David Cowan

Daniel Shaw

Battery Capacity

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

Battery Capacity is expressed in units of Amp hrs

Units

Constant discharge

Time in hrs of a full discharge

The total efficiency of a battery is expressed in Watt hrs

Units

Battery Capacity

Desired Output in Volts

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

Battery Capacity is additive when batteries are arranged in parallel but not when arranged in series

Battery Arrangement

Doubled Capacity

Doubled Output

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

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

Our ZAP car has six 12V Absorbent Glass Mat (AGM) deep cycle Lead Acid Batteries which take 100hrs to fully discharge

The ZAP Car

The ZAP Car

𝑇𝑜𝑡𝑎𝑙 𝑃𝑜𝑤𝑒𝑟=(100 A ) (72V )=7200WatthrsThe ZAP Car

For our ZAP Car

Battery Efficiency

Time it takes to fully discharge at this this rate

Rate of discharge