How long does a 25 amp charger take to charge a car battery?
About 1.4 h for a typical 60Ah car battery at half charge, and 2.7 h from nearly flat, using amp-hours to replace x 1.2 / 25 amps. A 25 amp unit works as a shop charger.
25A
A charger rated at 25 amps by its listing, the class this page is about.
How long for each battery size?
Hours at 25 amps from three starting points: 75 percent (about 12.4V resting), 50 percent (12.2V) and nearly flat (11.8V). The 1.2 factor covers charging losses and the slow absorption stage near full.
| Battery | From 75% | From 50% | From nearly flat |
|---|---|---|---|
| 40Ah | 0.5 h | 1.0 h | 1.8 h |
| 50Ah | 0.6 h | 1.2 h | 2.3 h |
| 60Ah | 0.7 h | 1.4 h | 2.7 h |
| 70Ah | 0.8 h | 1.7 h | 3.2 h |
| 80Ah | 1.0 h | 1.9 h | 3.6 h |
| 100Ah | 1.2 h | 2.4 h | 4.6 h |
Other charger sizes
Chargers near 25 amps
Amp ratings as stated in each listing. Prices change often.
Frequently asked questions
Is a 25 amp charger good for a car battery?
A 25 amp setting is for large truck batteries or quick recovery in a shop. On a small car battery it is more than 30 percent of capacity per hour, so use a lower setting or a smart charger that limits current to avoid heating and gassing.
Can I leave a 25 amp charger on overnight?
A modern smart charger switches to float or maintenance mode when the battery is full, so leaving it connected is safe. An old manual charger without automatic shutoff will overcharge if left on; unplug it when the battery reaches 12.6 to 12.7 volts at rest. Charge in a ventilated space either way.
How do I know my battery size in amp-hours?
Many labels list Ah or reserve capacity (RC) in minutes. Roughly, Ah is about half the RC figure: a 120-minute RC battery is close to 60Ah. Most cars use 45 to 70Ah; full-size trucks and diesels 70 to 100Ah, often in pairs.