Battery Capacity
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Transcript of Battery Capacity
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David Cowan
Daniel Shaw
Battery Capacity
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The duration of time which a battery can withstand a constant draw of one Amp while maintaining a constant voltage
(output)
Battery Capacity quantifies the amount of useable energy that a battery can
store
Battery Capacity
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Battery Capacity is expressed in units of Amp hrs
Units
Constant discharge
Time in hrs of a full discharge
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The total efficiency of a battery is expressed in Watt hrs
Units
Battery Capacity
Desired Output in Volts
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Available Capacity (Puekert’s Law)
Current of discharge
Time in hrs of a full discharge
Peukert’s Constant (only for lead acid batteries) *not spring constant!*
* Puekert’s Constant is always
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Battery Capacity is additive when batteries are arranged in parallel but not when arranged in series
Battery Arrangement
Doubled Capacity
Doubled Output
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Battery ArrangementHowever, if you arrange multiple batteries in a way so that you have a series of parallel batteries, then you can double both the output and the capacity
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One of the dangers of having an EV with a Lithium Ion battery is; battery gassing. Battery gassing occurs when you overcharge the battery. This leads to thermal runaway which is essentially when your battery heats up so much that it explodes
Battery Gassing
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Our ZAP car has six 12V Absorbent Glass Mat (AGM) deep cycle Lead Acid Batteries which take 100hrs to fully discharge
The ZAP Car
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The ZAP Car
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𝑇𝑜𝑡𝑎𝑙 𝑃𝑜𝑤𝑒𝑟=(100 A ) (72V )=7200WatthrsThe ZAP Car
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For our ZAP Car
Battery Efficiency
Time it takes to fully discharge at this this rate
Rate of discharge