自 1947 年推出 Tama 電動(dòng)車到最近展示的 ZEV BladeGlider 先進(jìn)電動(dòng)跑車概念原型，日產(chǎn) (Nissan) 對(duì)電動(dòng)動(dòng)力系統(tǒng)研發(fā)從未停歇。這家汽車制造商一直在不斷改良電動(dòng)推進(jìn)系統(tǒng)解決方案，而電動(dòng)汽車技術(shù)的研發(fā)仍有很長(zhǎng)一段路要走。
繼 2010 年推出世界上首款現(xiàn)代純電動(dòng)乘用車后，日產(chǎn) (Nissan) 一直將自身定位為零排放汽車(ZEV)技術(shù)領(lǐng)導(dǎo)者。據(jù)了解，第二代聆風(fēng) (Leaf) 將在今年 9 月上市。
目前，日產(chǎn)歐洲公司 (Nissan Europe) 正帶領(lǐng)一個(gè)英國(guó)研究團(tuán)隊(duì)開(kāi)展“高能量密度電池 (HEDB) 項(xiàng)目”(High Energy Density Battery - HEDB)，聯(lián)手研發(fā)下一代高能量密度電池，為電動(dòng)車和混合電動(dòng)車提供高性能的多功能電池系統(tǒng)。目前，日產(chǎn)的電動(dòng)汽車電池組生產(chǎn)仍在英國(guó)的桑德蘭工廠進(jìn)行。
簡(jiǎn)單來(lái)說(shuō)，該研究團(tuán)隊(duì)將通過(guò)多項(xiàng)具體試點(diǎn)項(xiàng)目，實(shí)現(xiàn)電池產(chǎn)品的多樣化和工藝改進(jìn)。作為項(xiàng)目的核心成員之一，Hyperdrive Innovation 公司創(chuàng)始人、常務(wù)執(zhí)行董事 Stephen Irish 最近接受了《國(guó)際汽車工程》的采訪。 Irish 指出，盡管電池化學(xué)領(lǐng)域在最近幾年中已經(jīng)取得了大量進(jìn)展，“但并未出現(xiàn)可以顯著優(yōu)化電池密度的‘神奇’解決方案。”然而，Irish 認(rèn)為，憑借“高能量密度電池”項(xiàng)目取得的電池組級(jí)優(yōu)化成果及 Hyperdrive 公司的電池管理系統(tǒng) (BMS)，電動(dòng)汽車電池的使用壽命和能效均能得到保證，并可以支持“機(jī)會(huì)充電”(opportunity charging)。
電池開(kāi)發(fā)工作的重點(diǎn)在于深刻理解特定車型的占空比，并時(shí)時(shí)權(quán)衡成本。Irish 表示：“如何才能取得最大價(jià)值？車輛或設(shè)備的使用頻率如何？如何進(jìn)行充電？能源又從哪里來(lái)？我們總是不斷問(wèn)自己這些問(wèn)題。”此外，電池的開(kāi)發(fā)也不能忽視車輛重量、電子元件及其工作方式的相互影響。
盡管 Hyperdrive 公司的主要任務(wù)是電池管理系統(tǒng)的開(kāi)發(fā)，但創(chuàng)新的化學(xué)解決方案也是公司需要投入精力的地方。這家公司最近已經(jīng)開(kāi)始進(jìn)行鋰硫電池的相關(guān)研發(fā)。理論上講，鋰硫電池的能量密度可以達(dá)到鋰離子電池的 5 倍。不過(guò)，Irish 透露，鋰硫電池目前仍處于研發(fā)階段，且在真實(shí)世界中也可能無(wú)法達(dá)到理想能量密度。
“我們雖然不是化學(xué)家，但也必須了解電池化學(xué)領(lǐng)域的最新進(jìn)展，并將其充分融入至我們的技術(shù)研發(fā)和產(chǎn)品設(shè)計(jì)中。”Irish 解釋說(shuō)，“與OEM一樣，我們也需要清晰的產(chǎn)品上市路線。”
電池尺寸很重要
Irish 說(shuō)，由于電池市場(chǎng)中存在一些“極端用戶”，要解決的問(wèn)題有時(shí)會(huì)變得更加復(fù)雜。其中一部分極端用戶并不關(guān)心電池壽命，一心只想著最大程度地延長(zhǎng)電池工作時(shí)長(zhǎng)、提高電池儲(chǔ)能容量以及縮短電池充電時(shí)間；而另一部分極端用戶則最看重電池及其相關(guān)電子系統(tǒng)的使用壽命，以及在電池產(chǎn)品的完整生命周期中實(shí)現(xiàn)電池價(jià)值最大化。
Irish 表示，“我個(gè)人傾向于盡量縮小電池體積，只要可以滿足車主的日常通勤需求即可，這可以同時(shí)降低重量和成本。大多數(shù)人開(kāi)車也只是上上班而已，并不會(huì)像自己以為的那樣，會(huì)經(jīng)常進(jìn)行長(zhǎng)距離駕駛。”然而，值得注意的是，最終用戶總是希望獲得更長(zhǎng)的續(xù)航里程，這也是我們需要面對(duì)的市場(chǎng)壁壘以及必須克服的挑戰(zhàn)。”
Irish 指出，在放電率維持在 80% 的情況下，典型電動(dòng)汽車電池的使用壽命通常在 5000 到 6000 次充放之間。但如果放電率達(dá)到 100%，電池的使用壽命則將縮短三分之二。此外，一些二級(jí)再用系統(tǒng)的應(yīng)用，也將有助于電池取得最高能效。
