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Test requirements for 42 volt battery systems

Test requirements for 42 volt battery systems. Mike Weighall MJW Associates. 12 volt SLI BATTERY. Main requirements: Engine Cranking Support electrical systems when engine is not running Key performance parameter: Cold cranking current at -18°C

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Test requirements for 42 volt battery systems

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  1. Test requirements for 42 volt battery systems Mike Weighall MJW Associates

  2. 12 volt SLI BATTERY • Main requirements: • Engine Cranking • Support electrical systems when engine is not running • Key performance parameter: • Cold cranking current at -18°C • Starter motor only needs to turn for a few seconds

  3. 42 volt PowerNet • Changes in automotive vehicle design and electrical systems: • Combined Starter/ Alternator (CSA) • Integrated Starter/ Generator (ISG) • Electric Power Steering • Electric Brakes • Brake-by-wire • Steer-by-wire

  4. 42 volt PowerNet • New battery peformance requirements include: • Idle stop operation requiring high peak power • Regenerative braking • Boost/ launch assist • PSOC cycling

  5. 42 volt PowerNet: Cold Cranking Requirement • Potential benefit: • Higher voltage resulting in lower cold cranking current • For example, a cold crank current requirement of 500 amps for a 12 volt battery could be reduced to about 167 amps for a 36 volt battery • Therefore significant reduction in cable sizes. (The heating effect in the current carrying cables is proportional to the square of the current).

  6. Integrated Starter Generator • The integrated starter generator is a recent development • ISG with idle stop requires significantly higher power than CSA • In the example on the previous slide, CCA of 500 amps may still be needed for the 36 volt battery on a vehicle with ISG and idle stop • This will have an important impact on the battery design and battery sizing for the ISG application

  7. Typical Performance Parameters • Maximum kW output • Average and Peak Power (W) • Power Performance W/kg & Wh/kg • Power output over wide SOC range • Power output over wide temperature range (ideally + 50°C to –20°C or –30°C) • Charge acceptance • Cycle life for shallow and deep discharges • Cycle life in PSOC operation • Calendar life

  8. Implications of idle-stop operation • ISG allows stop-go movement in city traffic and assists engine in normal running (boost/launch assist) • Enables regenerative energy to be returned to the battery during vehicle braking • Battery experiences shallow discharge cycles in partial state of charge (PSOC)

  9. PSOC Operation • What will typical duty cycle be? • Average state of charge? • Average level of discharge around this SOC? • Required number of shallow discharge cycles? • How to size battery if duty cycle is not known?

  10. PSOC Operation • Ford have suggested sizing the battery so that stop/go driving can be handled without exceeding ± 5% SOC. • Stop/start events should be managed by the vehicle system controller so that consecutive loss of SOC does not accumulate to more than 15% of nominal (AABC 2001)

  11. DOD vs. Battery Life NiMH and Lead-Acid chemistries are compared. Life performance of NiMH is substantially better than lead-acid particularly at shallow discharge depths (Ford, AABC 2001)

  12. Power Performance • Power Performance needs to be considered as well as specific energy • Specific Energy of VRLA relatively low compared with NiMH or Li-ion • Power performance of low impedance VRLA designs is very good, and comparable with NiMH and Li-ion • Output power and input power are directly related to battery state of charge

  13. Output and Input Power (Yuasa VRLA battery. From Batteries International, April 2001, p.78)

  14. Peak Pulse Power • This is a key parameter • The requirement is higher for ISG than for CSA • e.g. 600a for ISG compared with 225a for CSA • The current is required for a very short time (e.g. 0.4s) • for start-stop operation the battery may be required to deliver a large number of these high current pulses

  15. Peak Pulse Power • For a “mild hybrid” ISG in which the battery is used to boost acceleration, the high current pulse may be needed for up to 30s • These differences will influence battery sizing for different applications • Difficulty of designing and interpreting a standard shallow cycle test • the duty cycle will be dependent on the application

  16. Influence of Battery Temperature • NiMh has higher specific power at 25°C (1000 cf. 600 W/kg). • Crossover point at 4°C. • VRLA better at -20°C (450W/kg for VRLA compared with 200W/kg for NiMH) • Lead-acid is essential for cold temperature starts in all 42-volt architectures Panasonic Battery Temperature Comparison.

  17. Charge Acceptance • More critical for the 42 volt PowerNet than for conventional 12 volt SLI batteries because of regenerative braking. • Charge acceptance from high inrush currents may be a problem with VRLA, particularly if it is already at high SOC • may also be a problem with NiMH at high temperatures • Battery management system may need to “switch off” regenerative braking when battery is in high SOC.

