Is slow charging bad for your Tesla? What about trickle charging? Search up this question and you will find a range of answers, some of them contradictory and very few of them definitive.

Is it better for your Tesla battery to charge slowly and not suffer degradation due to heat, or is it better to charge slowly even if the longer charging time might result in battery damage? 

Key Takeaways:

While most tires on fossil fuel vehicles last an average of 50k-60k miles (about 4 years), tires on electric vehicles don’t last nearly as long and you may need to change them as soon as 15-20K miles.

As a general rule, you should start shopping for new tires one the tread pattern has about 4/32″ of an inch remaining.

While many tires are warranted between 45k-60k miles, electric vehicles like Teslas wear out much faster, meaning replacement can come as soon as 15k miles.

If you have a Tesla or are in the market for one, don’t worry unnecessarily about slow charging vs. supercharging.

Do what is best for you in terms of access, convenience, and your driving needs. Just make sure you follow Tesla’s existing guidance when it comes to battery charging. 

What Is Tesla’s Guidance on Battery Charging? 

Tesla doesn’t specify whether you should use supercharging or slow charging (or a combination) for your battery, since every driver has different needs.

Some people live close to a supercharging station, while others don’t have access. 

Some people may only need to charge their Tesla at home and not worry about supercharging, while others use their cars frequently and cannot wait the hours it would take for slow charging. 

Tesla engineers have taken all of this into consideration and made the batteries able to charge both ways efficiently and safely. 

Tesla has two official pieces of guidance when it comes to charging:

1. When you aren’t driving or charging your Tesla, try to keep the battery between 20%-80% capacity. Over or under-charging your battery will reduce battery life. 
2. Only charge your battery over 90% when going on a long trip or when you need additional battery life (you will not be near a charger, etc.).

Ok, so for sure you need to follow this advice. As far as whether to supercharge or slow charge, know that Tesla engineers are aware of the issues with both and are working to design the batteries accordingly. 

Is Supercharging Bad for Your Tesla?

It is true that in many cases, the increased current coming into a battery will increase the heat within the battery, and heat can lead to battery degradation.

For this reason, many Tesla owners have worried that supercharging with DC current (at Supercharger, Ionity or CHAdeMO) will reduce the life of their batteries. 

To combat degradation due to heat, Tesla has devised cooling systems that work to keep the batteries at a safe temperature during supercharging and include systems that monitor and reduce charging speed when safety and battery life require it. 

If you only supercharge your car occasionally, you probably don’t need to worry about the degradation of your battery due to heat from supercharging, as Teslas are designed to alleviate this problem.

But it is worth asking if slow charging is any better for your battery. 

Why is Slow Charging Bad for Teslas?

Slow charging (as compared to supercharging) uses AC current and is what you will find in most home-charging setups.

Slow charging certainly doesn’t generate the heat that supercharging does, so it would seem that it wouldn’t create the same risk of battery degradation as supercharging.

However, it has come up recently that there are other drawbacks to slow charging when it comes to battery life.

Engineers and owners disagree on the degree of damage done by slow charging, so until more information and data is available, you may have to charge simply according to what works for you.  

The inefficiency of Slow Charging

If you slow charge for long periods, charging losses will occur because more power will be lost through the resistance of the cables and connectors.

It is possible you will not even notice the difference; however, supercharging may be the most efficient charging option. 

Battery Damage due to “Parasitic Effects”

Charging a lithium-ion battery causes chemical effects to happen within the battery.

Recent evidence from research by Jeff Dahn and other battery researchers shows that the longer a battery is charging (whether fast or slow), the more likely these effects will be to degrade the life of your battery.

It seems to be the voltage rather than the power that is responsible for these effects.

In other words, your Tesla is exposed to a lot more harmful charging voltage over the course of a slow charge than a fast supercharge. 

Further, a slowly-charged battery may not reach its ideal temperature range for charging, which can increase battery damage due to parasitic effects. 

These issues can be addressed through temperature regulation and battery chemistry, and it appears that Tesla is working on these problems.

There are disadvantages to both supercharging and slow charging. Supercharging does heat batteries, and heat can lead to degradation. Slow charging can be more inefficient and may lead to damage due to charging duration. That said, if you follow Tesla’s charging guidance, your battery will most likely perform well and not be unnecessarily degraded. 

Is Trickle Charging Bad for Tesla?

Trickle charging is basically plugging your Tesla into a wall outlet and letting it charge slowly over the course of many hours or days. 

It will not overheat your battery or cause any of the harm that supercharging will, and some Tesla owners swear that they have close to zero battery degradation when using this method exclusively. 

This is a fine choice if it suits your lifestyle and amount of driving. If you can leave your car plugged in for long amounts of time, or you don’t need to charge up quickly for a long trip or several days of driving, it might be right for you. 

Keep in mind that you will experience the same parasitic effects of long charging by using this method, and you will have some charging losses due to the long time horizon and low power. 

Some Tesla owners prefer faster charging if they live in places with off-hour charging rates–for example if it is cheaper to only charge the car overnight.

Trickle charging will not allow you to take advantage of the cheaper rates at certain times of day. 

So Do I Charge My Tesla Fast or Slow?

Research is ongoing about what is the ideal way (or combination of ways) to charge your Tesla. 

For the most part, battery degradation has been fairly limited in Tesla batteries so far, so if you do what is right for your lifestyle, you probably won’t have many problems.