If you’re looking at a BMW i4, or already own one, battery state of health (SOH) is one of the most important numbers you’ll never see on the dash. It quietly tells you how much usable capacity your high‑voltage pack has left compared with when it was new, and it directly affects real‑world range, performance, and value, especially on a used i4.
Quick definition
On a BMW i4, state of health is the battery’s remaining usable capacity as a percentage of its original capacity (for example, 96% SOH means roughly 4% degradation). It’s calculated by the car’s battery‑management system, not by any single drive or charging session.
What “state of health” means on a BMW i4
Every BMW i4, eDrive35, eDrive40, xDrive40, M50, and the newer M60, uses a large lithium‑ion pack managed by a sophisticated battery‑management system (BMS). The BMS constantly estimates two things:
- State of charge (SOC): how full the battery is right now (0–100%), what you see on the dash.
- State of health (SOH): how big the “tank” still is compared with when the car left the factory. This is not shown directly in the BMW app or iDrive menus.
SOH is influenced by age, mileage, fast‑charging frequency, depth of discharge, temperature, and how the car has been treated overall. A new pack starts near 100% SOH. Over time, chemical aging reduces capacity, so SOH gradually falls, typically faster in the first couple of years and then more slowly.
Important nuance
Different tools estimate SOH slightly differently. BMW’s internal BMS value, a dealer diagnostic report, and a third‑party scan tool can produce SOH numbers that differ by a few percentage points. You’re looking for trends and ballpark values, not an exact lab measurement.
BMW i4 battery specs and what “normal” degradation looks like
BMW i4 battery at a glance
BMW doesn’t publish an official SOH curve for the i4, but real‑world owners who have logged long trips and charging data give a consistent picture. Many report SOH values in the mid‑90s after 2–3 years and tens of thousands of miles, and usable capacities around 76–77 kWh on the large pack based on trip‑energy calculations and BMS readouts. That’s exactly what you’d expect from a modern liquid‑cooled pack used daily.
Gross vs net vs real‑world capacity
The i4’s gross capacity is about 83.9 kWh. BMW reserves a buffer at the top and bottom, so the net usable capacity when new is about 80–81 kWh. In real‑world tests, owners often measure ~76 kWh usable on a healthy pack after a year or two due to both the buffer and a small amount of natural degradation.
Put differently: a 2–3 year‑old i4 that shows an estimated 75–77 kWh usable is almost certainly healthy. That corresponds roughly to a BMS SOH in the mid‑90s. You should only start to worry if repeated tests point to dramatically lower usable capacity, say the equivalent of low‑70s kWh or below, well before the pack has many years or miles on it.
How to check BMW i4 battery state of health in practice
On a BMW i4, you can’t tap a menu and see a big "SOH 94%" badge. But you can still get a very good picture of battery health using three levels of detail, from simple to technical.
Three ways to assess BMW i4 battery health
From quick checks to data‑driven testing
1. Quick range sanity check
Start with the basics:
- Fully charge to 100% once.
- Note the estimated range on the dash.
- Compare with EPA ratings for your trim and wheel size.
The estimate can be skewed by recent driving, but if it’s dramatically low for no obvious reason, it’s a flag to look deeper.
2. Trip‑based capacity estimate
Use real energy data:
- Charge to a known SOC (for example, 90%).
- Drive a long, steady trip (ideally 100+ miles).
- Record energy used (kWh) and % battery drop from the My BMW app.
Divide kWh by the SOC fraction used to estimate usable capacity (for example, 34 kWh / 0.44 ≈ 77 kWh).
3. BMS readout via diagnostics
For a deeper look:
- Use a BMW‑compatible OBD dongle and app, or
- Have a BMW dealer or EV specialist run a high‑voltage battery test.
These tools can read the BMS’s internal SOH value and cell‑balance data, ideal when you’re making a big purchase decision.
Do‑it‑yourself SOH sanity check: step‑by‑step
1. Start with a high, known SOC
Charge the car to 90–100% on Level 2 at home. Note the starting state of charge and reset trip data so you can track energy used.
2. Drive a long, mixed‑driving route
Aim for at least 100 miles of mostly steady driving, highway plus some city, without giant elevation changes or extreme weather if you can avoid it.
3. Capture kWh used and SOC drop
At the end of the drive, record <strong>kWh used</strong> and ending SOC (for example, started at 95%, ended at 35%, used 60% of the pack and 46 kWh).
