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Future Opportunities for Lead Batteries:

A Manufacturer’s Perspective

Rainer Wagner

Moll Batterien

Bad Staffelstein, Germany

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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.

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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

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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.

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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

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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.

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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

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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 / %

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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

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Lead Batteries for Automobiles

Lead Batteries for Electric Vehicles

1900 USA

38 % Electric Vehicles

1930 Municipal Vehicles, Post,

Delivery Vehicles…100% electric

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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

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Lead Batteries for Automobiles

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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

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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.

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Lead Batteries for Automobiles

Book mold gravity cast

ConCast

Expanded metal

Punched

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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.

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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).

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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

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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.

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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.

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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.

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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.

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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.

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Micro-Hybrid

Comparison Conventional OE – AGM – Advanced EFB

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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

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Micro-Hybrid

615 times nominal capacity through puts at 17,5% DoD cycling

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Micro-Hybrid

17,5% DoD cycling

Impact of positive and negative active material on cycling performance

NAM - A

NAM - B

NAM - C

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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

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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

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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

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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

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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.

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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.

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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.

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Future Development

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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.

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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.

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Market Development

Mild Hybrid

Optimized

Micro-Hybrid

Micro-Hybrid will dominate

Start-Stop

Micro-Hybrid

Start-Stop +

Recuperation

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Market Development

Car production worldwide in 2018: appr. 100 Mill. (2014: 80 Mill.)

Market share Micro–Hybrid: 25 % worldwide

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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.

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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.

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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,

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Conclusions

The Lead Battery has still

much Potential for further

Improvement