WP 2 Report on Design Guidelines for New Concepts of Eltvs
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WP 2 Report on Design Guidelines for New Concepts of ELTVs Project nº 266222 Co-financed by European Commission D2.4 – REPORT ON DESIGN GUIDELINES FOR NEW CONCEPTS OF ELTVs Project Acronym: OPTIBODY Project Full Title: “Optimized Structural Components and Add-ons to Improve Passive Safety in New Electric Light Trucks and Vans (ELTVs) " Grant Agreement No.: 266222 Responsible: UNIZAR Internal Quality Reviewer: POLITO Version: 3 (2012-11-30) Dissemination level: Public EXECUTIVE SUMMARY: This document is divided into 9 chapters. Chapter 1 is completely introductory. It explains the objectives and scope of the document. It is explained that at the end of the project, a book titled “Recommended Practices in the Design and Manufacture of Electric Light Trucks and Vans (ELTV)” will be generated. This book will collect the most relevant project technical results. Chapter 2 takes into consideration what the standards specify for the different vehicle categories in terms of total weight, nominal power, etc. OPTIBODY focuses on L7e vehicle category (unladen mass not more than 400 kg or 550 kg for vehicles intended for carrying goods, not including the mass of batteries in the case of electric Page 1 of 188 WP 2 Report on Design Guidelines for New Concepts of ELTVs Project nº 266222 Co-financed by European Commission vehicles, and whose maximum net engine power does not exceed 15 kW). Chapter 3 expresses, derived from a benchmarking analysis of ELTVs in the market, the global expected specifications for a new electric light truck: NOMINAL POWER: up to 4 kW for L6e category; up to 15 kW for L7e; no limitation for N1 category. ENERGY CONSUMPTION: the average value for all vehicles included in the database (used for the benchmarking analysis) is around 140 kWh/km. RANGE: the average value for all vehicles included in the database is around 82 km. Some vehicles “declare” 100 km and just a few of the given greater range values. MAXIMUM VELOCITY: standards fix the maximum speed only for L6e category. For them, the maximum velocity is limited to 45 km/h. The average value for all vehicles in the database is around 50 km/h. Some L7e vehicles “declare” 60 km/h, some declare 80 km/h. TOTAL WEIGHT: standards regulate the weight of vehicles in the following way: L6e: unladen mass not more than 350 kg, not including the mass of the batteries in case of electric vehicles. L7e: unladen mass not more than 400 kg or 550 kg for vehicles intended for carrying goods, not including the mass of batteries in the case of electric vehicles. N1: The total vehicle weight must be less than 3.5 tons (including the payload). The average value for all vehicles in the database is around 725 kg. BATTERY CAPACITY: the average value for all vehicles in the database is around 11 kWh. Values go from 9 to 15 kWh. BATTERY WEIGHT: the average value for all vehicles in the database is around 230 kg. Values go from 160 to 380kg. Chapter 4 covers the main issues related to the vehicle battery pack. The design guidelines related to energy storage devices are: SPECIFICATIONS ACCORDING TO STANDARDS: quadricycles (L7e), also referred to as Heavy Quadricycles, are defined by Framework Directive 2002/24/EC as motor vehicles with four wheels "other than those referred to (as light quadricycles), whose unladen mass is not more than 400 kg (category L7e) (550 kg for vehicles intended for carrying goods), not including the mass of batteries in the case of electric vehicles, and whose maximum net engine power does not exceed 15 kW. These vehicles shall be considered to be motor tricycles and shall fulfil the technical requirements applicable to motor tricycles of category L5e unless specified differently in any of the separate Directives". WEIGHT OF THE BATTERY PACK ACCORDING TO VEHICLE CATEGORY: as the Page 2 of 188 WP 2 Report on Design Guidelines for New Concepts of ELTVs Project nº 266222 Co-financed by European Commission total allowed power is only 15 kW, the total vehicle weight (400 Kg or 550 without batteries) should be kept as small as possible to increase vehicle performance, and in consequence, the weight of the battery pack must be optimized. GENERAL REQUIREMENTS FOR TRACTION BATTERIES: the general requirements are, as for all battery applications: low cost, long life (more than 1000 cycles), low self-discharge rates (less than 5% per month) and low maintenance are basic requirements for all applications. But traction batteries have added requirements: generally operate in very harsh operating environments and must withstand wide temperature ranges (-30°C to +65°C) as well as shock, vibration and abuse. Also, low weight is however essential for high capacity automotive EV and HEV batteries used in passenger vehicles. Protection circuits are also essential for batteries using non-lead acid chemistries. BATTERY CHARGING: use of the recently approved European Charging connector. BATTERY PLACEMENT: battery placement is therefore critical. The battery pack is heavy and voluminous. In passenger cars typical, if only possible, solutions are: 1. Under the bonnet/hood. 2. In the tunnel. 