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1
Future Opportunities for Lead Batteries:
A Manufacturer’s Perspective
Rainer Wagner
Moll Batterien
Bad Staffelstein, Germany
2
Introduction
• Lead batteries have been used for more than 140 years in
numerous applications.
• Over many decades, the performance level has been improved steadily.
• It is an extremely robust and reliable product and it can be used in a wide
temperature range between -30°C and 80°C.
• There is a well established recycling system resulting in close loop of the
raw materials.
• In spite of increasing volume of alternative systems, particularly lithium:
• The lead battery remains world’s most important secondary power source.
3
Introduction
Major applications of Lead Batteries:
Automotive
Starter battery (SLI)
Micro-Hybrid (start-stop, recuperation, …)
Stationary
Stand-by / UPS / Telecom
Utility / Solar Power
Traction
Heavy cycling
Semi / Small cycling
4
Industrial Batteries
For a long time, industrial batteries for stationary and traction applications
were produced only as flooded design.
Later, especially for stationary duty, VRLA types were introduced.
AGM (Absorbent Glass Mat separator)
Gel (gelled electrolyte by using silica acid)
This results in maintenance-free products without any need of topping up with
water over the whole life of the battery.
5
Industrial Batteries
Stationary
Stand-by / UPS / Telecom
often not much cycling except ofunstable power grids regions
Solar Power
cycling, off-grid applications oron-grid duty for own consumptionof solar energy
Utility
cycling for peak shaving,load levelling,frequency regulation
6
Industrial Batteries
Stationary
Such batteries have already achieved a rather high level of performance.
There is, however, still much potential for further improvements.
In future, by using more favourable lead alloys and manufacturing processes,
grid corrosion can be further repressed resulting in even longer service life.
Moreover, by taking advanced cell designs and paste recipes with certain
additives, even higher discharge rates will be possible.
Charge acceptance can also be improved by such measures.
7
Industrial Batteries
Traction
Very robust batteries with positive tubular
or thick flat plate design
Heavy cycling
Various material handling equipment,
fork lifts, heavy duty with 80 % DoD
Small / Semi traction
Cleaning machines, lawn movers, golf caddies,
wheel chairs etc.
Cross section
tubular plate
8
Industrial Batteries
For traction, cycling performance is most important.
Consequently, there have been many projects
with the objective to improve this feature.
The key point is the softening
of positive active material
that finally limits cycle life.
To overcome this problem,
DoD has to be restricted,
sometimes even to 50%.DoD / %
9
Industrial Batteries
In principle, there appears to be no reason why
the softening process cannot be slowed down
even more in future.
Ideally, PbO2 should be deposited exactly at the
place from which it had previously been
dissolved no change in crystalline structure.
Advantageous additives and ingenious paste
recipes have been useful for improvement.
Intensive R&D work is needed to slow down even more the softening process.
Crystalline structure of
positive active material
Schematic of an ideal
dissolution-precipitation
process
10
Lead Batteries for Automobiles
Lead Batteries for Electric Vehicles
1900 USA
38 % Electric Vehicles
1930 Municipal Vehicles, Post,
Delivery Vehicles…100% electric
11
Lead Batteries for Automobiles
More than hundred years ago:
Hand cranking starter motor + battery
In the beginning:
Focus on cranking function
Over the past decades:
steadily increasing number of
electric equipment
Starter- and on board power supply battery
12
Lead Batteries for Automobiles
13
Lead Batteries for Automobiles
There are numerous electric equipment in modern cars and,
when the engine / alternator is not running
The battery is the only electric power source.
More electric equipment means:
More cycling
Battery needed with higher cycling performance
However:
Without reduction in cold cranking power
14
Lead Batteries for Automobiles
Over the past decades, starter batteries have steadily been improved to
higher cycling and cold cranking performance.
In parallel, water loss was reduced significantly.
maintenance-free types.
Change from antimony to calcium for grid alloys.
Intensive work on battery design and manufacturing process to achieve good
cycling performance without antimony.
