 1990. It subsequently made outstanding astronomical discoveries with its 8-foot (2.4-meter) telescope and other scientific instruments. Critical to the successful observations was continuous availability of power from its solar arrays during sunlit periods, and from nickel-hydrogen batteries when the satellite was in the Earth's shadow. The adopted nickel-hydrogen batteries were carefully selected and tested to confirm their depth-of-discharge and operating temperature that delivered the longest life in charge/discharge cycling service. These batteries had a design life of 7 years. At 12 years after launch the Hubble batteries have delivered more charge/discharge cycles than any other batteries in low-Earth orbit. However, the Hubble batteries have been subjected to many unexpected stresses, and peculiar reductions in battery capacity have been observed. Battery replacement requires a costly trip to the Hubble Space Telescope by astronauts, so the remaining useful life of the batteries must be predicted. Already in four servicing missions, astronauts have replaced or modified optics, solar arrays, a power control unit, and various science packages. A fifth servicing mission is scheduled in 2004. This paper discusses battery charging hardware and software controls, history of battery events in Hubble, cell performance model and spare battery tests, and capacity walkdown.     

Electric-vehicle batteries

Electric vehicles that can't reach trolley wires need batteries. In the early 1900's electric cars disappeared when owners found that replacing the car's worn-out lead-acid battery costs more than a new gasoline-powered car. Most of today's electric cars are still propelled by lead-acid batteries. General Motors in their prototype Impact, for example, used starting-lighting-ignition batteries, which deliver lots of power for demonstrations, but have a life of less than 100 deep discharges. Now promising alternative technology has challenged the world-wide lead miners, refiners, and battery makers into forming a consortium that sponsors research into making better lead-acid batteries. Horizon's new bipolar battery delivered 50 watt-hours per kg (Wh/kg), compared with 20 for ordinary transport-vehicle batteries. The alternatives are delivering from 80 Wh/kg (nickel-metal hydride) up to 200 Wh/kg (zinc-bromine). A Fiat Panda traveled 260 km on a single charge of its zinc-bromine battery. A German 3.5-ton postal truck traveled 300 km with a single charge in its 650-kg (146 Wh/kg) zinc-air battery. Its top speed was 110 km per hour     

Considerations regarding the comparison of traction batteries

S.E.A. has been developing, since 1983, the zinc-flow-battery to be ready for mass production. In 1993 the Boston based Power Cell Corporation (PCC) acquired S.E.A. and the new company intends to erect a facility to produce 150.000 kWh at the end of 1994. Since 1985 zinc-flow-batteries are used to power electric-vehicles in capacities between 5 kWh and 45 kWh at voltages between 48 V and 216 V. A 22.5 kWh/96 V battery assembled in a Fiat-Panda is shown, which achieves 260 km per charge at 50 km/h constant. This Panda participated in several rallies. A purpose designed 15 kWh/144 V battery for the Hotzenblitz-EV is also shown, which demonstrates the design-flexibility of the battery. The battery is mounted from underneath the car body between the four wheels and does not consume valuable space in the front or rear of the car. This position is a significant contribution to the safety of passengers. Mass production for this EV is foreseen in 1995. About 50,000 kms of testing experience partially in direct comparison with originally assembled lead acid batteries showed results with zinc-flow-battery equipped EVs, which were significant better than was expected. Referring to about the same battery weight a two- to threefold range was experienced with the zinc-flow-system independent of the driving cycle and independent of the battery capacity compared     

The Analysis of Voltage-Limited Battery Charging Systems

This paper discusses the techniques and problem areas associated with the charging of sealed secondary batteries for spacecraft, and the operating characteristics of the modified voltage-limited charging system. An approach is described for the characterization of battery parameters. The method of selection of a suitable voltage-temperature limit, with regard to battery parameters and system performance requirements, is described. A 4 ampere-hour battery system is analyzed, and its capability is defined parametrically.     

Battery configurations for multi-megawatt pulse power

The capability of lead-acid batteries for supplying very high power for a short time is explored. The application of such a battery for accelerating a hypersonic plane is used to illustrate the requirements. A technique for analyzing batteries and controlling voltage for pulse loads is described. Evaluation of lead-acid batteries in production and voltage regulation by switching batteries in and out are covered. Alternatives to batteries, including superconducting magnetic energy storage, are discussed     

航空电瓶内阻测量与剩余容量探讨

论述了电瓶内阻的基本测量方法。利用３５５０电瓶内阻测试仪对典型的航空电瓶进行实际测量，结果表明，对于酸性电瓶判断比较正确，而对碱性电瓶判断不正确。     

Fast equalization for large lithium ion batteries

Slight differences between the series connected cells in a lithium ion (Lilon) battery pack can produce imbalances in the cell voltages, and this greatly reduces the charge capacity. These batteries cannot be trickle-charged like a lead acid battery since this would slightly overcharge some cells and may cause these cells to ignite. Therefore, an electronic equalizer (EQU) should be used to balance the cell voltages individually. The targeted EQU described herein can be connected to any cell via a set of sealed relays to provide much faster equalization and higher efficiency than previous methods.     

