Green Seal® Technology: Revolutionizing Battery Design

Maria Penafrancia Roma, Julius Regalado and Edward Shaffer II Advanced Battery Concepts LLC

8 Consumers Energy Parkway, Clare, MI, 48617 mroma@advancedbatteryconcepts.com / 1-989-424-6645

Abstract: A new battery design geared towards large-

format energy applications has increased the performance

of lead batteries and transformed the way they are made.

The bipolar battery design termed “GreenSeal®” has

allowed it to break the specific energy density bar of 50

Wh/kg, lower the weight by 35%, reduce the lead content

by 46% and increase the cycle life by 300%. Material

substitutions and cell design modifications reduce the

amount of lead used but still deliver equivalent capacity.

GreenSeal® technology facilitates high voltage battery

designs up to 96V and a wide-range of large format battery

types. This patented cell assembly process allows for a

completely sealed, leak-free absorbed glass mat (AGM)

battery design that can withstand severe impact conditions

and high-vibration applications making it safer for abusive

usages and harsh environments. The construction of

bipolar electrodes uses common materials used in the lead

battery industry with a more precise, cleaner process

compared to traditional lead grid production. Integration

with an existing battery production facility is not capital

intensive and 100% of the materials are recyclable.

Construction of a 1.5kWh bipolar battery for golf cart (GC)

applications using GreenSeal® technology and processes

resulted a in specific energy density of 55 Wh/kg and a

cycle life predicted to be greater than premium products

commercially available on the market.

Keywords: bipolar lead battery; GreenSeal®; golf cart

battery; lead acid battery; VRLA; AGM

Introduction Power and energy dominate the resource demand pyramid

today and will continue to do so over the next 10 years

and beyond. Powered by the growth of portable

consumer products, progress in electric vehicle (EV)

development, as well as the expansion of energy storage

systems (ESS), worldwide rechargeable battery demand is

predicted to reach up to 775 GWh by 2025 [1]. Although

the greatest growth is anticipated to be from lithium ion

batteries (LIB), lead acid batteries (LAB) will still retain a

majority share of 600GWh, or approximately 75% of the

projected demand. For the lead battery industry, this

means an $85B market ripe for the taking. The outlook

may seem optimistic and encouraging but there are

serious challenges that the industry must urgently resolve.

Low product performance, strict environmental

regulations, and poor profitability are among the major

issues that make new and emerging battery chemistries

very attractive alternative energy sources [2]. A bipolar

battery design increases performance by increasing

material utilization and energy density due to the uniform

current flow across the electrode. GreenSeal®

Technology

utilizes these advantages to address LAB challenges

through product and process designs based on sound

engineering and scientific principles. The key advantage

over other bipolar technologies under development is the

ability of GreenSeal® technology to use existing raw

materials and innovative production processes that easily

scale up cell design prototypes to multi-cell large format

products [3]. The objectives are to meet higher

performance requirements not only of existing

applications but also of emerging high growth markets at

commercial levels while managing environmentally

friendly operations. In this study, 1.5kWh GreenSeal®

bipolar batteries are designed, assembled, and tested.

Results are compared with commercially available

products.

Materials and Methods A traditional GC battery configuration is termed prismatic

and flooded when there is free electrolyte present. On the

other hand, within a prismatic AGM configuration there is

no free moving electrolyte as it is adsorbed/absorbed

within the separator and electrodes, (fill level < 100% of

saturation volume). Table 1 shows a range of claimed

and computed technical data for available GC batteries on

the market.

Table 1. Claimed product performance of commercially

available GC batteries

Battery Type Prismatic Flooded

Prismatic AGM VRLA

Voltage, V 6 6

C/20 Capacity, Ah 225-242 190-225

C/20 Energy, Wh 1350-1452 1140-1350

Reserve Capacity, min 447-562 380-500

Weight, kg 28-32 30-33

Specific energy, Wh/kg 43-48 36-45

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5-4

Figure 1. GreenSeal

® Technology Process Flow

Materials: One of the most popular batteries on the market

was used as a benchmark product. Using GreenSeal®

Technology, a bipolar battery was designed to an

equivalent C/20 Rate of 1350 Wh (6v-225Ah vs. 48V-

28.1Ah).

