When I bought my Nissan Leaf at 3 years old, it had 88% battery “health” as reported by the car. Battery degradation is inevitable with electric vehicles, it’s just a question of how much. If you’re interested in what affects battery degradation, I recommend Euan McTurk’s “Plug life Television” channel on YouTube.

The Hyundai Ioniq also reports battery health. At 30 months and 27,000 miles the car is reporting 100% via the “Torque” app which reports parameters from the battery management system. Note this is not the same as 100% charged. Even a very degraded battery can be 100% charged, but like an old phone, won’t run for long. Now we don’t know exactly how either Nissan or Hyundai calculate the “battery health”. And why should we care? What matters is how much charge the battery can accept- and, ultimately, the range.

I calculated roughly how much charge the Ioniq can take by charging from a fairly low state of charge. Naturally all the figures rely on some assumptions but let’s see how many kWh the battery can take-

The car showed 20 miles remaining out of 125 mile range, that’s 16% on the pack or 4.5kWh remaining. The Polar charger reports I used 25.7kWh at 7kW, which I know from a previous measurement is 95% efficient. So I added ~24.4kWh to the car. 24.4+4.5 = 28.9kWh

Compared to a nominal capacity of 28kWh (since I didn’t own the car from new, I don’t know how it behaved then), there’s little or no degradation there.

It’s entirely possible that the battery starts life at above 100%, a capacity of more than 28kWh, say 30kWh, and for the first few years degradation is hidden. Since the capacity depends on battery temperature, it’s hard to give a fixed figure. What matters is when the battery capacity drops below 28kWh and degradation starts to be noticed, in terms of how many miles the car can travel.

We do know that the Ioniq charges to only 95% of the batteries true capacity; to roughly 4.1 volts when it could be charged to 4.15 volts.This will help battery life.

Compared to my Leaf24 at a similar age, the car is at least twice as useful to me. I say this because the Leaf only ever managed one commute before needing a charge. It just didn’t quite have enough for even a gentle second commute on a short B-road route. The Ioniq can do two commutes, even using the motorway driving at the UK speed limit (70mph).

Conclusions I can make so far: the range is still healthy at 125 miles in winter and 150 miles in spring; the battery seems to be accepting more than the nominal 28kWh.

It’s also worth mentioning that some manufacturers quote gross battery capacity (Nissan, Tesla), others net, or useable capacity (Hyundai). Personally I think battery capacity as a nameplate figure is misleading, it’s like quoting fuel tank size. There’s much more to consider with EVs than just the fuel tank size!

3 thoughts on “Ioniq electric battery health at 2.5 years old- very healthy

  1. The battery charging total will always be higher than the battery delivery total. The difference results because of resistive (heat) losses within the cells, and within the charging circuitry. Further losses occur within the motor control electronics, so the power consumption measurements might need to be adjusted, depending upon which point in the control circuitry is being used. Modern Lithium-based batteries are well above 90% efficient during charging (i.e. total output power will be at least 90% of total charging power), when new, but Lead acid batteries are around 65% efficient when new (i.e total output power will be about 65% of total charging power. As cells age, their efficiency gradually decreases.


    1. You’re right, there are certainly losses. I previously measured a 5% loss on charging at 7kW, so included that here. This article is more concerned with the loss of battery capacity with time, due to time and charge cycles.


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