If your external car battery charger can charge at different rates say 2,5,10, or 20 amps, you may opt to charge it at the highest 20 amps rate (for this charger) for the shortest charge time.
If this is you then you’d probably want to know the implications on battery life and your own safety if any at all.
Or even, how you go about selecting a suitable charge rate for your car’s battery?
In this post, you’ll find advice on whether you should charge your car’s battery at 20 amps, whether it is safe to do so, and how you should go about selecting a suitable charge rate for your car’s battery.
Whether to Charge a Car Battery at 20 Amps
You can use a 20 amp intelligent charger to charge a car battery. This assumes the battery capacity (Ah) is in the range 31 – 50 Ah range.
Much as it is a 20 amp charger, expect the charge rate (amps) to reduce as the battery tends to full charge.
Is it Safe?
If you use a good quality charger set to charge the car battery type you’re using, whether AGM or Flooded with automatic shut-off when the battery is fully charged then it should be safe to charge it at 20 amps.
Additionally, follow the recommended manufacturer safety precautions when charging the car batteries to minimize the risk of fire, explosion, injury, or damage to the batteries.
Do not attempt to charge car batteries that show signs of damage to minimize the risk of accidents.
The Dangers of Charging a Car battery at Higher Charge Rate
If you use a higher than recommended charge rate for your battery, in case of a flooded lead acid battery, expect the battery to become extremely hot and to boil over.
For a sealed battery, the sides can buckle. Suffice it to say that, using higher than recommended charge rates can damage the car battery permanently.
How Long it Takes to Charge a Car Battery
The charge time depends on several variables including how deeply discharged the battery is, the battery capacity, and the charge rate used. Even then the charge times are estimates.
Assuming a 55Ah car battery discharged to 50% of its capacity, the estimated charge rate using a 20 amp charger is about 1.7 hours.
You can also use the formula below to work out the estimated charge time.
Charge time = (Battery capacity x assumed discharge of 50%)/ charging rate, i.e (55 Ah x 50%)/ 20 amps charge rate.
If the battery is partially discharged or more deeply discharged expect the charge to decrease or increase correspondingly.
You can use the lower charge rates of 2, 5, 10, or even 15 amps too only that the time to fully charge is longer.
How to Tell if a Battery is Fully Charged
It is best to use an automatic, smart charger, with an automatic shut-off feature. suited to your car battery type and capacity.
Provided you’ve selected the corrected battery type it should automatically stop the charging process and indicates that the battery is fully charged.
Closing Thoughts
You can use a 20 amp charger to charge your car’s battery. Make sure it is a smart, automatic shutoff charger suited to charge your car battery type and capacity.
Follow the manufacturer-recommended charging instructions.
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