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How Many Amps Should I Use to Charge My Car Battery? Lectron EV

How Many Amps Should I Use to Charge My Car Battery?

After reading all the electric vehicle primers available online, you might think that you already know everything about the EV charging process - from the different types of chargers to the charging alternatives in the stickiest situations.


But, little is written about how many amps your car battery charger should REALLY be.

This question has more to do with charge rate. It's important for you to know how long your car's battery takes to fully charge, so you can plan ahead and not waste your precious time.

Knowing what charger to use is also crucial in determining how long a full charge takes to avoid over charging or overheating.

So, what amp charger for a car battery is right for you? Is it a 2 amp or a 10 amp charger?

How many amps to charge a car battery?

Knowing how many amps your car battery needs can be a lifesaver for your battery. With too many amps, you risk overheating your battery, which may lead to an explosion. With too few amps, your car battery will take forever to charge!

The safest amp to charge car batteries is from 4 to 7.5 amps. Charging within this range ensures the vehicle battery won't overcharge, overheat, or be damaged in the process.

Yes, you can safely charge a minimum voltage 12-volt battery with this amp rating, though it will be pretty slow. To increase the charge rate, you'll need at least 12.9 volts.

You can charge your automobile battery at higher voltages as long as it's not yet fully charged.

This means that the alternator voltages and the vehicle charger voltages could safely get 15 volts while ensuring the battery won't get overcharged.

The higher the voltage, the faster a charge cycle is completed.

How many amps do I need to charge a 12v battery?

Deep cycle batteries at 12v cannot handle more than 30 amps of charge current. Fast charging is not recommended for this type of battery, so stick to 10 amps for safety.

Keep in mind that 20 amps is already fast charging, and repeated use of high charging amps may result in bad battery health.

Should I charge my battery at 2-amps or 10-Amps?

The rule of thumb is, lower amps result in a slow charge and higher amps result in higher charging rate.

While safe for your car battery, charging at 2 amps is very slow. You're highly unlikely to end up with dead batteries, but a battery at 50-amp hours will take 24 hours to be fully charged.

A 10 amp charger can charge a car battery in about 5 hours. There's a low chance of overheating, but if a short develops, it may cause car batteries to fail.

If a car battery fails, dangerous chemicals could leak. Immediately disconnect the charger from the power source and contact a mechanic.

Can I charge a car battery at 50 amps?

Charging car batteries at 50 amps is already considered fast charging. At 50 amps, you can charge a 50-amp battery in just 1 hour. Use these types of battery chargers in moderation if you want your cars to be safely charged as frequent fast charging may result in decreased battery capacity and poor battery health.

Can you overcharge a battery at 2 amps?

If you leave your car charging continuously, there is still a possibility of overcharging even at a mere 2 amps.

Overcharging your car battery produces excessive gas when electrolytes heat up and both hydrogen and oxygen are produced, eventually leaving you with a completely dead battery.

To avoid this, take note of your vehicle battery capacity to know how many amp hours it'll take to fully charge.

Do amps matter when charging a battery?

The amperage matters during a charging process if you want to maintain a healthy battery. Most batteries used in electric cars can handle up to 32 amps.

A 32-amp charger can give your car battery up to 25 miles of range per hour.

An average deep cycle battery has a voltage of 12, but this doesn't necessarily mean that you can just grab any 12-volt car charger and assume it can be fully charged safely.

If the charger exceeds 10% of the ah rating or the amp-hour capacity of your battery, you run the risk of overheating it. The amps can make or break your car's battery.

How long does it take to charge a car battery

The more discharged your car's battery is, the longer it takes for you to get a fully charged battery. As the charge dissipates, you may notice that some of your car's features won't work properly. Your car engine might not even start, especially in a cold environment when your battery needs to work double time. This is because there's not enough power in the batteries to keep them powered-on. Or you don't have enough cold cranking amps.

When this happens, an indicator light will show up on your dashboard, signaling that your car's battery needs some charging.

The charging rate will depend on the kind of battery you're charging and its capacity. To know how long your battery will take to charge, you'll have to find out the reserve capacity of your battery and your charger's output charging current.

A battery with 100 amp hours of capacity can be charged by a 10 amp charger in 10 hours.

If you're charging a flooded lead acid battery, it'll take more time as it is charged in phases. Voltage is held at a constant during the absorption phase, while current decreases. So, you can't increase the current and expect faster charging in lead acid batteries.

Tips on how to use your battery charger properly

Investing in a smart charger can save you money in the long run. These chargers communicate with your car, the charging operator, and your utility company through data connections. This optimizes your energy consumption and costs.


Do I need to disconnect my car battery before charging it?

You don't have to disconnect your car battery before charging as long as you're using a smart charger that's microprocessor-controlled. These chargers are designed to prevent any damage to your car.

What if my charger isn’t working on my dead battery?

If your battery refuses to charge, this is not due to the amperage or your charger. It's because the charger cannot recognize your battery's low voltage.

For a charger to recognize a battery that's hooked up, it must meet the minimum voltage requirement. This voltage varies from manufacturer to manufacturer, but the standard voltage is between 9.5 to 10 volts.

What if my battery won't charge?

If the charger is not the issue, do some investigation on the EV. Most EVs have a secondary lead acid battery with reserve capacity to support other vehicle features independent of the main battery. This lead acid battery also requires maintenance.

There might also be sulfation and grid corrosion in the battery, which increases internal resistance. Internal resistance opposes the flow of the current, inhibiting power delivery.

How many amps should my battery charger be?

Use a charger with an amp rating that's about 10% of the total amp hour battery capacity or less. For example, a battery with a rating of 100 amp hours must use a charger rated 10 amps or less. If the battery has 50 amp hours of rating, a 5 amp charger is suitable. Most EV batteries have between 50 amp hours to 70 amp hours of rating, so you'll want to use a charger with 5 to 7.5 amp.

Can I charge a car battery with a 20 amp charger?

Yes, most EV batteries can handle up to 32 amps, so it's safe to charge your car battery with a 20 amp charger. It can give you a full battery charge in just 2.5 hours!

Can you charge a car battery with a 15 amp charger?

A 15 amp charger is perfectly fine to be used with a car battery.

Is it better to charge a battery at 2 amps or 10 amps?

If you want a faster battery charge rate, go with the 10 amps. Low charging current at 2 amps can be unreliable, but it won't hurt if you have two chargers.

Is it safe to charge a car battery at 10 amps?

Yes, it's safe to charge at 10 amps. You can have a full charge in just 5 hours!

Is it better to charge a car battery at 2 amps or 6 amps?

The general rule of thumb is, the higher the amp, the faster the charging rate. Charging at 6 amps is more reliable than charging at 2 amps.

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