In the electric vehicle (EV) world, understanding the state of health (SOH) of a battery is critical. Many drivers, especially those with the latest EVs, are increasingly turning to OBD2 scanners to check the condition of their vehicle’s battery. Recently, Jakob S., a Hyundai Ioniq 6 owner, shared an intriguing post in a forum after using an OBD2 scanner to check the battery’s SOH after 35,000 kilometers (roughly 22,000 miles). Jakob found that his vehicle’s battery was still showing 100% SOH, but he had doubts about the accuracy of this reading, asking if it was a hoax or if the battery health would suddenly drop as time went on.
Jakob says, “I just bought myself an OBD2 scanner because I was too curious about the state of health of the battery after roughly 35,000 km (sorry for using the metric system, but consider it a helpful nudge to start using a proper system of measurement). Turns out, the state of health (SOH) is still 100 percent. My question is whether this is truly accurate or if, at some point, it might suddenly drop from 100 to, for instance, 95 percent, like some of the iPhones I've had. In other words, is it a hoax due to a measurement error, or can it be that it’s still at 100 percent? I charge at home 95 out of 100 times, usually in the range of 20-80 percent, with half the time spent in a more narrow range from around 35 to 70 percent. By the way, if anyone knows how to set up an API and import data to R automatically, please let me know.”
Jakob’s question resonated with many members of the community, sparking a range of responses and offering a deeper dive into how the SOH is calculated in modern EVs. After all, understanding the science behind battery health is not just about curiosity, it could potentially influence how we drive and maintain our cars over time.
Understanding the State of Health (SOH) of EV Batteries
State of health (SOH) refers to the overall condition of a battery relative to its original performance and capacity. SOH is crucial because it helps you understand the potential lifespan of your EV's battery and whether its performance is degrading over time. However, while most people are familiar with the concept of battery degradation in smartphones (where the battery's health tends to drop noticeably after a few years), EV batteries tend to degrade at a much slower pace, especially if they are charged and maintained properly.
But how is this SOH value calculated? In most cases, SOH is determined by comparing the current capacity of the battery to its original capacity when it was new. The higher the number, the healthier the battery. Some manufacturers use complex algorithms to estimate the SOH based on a variety of parameters such as the battery's voltage, temperature, and charging cycles. However, unlike smartphones, where the degradation is often reported through direct observations (e.g., shorter battery life between charges), electric car manufacturers may have their own methods for calculating SOH, which can sometimes make it difficult to determine whether the reading is 100% accurate.
The Mystery of the 100% SOH
Jakob’s case raised an interesting question: is it possible for an EV battery to maintain 100% SOH even after 35,000 kilometers? Some users weighed in with their insights. For instance, Fernando Miguel, a member of the forum, shared an explanation about the Hyundai Ioniq 6's system. He stated, “EGMP systems (Hyundai/Kia) tend to report state of health (SOH) differently from other manufacturers. Since they don't consider the buffer as part of the SOH report, it will show 100% for a longer period compared to other systems. This could also explain why your vehicle is still reporting 100%.”
This brings us to a critical point: SOH readings can vary between manufacturers and models. Hyundai’s method of calculating SOH may be different from that of other automakers. For instance, the battery management systems (BMS) in many Hyundai and Kia vehicles, such as the Ioniq 6, don’t count the buffer, an extra portion of the battery’s capacity that is intentionally left unused to prolong battery life, as part of the total battery capacity. This could lead to the vehicle reporting 100% health for a longer period, even though the battery’s usable capacity may have decreased slightly.
On the other hand, Bogdan Teleman, another forum user, offered a counterpoint, suggesting that a more direct approach to measuring battery health could reveal degradation. He said, “It is not true. You can charge it to 100% and see the battery capacity. For a new car, it is ~74 kWh. Yours will be ~71.” According to Bogdan, the actual usable capacity of the battery might have decreased over time, even though the SOH percentage remains at 100%. This highlights the fact that while the SOH percentage might look pristine, the actual battery performance could have changed, albeit subtly.
The Search for Technical Details on SOH Calculation
David Rasmussen, another member of the forum, expressed frustration over the lack of clear technical details regarding how the SOH is calculated, saying, “I cannot find any technical details on how the SOH is calculated for our cars.” This is a common issue for many EV owners. While we can check the health of a battery using tools like OBD2 scanners, manufacturers often do not release detailed information on how exactly the SOH is calculated, leaving many drivers to wonder whether the readings are truly accurate or whether they are being misled by vague or overly optimistic readings.
In many ways, this lack of transparency adds to the mystery surrounding EV battery health. Without access to the underlying algorithms or formulas used by manufacturers, drivers are left in the dark about how their vehicles’ battery health is being assessed. It also creates confusion for drivers who are trying to understand whether their battery will experience a sudden drop in capacity or if the current state of health is genuinely reflective of the battery’s true condition.
EV Battery Degradation: What to Expect?
One thing is certain: EV batteries do degrade over time, and this degradation is usually a gradual process. While modern EV batteries are designed to last for several hundred thousand kilometers, it’s important to keep in mind that all batteries will eventually lose some capacity. Several factors contribute to battery degradation, including charging habits, climate, and the number of charge cycles.
