Scoring Methodology

How is the vsNEW score calculated?

vsNEW does 3 things - 1) show your battery’s current capacity and degradation, 2) tell you if there are any warning signs of premature failure, and 3) check for any indication of physical damage. All three of these factors go into your vsNEW score.

Our goal is to do this within 2 minutes, regardless of the temperature or charge level of the battery.

1) Battery capacity and degradation

While EV batteries degrade over time, most EVs retain more than 80% of their capacity even at 10 years of age. However, depending on individual charging and driving habits, batteries may degrade faster. For this reason, it is important for used EV buyers to look at vehicle specific battery data, since average degradation statistics aren't meaningful to any given EV.

The only perfect way of measuring a battery's capacity is coulomb counting, where you drain a battery and then slow charge it, counting how much energy goes into the battery, all while keeping it at an optimal 70F temperature. However, this method takes between 8-24 hours and requires an EV to be plugged into a charger. Dealerships and most people aren't going to do this.

However, every OEM measures and tracks various metrics related to battery capacity for each of their vehicles and stores this information in the vehicle’s BMS (battery management system). Many OEMs use this value to determine if a battery should be replaced under warranty, which indicates how reliable OEMs consider this value is to be. vsNEW uses this same value to show your battery’s capacity.

2) Premature battery failure

There are several causes of premature battery failure, with the most common being individual cell failure. In these cases, the battery becomes irreparably out of balance, and the BMS will restrict the max state of charge to prevent a possible safety risk. Based on our data, we expect cell failure to occur in 5% - 10% of original EV batteries, with most incidents occuring within the warranty period. We expect higher failure rates for remanufactered batteries, which are often used as warranty replacements.

We collect all available data from the BMS including - 96 or more individual cell voltage sensors, temperature sensors, logs of fast (DC) and slow (AC) charging cycles, incidents of storage at 100% or 0% charge levels, internal resistance values (which measures battery degradation on a per cell or module basis), and other metrics.

We use this data from your EV, combined with our database of thousands of similar EVs, and a set of continuously refined algorithms to determine signs of premature battery failure.

3) Physical battery pack damage

Physical damage can also lead to battery pack failure. Possible causes are accidents, poor repairs, and even normal wear and tear over time. In many cases, physical battery pack damage is hard to see.

The BMS tracks several measures of the battery pack's physical integrity, which vsNEW uses to determine signs of possible damage.

How we get BMS data

By plugging into your vehicle, we read your BMS data within 2 minutes, upload your data into our cloud AI system, and generate a battery health report.

Common questions -

Why can’t I look at the dashboard and divide the displayed range by battery charge level to see my max remaining range?

Most OEMs vary the displayed range based on temperature and recent driving history. Called the guess-o-meter in these cases, the displayed range is unreliable as a measure of ideal range. In the case of Tesla, the displayed range is closer to an ideal range, but does not include reserve capacity and has been alleged to be unreliable at higher charge levels.

In our testing, this calculation’s error is up to 20% of OEM measured capacity. In addition, this method ignores the risk of cell failure or physical damage, which may not be apparent with a visual inspection.

What about range reports that are based on telematics data?

Telematics data offers displayed range, charge level, and a few other metrics. We believe these reports are helpful to owners to track driving and charging habits, but the data is insufficient to determine battery capacity, premature battery failure, or battery health. Our testing shows the same error of up to 20% of OEM measured capacity. Again, this method ignores the risk of cell failure or physical damage, which may not be apparent with a visual inspection.