How Long Does It Take to Charge a Car Battery?
Last updated: May 2026 · By the ChargeWiseHub Team
The honest answer: it depends on three things — the charger's amperage, the battery's capacity (Ah), and how flat it is. Here's the full breakdown for Australian drivers.
Quick Reference — Charge Times by Charger Type
| Charger Type | Amperage | 60Ah Battery (flat) | 100Ah Battery (flat) |
|---|---|---|---|
| Trickle charger | 1–2A | 30–60 hours | 50–100 hours |
| Standard slow charger | 4–6A | 10–15 hours | 16–25 hours |
| Smart charger (10A) | 10A | 4–8 hours | 8–12 hours |
| Fast smart charger (25A) | 25A | 2–3 hours | 4–6 hours |
Note: Times assume battery is at 20% charge. A completely dead battery may need a recondition cycle first.
The Formula
To calculate charge time yourself: Battery Ah ÷ Charger Amps × 1.2 = Hours
Example: 60Ah battery, 10A charger → 60 ÷ 10 × 1.2 = 7.2 hours
The 1.2 multiplier accounts for the ~20% energy lost as heat during charging — this is normal.
What About a Completely Dead Battery?
A battery that's sat flat for weeks is a different story. It may have sulphated — the lead plates have developed a layer of lead sulphate crystals that a normal charge cycle can't break through. You need a charger with a desulphation or recondition mode.
The CTEK MXS 5.0 ($119 AU) has the best recondition mode on the market — it pulses high-voltage current to break down sulphation before beginning a normal charge. The Projecta IC2500 also handles this well.
With recondition mode: add 4–12 hours to the total charge time.
Does Driving Charge the Battery?
Yes — your alternator charges the battery while the engine runs. But it's not efficient. Highway driving charges better than stop-start city traffic. A typical alternator puts out 13.5–14.7V and around 40–120A. In practice, you need 30–45 minutes of highway driving to meaningfully recharge a battery.
If your battery regularly goes flat, driving won't fix an underlying problem — get it load-tested first.
Best Chargers for Fast, Safe Charging in Australia
- NOCO Genius 10 (~$149) — 10A, handles lithium + AGM, Bluetooth app. Amazon AU →
- CTEK MXS 5.0 (~$119) — 5A, best recondition mode. Amazon AU →
- Projecta IC2500 (~$89) — 25A, fastest for big batteries, Aussie brand. Amazon AU →
FAQ
How long does it take to charge a car battery?
With a 10A smart charger: 4–8 hours for a standard 60Ah battery. Trickle charger: 12–24 hours. Completely flat battery: up to 48 hours including recondition.
Can I overcharge a car battery?
With a modern smart charger — no. They automatically drop to float/maintenance mode when full. With a cheap fixed-rate charger — yes, and it can destroy the battery. Always use a smart charger.
How do I know when my car battery is fully charged?
A smart charger will show a FULL or READY light. With a multimeter: 12.6–12.8V at rest = fully charged. Below 12.4V = less than 75% charge.