Implementation of new grid technologies for continuous plate production.
15
Lead Batteries for Automobiles
Book mold gravity cast
ConCast
Expanded metal
Punched
16
Lead Batteries for Automobiles
Changes to more duties of the battery is still going on:
In the distant past: Mainly Cranking
Over last decades: Power supply for steadily more electric equipment
Today / Future: Start Stop / Micro-Hybrid
Such functions are implemented by car manufacturer in order to get to less
fuel consumption and lower CO2 emission in traffic.
17
Micro-Hybrid
Start – Stop automatic
Engine idle when car is stopped, e.g. at red light
or stop and go traffic.
During this phase: Electric power supply only by the battery.
Recuperation
Charge of the battery preferably when car speed is reduced
(unfueled deceleration phase).
18
Micro-Hybrid
Less battery charging during acceleration phase.
Minimizing electric generation during fueled driving.
Fuel savings often between 5 % and even more than 10 % *
*Depending on drive test / car concept / individual driving pattern
19
Micro-Hybrid
Implementation of Start – Stop / Micro – Hybrid function:
The time for implementation is very short because of the
ambitious plans for reduction of CO2 emission.
Additional requirements to the Micro-Hybrid battery, much higher in comparison to SLI, e.g. 3 times higher cycling performance.
For battery manufacturer this means that R&D work for
improvements from fundamental research to series production
must be extremely fast.
20
Micro-Hybrid
A few years ago, there was the generally held believe, that only batteries
of AGM design can fulfill such hard requirements.
Consequently, special AGM batteries were developed and introduced in
the market for cars with start-stop function and recuperation.
21
Micro-Hybrid
Afterwards, however, there have been many efforts to get to
the same high performance level by special flooded design.
EFB (Enhanced Flooded Battery)
After intensive R&D activities it has become possible, to
make flooded batteries of the EFB type that can be used as
an alternative to AGM for Micro-Hybrid applications.
22
Micro-Hybrid
The combination of
negative carbon addition and use of other additives
positive and negative electrode structure / active material optimization
was the base for the successful development of a new battery type
MOLL EFB
fulfilling all requirements of car manufacturers for Micro-Hybrid applications.
23
Micro-Hybrid
Nowadays, steadily more car manufacturer are replacing AGM by EFB
for Micro-Hybrid applications.
Number of EFB for OEM supply is increasing substantially in Europe.
Demand for Micro-Hybrid aftermarket batteries will increase soon.
24
Micro-Hybrid
Comparison Conventional OE – AGM – Advanced EFB
25
Micro-Hybrid
Cycling 50% DoD, conventional OE flooded, EFB and advanced EFB
cycles
dis
ch
arg
e v
olt
ag
e [
V]
requirement OE
conventional
flooded
requirement
VDA EFBrequirement
VDA AGM
Advanced EFB
conventional
OE flooded
battery
EFB first
generation
26
Micro-Hybrid
615 times nominal capacity through puts at 17,5% DoD cycling
27
Micro-Hybrid
17,5% DoD cycling
Impact of positive and negative active material on cycling performance
NAM - A
NAM - B
NAM - C
28
Micro-Hybrid
1) break: 10s 4) IDCH: 300A; tDCH (300A): 1s, UDCH(300A) : >9.5V
2) ICHA: 100A; UCHA: 14.0V; tCHA: 134s 5) break: 12h
3) IDCH: 48A; tDCH (48A): 133s
Steps 1 – 4
100 times
Steps 1 – 5
until UDCH (300A) :
≤ 9.5V
29
Micro-Hybrid
NAM
Lead sulfate
at very outside
NAM
Lead sulfate
plate average
Tear-down of batteries
after end of micro-cycle
test
The failure mode is
sulphation of NAM
PCL 3 Effect
Sulphation at the very
outside is proceeding
continuously with
increasing cycle number
30
Micro-Hybrid
Cycling with substantial DoD change
No recharge problem of the negative plate.
