First: What is battery health for a Tesla?

Battery health is a difficult concept to define precisely. In simple terms, it refers to how well a battery performs compared to when it was new. In scientific literature, battery health is often referred to as "state of health" (SoH), a metric used to assess the overall condition of a battery. But what exactly this means – and how you measure it – can vary. 

One of the most straightforward ways to measure battery health is by comparing the original battery capacity, measured in kilowatt-hours (kWh), to its current capacity. 

The difference between these values indicates how much capacity the battery has lost over time. This is called capacity fade. Various methods can be used to measure this, including tracking energy input and output during charging and discharging. 

A more nuanced aspect of battery health is power fade, which refers to an increase in internal resistance that hampers the battery’s performance. This degradation is caused by unwanted chemical reactions inside the battery that obstruct energy flow. Power fade often goes hand in hand with capacity fade, but it's harder to diagnose.

While battery health is often a mix of both capacity and power fade, for EV drivers, it ultimately means how far the car can go on a charge and whether it still accelerates as efficiently as when it was new. Though the concept is complex, there are several ways to measure battery health, from tracking capacity loss to monitoring power fade, ensuring you have the information needed to assess a battery's condition.

Checking battery health: Tesla ‘grading its own homework’

Tesla offers two battery health diagnostics. The first is 

• A quick, in-app scan that can alert you to any obvious issues.
• A 24-hour, in depth process that requires you to put your car in “service” mode, which is not for the faint of heart. 

Andy Slye performed the service mode test here. 

The simpler version – an app-based diagnostic – requires you to log in, tap “Request Service,” select “Battery & Charging,” and then choose “Range.” This will compare your car against expected degradation and battery health metrics. 

Checking the battery with 3rd party Tesla analysts

If you’re looking for a trusted, data-driven solution to understand your Tesla’s battery performance, Recurrent now offers Battery History for Tesla drivers. Battery History is an estimate of the battery’s current capacity to be compared to the marketed capacity of this vehicle when new. 

This is free for Tesla owners in the US. Simply connect to the Recurrent platform to get started. It can take a week to calculate an accurate reading, and will update its data each week after that. 

Checking the battery if you don’t own the car

If you watched the Andy Slye video (above), you’ll see that he mentioned Range Score, which is available for most used EVs in the US. Enter the car’s VIN here to look at the Recurrent Report. 

Range Score compares expected range today to the vehicle’s range when new. It’s a number out of 100, that can actually go above 100 for some vehicles. Range Score values are also displayed for car shoppers on many marketplace sites, like Cars.com.

Range Score does not replace a test drive or a formal battery diagnostic, but it provides an expectation that you can confirm when evaluating the car in person.

What Can You Do About a Bad Battery?

If you’re concerned about the health or performance of your Tesla battery, it’s a good idea to connect to a service like Recurrent to keep tabs on it. Then, you may consider getting an add-on battery insurance from a company like Amber or XCare, both of which have partnered with Recurrent to give our drivers and readers promotions for their battery warranties. 

However, most EV batteries are lasting much longer than people expected. That should give you confidence as a Tesla owner.