降低電池和電池管理系統(tǒng)的成本是一場(chǎng)持久戰(zhàn)，其中通用化設(shè)計(jì)可以實(shí)現(xiàn)的規(guī)模經(jīng)濟(jì)效益非常顯著。Irish 解釋說(shuō)，“如果我們選擇定制系統(tǒng)，則必須重復(fù)支付一次性工程費(fèi)用（NRE），而考慮到研發(fā)工具和驗(yàn)證測(cè)試需求，這筆開(kāi)支可能非常龐大。”對(duì)比之下，Hyperdrive 公司打造的一系列標(biāo)準(zhǔn)模塊化產(chǎn)品不但可以降低成本，而且還能縮短產(chǎn)品上市時(shí)間。
此外，Hyperdrive 公司還設(shè)計(jì)了一款適用于商用車輛和部分非公路設(shè)備的模塊化電池系統(tǒng)。此外，Hyperdrive 公司還聯(lián)手德事隆(Textron) 旗下 Douglas Equipment 公司，設(shè)計(jì)了一款后推式輕度混合牽引器。
低溫運(yùn)行技術(shù)研究
低溫運(yùn)行是電動(dòng)汽車研發(fā)工作中最值得關(guān)注的領(lǐng)域之一。為了積累相關(guān)經(jīng)驗(yàn)，Hyperdrive 還聯(lián)手英國(guó)南極科考隊(duì)，共同開(kāi)展聯(lián)合項(xiàng)目。一些低電流應(yīng)用主要采用非牽引型電池，該項(xiàng)目的研究目的是盡量了解電池及其相關(guān)系統(tǒng)在接近零下 50°C的極端低溫下的性能。一般來(lái)說(shuō)，內(nèi)燃機(jī)在極端低溫下的性能很差，通常需要通宵預(yù)熱發(fā)動(dòng)機(jī)。
Irish 對(duì)電動(dòng)汽車在低溫（盡管不是極端低溫）下的表現(xiàn)非常有信心。他說(shuō)，“由于電動(dòng)汽車通常需要在夜間充電，因此早上的車艙環(huán)境將會(huì)較為溫暖舒適，擋風(fēng)玻璃也不會(huì)結(jié)霜。”
Irish 表示，Hyperdrive 公司在進(jìn)行電池管理系統(tǒng)研發(fā)時(shí)已經(jīng)考慮了溫度的要求，該系統(tǒng)將通過(guò)主動(dòng)控制電池充放電，盡量避免對(duì)電池的損害。然而，一些應(yīng)用場(chǎng)景仍離不開(kāi)熱管理系統(tǒng)。
Irish 的工作經(jīng)驗(yàn)非常豐富，曾多次參與捷豹路虎 (JaguarLand Rover) 和 NSK轉(zhuǎn)向系統(tǒng) (NSK Steering Systems) 的開(kāi)發(fā)項(xiàng)目。Irish 在 5 年前成立 Hyperdrive公司，目前與日產(chǎn)的合作包括在各類電動(dòng)車中安裝采用日產(chǎn)電池技術(shù)的高性能系統(tǒng)和電池儲(chǔ)能系統(tǒng)。另外，日產(chǎn)歐洲聯(lián)合研究團(tuán)隊(duì)中的其他成員包括：華威制造集團(tuán) (Warwick Manufacturing Group)、華威大學(xué) (University of Warwick)、紐卡斯?fàn)柎髮W(xué) (Newcastle University)、零碳未來(lái)公司 (Zero CarbonFutures) 等。
It’s been a long road for Nissan from its 1947 Tama EV to its advanced prototype ZEV BladeGlider sports car, but that road still stretches to—and far beyond—the technology horizon, as it continues to refine electric propulsion solutions.
The company claims world leadership in ZEV technology following the 2010 introduction of the Leaf EV, the first modern-era battery-electric passenger car. The second generation Leaf will make its premiere in September.
As previously reported in Automotive Engineeering (http://articles.sae.org/14604/), Nissan Europe is leading a U.K. consortium to research and develop future generation batteries via the High Energy Density Battery (HEDB) project. Its aim is to deliver multifunctional battery systems for EVs and HEVs. Nissan manufactures EV battery packs at its Sunderland, U.K. plant.