Method: GreenSeal® has a total suite of technology that is

used to assemble and produce a bipolar lead acid battery

[4]. It starts with a design to determine the bipolar plate and

battery configuration using models developed to compute

power, energy as a function of size, discharge rate, and

temperature. The model uses a modified Peukert equation

to provide discharge data, energy density, cold cranking

ampere (CCA) capacity, and reserve capacity in minutes

(RCM) at 25A discharge. The next step is to assemble the

actual batteries for testing: electrode assembly, stack

assembly, battery assembly, and battery formation, which

can all be further broken down into sub-processes as shown

in Figure 1.

Electrode Assembly: Unlike prismatic batteries,

GreenSeal® bipolar batteries do not need cast or expanded

lead grids but instead use injection molded polymer

substrates with Pb foils on both sides as electrodes. One

side is designated as the positive electrode and the other as

the negative electrode. Electrical connections between the

two sides are achieved by stenciling a quaternary Pb-based

solder into the substrate, which is then reflowed under heat

and pressure after Pb foil attachment. This alone reduces

the amount of lead used by about 7 kg or 88 %. Moreover,

no casting, grid punching, or grid expanding machines are

needed to make bipolar electrodes.

Stack Assembly: Pasting of the active material is

accomplished through another unique process,

PrecisionAMTM

Pasting (patent pending). In this process,

active material paste is transferred directly onto the bipolar

electrode assembly. This process does not utilize belt

pasters and does not generate waste slurries. Paste

thickness is controlled by a constant depth in the machine

and less than 2% variation in the paste weight has been

measured. Active material adhesion is best achieved by

stacking the electrodes under pressure while undergoing the

curing and drying process. Unlike traditional processes,

lead plates are not manually handled or exposed to the

environment after pasting. Lead dust generated after curing

due to stacking at the enveloping and cast-on-strap (COS)

lines is eliminated.

Battery Assembly: After curing and drying, the stacked

bipolar electrodes are encased with the same polymer

material as the electrode in the RapidSeal® process (patent

pending), where cells are isolated ionically from each other.

Previously developed bipolar batteries failed due to edge

seal rupture, which allowed not only electrolyte to cross

into cells but also oxygen ingress. With GreenSeal®

technology, this issue is resolved.

Battery Formation: The final process involves the

transformation of cured and dried paste into active material

through the input of electric energy. Sulfuric acid is

introduced into the battery by the SureFillTM

[5] process,

which saturates the AGM separator and the paste material

with electrolyte. To achieve the designed battery

performance, an optimized formation schedule is

implemented, battery temperature is strictly regulated, and

a desaturation process is strictly controlled.

Figure 2. A GreenSeal® GC2 48V 1350 Wh Module

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Battery Testing: A series of short-term and long-term tests

are scheduled to characterize the performance of the

battery’s capacity, durability, and reliability.

Table 2. Schedule of short-term and long-term testing

Short Term Long Term

Capacity Workup Test Cycle Life

Energy Capacity-Peukert Sweep Vibration Life

Tafel testing Stand Life

Power Testing (IEC 61056) Float Life

Results Capacity tests show higher power and energy performances

of the GreenSeal® GC2-48V with 31.8Ah at the C20 rate,

yielding an energy value of 1526Wh. This exceeds the

design capacity of 1350Wh, translating into a specific

energy density of 55 Wh/kg, which is 30% better than the

highest rated commercial AGM battery. A comparison of

the Peukert power curves in Figure 3 shows that

GreenSeal® can deliver 38% more energy than commercial

batteries on the 2-hour rate. Moreover, computations of the

power index (V2/4R) show that GreenSeal

® is about 300%

higher than the highest rated AGM battery. The GreenSeal®

GC2 curve is predicted from actual Peukert sweep while

other AGM and flooded (FLD) batteries are based on

published discharge data.

Figure 3. Peukert Power Curves

The increase in specific energy density in the GreenSeal®

battery is due to the 46% decrease in lead content in this

design. This is a result of the elimination of top lead or

cast-on-strap (COS) configurations to connect cells in

series, in addition to the elimination of lead based grids

serving as electrodes. This change in the cell

interconnection design results in an almost 10kg lead

reduction per battery. This is made possible by multiple

solder joint connections across the surface of the plate

which allow a more uniform electron flow across the

electrode in contrast to the traditional pathway from the

grids to the lugs.

Life Cycle Testing: Cycle life performance using the BCIS-

06 Cycle Life [6] tests show that the GreenSeal® GC2-48V

has 2.3x more life than the leading AGM battery as shown

in Figure 4.

