If your battery is deeply discharged from leaving the headlights on or leaving it parked for an extended period without driving it then you will need an external charger to get its voltage back up.
Having a 10 amp charger is one thing. You may need to determine how long it will take to fully charge your car battery.
This post aims to answer this question for you in addition to arming you with what you need to charge the battery safely and also look for a new charger if for whatever reason you need to replace or acquire one.
So read on!
How Long to Charge a 12V Car Battery at 10 Amps
How long a car battery takes to charge at 10 amps depends mainly on the battery capacity (Ah) and how deeply discharged the battery is.
A larger capacity battery that is deeply discharged takes longer to charge than a lower capacity battery or one that is only partially charged.
As a rough guide though, a 40-50 Ah car battery that is discharged to 50% of its capacity takes about 3 hours or so to fully charge.
Since your car battery capacity may be different, refer to the table below for an indicative guide on how long your car battery takes to charge.
| No. | Battery Capacity (Ah) | Estimated Charge time (hours) |
| 1 | 20 | 1.5 |
| 2 | 40 | 3 |
| 3 | 80 | 6 |
| 4 | 100 | 7 |
| 5 | 230 | 17.3 |
Credits: Noco genius 10 car battery charger manual
Charging Time for a Completely Dead 12V Battery
Actual charging time for a 40-50 Ah battery will likely last over 6 hours.
Ultimately, the time to full charge depends on how deeply discharged the battery is and the capacity of the battery.
Charging a 12V Car Battery Safely
In addition, read the specific safety instructions of your charger
To avoid any accidents – battery explosions that can cause serious injury or death, take note of the following:
- Do not attach to charge any battery that shows any signs of damage. This may be because the battery is bulging, cracked, or even leaking.
- Make sure that you set the charger setting to match the battery type being charged. If it an an AGM. LiFEPo4, make sure that the battery charger is set to charge the correct battery type.
- If you are charging the car battery while it is still installed in the car, make sure that all car electronics are switched off to minimize battery drain otherwise the battery will take a longer time to charge or not charge fully.
Connecting the Charger to The Battery
1. Before plugging in the charger in the mains, connect the positive terminal of the charger to the positive battery terminal and the negative terminal of the charger to the negative battery terminal.
2. Confirm that the charger is set to charge the battery type – AGM, LiFEP04 that matches your battery type.
3. Switch on the charger.
4. Check if the charger uses time-based charging in which case you need to switch it off after an elapsed time or whether it automatically switches itself off once the battery is full.
Either way, I’d recommend that you monitor the charger after the estimated charging time to confirm that the battery is fully charged.
Disconnecting the Charger from the Battery
To disconnect the charger, switch off the charger at the mains. Usually, disconnect the negative cable first from the negative battery terminal followed by the positive cable from the positive battery terminal.
What Capacity of Battery to Charge with a 10 Amp Charger?
Do not use the battery charger to charge a car battery with a capacity under 20 Ah as you risk damaging the battery. from over-discharging.
Which 10 amp Battery Charger to Buy?
1. Go for a charger with good genuine feedback on reliability and safety. When choosing a 10 amp battery charger, in addition to looking out for a well-regarded charger based on genuine user feedback, consider selecting one with the following additional features.
2. Check if the battery charger can charge batteries with voltages as low as 1V. Not all chargers can do this.
Buying a charger that can will increase the chances of restoring a severely discharged battery to full charge.
3. Get a battery charger that Can support more than one battery chemistry. Look out for a charger that is able to charge various battery types such as AGM, Gel, Lithium, or Flooded batteries, or at least the types you have.
You can take comfort in being able to charge the different battery types without buying another charger.
Should You Leave a 10 Amp Charger Connected to a Battery?
If you have a good quality 10 amp charger with a maintain or float function, then you can leave it connected to your 12v battery if you plan to leave the car parked for an extended period without the worry of overcharging and damaging your battery.
I would personally monitor the charging process during the initial phase of charging to make sure that the battery is charging and close to the expected time to full charge to confirm that the charge has stopped charging.
Related questions
Can You Overcharge a 12 v Battery Using a 10 Amp Charger?
Yes, you can overcharge a 12V battery with a 10 amp charger that constantly charges with a peak current of 10 amps regardless of what state of charge your battery is.
Use a good quality 10 amp smart battery charger and maintainer suited to your battery type (AGM, wet, or Lithium) that makes adjustments to the actual voltage and current to avoid overcharging and damage to the battery.
Final Thoughts
A 10 amp car battery charger charges a 20 – 230Ah car battery, discharged to 50% of its capacity in about 1.5-17 hours.
The actual time to charge depends on how deeply discharged the battery is its age, capacity, and temperature.
If the charger has a float or maintainer feature, you can leave it connected to the battery for an extended period without worrying about overcharging and damaging it.
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