Micro-cycling with 1 - 2 % DoD change
Negative plate recharge problem (sulphation).
AGM: oxygen recombination
Negative depolarization / lower negative overvoltage
EFB:
Negative plate polarized / higher negative overvoltage
31
Micro-Hybrid
Polarization of the positive electrode at different cell voltages. For
flooded it is assumed that overvoltage positive and negative is the same
(a) flooded (b) gel, new (c) AGM, low recombination
(d) gel, after prolonged periods of use (e) AGM, high recombination
32
Micro-Hybrid
MOLL EFB Excellent Micro-Cycling performance due to:
Advanced paste recipes and manufacturing processes
Higher negative polarization
(advantage in comparison to AGM)
Results on DCA testing also indicates higher charge currents with EFB
in comparison to AGM.
The successful development of EFB confirms:
Significant improvements of lead batteries are still possible
and, they are essential because of increasing demands by car manufacturers.
33
Future Development
A new generation of Micro-Hybrid duties includes additional features:
Sailing
Switching-off the engine temporarily during driving
Boosting
Electric torque assistance for car acceleration
by belt-driven integrated starter generator
More efficient recuperation
Use of larger generators (more than 3 kW)
Further improvements of batteries to extremely high charge acceptance.
34
Future Development
This is the next challenge for lead battery manufacturer.
It requires further improvements of the negative active material.
A key point is using more and very special additives.
And, the development of appropriate manufacturing processes
to achieve favorable crystalline structures of the active materials.
Intensive R&D work is running and first results are rather
promising.
35
Future Development
36
48 V Systems and the Role of Lead Batteries
Beside of on board power supply with a 12 V battery
use of 48 V electric systems are planned.
Actually, there are concepts installing two voltage levels and two batteries,
connected to each other by a DC/DC converter.
Dual battery system: 48 V + 12 V + DC/DC converter
+ Less power loss (steadily increasing high power demand)
Very efficient recuperation
- Higher cost (2 batteries + DC/DC converter)
Implementation at premium and luxury vehicles.
37
48 V Systems and the Role of Lead Batteries
For lower voltage level 12 V lead battery
For 48 V level currently, lithium is the favorite technology
Extremely high charge acceptance is essential for the 48 V battery.
Advanced lead batteries would be an alternative
(special designs).
Again, a real challenge for lead battery manufacturer
(intensive R&D work).
But no principle reason that lead batteries cannot be improved so much.
38
Market Development
Mild Hybrid
Optimized
Micro-Hybrid
Micro-Hybrid will dominate
Start-Stop
Micro-Hybrid
Start-Stop +
Recuperation
39
Market Development
Car production worldwide in 2018: appr. 100 Mill. (2014: 80 Mill.)
Market share Micro–Hybrid: 25 % worldwide
40
Conclusions
Contribution of Micro-Hybrid lead batteries to CO2 reduction in traffic
Reduced fuel consumption
Corresponding CO2 reduction
Electric vehicles much higher CO2 reduction per car, however:
There are already many millions of cars with Micro-Hybrid function in EU
and there will be much more in the next years.
Because of the very large number of such cars:
Total CO2 reduction by Micro-Hybrid larger in comparison to EV.
Without the new lead batteries, Micro-Hybrid would not be possible.
41
Conclusions
Lead Batteries will remain to be used in the majority of
automotive applications and also in many stationary and traction duties.
Worldwide, Lead and Lithium are the major rechargeable battery
technologies.
Both systems have their strengths and weaknesses.
Depending on the specific application, in some cases lithium
and in others lead will be the most appropriate choice.
42
Conclusions
The overall demand for batteries will continue to increase.
Without batteries, our modern world would stand idle.
Therefore, when lithium replaces lead in certain applications, it will not
automatically mean a decrease of the total volume of lead batteries.
Energy and power density, high rate discharge ability,
cycling performance and charge acceptance have been
optimized significantly over the past years and,
43
Conclusions
The Lead Battery has still
much Potential for further
Improvement