Charge measurement circuit for electric vehicle batteries

Calculating the state of charge (SOC) of an electric vehicle (EV) battery is an inherently error prone process that depends on several variables. However, the accuracy of the required charge flow measurements can be greatly improved by using a voltage to frequency (V/F) converter in conjunction with a digital counter to integrate the measured battery current.     

Rotorcraft flight endurance estimation based on a new battery discharge model

To avoid the numerical complexities of the battery discharge law of electric-powered rotorcrafts,this study uses the Kriging method to model the discharge characteristics of Li-Po batteries under standard conditions.A linear current compensation term and an ambient temperature compensation term based on radial basis functions are then applied to the trained Kriging model,leading to the complete discharged capacity-terminal voltage model.Using an orthogonal experimental design and a sequential method,the coefficients of the current and ambient temperature compensation terms are determined through robust optimization.An endurance calculation model for electric-powered rotorcrafts is then established,based on the battery discharge model,through numerical integration.Laboratory tests show that the maximum relative error of the proposed discharged capacity-terminal voltage model at detection points is 0.0086,and that of the rotorcraft endurance calculation model is 0.0195,thus verifying their accuracy.A flight test further demonstrates the applicability of the proposed endurance model to general electric-powered rotorcrafts.     

Life cycle testing of a sealed 24-V, 42-Ah nickel-cadmium aircraftbattery

Extensive research has been conducted in the design and manufacture of very long life sealed maintenance free nickel-cadmium aircraft batteries. This study presents data on a 100% depth of discharge (DOD) life test performed on a nominal capacity 42-Ah battery. The purpose of this study is to validate design concepts, determine the life characteristics of the newly designed sealed Ni-Cd batteries, and develop baseline information on failure rates and mechanisms. The data from this experiment can be used to compare depth of discharge versus battery life with similar tests such as the lower DOD experiments performed on spacecraft batteries. This information is important in the ongoing development of long life batteries and in developing failure models for life prediction     

Jump starting 42V PowerNet vehicles

The introduction of a 36V battery along side of the 12V battery will enhance starting reliability, but it also creates new risks and, therefore, a strategy for jump start is needed. This paper discusses the issues that must be addressed with respect to charging and jump starting the batteries in the 42V/14V dual voltage systems     

Field evaluation of Honda's EV PLUS battery packs

The EV PLUS demonstration program provides an opportunity to evaluate battery life while gaining expertise in managing Ni-MH battery technology under real-world conditions. Since individual customers use the vehicles, Honda developed a battery service and evaluation system convenient to customers, yet not burdensome to dealer service. This paper discusses the method of detection of low battery capacity, the technique used to convey this information to users, the bench evaluation system of returned batteries, and explains how the analysis is utilized to enhance the EV PLUS' battery control strategy.     

Safety tests of lithium 9-volt batteries for Navy applications

COTS batteries are relatively inexpensive, readily accessible, and extremely versatile. These attributes allow the military to save time and money during the research and development stages. Of these COTS batteries, a 9-Volt (9 V) lithium/manganese dioxide battery is the subject of this paper. This 9 V battery has the ability to provide a low magnetic signature, which is very important to the Navy for many applications, Also, it is Underwriters Laboratories (UL) listed at the unit level; however, these UL tests cannot be directly related to the safety of these 9 V batteries when they are combined in various series and parallel configurations. Naval Surface Warfare Center (NSWC) Carderock was tasked to rate the safety of several such specialized battery packs. It was found that packs consisting of two 9 V batteries in parallel were relatively safe, experiencing no violent behavior. Battery packs with six 9 Vs in parallel vented and deformed the 9 V batteries, but no smoke or flames were noticed. A battery pack with thirty 9 V batteries, 2 in series with 15 legs, experienced venting, smoke, and flames under certain circumstances, After testing, the six and thirty 9 V packs were required to include the addition of various safety devices     

燃料电池无人机动力系统方案设计与试验

针对燃料电池为主能源的无人机（UAV）动力系统,设计了纯燃料电池动力系统、燃料电池/蓄电池（简称燃蓄）被/主动混合动力系统3种拓扑结构方案。以空冷质子交换膜燃料电池为例,搭建了燃料电池动力系统方案一体化试验平台。考虑阶梯型和阶跃型2种加载形式,试验研究了燃料电池自身的动态特性和启动特性。以阶梯型功率剖面的加载形式,试验研究了纯燃料电池动力系统放电特性;以无人机典型任务剖面作为加载形式,开展燃蓄被/主动混合动力系统对比试验研究。试验结果表明：纯燃料电池动力方案适用于低机动小型无人机,燃蓄被动混合方案可满足小型无人机大机动飞行,燃蓄主动混合方案系统可适应中大型无人机更长航时飞行。