The consortium will embrace pilot projects, product diversification and process improvement. A key member is Hyperdrive Innovation, whose founder and Commercial Managing Director, Stephen Irish, spoke recently with AE. He noted that while substantial improvements in cell chemistry have been made in recent years, "there is no magic solution regarding enhancing energy density." However, he sees potential for pack-level improvements through the consortium as well as the Battery Management Systems (BMS) developed by Hyperdrive to ensure cell longevity and efficiency while accommodating "opportunity charging.”
Vital to battery development work is understanding the duty cycles of specific vehicle types as well as cost, said Irish: “We ask ourselves where best value will be achieved—how, and how frequently, a vehicle or machine is to be used, how it’s charged, where the energy comes from." Making that energy go further concerns vehicle weight and power electronics and how they work.
While Hyperdrive’s focus is BMS development, novel chemistry solutions need to be considered, too. The company has recently worked with lithium sulfur which, in theory, can deliver specific energy density that is five times that of lithium-ion. However, Li-S is still in development "and in the real world it could be less," Irish said.
"We are not chemists but we do need to know about these developments to spot trends and to be able to develop our technologies and absorb them into our products," he explained. "For us, just as for an OEM, there has to be a clear route to market.”
Battery size matters
Sometimes, that market is complicated by what Irish terms “extreme outliers”—users who care less about a battery’s life and just want to max up-time and extract as much energy as possible from it and also charge it as quickly as possible. The other extreme concerns users who require optimal longevity for the battery and its associated electronic systems, to achieve best possible value over time.
“Personally, I would argue for the smallest battery possible for a daily commuting vehicle, saving weight and cost. Most people do not drive as far in a week or month as they think they do," Irish said. "However, it is still the market barrier of increased range that end-users want. It has to be overcome.”
Typical EV battery life expectancy is 5000 to 6000 cycles at consistent 80% discharge rates, Irish noted. Taking it to 100% discharge cuts its life by two-thirds, he said, adding that secondary re-use applications will help harvest maximum value from the cells.
Getting battery and BMS costs down is a constant battle. Achieving economies of scale is significant; supporting this is designing for commonality. “If we do bespoke systems we have to pass on non-recurring engineering (NRE) costs, which can be substantial in terms of tooling and validation testing," Irish explained. A more standard suite of products, as Hyperdrive has created, allows on-costs to be reduced while enabling faster time-to-market.
Hyperdrive also has designed a modular universal battery suitable for commercial vehicles and some off-highway applications. Together with Douglas Equipment, part of Textron, the company has developed a push-back mild hybrid tractor.
Low-temperature research
A particular area of concern for EVs is low-temperature operation. To gain experience, Hyperdrive carried out a project with the British Antarctic Survey team. Batteries were non-traction types with low current applications. The research aim was to learn as much as possible about battery and associated systems’ performance at temperature extremes of around -50°C. ICEs have problems at very low temperatures and need overnight engine heating.
Irish is confident of EV performance meeting low temperature challenges, albeit not down to extreme levels. “And an electric vehicle charging overnight will be warm in the morning with comfortable cabin and clear windshield.”
Hyperdrive's BMS has been developed to take account of temperature; it actively controls charge and discharge of the battery cells to obviate potential damage but thermal management would be needed in some applications, said Irish.
Following a broad range of engineering experience, including development projects at Jaguar Land Rover and NSK Steering Systems, Irish established Hyperdrive five years ago. Its partnership with Nissan includes installation of high performance systems incorporating Nisan cell technology into various EV and battery energy storage systems. Other consortium members are: Warwick Manufacturing Group, University of Warwick; Newcastle University; and Zero Carbon Futures.
Author: Stuart Birch
Source: SAE Automotive Engineering Magazine
日產(chǎn)公司的電動(dòng)傳動(dòng)系統(tǒng)研發(fā)始于 1947 年的 Tama 電動(dòng)車。（圖片來(lái)源：日產(chǎn)）
日產(chǎn)公司的BladeGlider 電動(dòng)概念跑車預(yù)示著未來(lái)電動(dòng)跑車的發(fā)展形態(tài)。（圖片來(lái)源：日產(chǎn)）
Hyperdrive 公司是 Flux Capacitor 的電池技術(shù)供應(yīng)商。圖中的 1970 款電動(dòng) Enfield 8000 曾在 2016年“四分之一英里沖刺賽”中取得了 9.86秒的好成績(jī)，達(dá)到了破紀(jì)錄電動(dòng)汽車車速 121mph(194.7km/h)。據(jù)了解，這些電池最初是用于貝爾超級(jí)眼鏡蛇 (Bell SuperCobra) 直升機(jī)的起動(dòng)系統(tǒng)。（圖片：Jonny Smith）
Hyperdrive Innovation 公司創(chuàng)始人 Stephen Irish 是“高能量密度電池”(High Energy Density Battery) 項(xiàng)目的核心成員之一，他認(rèn)為汽車電池僅需滿足車主的日常通勤需求即可。（圖片來(lái)源：Hyperdrive Innovation）