4. Estimate usable capacity
Divide energy used by the SOC fraction used. Example: 46 kWh / 0.60 ≈ 76.7 kWh. This is your rough usable capacity from 100–0%.
5. Repeat and average
Repeat this test on 2–3 different days. Small variations are normal; you’re looking for a consistent pattern in the mid‑70s kWh on a healthy large‑pack i4.
6. Follow up if numbers look off
If repeated tests point to much lower capacity than expected, it’s time for a more formal diagnostic, especially if the car is still under battery warranty.
Use the My BMW app wisely
The My BMW app logs energy used in kWh and battery‑percentage change for each trip. That’s exactly the data you need to reverse‑calculate usable capacity over longer drives and build your own picture of SOH over time.
Range readout vs true SOH: don’t confuse the two
Many i4 owners worry about battery health because the car shows a lower range estimate than expected, especially right after delivery or when buying used. But the number on the dash is a guess‑o‑meter, not a direct SOH indicator.
Why the range estimate can look “bad”
- The i4 bases its estimate on recent driving history. A week of high‑speed, cold‑weather driving with climate control blasting can drag the estimate down.
- Short trips, lots of pre‑conditioning, and sitting in traffic all burn energy with little mileage, confusing the prediction model.
- Used cars that lived on the Autobahn or in harsh climates may need several normal commutes before the range estimate “re‑learns” your style.
What really reflects SOH
- Trip‑based capacity calculations over long drives give you a far better window into usable kWh than a single range estimate.
- BMS SOH from diagnostics (via dealer or scan tool) is the most direct metric, often landing in the mid‑90s on 2–3 year‑old i4s.
- The car’s ability to hit expected DC fast‑charge speeds at low‑to‑mid SOC is another indirect sign the pack is healthy and well‑balanced.
Real‑world example
It’s common to see a used i4 show an initially low range at 100% (say, ~250 miles) and then creep upward after a few longer, efficient drives. In many of those cases, owners later calculate usable capacities around mid‑70s kWh and SOH values in the mid‑90s, totally normal for a young pack.
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BMW i4 battery warranty and SOH thresholds
Beyond the numbers you can calculate at home, the BMW factory warranty sets an important floor for acceptable state of health. That matters for peace of mind, and it matters for resale value if you’re buying a used i4 today.
BMW i4 high‑voltage battery warranty basics (U.S.)
Key warranty terms that relate to state of health for the BMW i4 in the U.S. market. Always verify details for your specific model year and state.
| Item | Typical Coverage | What It Means for SOH |
|---|---|---|
| High‑voltage battery warranty | 8 years / 100,000 miles | Coverage against defects in materials or workmanship for the i4’s battery pack. |
| Capacity guarantee threshold | ~70% usable capacity | If usable capacity falls below ~70% of original within the warranty period, BMW will repair or replace the pack. |
| CARB‑state nuances | Some BMW EVs get longer coverage in CARB states | In certain states, emissions‑related HV battery coverage can extend to 10 years; check your warranty booklet for your i4. |
| Transferability | Applies to subsequent owners within term | If you buy a used i4, remaining battery warranty (including capacity guarantee) usually transfers with the car. |
Warranty terms can change by model year and market; confirm with BMW USA or a dealer for your specific VIN.
Always check your specific VIN
BMW has updated U.S. battery coverage over time, for example, extending high‑voltage battery warranty on newer EVs to 8 years / 100,000 miles with a 70% capacity floor. Before you rely on a number you saw online, read the warranty booklet tied to your VIN or ask a BMW dealer to print it.
Buying a used BMW i4? Battery‑health checklist
Used BMW i4s are becoming a sweet spot in the EV market, especially as early‑build 2022 and 2023 cars roll off lease. But two otherwise identical i4s can have very different battery histories. Here’s how to structure your evaluation so SOH isn’t a mystery.
Used BMW i4 battery‑health checklist
1. Confirm warranty time and mileage left
Ask the seller for the in‑service date and current mileage. Make sure the car is still within BMW’s high‑voltage battery warranty window, and note how many years and miles remain.
2. Review range behavior on a test drive
Charge to at least 80–90% before a longer test drive. Watch how quickly SOC drops over 30–50 miles of mixed driving. Abrupt, inconsistent drops can be a sign to investigate further.
