EV batteries, explained

Kilowatt-hours (kWh) measure how much energy a battery holds, a bit like the size of a fuel tank. Kilowatts (kW) measure the rate energy flows: how fast a charger can deliver it, or how much power the motor produces.

Manufacturers may quote gross capacity (the whole pack) or usable capacity (what you can actually draw on). Usable is the more useful number when comparing range.

Most EVs sold in Australia use one of two lithium-ion families. Lithium iron phosphate (LFP) is common in many entry and mid-level models; it's known for durability and is often fine to charge to 100% regularly. Nickel-based chemistries such as NMC typically offer more energy for their weight and are often recommended to sit at a lower daily charge limit.

The right daily charge level depends on your car. Follow the manufacturer's guidance in the owner's manual or app rather than a one-size-fits-all rule.

All lithium-ion batteries gradually lose some capacity over time. How quickly varies with the chemistry, the climate, how the pack is cooled, how often it's DC fast-charged and how long it sits at very high or very low charge.

State of Health (SoH) is the usual measure: the battery's current usable capacity compared with when it was new. Modern packs with active thermal management have generally held up well, but every vehicle is different, which is why a battery health check matters when buying used.

Most manufacturers offer a separate battery warranty that is longer than the vehicle warranty, often around eight years with a distance limit and a minimum retained-capacity threshold. Terms vary by brand and model, and some differ between private and commercial use, so read the specific warranty for the vehicle you're considering.

A few habits that are generally kind to a battery (your manual has the final word):

• Use your car's recommended daily charge limit.
• Avoid leaving the car at very low charge for long periods.
• Use AC charging for everyday top-ups and save DC fast charging for when you need it.
• In hot weather, park in shade or under cover where you can.
• Keep the car's software up to date.

Heat is harder on batteries than cold over the long run. Most current EVs actively cool the pack, but some earlier models (for example, early Nissan Leaf generations) relied on passive air cooling. If you're looking at an older EV, a battery health report is especially worthwhile.