Figure 4. BCIS-06 Cycle Test Results

Vibration Testing: Another measure of durability is the

vibration resistance to extreme stress conditions. Results of

the SAE J930 Test (Vibration Life for Storage Batteries for

Off Road Self Propelled Work Machines) [7] show that

GreenSeal® GC2-48V batteries exceeded commercial GC2

batteries by 20x (Table 3). This test is an 18-hour test at a

5.0 peak G-force on the vertical axis at 30-36 Hz.

Previous long-term test data on developmental prototypes

have shown that batteries designed and assembled with the

GreenSeal® Technology perform on par with or better than

the leading AGM brands. One example is the stand life

data, which has shown values exceeding other battery

chemistries.

Table 3. Summary of Results of Battery Tests

Product Name Prismatic

AGM VRLA

GreenSeal ®

48V GC

Battery Type Prismatic AGM

VRLA Bipolar AGM

VRLA

Specific energy, Wh/kg 36-45 55

Cycle Life, 100% DOD C2 to 50% capacity

75-250 780

Vibration Life SAE J930 Level 2 10-30 h 620h

Stand Life Test -% Loss , dV/mo,25°C

1-3% 0.50 %

(> 2 yrs)

Stand Life Testing: This test measures the self-discharge

rate of the battery in an open circuit. There are several test

standards available but in this experiment, open circuit

voltage (OCV) monitoring at 25°C in air shows less than a

0.5% change in OCV in over 2 years, a value which is

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almost 6x lower than other AGM batteries. This behavior is

a function of the GreenSeal® battery design and

configuration and can still be improved with stricter

controls on the levels of impurities in the raw materials.

Summary Undeniably, there are clear advantages of this design over

existing products made from established production

processes, even at research and prototype stages:

Higher energy density – 30% better

Longer Cycle Life – 300% increase

Better vibration resistance – 20x more resistance

Extended Stand Life – 6x longer

Reduced Lead Usage – 46% less

As the technology matures and transitions into the

manufacturing phase, the opportunity for the first movers to

exceed the incumbent legacy technology benchmarks for

performance and reduced manufacturing cost is

considerable. GreenSeal® solves the century-old puzzle that

the original bipolar battery patent holder, P. Kapitsa [8] and

his successors were never able to unravel. Moreover, this

technology utilizes a majority of the raw materials of

existing LAB manufacturing operations and thus uses the

same environmental infrastructure presently in place. In

fact, it also provides a relief from stricter regulatory

controls by reducing lead usage, using cleaner operations,

and minimizing hazardous waste handling.

Future Actions While waiting for the results of ongoing long-term

validation tests, existing data have shown that there are

additional opportunities to improve battery energy and

power densities. After considering the data gathered from

process and product validation runs, design recalculations

have shown that a 70Wh/kg energy density can be

achieved. This is possible with the following

improvements: use of lower density substrate materials,

higher purity raw materials, and energy- or power-

enhancing paste additives. There are also opportunities to

optimize electrode configuration, active material utilization,

and formation processes. In the future, there are several

prospects for expansion to other applications. While the

bipolar battery design with GreenSeal® technology is

projected to serve emerging markets like grid storage and

electric mobile transports, existing military applications can

also greatly benefit from the new lead battery design.

Acknowledgement The authors would like to acknowledge Advanced Battery

Concepts, LLC for allowing the publication of design and

validation results for this report.

References 1. Pillot, C., “The Rechargeable Battery Market and

Main Trends 2015-2025”, 18th International Meeting

on Lithium Batteries, Chicago, IL, June 20, 2016.

2. Shaffer, E., “Approaches to Improving Lead Battery

Performance”, The Battery Show, North America

2017, Novi, MI, September 11, 2017.

3. Shaffer, E., “Advanced Battery Concepts, LLC and

GreenSeal® Battery Technology”, 2018 NAATBatt

International Annual Meeting & Conference, San

Antonio, TX, March 21, 2017.

4. Shaffer, E., Brecht, W., “Bipolar Battery Assembly”,

US Patent No. 8357469, January 22, 2013.

5. Shaffer, E., Hobday, D., “Bipolar Battery Assembly”,

US Patent No. 9553329, January 24, 2017.

6. BCIS-06 , “Cycle Life Testing of Electric Vehicle &

Cycling Batteries, rev. May 10, 2010

7. SAE J930, “Storage Batteries for Off-Road Self-

Propelled Work Machines”, 2016 Ed. May 1, 2016.

8. Kapitsa, P. L., Proceedings of the Royal Society A,

105, 691, 1924.

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