  18. Standardisation Issues • The first vehicles using the 42 volt Powernet may appear before the International Standards have been finalised • The relevant ISO standard is Technical Programme TC22/SC3/WG14 (Document ISO/WD 21848) • The Working Draft Study has been initiated and the target date is 31st March 2004 • Website addresses: • www.iso.ch • www.sae.org

  19. Possible 36 volt battery requirements • 4 year life • SOC control/ PSOC operation • e.g. SOC range 50-70% or 70-90% • Discharge Power • 6.5kW for 10 sec @ 25°C • 15kW for 0.2 sec @ 25°C • Discharge rate max 15C • Charge rate max 8C

  20. Existing Test Schedules • ECE 15L • Power Assist Profile • ISS (Idling Stop System) (Japan) • US06 Power Profile • PNGV Battery Test Manual • New European Driving Cycle • Etc….

  21. Example Test Profiles

  22. New European Driving Cycle Taken from a presentation by R.Knorr of Siemens at AABC1, Las Vegas,Feb.2001

  23. Battery Design Options • Part of the vehicle electrical system needs to stay at 12 volts (e.g. lighting) • 2-battery system in which one battery is the “power” battery and the other is the “energy” battery • e.g. 36 volt VRLA “power” battery with thin grids or spiral wound design • 12 volt energy battery with cycle capability • Single “Universal” 36 volt battery with DC/DC converter for the 12 volt loads. • Battery will be a compromise between a “power” battery and an “energy” battery.

  24. Battery Design Options (2) • The initial implementation of the 42 volt PowerNet will be with a 2 battery system • Longer term, a single battery system is preferred • lower cost, weight and size • As automotive systems move to ISA(ISG) and regenerative braking the battery used for engine starting will also experience some cycle duty. This tends to negate the argument for a dual battery system.

  25. A Mild Hybrid System The Toyota THS-M mild hybrid system uses a motor generator powered by a 36 volt battery which can act either as a motor or a generator. This enables idle stop operation and initial vehicle acceleration. A separate 12 volt battery is used for engine starting. When accelerating from rest, the 36v battery is used to power the motor generator for vehicle acceleration, while the 12v battery restarts the engine. During cruising, the engine drives the vehicle, and the battery is charged from the motor generator

  26. Toyota THS-M Mild Hybrid • Unusually for a 2-battery system, the 12 volt battery is used for engine starting and the 36 volt battery is used for acceleration. • It is not known which battery deals with the low current loads • This contrasts with the accepted wisdom for a 2-battery system • 36 volt battery used for engine starting and 12 volt battery used for low current loads

  27. 42V - Vehicle Battery Systems

  28. Test Equipment • Because the battery test specifications have not yet been finalised, it is essential that the test equipment is flexible enough to carry out a wide range of different tests. • This can be achieved with test equipment from Digatron/ Firing Circuits, for example the equipment shown in the following slides

  29. 42V - Vehicle Battery Systems • Standard Applications - Cycling - Life Endurance - Recharge - Other tests acc. IEC • Special Applications - Cold Cranking - Starter-Alternator Load Simulation

  30. LCT Test Equipment • Central control through host computer • Control of current, voltage, power and resistance, ramp function • Switching parameters during charge and discharge: • time, voltage, current, Ah, Wh, temp • Functions: • charge, discharge, pause, cycles, cycle in cycle • Up to 3000 program steps • Temperature sensor option

  31. UBT 50-60-6 for Standard Application

  32. Charge/discharge current range 0.05 - 50ACharge voltage range 10 - 60VDischarge voltage range 5 - 60 VAccuracy in the range of 10 - 100 % FS +/- 0.5 % of readings < 10 % FS +/- 0.05 % FSResolution +/- 15 bitData acquisition rate 100msTransition charge/discharge Contactors, 3sec. Technology: Transistors Cooling: Fans Power Supply: 3-phase, 50/60 Hz app. 24 kVA Dimensions (H x W x D): 1950x700x1100 mm Weight: app. 500 kgs Technical Data

  33. BNT 700/250-60 for special Applications

  34. Charge current range: 0.3 - 250 A Charge voltage range: 8 - 60 V Discharge current range: Puls discharge 10 sec: max. 700 A 10 sec - 3 min/Cranking: max. 500 A Discharge voltage range: 45 V - 8 V Contionuous power: 15 kW Data acquisition rate for I and V: 100 msec Transition charge/discharge electronic, < 300ms Technology: Transistors Cooling: Fans Power supply: 3-phase, 50/60 Hz app. 20 kVA Dimensions (H x W x D): 1950x700x110 mm Gewicht: app. 500 kg Technical Data

  35. MBT pulse control for slew rates < 5 ms • Temperature measurement -30°C to +100°C • Datalogger Interface • CAN Interface • Climatic Chamber Interface • Relay Output Board • 6-Channel 700A-Multiplexer to connect to UBT 50-60-6 Options: HEW 700/250 - 60

  36. Complete 42V Battery Test Installation BNT 300A/600A - 60V Thy

  37. Main Control Screen

  38. Main Program Editor

  39. Graphical Display

  40. Thank You!

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