If you’re concerned about EV battery health, there are a few things you can do to maximize the lifespan of your battery:
- Avoid frequent fast charging: Rapid charging generates more heat, which can accelerate battery degradation. Opt for regular charging at home whenever possible.
- Keep the battery charge between 20% and 80%: Charging the battery to its full capacity or letting it drop too low can also strain the battery.
- Monitor battery temperature: Extreme temperatures can damage batteries, so try to avoid exposing your car to prolonged heat or cold.
Additionally, if you're wondering about EV battery technology and what the future holds, recent innovations promise even better battery performance and longevity. In fact, EV battery makers have promised quicker charge times and longer range as part of the next wave of battery technology. For instance, manufacturers have announced that new technology could soon enable 5-minute charge times and better battery range, further reducing concerns about battery degradation over time.
The Bigger Picture
In conclusion, while it’s certainly possible that Jakob's Hyundai Ioniq 6 is indeed showing 100% SOH after 35,000 kilometers, it's important to understand that the way SOH is calculated can vary significantly between different manufacturers and models. The value might not reflect the actual usable capacity of the battery, and some vehicles (like the Hyundai Ioniq 6) may show artificially high SOH readings due to the way the system handles buffers and capacity estimation.
This highlights an important lesson for all EV owners: it's crucial to understand that SOH readings, while useful, are just one piece of the puzzle. To get a clearer picture of your vehicle's battery health, it's important to also consider other factors such as charging habits, temperature, and the battery's actual performance over time. As manufacturers continue to improve their BMS systems and release more detailed information, we may be able to gain a clearer understanding of how EV battery health is truly calculated.
If you're looking for more insight into your EV’s battery, you might find this detailed breakdown of common EV charging problems helpful: I’ve Been Getting an Annoying Dialog Box When Charging My Hyundai Ioniq 6 and My Car Will Turn.
Moreover, if you're curious about how the Ioniq 6 compares to other models, like the Model 3, this comparative review of the Ioniq 6 and the Tesla Model 3 could be an interesting read: New Ioniq 6 Owner Compares It to Her Previous Model 3, Presenting a Contrasting Viewpoint.
Engagement Questions for the Comment Section:
- Have you ever checked the state of health of your EV battery? If so, what did you find, and were you surprised by the results?
- What are your thoughts on the differences in SOH calculations between various EV manufacturers? How transparent do you think they should be about these processes?
Narek Hareyan is a young automotive journalist with experience in a golf cart dealership and an interest in the automotive industry. Follow Narek on X for daily news coverage about cars.
Comments
This is because like other…
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This is because like other manufacturers, Hyundai slowly unlocks some of the buffer (unusable capacity) of the battery over time to hide degradation. On an Ioniq 5/6, the SOH PID will show 100% for many years and won't drop below that until about 7% of the capacity has been lost.
As a retired EE, lithium…
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As a retired EE, lithium battery lifespan is more about charging cycles. Most phone batteries get charged nearly daily. So in 3-4 years time it is charged ~1000-1200 cycles. By this time the batteries are never close to new SOH. This helps explain the mysterious long life of many EVs. A wise person doesn't recharge daily (Level 2 home chargers) UNLESS it's absolutely necessary to get to your destination.
On the ICCU failures, which is distressing to say the least, remember our Hyundai & Kia products are common when electrically speaking. They share a 800V architecture while most are limited to 400V. When AC charging, HV MOSFETS are used to convert AC to DC in order to charge the main bank. Switching transients can damage these devices IF voltage limiting devices, MOV (metal oxide varistors) are not used. These devices vary in size based on the peak SAFE voltage. Go over this level and they become low resistance, thereby protecting from damaging voltage transients. Then there's the potential for transient shorts when the AC sine wave crosses the zero volt region.This is precisely when the rate of change is at a peak. I nearly spent $2k for a home charger like many do for convenience. Nightly charging will shorten it's lifespan. I'm retired and have 4 fast (DC) chargers less than a mile from my residence. A quick swing by and 20 mins later my I6 is at 80% percent of capacity.
Until Hyundai/Kia can make the needed updates to make it the ICCU 'bullet proof', by all means stick to DC charging on longer road trips. I will change my Aux battery to a LFP type which can sustain discharge to < 20% and recover without issue, while a lead acid often gives up below 50%. SOH, requiring towing + replacement. A 100 Ah LFP weights 1/4 that of a acid battery and provides 2X the capacity. So even if the ICCU develops a failure, you at least have 2X AUX capacity to get to a dealer, home or just off the freeway/Interstate highway. Monitoring the LFP voltage is the sole means to know if it crapped out at the last AC charger used. It is virtually impossible to damage the ICCU when Fast charging. Lithium batteries never "see" A/C voltage when this tactic is used. A group 47 LFP can be had for ~$250. Not much more than a 'ancient' flooded type, AGM or not. It is cheap insurance. Flooded batteries are intended for constant charging also. LFPs can handle constant charging without issue. Enjoy your EV but when you truly don't want to risk a breakdown use DC charging and plan your stops accordingly.. I realize this may not be possible based on your route. Reliability of some charging stations are not adequately maintained to ensure availability. Boycott these businesses if possible. The Korean's are smart, but may not have protection where it's needed presently. They will figure it out and modify every ICCU if necessary. Stay safe everyone and enjoy your EV.