How Long to Charge a 12V Car Battery at 2 Amps?

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If you have a flat or partially discharged car battery and are considering charging it with a charger, particularly chargers with options to charge at different rates, it can be quite confusing which amp rate you should use for your charger.

In this post, I cover:

  • how long it takes to charge a 12V battery at 2 amps,
  • how to get the best performance using a 2 amp battery charger,

when to use it as well as the downsides to a 2 amp battery charger.

How Long to Charge a 12V Car Battery at 2 Amps?

A 2 amp battery charger takes about 12 – 30 hours to fully charge a 12V car battery, depending on the battery’s capacity, depth of discharge, and battery temperature.

A smaller battery like a 42Ah battery will probably charge in about 12 hours while a larger 140Ah battery is approximately 30 hours.

These are estimates and assume that the battery is only 50% discharged.

A completely drained battery will take a longer time to fully charge compared to a partially discharged battery also.

Good quality chargers also make adjustments to the way the battery is charged.

For example, the charging current may be lowered or increased to keep the battery temperature within the limits that is necessary for keeping it working as long as possible.

All of these factors – temperature, depth of discharge, and battery capacity affect how long the car battery will take to charge with a 2 amp charger.

How to Use a 2 Amp Battery Charger (3 Tips!)?

#1. Select the correct mode on the charger that matches the battery type

2 Amp chargers can have various modes depending on which battery type AGM, Lithium or Wet battery t is being charged.

Make sure you select the correct battery type on the charger that matches your battery type so that your battery is charged as required by the battery manufacturer.

A wrong battery type selection may cause your battery to be undercharged or overcharged. For example, 12V AGM is usually charged to 14.8V, Lithium 14.6V.

#2. Switch off car accessories

The 2 amp battery charger is a slow charger and generally takes a long time to charge compared to the higher amperage chargers.

To get the most of it, make sure that all car accessories are switched off to minimize battery drain otherwise the battery will take a longer time to charge or not charge fully.

#3. Monitor the battery charging

As your battery charges, check on its charge status from time to time, else the charging process is interrupted.

Some battery chargers stop the charging process altogether before the battery is fully charged.

This happens when they see an unusually high battery drain for a predetermined period, leaving a partially charged battery.

Why You Should Consider Using a 2 Amp Charger for Your 12 v Battery?

2 amp chargers can be a cost-effective way to charge and maintain battery capacities of about 40Ah.

If you have a battery size of up to 40Ah and need a charging solution to both charge and maintain your battery charge for a long period, then definitely consider a 2 amp 12V battery charger and maintainer.

The Downsides of Using a 2 Amp Charger

  • Slow Battery Chargers

2 amp chargers are generally slow chargers, may take at least 12 hours to fully charge a 42Ah battery for example.

If your battery is deeply drained, it will take a longer time.

This will not work for you if you want your battery to be charged in 4-6 hours an example.

  • Not suited to charging large capacity batteries

2 Amp chargers tend to have a maximum battery capacity that they can best charge about 40Ah.

Consult your charger documentation to confirm whether it is suitable to use with your battery capacity.

They are not suitable if you need to charge your battery in a short time – overnight or sooner especially when you have a large battery capacity or your battery is deeply drained.

Can You Leave a 2 Amp Charger on Your 12 v Battery?

A 2 amp float charger or battery maintainer can be left to charge your 12V battery over a long period – overnight, for several weeks, or over the winter to maintain your battery charge without the worry of overcharging your car battery.

These types of charges charge at peak 2 amps but make adjustments so that just the right amount of current is supplied to maintain the recommended battery voltage without damaging it.

Avoid dumb 2 amp charges that do not make adjustments to the voltage and current that is supplied to your car battery – these wear your battery in no time!

Therefore, check that your battery charger type is designed for float or battery maintenance applications before connecting it to your battery for a long period.

Which 12V battery capacity (Ah) for 2 amp battery charger?

A 40 Ah battery capacity is suitable for use with a 2 amp charger. It charges this battery size in about 15 hours assuming it is discharged to only 50% of its capacity.

Related questions

Can You Overcharge a 12 v Battery Using a 2 Amp Charger?

Yes, you can still overcharge a 12V battery with a dumb 2 amp charger that constantly charges a peak current of 2 amps regardless of what state of charge your battery is.

You can avoid overcharging and damage to your battery by using a good quality 2 amp smart battery charger and maintainer suited to your battery type (AGM, wet, or Lithium).

These make adjustments to the actual voltage and current that your battery is subjected to keep it fully charged for a long time.

Final Thoughts

A 2 amp car battery charger will charge a 40Ah car battery that is discharged to 50% of its capacity in about 12-15 hours.

The actual charging time varies though depending on how deeply discharged the battery is, its age, capacity, and temperature.

If you are planning to leave the charger connected to your car battery for a long time, make sure that it is of the battery maintainer type to prevent damage to your battery from overcharging.

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