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Title
Interfaces for Battery Condition
Monitoring First Meeting Detroit, January 18,
2001
Dr. Hans-Peter Schöner Senior Manager "Actuators
und Mechatronics" DaimlerChrysler AG, Research
Laboratory Frankfurt Peter.Schoener_at_DaimlerChrysle
r.com Tel. [phone], Fax -412
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Future vehicles will need a battery monitoring
system !

• Vehicle systems will depend on electrical
  energyfor control electronics incl. sensors and
  actuators
• Redundant systems are to be designed
• Availability of energy and power must be
  monitored
• Such systems need to work with batteries
  fromdifferent suppliers
• Key parameters must be available from the battery

Coordination is needed !
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Questions of a System Designer
From Nagoya presentation
Presentation at the MIT Consortium Meeting,
Nagoya, October 2000
What does a system designer need to know about
his energy storage?

• Discharge Ability
• How much energy is available in the storage ?
• With what power can I draw this energy from the
  storage ?
• May I still perform a certain (critical) function
  relying on the storage ?
• How long can I still continue drawing a certain
  power ?
• Recharge Ability
• How much energy can I still store into the
  storage ?
• How fast (with what power or current) can I store
  energy into the storage ?
• What will be my energy losses under different
  charging conditions ?

SOC, SOH, and RUC do not give direct answers to
these questions, but they are the first steps !
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Remaining Usable Charge RUC
From Nagoya presentation
Remaining Usable Charge (RUC) of a partially
discharged battery
qD,aged f(I,J, cond.)
where
Ieff is the battery current, which effectively
discharges the battery KN is the nominal capacity
of the battery QD is a table of usable charge
RUC multiplied by nominal capacity indicates the
remaining usable charge in Ah
Remark we need at least current, temperature,
and nominal capacity for determination of RUC
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Open Circuit Voltage
From Nagoya presentation
Linear relation between SOC and open circuit
voltage for SOCgt30 relation depends on battery
design
Open circuit voltage (after a long resting
period) may be used as a measure for SOC, but it
is hard to measure !
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Battery Voltage Model
From Nagoya presentation
Battery voltage components
Not all terms are easy to model, observer
necessary
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Boundary conditions

• Battery will stay a replacement part
• Battery monitoring system will likely be placed
  into a vehicle electronics box (not within the
  battery)
• Battery replacement must be identified
• Key parameters of a new battery must be
  availableto the system before the vehicle starts
  drivingin order to judge energy / power
  availability
• Cost !

Implementation in any battery should be possible
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Key parameters of the battery (which are hard to
measure from outside)

• Nominal capacity
• Design parameters (relative acid content, full
  charge o.c. voltage,internal resistance)
• Proposed charging voltage
• Battery temperature (this is a variable !)
• . . .

Needs to be defined !
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Ways to provide the information ...

• Mechanical coding
• Analog electrical signals
• Digital electrical signals
• Electrical signals transmitted via separate
  contact
• Electrical signals modulated on main contacts
• Wireless transmission
• . . .

Needs to be defined !
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Discussion from 36V battery termination group
Proposal for third pole usage
(may be a feature of only some batteries others
may just connect third pole to minus poleor
ommit the third pole completely)
3. Switch closed, impedance set by R
measure temperature
2. Switch is open, high impedance measure
battery voltage minus zener voltagededuct
nominal capacity from value
1. Third contact closes last, opens first
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Summary

• We will need a battery monitoring interfacesince
  we will need replacement of batteries
• We will need to define the information which we
  want to exchange
• We will need to define the way, how the
  information may be transmitted to the monitoring
  electronics