A lecture about batteries for Electric vehicles.pdf

A lecture about batteries for EVs

1. ELEC 439/6471
Electric/Hybrid Electric Vehicle
Power System Design and Control
Winter 2011
Prof. Sheldon S. Williamson
Department of Electrical and Computer Engineering
1455 de Maisonneuve West, S-EV5.243
Montreal, Quebec H3G 1M8
Tel: [phone], ext. 8741
Fax: [phone]
EML:
[email protected]

2. Electric/Hybrid Electric Vehicle
Battery Performance Characteristics

3. EV/HEV Battery Characteristics

4. Comparison of Energy Sources

5. Battery Basics

6. Battery Cell Components

7. electrolyte anode + cathode -
charger
current
During Charge
voltage and energy increases
energy
heat
heat
chemical
reaction

8. electrolyte anode + cathode -
load
current
During Discharge
voltage and energy decreases
work
heat
heat
chemical
reaction

10. Battery Types

11. Batteries: In Depth

12. Lead-Acid Battery

15. Battery Parameters

18. Technical Characteristics

25. U.S. Advanced Battery Consortium

26. Standard Driving Cycles

27. EV Battery Requirements: High Power
Power = Watts = Volts x Amps
Typically rated in terms of “C” – the current ratio between max current and current to drain battery
in 1 hour; example 3C for a 100 Ah cell is 300A.
Battery voltage changes with current level and dire ction, and state of charge.
1 Horsepower = 746 Watts.
Charger efficiency = ~90%.
Battery charge and discharge efficiency = ~95%.
Drive system efficiency = ~85% AC, 75% DC.
batteries
motor
controller
motor
heat
heat
heat shaft
charger
heat
100% in60% - 68% out 32% - 40% lost to heat

28. EV Battery Requirements: High Power
Example
Accelerating or driving up a steep hill
Motor Shaft Power = ~50 HP or ~37,000 W
Battery Power = ~50,000 W DC, ~44,000 W AC
Battery Current
~400A for 144V nominal pack with DC drive
~170A for 288V nominal pack with AC drive
Driving steady state on flat ground
Motor Shaft Power = ~20 HP or ~15,000 W
Battery Power = ~20,000 W DC, ~18,000 AC
Battery Current
~150A for 144V nominal pack with DC drive
~70A for 288V nominal pack with AC drive
Charging
Depends on battery type, charger power and AC outle t rating
Example: for 3,300 W, 160V, 20A DC for 3,800 W, 240 V, 16A AC

29. EV Battery Requirements: High Capacity
Higher capacity = higher driving range between char ges.
Energy = Watts x Hours = Volts x Amp-Hours.
Watt-hours can be somewhat reduced with higher disc harge current due to internal
resistance heating loss.
Amp-Hours can be significantly reduced with higher discharge current seen in EVs due to
PeukertEffect.
Amp-Hours can be significantly reduced in cold weat her without heaters and insulation.
Example:
48 3.2V 100 Amp-Hour cells with negligible PeukertEffect and 95% efficiencies.
Pack capacity = 48 * 3.2 Volts * 100 Amp-Hours * 0. 95 efficiency = 14,592 Wh.
340 Watt–Hours per mile vehicle consumption rate.
Vehicle range = 14,592 Wh / 340 Wh/mile = 42 miles.

30. EV Battery Requirements: Small and Light
Cars only have so much safe payload for handling an d reliability.
Cars only have so much space to put batteries, and they can’t go anywhere for safety
reasons.
Specific Power = power to weight ratio = Watts/kg.
Specific Energy = energy capacity to weight ratio = Watt-Hours/kg.
Power Density = power to volume ratio = Watts / lit er.
Energy Density = energy to capacity to volume ratio = Watt-Hours /liter.
1 liter = 1 million cubic millimeters.
Example:
1 module with 3,840 W peak power, 1,208 Wh actual en ergy, 15.8 kg, 260 x 173 x
225mm = 10.1 liters.
Specific Power = 3,840 W / 15.8 kg = 243 W/kg.
Specific Energy = 1,208 Wh / 15.8 kg = 76 Wh/kg.
Power Density = 3,840 W / 10.1 l = 380 W/liter.
Energy Density = 1,208 Wh / 10.1 l = 119 Wh/liter.

