The problem
Large diesel engines need a very high current for a few seconds to crank. Lead-acid batteries struggle with that surge when they are cold, ageing or partly discharged, and an engine that will not start can stop a whole system. The goal was a cranking source that delivers the surge reliably, recharges quickly and can be carried to the engine.
What we built
- A 24 V, 1200 F supercapacitor bank built from forty 2.7 V, 3,000 F cells arranged 10 in series and 4 in parallel.
- Cell balancing on every series group, so no cell is over-voltaged during charging.
- A portable enclosure in a briefcase/trolley format of about 580 × 510 × 230 mm, with a front voltmeter, a DC breaker, charging posts and heavy copper cranking terminals.
- A 24 V direct cranking panel rated for 600 A continuous and 2,000 A peak.
- Fast-charging research. We studied charger topologies for fast charging of the bank, including a high-frequency matrix-converter approach published at IEEE ICETAS 2019.
The demonstration
In the field demonstration the bank cranked a 430 kW diesel engine without a battery. The surge peaked at about 1,900 A, the bank voltage dipped by about 6 V, and the cranking event lasted roughly five seconds. The same set-up was also tried on diesel generator sets.
Why it matters
Supercapacitors deliver very high current, tolerate temperature extremes better than batteries for short bursts, and last for hundreds of thousands of cycles. A cranking bank built on them can back up or replace a starting battery where a failed start is not acceptable.
This work was carried out for a national defence R&D programme. The programme and its partners are not named here. Further details are shared only with the programme's permission.