Why is My Tesla Charging Slowly? This is Why!

Most Tesla owners charge their vehicles daily at home, but what happens when the charging time reduces or is slower than normal? Read on to find out why this is happening.

Reasons your Tesla is charging slowly include:

  • Battery too cold
  • Supercharger at 80%
  • Charge cable too long
  • An update has occurred
  • Your Tesla has some age

In this article, we’ll look at why your Tesla is charging slowly and how to fix the problem.

Tesla parked on snow covered street

Tesla Battery Too Cold

If your Tesla is not sufficiently heated or preheated, then charging your vehicle will take longer.

The onboard computers in your Tesla communicate with the charging system, and although charging will begin, the charge rate will be slower if the ambient temperature is low. This protects the high-voltage battery from getting too hot too quickly and damaging the Lithium Ion cells.

This problem is more prevalent if you live in a colder climate, but that doesn’t mean you have to give up your EV dream! Norway has the highest proportion of EVs to ICE (Internal combustion Engines) at 65%. Tesla thinks of everything. Before you charge in cold conditions, you can set up a Schedule Departure.

  • Open the Tesla App
  • Select Schedule Departure
  • Enter the time that you think you are going to depart
  • Select Climate
  • Turn On
  • Defrost On

This will warm the car before charging and still have your car charged when you are ready to leave. This is the car and computer’s way of preheating the Lithium Ion cells in your battery to the correct temperature so that normal charging can occur.

Supercharger at 80%

Supercharging differs from charging at home because it uses DC (Direct Charge). This is a much faster way of charging your Tesla; however, the heat being transferred to the high-voltage battery is greatly increased.

When you connect to the Supercharger, the charging level will quickly increase to 80%, and then the speed drastically reduces as it grows from 80%-100%.

The reality is that unless you’re going on a long journey and need 100%, then 80% is sufficient for a charge. Although Supercharging is the Tesla network and it is there to be used, it is recommended by Tesla only to Supercharge when necessary and to only charge 80%.

Supercharger Faulty

The Tesla Superchargers are constantly monitored and serviced, but let’s face it; there is over 3000 plus of them! And occasionally, you’ll plug in, and there’s a fault. The fault may not be with your Tesla but with the Supercharger, and it may not be instantly apparent. Your car might be charging but at a much lower rate than normal.

The solution is to move to another charger (if available) and restart your charger. It’s unlikely that another charger at the same location is also faulty, but it does happen.

My best advice is to move to where a car has just finished charging as you know it is working properly.

Shared Supercharger

If you are at a Supercharger that someone else is already charging at, on the other side, the charger may be reduced in speed when you begin to share.

There’s only so much power available at a charging station, and sometimes, this can be reduced by the grid being limited at certain times of the day or week if a station is more popular than normal; Tesla combats this by limiting the charge for everyone to 80% so everyone can get in and out as quickly as possible.

In this case, it’s no fault of the Tesla driver, but merely everyone has decided to charge simultaneously. You could try an alternative location if 100% necessary.

Charge Cable Too Long

The charge cable supplied with your Tesla or Tesla Level 2 setup is the optimum length.

But not everyone’s charging situation is standard. You may not be able to park directly beside your charging station (Level 1b or Level 2), and the only option is to order a longer cable.

Needs must sometimes! But the charging of your car may take longer than the suggested time with a longer cable.

This is because the longer the cord, the higher the electrical resistance. If we get a bit scientific for a minute: Resistivity = Length / cross-sectional area, meaning it will take longer to charge your car.

However, EV cables are made of high gauge, and this will hopefully negate the resistance. The higher the cable quality and the thicker the cable will reduce the resistance of the electricity.

An Update Has Occurred

Tesla constantly sends OTA (Over the Air) updates to your car to increase driveability and overall performance.

Sometimes the OTA updates can cause glitchiness, which can materialize as a slowing down in charging.

But this is nothing to be overly concerned about, as it means your Tesla needs to get back in sync.

The easiest way to do this is by completing a Soft Reboot or Reset.

This is done as follows:

Soft Reset

  • Shift into Park
  • Remove any devices
  • Hold both scroll wheels on the steering wheel for 10-15 seconds
  • The touchscreen turns black
  • Tesla Logo reappears
  • Everything will once again be available

Suppose the problem persists, and you feel the latest update is the reason for your slower charging. In that case, it is worth trying to install the update again, as occasionally updates don’t fully download properly or completely and can cause other problems.

I wrote an article all about Tesla downloads which you may find useful – Tesla won’t download update

Your Tesla has Some Age

Like any machinery, or for that matter, computers, items, and components wear out over time. Your Tesla’s battery is no different and will not perform as it once did as it gets some age behind it.

Tesla batteries can last 300,000 to 500,000 miles or 1500 battery cycles.

Although the battery will last up to 25 years, the warranty is much less than this. Each Tesla has an 8-year / 150000-mile warranty and a 70% minimum battery retention.

But your battery’s life depends on how you look after it. In general, it’s expected to lose 2-3% retention per year, and as the miles and years clock up, this can increase to 20-25% on a Tesla with 300k miles.

You should keep your SOC (State of Charge) between 20-80%. Continually allowing your Tesla to drop below 20% can degrade the battery quicker, and the same can be said for charging to 100%.

Battery management is important to ensure your Tesla will normally charge even as it ages. If you own an older Tesla or a Tesla with high miles, you can easily check your battery health by doing the following.

To calculate the health of your battery, you’ll need to complete a long journey and gather the following information:

  1. Watt Hours per Mile
  2. Projected Range
  3. % of current battery
  4. kW Size of your Battery from new

To get the information you:

  • Go to your Touch Screen
  • Select Energy
  • Wh/M is the start of the graph
  • The projected Range is the endpoint
  • Battery % is Top Left Screen

The calculation is as follows:

Step 1Wh Miles * PR / 1000 = kWHours
Step 2Ans to step 1 Divided By Battery %
Step 3Ans to step 2 Divided By Original Battery Size

An example with actual figures inserted looks like the following:

Wh Miles: 280

Projected Range: 50 miles

Battery Range Remaining: 25%

Original Battery: 75kW

Inserting these figures into the formula then calculates as follows:

Step 1280 * 50 / 1000 = 14
Step 214 Divided By 25% = 56
Step 356 Divided By 75 (Depending on the model you own and year) = 0.746
= 75% range still available when charged to 100%

Upgrading some of the Li-Ion cells is possible but costly if you’re out of warranty. Tesla will check your battery and only switch out dead cells, but this can cost upwards of $3000-5000. But this does not include labor which can then push the cost to $10000!

It certainly helps to protect your battery health over time. No one wants a slow charge, but more importantly, no one wants an enormous auto bill.

I’ve written a ton on common Tesla issues, which hopefully you won’t ever experience, but if you do, we have you covered with these posts:

Check out the Tesla charging page for common Tesla charging problems.

Check out the Tesla troubleshooting page for problem Teslas.

Check out the Tesla category page for a list of popular Tesla posts.

If you are curious about other EV models, check out the EV FAQ category.

John Cunningham

John Cunningham is a technical writer here at EVjuicedup.com. He's a Red Seal qualified Auto Service Technician with over twenty-five years experience working on Classic and Modern Cars. He's worked for GM, Jaguar, Land Rover, Volvo, Audi, and VW main dealers.

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