3. Pull trip‑energy data from the app
If the seller has the My BMW app connected, glance at a few recent trips. Note kWh used and % battery used on longer drives; this can give a quick, rough sense of usable capacity.
4. Ask for BMS or dealer battery report
On a higher‑value purchase, it’s completely reasonable to request a <strong>dealer battery test</strong> or a third‑party BMS readout. You want to see a clear SOH value and no major cell‑imbalance flags.
5. Check charging history and habits
Ask how the car was charged: mostly home Level 2 to ~80–90% is ideal. A life of daily 100% charges and heavy DC fast‑charging isn’t an automatic deal‑breaker, but it does raise the bar for documentation.
6. Look for software updates and faults
Scan for any battery‑related warning messages, fault codes, or outstanding recalls. A clean record combined with healthy capacity numbers is a strong sign of a well‑cared‑for pack.
Consider a professionally vetted car
If you’d rather not reverse‑engineer SOH yourself, a marketplace designed around used EV transparency, like Recharged, can do the heavy lifting. Every EV on Recharged includes a Recharged Score battery‑health report, fair‑market pricing, and EV‑specialist support so you can shop i4s with clear capacity data in hand.
How Recharged evaluates BMW i4 battery health
Because the pack is the most valuable component in any EV, Recharged treats BMW i4 state of health as a first‑class data point rather than a footnote. When we inspect an i4 for our marketplace or for an instant offer, we focus on three pillars: objective data, history, and real‑world behavior.
Inside a Recharged BMW i4 battery‑health evaluation
More than just reading a number off a screen
1. Objective diagnostics
We connect to the car’s high‑voltage system using professional‑grade tools to:
- Read the BMS‑reported state of health.
- Review cell‑group voltages and balance.
- Check for stored battery or thermal‑management fault codes.
2. Usage & charging history
Where possible, we review:
- Prior owner mileage patterns.
- Charging mix (home vs DC fast‑charging).
- Service records and software updates.
This context helps explain why one i4’s SOH might differ from another’s.
3. Real‑world range behavior
We correlate diagnostic data with how the car behaves on the road:
- Energy use on standardized drive routes.
- Range consistency over repeated trips.
- DC fast‑charge curves at public stations.
Those results, together with diagnostics, roll up into the Recharged Score you see on each listing.
The end result is a clear view of whether an i4’s battery is behaving like a healthy pack for its age and mileage, or whether the numbers suggest accelerated degradation or other issues. That transparency is critical when you’re deciding between several used i4s that look identical on paper.
Driving and charging habits that protect SOH
Once you’ve confirmed that your BMW i4 has a healthy pack, the next goal is to keep it that way. You don’t have to baby the car, but a few habits meaningfully slow SOH decline, especially in hot or cold climates.
- Avoid living at 100%. It’s fine to charge to 100% for road trips, but for daily use, target 70–90% and let the car sit at moderate SOC when parked.
- Limit deep discharges. Running the car down to single‑digit SOC occasionally is fine, but repeated 0–5% to 100% cycles are harder on the pack.
- Use DC fast‑charging strategically. The i4 handles DCFC well, but constant high‑power fast‑charging, especially in heat, can accelerate aging. Mix in plenty of Level 2 charging when you can.
- Pre‑condition in extremes. Use the app or in‑car scheduling so the battery is at a comfortable temperature before hard driving or fast‑charging in very hot or cold weather.
- Keep software current. BMW continuously refines charging and thermal‑management logic. Staying current on updates helps the car look after its battery more effectively.
Heat is the real enemy
High temperature is the single biggest accelerator of lithium‑ion battery aging. Avoid parking at 100% in direct sun on very hot days, and give the car time to cool the pack after a long, fast‑charged road segment before shutting it down for hours.
FAQ: BMW i4 state of health and used‑car shopping
Frequently asked questions about BMW i4 state of health
Battery state of health is no longer an abstract engineering metric, it’s central to how you evaluate, buy, and live with a BMW i4. The good news is that early data shows the i4’s pack aging gracefully in normal use, and BMW backs it with a capacity‑based warranty floor. Whether you’re cross‑shopping used i4s or making sure your own car stays healthy, a mix of real‑world trip data, proper diagnostics, and smart charging habits will keep surprises to a minimum, and keep your i4 delivering the range and performance you bought it for.