3. In the trunk/luggage compartment. (The assumption is made that all the battery assembly is kept in a single pack). POSITIONING IN THE VEHICLE: Batteries in the tunnel: the battery pack is set in the tunnel, where usually is place for the transmission shaft to the rear differential in a rear-wheel traction or 4WD system. Placing the battery in the tunnel offers the following advantages: Dynamics: masses are distributed along the centre axis of the vehicle and in the lowest position; Crash: batteries are in a “safe” place with respect to side crash; Production: batteries are assembled with the drivetrain, no need to package batteries at the end of the assembly process; Economics: there are just a few changes on the chassis. Batteries in the trunk: above the rear axle. The battery pack is set above the rear axle, behind the second row of seats. In the case of a freight transport vehicle it would be behind the cabin. Placing the battery in the trunk offers the following advantages: Dimensions: there are few limitations on the size of the battery pack and its shape; several configurations of the battery pack can be adopted; Crash: batteries are placed in a secure place with respect to side crash; Economics: limited changes in the chassis; the pack is installed at the end of the assembly line in the trunk; drawbacks are the following: Dynamics: suspensions must be reinforced since a higher mass is standing on the rear axle; moreover, the dynamic behaviour of the Page 3 of 188 WP 2 Report on Design Guidelines for New Concepts of ELTVs Project nº 266222 Co-financed by European Commission vehicle will be affected by a different disposition of the masses; Production: batteries are separated from the drivetrain; therefore, they are installed at the end of the assembly line in the trunk, requiring special areas in the plant for such installation and dedicated work-force; STANDARDS AND REGULATIONS REGARDING SAFETY: safety issues of battery electric vehicles are largely dealt with by the international standard ISO 6469. This document is divided in three parts dealing with specific issues: On-board electrical energy storage, i.e. the battery; Functional safety means and protection against failures; Protection of persons against electrical hazards. Chapter 5 focuses on the powertrain, in particular in the traction motors. OPTIBODY contemplates the use of in-wheel motors. This chapter performs a detailed study of the specific performance of electric vehicles (EV) with in-wheel motors, compared to traditional architectures with internal combustion engines (ICE). The chapter concludes that the acceleration capacity is rather different. The impact of the motors mass on the tire vertical dynamics is also analysed. Corrective measures are proposed, based on the damper modification: an increment of about 70 – 80 % of the damping ratio corrects the vertical dynamic behaviour of the wheel. Chapter 6 indicates the vehicle weight reduction as a key design objective. Vehicle weight influence in fuel consumption is studied: not depending on the driving cycle used to calculate fuel consumption, there is a quasi-linear relationship between vehicle weight and fuel consumption. Vehicle weight evolution along the time is presented and the possible means to achieve substantial weight reductions are also described: optimised design and light materials. Chapter 7 deals with ELTVs crashworthiness. Basic technical issues are described. Crash compatibility for ELTVs is analysed in detail. Design guidelines derived from the contents of this chapter are: INTERIOR GEOMETRY: Seating position must offer a good overview of the traffic situation for the driver to enhance active safety. It is got with a rather upright seating position. Also seating position results a little shorter ride- down distances for upper body parts. Given an adequate restraint system, an upright position will reduce forward rotation of upper body parts and then decelerations will be lower, especially on the head. RESTRAINT SYSTEM: It is necessary to provide Page 4 of 188 WP 2 Report on Design Guidelines for New Concepts of ELTVs Project nº 266222 Co-financed by European Commission an additional ride-down space in the vehicle interior. The components ought to deform ideally at a constant load level and the restraint systems must become active as soon as possible. ABSORPTION OF COLLISION ENERGY: Low mass vehicles have small light drive trains. Most of the collision energy, lateral load components included, must be absorbed by front structure. Also it is necessary to avoid the deformation of the cabin and intrusion of components. It is necessary to design a deformable front structure which allows distributing energy absorption to all its structural elements.