SAFT_Stm5-100mre.ChargeMode (1).pdf

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S A F T
ADVANCED AND INDUSTRIAL BATTERIES
DESCRIPTION OF CHARGE MODE FOR LOW MAINTENANCE STM MODULES
STM 5-100 MRE
1)
1.1)
GENERAL FEATURES
Introduction
Due to the characteristic of low maintenance modules (designed for topping up only
during regular maintenance of the vehicle), their electrochemical behaviour does not
allow the detection of a voltage threshold at the end of the first phase of charging at
constant current or power, especially for temperatures above 30°C.
In addition, although more pronounced than for flooded STM modules, the
temperature variation at end of the first phase of charging at constant current or
power is not high enough to optimise charge management.
With this in mind, a charge mode that integrates a temperature-compensated voltage
switch threshold, a specific Ah meter (pilot meter) and a module temperature
measurement, has therefore been developed.
1.2)
Description of different types of charge
Five different types of charge are used:
Initialisation charge
This is carried out during battery commissioning by the garage technician using an
external command non accessible to the users.
Normal charge
This allows users to charge their batteries at home.
Equalisation charge
This is used to balance the battery to reduce capacity and voltage dispersion.
This charge offers a higher recharge coefficient than a normal charge. It is carried
out periodically and automatically according to vehicle specific criteria.
Maintenance charge
This is carried out during maintenance operations. The battery is fully charged and
the electrolyte is topped up. It is carried out by the garage technician using an
external command non accessible to the users.
Fast charge
This is carried out at a fast charge station, allowing a completely discharged battery
to be 75% charged in 30 minutes. This is not a full charging operation.
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ADVANCED AND INDUSTRIAL BATTERIES
Precharge (for normal equalisation and maintenance charge types)
The beginning of a charge on a fully or deep discharged stored battery causes a
voltage increase that may exceed the voltage switch threshold which occurs at the
end of constant current or power phase for the overcharge phase and will therefore
stop the charge prematurely. To avoid this problem, a precharge operates
automatically on low current, time limited criterion before effectively starting the
charging. If necessary, this precharge is carried out before a normal, equalisation or
maintenance charge.
2)
2.1)
Description of method of charging
End of charge criteria
Different charge management methods are deployed:
1)
the detection of a temperature-compensated voltage threshold in the form of
a bilinear function.
a charged and discharged amperehour meter which takes into account the
battery self discharge (pilot meter) and simulates voltage threshold detection
to allow charge management at any temperature.
2)
The criteria apply to the different types of charge used.
A specific amperehour meter is also used in which the overcharged capacity is
cumulated to determine when the electrolyte in the modules needs to be topped up.
This amperehour meter must be reset to zero when all the modules of the battery are
topped up.
2.2)
Operating the pilot meter
•
•
•
•
•
The meter is reset to zero for a charged module.
When the battery is inactive, the pilot meter increments the self discharge
capacity (calculated from a parametric model).
During discharge, the pilot meter increments the measured discharged capacity.
During charge, the pilot meter decrements the measured capacity charged. The
meter does not count down below zero.
The meter is set to zero at the end of a constant current or power charge when
one of the end of charge criteria (voltage threshold or pilot meter value) is
reached.
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S A F T
ADVANCED AND INDUSTRIAL BATTERIES
2.3)
Temperature Management during charge
2.3.1) Normal, maintenance and equalisation charges
The charge must only be used for the cases given in the following graphs.
N.B. The state of charge is given by the gauge.
Temperature
T2
Charge unadvisable
T1
Charge authorized
State of charge
EC1
100 %
The authorised T1 temperature value of +40°C must not be considered as a value to
start the charge systematically. Actual module temperature around +30°C is strongly
recommended in order to guarantee the life time and the performance of the battery.
2.3.2) Fast charge
The charge must only be utilised in the cases given in the following graph:
Temperature
T4
Charge unadvisable
T3
Charge authorized
TB
Charge unadvisable
State of charge
EC2
75 %
If the temperature exceeds these limits during charging, the charge must be
interrupted and restarted only when the temperature has dropped to the authorised
fast charge temperature.
2.4)
Detailed description of different types of charge
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S A F T
ADVANCED AND INDUSTRIAL BATTERIES
2.4.1) Precharge
For a fully discharged battery that has been stored for some time, the beginning of
the charge causes a voltage increase that may exceed the voltage switch threshold
of the constant current or power phase to the overcharge phase and hence stop the
charge prematurely without restoring the full capacity of the battery . The precharge
is automatically triggered at a low current and limited time before charging to avoid
this problem.
Before carrying out a normal, equalisation or maintenance charge, the battery
voltage should be checked. If it is lower than the UP threshold, carry out a precharge
at I2 during DP, then begin the desired charging.
If the voltage remains lower than UP after precharge a battery defect indication must
be displayed.
2.4.2) Initialisation charge
This charge is carried out to initialize the pilot meter and the battery when the vehicle
is commissioned. After this charge, the pilot meter must be reset to zero and the
electrolyte in the battery should be topped up.
This is a constant current charge.
2.4.2.1) Constant current Phase (I)
This is a I2 charge of duration DI with:
maximum initial module temperature T5
maximum module temperature during charging is T6.
2.4.2.2) Electrolyte topping-up phase
This second phase allows the topping up of modules to be optimised. It comprises
current pulses of I2 (lasting DM minutes every DR minutes applicable for a maximum
of 72 hours). The pulse charging can be stopped at any time, at least 30 minutes
after the overcharge phase is ended, to carry out topping up in a 30 minute period.
After the topping up the pulse charging is not restarted.
Status of meters at end of charge
At the end of this phase, the pilot meter is reset to zero.
The amperehour meter dedicated to cumulate overcharged capacity is reset to zero
after the electrolyte has been topped up.
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S A F T
ADVANCED AND INDUSTRIAL BATTERIES
2.4.3) Normal and equalisation charge
The charge profile is (I or P) - I1.
2.4.3.1) Constant current (I) or Constant power phase (P)
Detection of end of phase
•
using a temperature compensated threshold voltage
threshold Ue = f(T, L1, L2) as a bilinear function
for T > TR: Ue = Uo + L1 * (T-TR)
where T is the actual module temperature
for T < TR: Ue = Uo + L2 * (T-TR)
or
•
using the pilot meter value (VP1)
the first of the two conditions reached ends phase I or P.
Pilot meter status at end of Phase I or P
The pilot meter is reset to zero at the end of Phase I or P.
Safety
maximum time (t1)
If this criterion is met, the charge is stopped, the pilot meter is reset to zero and the
maintenance meter increments by one set overcharged capacity (VS1)
In this case, a «defective system» indication must be displayed.
2.4.3.2) Constant Current overcharge phase (Phase I1)
2.4.3.2.1) Normal charge
This is a I1 constant current overcharge phase. Its duration is a function of the
constant current or power phase charged capacity and must respect the value of the
K1 overcharge coefficient:
Phase I1 charged capacity
K1 =
Phase I or P charged capacity
Status of meters at end of charge:
During this phase, the pilot meter is reset to zero.
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