Jump Starting and Charging Batteries with the New 42V

1
Jump Starting and Charging Batteries with the New
42V PowerNet

• Wolf-Dieter Blauensteiner - DaimlerChrysler
• Jarvis Carter - Motorola Semiconductor
• Philippe Desroches - Seimens Automotive
• Alfons Graf - Infineon technologies
• Tom Keim - MIT
• Peter Miller - Motorola AIEG
• Paul Nicastri - Ford Motor Company

2
Jump Start Team

• DaimlerChrysler Motorola AIEG
• Delphi Motorola Semiconductor
• Ford Siemens Automotive
• Infineon Technologies Varta
• JCI Visteon
• MIT

3
Vision Statement

• Develop strategies for safely jump starting
  vehicles when the 42V PowerNet is available.
• Share the results with others in the industry to
  promote a common/compatible approach across all
  42V PowerNet vehicles.

4
Goal

• Strategies should consider
• Customer safety and convenience
• Electrical system protection
• Reliability, size, weight and cost
• Jump starts to/from other PowerNet vehicle.
• Jump starts to/from non-PowerNet vehicles
• Discharged only and defective batteries
• Improper voltage and polarity jump starts

5
Todays Situation

• Nearly all cars have 12V batteries.
• Jump starting is done using jumper cables with
  alligator style clamps connected battery to
  battery.
• All electrical components are designed to protect
  against reversed battery connections.
• Dual battery voltage (24V) jump starts are
  sometimes employed in cold climates.

6
Typical Jumper Cables
7
Present 14V Architecture
14V
GEN
12V
14V LOADS
LOADS
STARTER
12V BATTERY
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The Future Situation

• Vehicles may only have 12V batteries or could
  have both 12V and 36V batteries.
• 42V PowerNet vehicles may have DC/DC converters
  to power 14V loads from the 42V bus and, if the
  converter is bi-directional, power 42V loads from
  the 14V bus (enabling internal jump starts).
• System voltage specifications minimizes voltage
  range.

9
Proposed PowerNet Architecture
10
Forum Bordnetz Proposed Voltage Specification
11
Why Are Jump Starts Needed?

• Batteries can be drained
• Key-off loads
• Extended cranking
• Excessive electrical loads
• Batteries can be defective
• Engines can be difficult to start
• Poor fuel
• Improper maintenance
• Extreme conditions

12
Options Available When Your Car Wont Start

• Replace Battery
• Dealer/Auto Parts Stores Closed
• May need to be towed
• Recharge
• Need 36V battery charger and power source
• May need to be towed
• Jump Start
• Personal and vehicle safety

13
Jump Starting

• Ten alternatives were considered
• Pugh Analysis and FMEA were used to compare the
  functionality of alternatives
• Bi-directional DC/DC converters enable internal
  jump starts
• Operation with a defective battery may need to be
  prevented on future vehicles which rely on
  electronics for safe functionality

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Increasing Starting Reliability in the 42V
PowerNet
Behavior of SLI Batteries
Relative voltage u and internal resistance r of
lead/acid-batteries at constant discharge rates
as a function of state of discharge q and
temperature J from Schleuter "Elektrisches
Verhalten von Akkumulatoren", Diss. RWTH Aachen
1982
Increased internal resistance limits starting
capability
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Increasing Starting Reliability in the 42V
PowerNet
Behavior of SLI batteries
Change of internal resistance of lead acid
batteries with battery age
new
aged
Battery age in years
from Gerber "Lebensdaueruntersuchungen an
Röhrchenplatten-Akkumulatoren für stationären
Betrieb", 1976 Markierung bei 50 der Kapazität
from Schöner "Über die Auswertung des
elektrischen Verhaltens von Bleiakkumulatoren
beim Laden und Entladen", 1988 Verhalten
unterschiedlich alter Zellen
Steep increase of internal resistance is often
the reason for loss of starting capability in
aged batteries
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Increasing Starting Reliability in the 42V
PowerNet
Behavior of SLI batteries
Influence of charge pulses on discharge voltage
level
The voltage level of the battery is elevated
during the discharge of the same amount of charge
introduced shortly before. Reason small crystals
at easily discharged locations, time constant of
concentration-levelling about 0,25...0,5h.
From Schöner "Über die Auswertung des
elektrischen Verhaltens von Bleiakkumulatoren
beim Laden und Entladen", 1988
The internal resistance shortly after a charge
phase is significantly lowered the power
delivery capability increases.
17
Increasing Starting Reliability in the 42V
PowerNet
Current paths at different battery states for
explanation of behavior of the internal
resistance
3) Current paths during recharge of a partially
discharged battery
1) Current paths during discharge of a fully
charged battery
acid
lead
acid
lead
2) Current paths during discharge of a
partially discharged battery
4) Current paths during discharge of a
partially recharged battery
acid
lead
acid
lead
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A Minimal Approach
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A Mechanical Approach
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An Electronic Approach
Start Aid
Post
B
S1
Bidirectional
DC/DC Converter
Smart
Smart
S2
Battery
A
S3
Battery
Terminal
Terminal
42V
14V
Inaccessible
Inaccessible
Generator
Starter
12V
36V
Loads
Loads
Battery
Battery
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Recommendation

• The wide range of alternatives we considered
  provided varying degrees of protection. Each
  manufacturer will make the decision based on
  various criteria, such as safety, reliability,
  size, weight, cost and their customers
  expectations. At a minimum, the system should
  prevent connections between the 12V 36V
  batteries.

22
Summary

• In the initial stages of 42V PowerNet usage, it
  may be desirable to limit start aid to the low
  voltage bus, as few 42V vehicles will be
  available to give aid. As more 42V PowerNet
  vehicles are in use, the need to provide cost
  effective 36V battery jump start capability will
  drive manufacturers to pursue other approaches,
  but they need to be compatible.