PROJECT JOURNAL / TRACK PREPARATION
Lightweight performance batteries: saving weight for the track
Why we use a compact performance battery in our track builds, and what changes compared with a conventional road-car battery.
When we prepare a car for the track, we look at the weight it carries as well as the parts that make it go. A battery is an easy component to overlook: it sits quietly under the bonnet, yet replacing a larger unit with a suitable compact battery can remove useful weight. We use compact performance batteries in our track builds for exactly that reason.
The photograph shows an Odyssey Extreme PC680. We have improved the supplied workshop photo so you can take a closer look at the battery we are talking about.
What makes a track battery different?
A road-car battery is selected for the vehicle’s starting requirements and everyday electrical demands. Cold starts, repeated journeys and equipment running while the engine is off all matter. A track-focused choice can place more emphasis on low weight and compact packaging, provided it still meets the engine’s starting and electrical requirements.
“Race battery” describes an application, rather than one particular chemistry. The PC680 pictured here is a sealed AGM lead-acid battery; AGM stands for absorbed glass mat. Some road cars also use AGM batteries. Lithium motorsport batteries are another category with their own charging and protection requirements, so they should be assessed separately.
Conventional road battery versus compact track battery
| Consideration | Road-car specification | Compact track choice |
|---|---|---|
| Priority | Everyday starting and electrical demands. | Reduce mass while meeting the build’s needs. |
| Size and weight | Depends on the original vehicle specification. | Can save weight against a larger original unit; weigh both complete installations. |
| Stored capacity | Selected for the vehicle and its equipment. | A smaller-capacity choice leaves less reserve for the same engine-off loads. |
| Suitability | Use the vehicle’s approved specification. | Confirm starting ability, charging compatibility and secure fitment for the exact car. |
Our PC680 example
Odyssey lists the PC680, also identified as ODS-AGM16L, at approximately 7.0 kg, with a 12V, 16Ah specification. These are manufacturer figures for this model, not a weight-saving claim for every car. The actual saving depends on the battery being removed and the mounts, terminals and cables needed for the replacement.
Our approach is to weigh the complete old and new installations. Less vehicle mass improves the power-to-weight ratio without adding engine power. The effect on a particular car depends on its total weight and setup; we do not attach a promised lap-time gain to a battery swap.
The trade-off: starting power and reserve are different
A battery may deliver a strong burst to start an engine without storing as much energy as a larger unit. Cranking ratings describe starting performance, while ampere-hours describe capacity under specified test conditions. Compare like-for-like ratings: a brief pulse figure is not the same test as cold cranking amps.
Fans, pumps, lights and other equipment still draw power when the engine is off. With less usable reserve, extended paddock time with equipment switched on, repeated starting attempts or a car left connected between events need more attention. A compact battery that works well in a carefully prepared track car may be the wrong compromise for a daily driver.
Choose for the whole build
Before changing anything, confirm the engine’s starting needs, electrical loads, charging-system compatibility and any battery-management requirements. Check terminal polarity, cable routing and clearance. The battery needs a proper secure mounting and protected terminals; follow the manufacturer’s installation guidance and the requirements of your event or series.
Use charging and maintenance equipment approved for the exact battery. Do not assume an AGM battery and a lithium battery share the same charger settings. For a road-and-track car, retaining the correct road-car battery may be the better choice if everyday reliability and reserve matter more than the saving.
Small details add up
For us, a compact performance battery is one part of a considered track build. We want useful weight savings while keeping the car dependable enough to enjoy the day. Start with the car’s requirements, measure the actual saving and choose a battery that suits how the car is used.