Home » Blogs » Troubleshooting » Why Won’t My Tesla Charge To 100 Percent? [Solved!]

Why Won’t My Tesla Charge To 100 Percent? [Solved!]

Steve

October 5, 2024

9 comments

So if you are concerning that while charging your Tesla, it is not going beyond a specific percentage.

Tesla is not charging to 100% and stuck at somewhere around 90% or anywhere (which can be a recurring issue too).

Or it may also say that charging is complete while you see it stuck at incomplete charge level which is well below 100%.

In almost 99.99% case, this is a common internal battery charge level measurement related issue and you can solve it.

Apart from that, there could be some other wrong happenings as well, but it’s so simple to detect.

So I will show you everything about it here including why is your Tesla not charging to 100 percent and how you can solve it.

So let’s first look into the cause behind Tesla’s unable to fullly charge issue with its solution.

Why Is My Tesla Not Charging To 100 Percent

A Simple Cause Before Anything

So here a simple thing you just confirm first before you do anything else, just check the current charge limit set in your Tesla, if charge limit is set with certain percentage below 100% then it won’t let the battery to charge above it.

You can just go to charging controls either from in-car display or Tesla app and check.

If that is the issue then by altering the charge limit will solve this issue.

If you see that charge limit is not set or set to 100% already then you need to look at other things, I am going to explain here.

Important Note:

I am assuming that all the hardware including the charger and its components like cables, plugs, etc. are working perfectly. So you need to ensure that also.

But I am not delving into that side, because if Tesla is being charged perfectly till a point then probably all those hardware issues are not there.

Now let’s look at the thing which is something internal to the battery and battery management system, which has the highest chance of causing this issue.

Tesla Battery Charge Level Measurement Error

So if your Tesla is not charging to 100% then most probably this is the issue.

What happened is Tesla BMS (Battery Management System) failed to accurately measure the charge level.

That is a normal happening don’t worry!

Especially this happens inevitably with Lithium-ion batteries due to its internal chemistry. I will explain why.

Tesla uses Lithium ion batteries to power the drive.

The earlier model than 2021 were having Lithium Nickel-Cobalt-Aluminum Oxide (NCA) batteries.

But after 2021 Tesla started to use Lithium Iron Phosphate or lithium ferro-phosphate (LFP) batteries. They implemented this in their latest Tesla standard range model 3 and Y.

Because LFP batteries as of now showing more efficient performance in terms of lifespan and other qualities than NCA battery.

So, Tesla may introduce LFPs in more models coming time.

Essentially both are Lithium ion based batteries.

Root Cause of Battery Charge Level Measurement Error

In simple terms, the BMS measures the charge level by measuring the difference of level of voltages in battery cells at different storage potentials.

If battery cells are fully stored with potential voltages, then it will show you 100% State of Charge.

While gradually once the potential gets in use to drive the car and other things, the voltage level decreases in battery cells. And so you will see a decreasing State of Charge in terms of percentage.

But the thing with Lithium-ion batteries is, that the charge and discharge of voltages in cells happens so gradually that it becomes almost difficult for the BMS to show an accurate level of charge within battery cells.

However, Li-on batteries charge-discharge happens with sheer steep when at high voltage level or Depth of Discharge above of 90% and low voltage level or DoD below 10%.

So the journey between 90% and 10% is almost identical at every point.

At two different potential values, there is not much difference in voltages, so it becomes difficult for the BMS system to measure the actual charge level of battery.

As shown in the image below with the graph, comparing the charge-discharge curve of Lead-acid vs Lithium-ion batteries.

So what could happen at such time is, either while driving you get the wrong estimation of remaining range of Tesla because it failed to measure the actual charge level of the battery.

At such time your Tesla may have much left range but because it failed to measure the actual you may see much low charge level, or it may show higher level of charge but in reality nothing much has been left and then at a point the charge level will suddenly drop.

OR

While charging, you get wrong measurement of charge level vs actual charge level. So at that time you will see that Tesla is not charging to full 100%.