31. EV Battery Requirements
Large Format
Minimize the need for too many interconnects; example 100 Ah (6.2kWh or
500g of lithium).
Long Life
Minimize the need for battery replacement effort and cost .
Example: 2000 cycles at 100% Depth-of-Discharge to reach 80% capacity
charging at C/2; 5 years to 80% capacity on 13.8V float at 73C.
Low Overall Cost
Minimize the purchase and replacement cost of the batteri es.
Example: $10K pack replacement cost every 5 years driven 40 miles per day
down to 80% DOD = 1825 days, 73,000 miles, 14 cents per mile.

32. Higher Temperature Reduces Shelf Life
13 degrees reduces the life of lead acid batteries by half.

33. Comparison Between Existing Technologies
Type Power Energy Stability
Max
tempLife Toxicity Cost
LiFePO4 + + + ~ ~ + -
LiCO2 + + - - - + -
NiZn ~ ~ ~ ~ - + ~
NiCd - ~ ~ ~ + - +
PbA AGM + - + ~ - - +
PbA gel ~ - + ~ - - +
PbA flooded ~ - - ~ - - +

34. Peukert Effect
Dynasty AGM MPS Series 75 Ah
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 50 100 150 200 250
Constant Discharge Rate, Amps
Amp hours to 80% DOD (1.75 VPC, 10VP6C)
Lead Acid Battery “Peukert” Effect Reduces Range at EV Discharge Rates
A “75 Amp Hour” battery that provides 75 amp hours at the 20 hour C/20 rate or 3.75 amps only provides
42 amp-hours at 75 amps, a typical average EV disch arge rate, or 57% of the “nameplate” rating. Nicke l
and lithium batteries have far less Peukerteffect.

35. Lead Acid AGM Batteries are Better for High Current Discharge Rates
Gels have higher internal resistance.
Higher discharge rates are typical in heavier vehic les driven harder in higher gears with smaller pack s and
less efficient, higher current, lower voltage DC dr ive systems.

36. Lead Acid Batteries Need Heaters in Cold Climates
They lose 60% of their capacity at 0 degrees Fahren heit.

37. Gels Have a Longer Cycle Life
AGMs only last half as long, but as previously ment ioned can withstand higher discharge rates.

38. High Power, High Capacity Deep Cycle Large Format Batterie s Used in EVs:
LiFePO4 Hi Power
Thunder Sky LMP
Valence Technologies U-Charge XP, Epoch
PbA AGMBB Battery EVP
Concorde Lifeline
East Penn Deka Intimidator
EnerSys Hawker Genesis, Odyssey
Exide Orbital Extreme Cycle Duty
Optima Yellow Top, Blue Top
Gel East Penn Deka Dominator
Flooded Trojan Golf & Utility Vehicle
US Battery BB Series
NiCd Flooded Saft STM
NiZn SBS Evercel
Li Poly Kokam SLPB
Note: LiFePO4 are recommended, having the lowest we ight but highest initial purchase price. But they have
similar overall cost, and the rest have safety, tox icity or power issues.

39. Optima Blue Top AGM Sealed Lead Acid Batteries with PCHC-12V-
2 Amps.
Practical EV Battery Packs

40. Practical EV Battery Packs
Valence Module

41. Valence BMU
Practical EV Battery Packs

42. Valence batteries and BMU connected via RS485
Practical EV Battery Packs

43. Valence battery monitoring via CANBus and USB to la ptop
Practical EV Battery Packs

44. AC Propulsion tZero: drove 302 miles on a single charge at 60 MPH in 2003, Lithium Ion batteries
Solectria Sunrise: drove 375 miles on a single charge in 1996, NiMH batteries
EV Record Holders

45. EV Record Holders
Phoenix Motorcars SUT: charged 50 times in 10 minutes with no degradation in 2007; 130 mile range
DIT Nuna: drove 1877 miles averaging 55.97
MPH on solar power in 2007, LiPo batteries