Why Is My Car Charger So Slow? (5 Causes)

Just like blood is to the human body, so is charging to electric vehicles. However, unfortunately, there are some complications surrounding the EV charging process, which is a matter of concern to most electric car owners.

Usually, a charger’s actual power output doesn’t match the maximum as seen in most adverts. While this is a fact, there are several other reasons why your electric car may be charging slowly.

So, if you’re contemplating, “Why is my car charger so slow?” Five reasons have been explained in this article, as well as the strategy to increase the charging speed.

charger charging slow

Why Is My Car Charger So Slow?

Generally, most electric car charger power outputs do not match the maximum power output as advertised; hence, your EV may likely charge slower than the anticipated time frame.

However, besides this generic factor, the following are five reasons why your electric car charger is charging slowly.

State of charge

State of charge (SoC) refers to the current energy level of your electric car battery. The lithium-ion battery used in electric vehicles is designed to charge faster at a lower state of charge (e.g., 30%) than at a higher state of charge (e.g., 80%).

So, after plugging in electric car charger, your EV will most likely charge faster when the battery level is lower than when you have an almost full energy level. This is to help protect the battery from overheating and early damage.

Battery health

Electric vehicle batteries are designed to last for up to 10 – 20 years. However, as the battery ages with time, the resistance level increases. That means the amount of power the battery can accept declines as it ages to help sustain its life.

That being said, you can expect your electric car’s charging speed to decline as the battery starts ages.

Battery temperature

Outside temperature is another major factor that causes slow battery charge. Virtually all batteries, including those in electric vehicles, are designed to work best at an optimal temperature of 20°C. Any significant increase or decline in temperature can damage the battery.

So, EVs are built with a Battery Management System (BMS) that regulates the charging speed to match the current temperature level so that the battery is not damaged early. Also, during extreme temperatures, the EV may utilize some energy to warm up or cool down, reducing the charging speed.

Using other car systems while charging

In most cases, when you’re inside your EV while charging, the air conditioning system or heater, radio, or any other battery-consuming device may be on.

In that case, the charging rate will be relatively slow because some of the battery energy is utilized to sustain the devices or systems that are working while you charge.

Simultaneous charging

Lastly, if you have two chargers installed and connected to one power source, they must share the power output when you charge your electric car simultaneously with another EV. This can also slow down your car’s battery charging speed rate. Also, EV charging speeds are a function of the type of charger.

Is Slow Charging Bad For Car Battery?

No. Slow charging is okay for your electric car battery. EV experts recommend using slow chargers for your electric car battery because it utilizes low voltage and stabilizes the ion. But, you need to solve the issue of slow charging.

However, using a fast charger occasionally, especially to boost your EV’s battery for a longer trip, may not impact the battery. Nevertheless, fast charging your EV too often will cause the battery capacity to decline and reduce its lifespan in the long run.

How Can I Increase My Car Charging Speed?

Warming up or preconditioning your electric car is the major strategy to increase the charging capacity. Preconditioning is done around 30 – 45 minutes before arriving at a charging point, optimizing the battery’s temperature and preparing it for fast charging.

There are several ways to precondition your electric vehicle’s battery, manually and automatically. If you drive a Tesla, the Trip Planner is a valuable feature that can help you precondition the EV as you approach a supercharger location.

You can check your owner’s manual to find out the exact method of preconditioning your EV if you own any other brand.

Why Do EV Batteries Charge Slower When Almost Full?

EV batteries charge slower when almost full to prevent the battery from overheating, which can reduce the capacity and lifespan. Charging an electric car battery is like pouring water or wine into a glass.

Usually, you would be fast when you start pouring; then, you slow down gradually as the glass fills up to avoid spilling the liquid all over the place.

So it is for EV batteries, as they can charge fast from a lower charge state (e.g., 20%) and automatically decline and start charging slowly once the charge state attains around 80% or thereabout, depending on the EV.

No wonder most manufacturers recommend that you do not charge your EV battery full; first to avoid a decline in the battery capacity and lifespan. Secondly, to avoid always waiting unnecessarily for a full charge once your battery attains a specific high state of charge.


Do not panic unnecessarily when you notice your EV battery charging slow. It is either a regular occurrence, especially if the charging speed declines when the battery charge state increases to a certain level.

Also, if you experience this situation during winter, there’s no need to worry because it is not unnatural for EV batteries to charge slowly during cold weather. However, preconditioning the battery can be a way out.

Meanwhile, if any of the above is not the case, you’re still wondering, “Why is my car charger so slow?” Then, you should monitor the occurrence to see whether the cause aligns with any of the reasons stated in this article and contact your EV technician as soon as possible.


Mr. Shafiqule Islam is a graduated Mechanical Engineer and has more than 15 years experience of repairing and maintenance of different brand vehicles like Toyota, Mitsubishi, Ford, Mercedes, BMW etc. He is also giving training to Mechanics. He has started writing to share his practical knowledge to Vehicle Owners, Drivers and Mechanics to keep their cars at best fit.

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