Additional Reactions of Significance

• Oxygen Reaction Cycle:: ½O2 + Pb PbO

PbO + H2SO4 PbSO4 + H2O

Note: Oxygen reaction cycle is a benchmark characteristic of VRLA batteries. It is more pronounced with AGM than with gel constructions.

• Severe Overcharge Reaction: 2H2O O2 + 4H+ + 4e-

Note: This results in water loss due to venting of O2 and can be life limiting.

• Positive Grid Corrosion: Pb + 2H2O PbO2 + 4H+ + 2e-

Note: This results in water loss and can be life limiting.

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Battery Basics-Cell Chemistry

Optima AGM Battery Construction

Optima has lower internal resistance compared to flat plate batteries•Optima has less internal parts (~30) vs traditional batteries (120+)•Optima has over the partition, solid lead connectors vs through the partition inter-cell welds

• Factors affecting internal resistance of the battery– Size of lead conductors– Plate surface area– Plate spacing– Separator resistivity– Electrolyte type

• Gel has higher resistance than flooded or AGM designs which negatively impacts high rate and cold performance

– Electrolyte concentration– Temperature

Element Characteristics

Container/Cover Design

• Cylindrical cells provide superior mechanical structure to battery– Eliminates cell bulge– Permits higher valve

pressures, 7-8 psi, compared to flat plate, 1-5 psi

• Flat plate batteries can experience end wall bulge when pressure builds up on charge resulting in loss of performance

Gassing Characteristics

• Gassing– Less than flat plate/prismatic design

• Why?– Higher purity materials – 99.99% pure lead– Alloys – Optima uses a binary tin lead alloy

compared to a flooded battery that uses a multi component alloy (silver, tin, calcium, aluminum, etc… less impurities)

– Oxygen reaction cycle

Source: AGM Development Team

Discharge Monitor of Optima Group 31 vs. Competitive Group 31 Lead-Acid Batteries0.6kW to 10.50V Discharge Monitor - Ambient: 220C

10,0

10,5

11,0

11,5

12,0

12,5

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13,5

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0 10 20 30 40 50 60 70 80 90

Time (minutes)

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lta

ge

(V

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75Ah, Optima - 27.2kg

130Ah, Flooded - 30kg

98Ah, Gel - 31.4kg

Voltage cut-off: 10.5V

The Optima AdvantageLonger run time