It got stuck somewhere in between and not moving ahead in charging.

Or you may see Tesla will declare the charging as complete but actually, it will show the incomplete charge level, e.g. it will show that 94% is charged and charging is complete.

So here it may be possible that the battery is actually full but showing a lesser percentage or the battery charge level actually may be incomplete but BMS measurement error not allowing it to charge further.

However, this does not happen all the time, but this happens frequently.

Again, with different kinds of Lithium ion batteries, such things vary by frequency. Let’s look at that.

Tesla with NCA battery and LFP battery

Now, as you know Tesla uses two different kind of battery in their car, NCA and LFP in different models.

Now, if you have Tesla with NCA battery, you may not face this too frequently but if you have Tesla with LFP battery then you will see this happening quiet frequently.

This is because LFP battery has lowest voltage stored per cell compared to other batteries. So it shows the most and nearly flat curve of charge and discharge pattern, so BMS gets confused in measuring the actual charge level very often.

As shown in below image, LFP batteries show the flattest charge discharge curve among other Lithium ion based batteries like NCA and NMC.

It is because in daily use, we normally don’t get chance to charge Tesla to 100% or it normally remains between 20% and 80% or 90%.

So the battery cell voltage goes into imbalance, i.e. the cells won’t charge the voltages to its full capacity. And different cells will have stored different levels of voltages. That is called battery cell unbalancing.

That adds up to BMS not being able to read the actual charge level of battery.

Plus, as you know, the Li-on battery has a steep charge discharge curve below 10% SoC and nearly 100% SoC.

So only at that time BMS will get the accurate measurement of the actual charge level. Because at that time there is much potential voltage difference at two different points so it becomes easy for BMS to measure the charge level.

So anywhere in between 10% to 90% SoC, BMS won’t be able to measure the difference of voltages between two points of potential voltages, because there is not much difference of voltage level.

So two things come into play, cell unbalancing and BMS SoC reading error.

And possibility of this scenario is higher in LFP batteries than in NCA batteries.

So what you can do about it?

Solve The Issue of Tesla Not Charging to 100 Percent

A Temporary Solution for the Time being

Now, if you see that Tesla battery is stuck and not charging ahead, then you can try couple of ways as I will explain now.

Most of the cases it will work and solve the matter for time being and your Tesla battery will continue to charge to 100%.

This would calibrate the battery and so Tesla BMS will allow to charge ahead.

But if that doesn’t work, you need to fully calibrate the Tesla battery, I will explain in later section how to do.

As of now try the steps below,

Steps,

• Use the Tesla battery for some 5% then again start to charge.
• Either you can drive your Tesla a bit or use with enabling climate control.
• Then continue charging session, so you may see Tesla continues to charge to 100%

OR

• Wait for some time and then start the charging from Tesla app.
• This may continue the charging session.

If this worked then again remember you still need to calibrate the battery at the earliest opportunity.

And, if this doesn’t solve the issue for the time then you need to fully calibrate the battery.

Recalibrate the Battery Management System – Proper Solution

The only thing it needs is, if you reset the battery or recalibrate the battery in Tesla it will then make the charge level easy to read and measure for BMS.

Now it has two things in the issue involved, cell balancing and calibration.

Both has to be in its proper place to solve this issue.

As you know the BMS can get accurate charge level measurement only when battery is below 10% or above 90%.

So to reset the system or recalibrate, in laymen terms you need to charge Tesla battery from nearly empty to 100% fully.

That will make the BMS system again calibrated with cells properly balanced with stored voltages and BMS will show you accurate battery percentage.

But as it involves cell balancing and calibration to solve the issue, you need to follow certain important steps.

You can follow the below steps explained in-detail with certain things to take care to properly calibrate the Tesla battery and balance the battery cells.

Steps,

First Do Battery Calibration For BMS

• Let Tesla battery fall below 10%
• Let it remain for few hours at that SoC (2-4 hours at least)
• Make sure Tesla car remains in deep sleep (i.e. no sentry mode and turn OFF any apps which makes it awake)

This will calibrate the Battery Management System. And also the battery cells will be fallen to same voltage stored in each by then.

