The comparison between super capacitors and batteries.
Currently, supercaps and batteries somewhat complement one another, whereby both present opposite strengths and weaknesses. Therefore, comparing the following Li-Ion battery and super capacitor characteristics reveal the following:
- Charge durations: Super capacitors are far superior in charging times, with a full charge achieved within 1 to 10 seconds. However, batteries may take anything from 10 to 60 minutes to achieve a full charge.
- Specific energy (total energy stored per unit mass): This is unfortunately the primary weakness of super capacitors, with around 10Wh/kg, compared to 100-200 for batteries. As a relatable comparison, normal octane fuel boasts around 3700 Wh/kg (factoring in a 30% efficiency of combustion engines), whereby supercaps are around 15Wh/L and 1200 Wh/L for batteries. Therefore, an iPhone powered by supercaps will be 2 inches thick.
- Specific power: Due to the rapid charging capabilities of supercaps, they also discharge rapidly, delivering power of around 10000 W/kg, whereby batteries discharge around 2000-3000 W/kg.
- Cost: As supercaps are a reasonably new technology, they are considerably more expensive than batteries.
- Further issues with supercaps are their voltages diminish linearly compared to the charge, while battery voltage levels are somewhat held constant while discharging. However, Li-Ion batteries demonstrate safety issues with combustion, which supercaps don’t.
As technology improves, so do the weaknesses of both super capacitors and batteries. However, cost is a major factor determining the decision in selecting batteries or supercaps, while considering both pros and cons. We at Ecotech Energy have started considering both technologies while designing our renewable energy systems, and will continue to monitor both battery and super capacitor technology progressions into the future.