And then you can do cell balancing.

Then Do Cell Balancing

• Now you put Tesla to charge
• Charge Tesla to Full battery
• You can set the charge limit to 100%
• Now, even if you see Tesla showing 100% charged but still drawing energy, then let it draw
• Leave it until it indicates no charging or energy is being added to battery

(This can even take hour or more even after showing 100% SoC to stop drawing the energy)

• Eventually, the battery will stop charging

So this will do BMS calibration and cell balancing and it will solve the issue of Tesla not charging to 100% or full.

Some Confusion Regarding Battery Degradation

Now, this cell unbalancing happens frequently in LFP batteries.

So Teslas with LFP batteries now getting charge limit recommendation of 100% even in daily use.

Plus, Tesla recommends that at least once per week you should charge Tesla 100% if daily is not possible for you.

But then some people are discussing that earlier Tesla recommended setting charge limit of no more than 80% because it would be best option as least impacted battery degradation, but now asking to set charge limit of 100%.

Many Tesla owners are getting a notification in their Tesla in-car display and in Tesla app to set charge limit of 100% even in daily use and asking to charge Tesla to 100% at least once a week.

So it is because of certain behaviour of LFP battery, that Tesla recommends to set charge limit of 100%, for cell balancing and calibration.

However, the battery irrespective of NCA or LFP subjects to degradation at high State of Charge or Depth of Discharge.

But, due to low voltage per cell and battery chemistry LFP battery shows lesser degradation and overall longer lifespan than NCA batteries.

So it is totally Ok to set charge limit of 100% in Tesla with LFP batteries without worrying about battery degradation.

However you can continue to have regular charging practice and recommendation if your Tesla is equipped with NCA battery.

You can refer to more details about recommended charge limit and battery degradation of Tesla in this article.

Conclusion

I hope now you are clear about why your Tesla won’t charge to 100 percent knowing the underlying issue and how to solve it.

Ok then I will see you in the next article!

FAQs

Why doesn’t Tesla charge to 100%? | Why is my Tesla not charging fully?

The main reason is battery cell unbalancing causing Tesla’s BMS (Battery Management System) to have an error measuring the actual charge level. So it will show you Tesla charging is complete even before it hits to 100%. For this, you have to do cell balancing and BMS calibration to solve this error. It will solve the issue and you will be able to charge your Tesla to 100%. This is common with Lithium-ion batteries used in EVs, especially more with EVs having Lithium Iron Phosphate (LFP) batteries.

Apart from that a common reason is a charge limit is set well below 100%. In this case, it won’t charge to 100%, it will stop charging once it reaches the charge limit. So unless you remove or increase the charge limit charge level won’t go beyond that limit. This is a very common human error causing this issue. Sometimes looking at your charging habits Tesla automatically fixes a limit to protect battery health, while sometimes you have set a limit and forgot about it. So in both cases, you have to disable or increase the charge limit to charge your Tesla fully.

Can you charge LFP to 100%?

Yes, you can charge and you should charge 100% at least a week or twice a month. LFP batteries are more stable and show a flatter charge-discharge curve resulting in cell imbalancing making BMS mismeasure battery level percentage more often. So

Is it OK to charge Tesla battery to 100?

Yes, it is completely OK to charge Tesla to 100%. But it more depends on the type of Lithium-ion battery your Tesla has. With Nickel-Cobalt-Aluminum (NCA) and Nickel-Cobalt-Magnesium (NCM) batteries, concerning battery health, it is best to stick to occasional charging to 100% when needed unless you regularly drive 100 or 200+ miles a day. While Tesla with Lithium-Iron-Phosphate (LFP) battery concerning cell imbalance you should let it fall below 10% and charge to 100% at least once a week or twice a month. Because, NCA and NCM batteries show less cell imbalance but more degradation at very high and low SoC while LFP shows more cell imbalance and lesser degradation at high and low State of Charge (SoC).