Battery options & usable capacity
BMW’s 120 Ah specification lists 42.2 kWh gross and 37.9 kWh net. Use 37.9 kWh as the original usable baseline only for the matching 120 Ah configuration; do not apply it to earlier battery versions.
| Reference configuration | Original usable capacity | Provenance |
|---|---|---|
| 2019 US 120 Ah — 37.9 kWh net | 37.9 kWh42.2 kWh gross — separate figure | Manufacturer · Source |
Charging capability
Confirm the actual AC and DC equipment, especially when comparing cars from different build periods or markets. A bigger home wallbox cannot override the car’s on-board charging limit.
120 Ah, 42.2 kWh gross and 37.9 kWh net describe different things
BMW’s cited 2019 US 120 Ah reference gives both gross and net energy. The 120 Ah designation is not a 120 kWh battery, and earlier i3 versions need their own source. For the matching reference, 37.9 kWh is the denominator for a usable-capacity comparison.
An illustrative current usable measurement of 34 kWh gives 89.7% retention against 37.9 kWh. Dividing by the 42.2 kWh gross figure instead gives 80.6%. That large apparent difference comes entirely from mixing definitions. Check the report’s method and reference before treating a lower percentage as evidence of a worse battery.
Check the longer journey as well as the daily commute
Using the original 37.9 kWh net reference, an 80–10% charge window contains 26.53 kWh. At illustrative consumption of 16 kWh/100 km it gives about 166 km; at 21 it gives about 126 km. Those are calculations under selected conditions, not observed i3 range. They show why a car that comfortably covers a commute can need a different charging plan for a longer winter trip.
Check AC and DC equipment on the actual car rather than treating all build periods as equivalent. Ask for a demonstration of the charge type you will use, and retain replacement-pack documents if applicable. The historical technical source here does not settle remaining warranty, so obtain the original regional terms separately.
Plan a journey with this battery reference
| Exact reference | At 18 kWh/100 km | At 22 kWh/100 km |
|---|---|---|
| 2019 US 120 Ah — 37.9 kWh net | 147 km / 92 miles | 121 km / 75 miles |
Calculation: usable kWh × 0.70 ÷ kWh/100 km × 100. A used battery may have less usable energy; these scenarios do not establish its condition.
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Battery warranty
Check the original regional warranty, start date and any replacement-battery terms. This historical technical sheet is not a warranty certificate.
Things worth checking before purchase
- Confirm the 120 Ah configuration from the vehicle documents rather than registration date alone.
- Distinguish the battery-electric version from a range-extender vehicle when budgeting fuel and service.
- Compare usable kWh with usable kWh; 42.2 versus 37.9 is a buffer distinction, not degradation.
- Check charge-port operation and obtain a diagnostic report relevant to the installed pack.
A BMW i3 viewing: record the battery version precisely
Ask for the exact battery version and whether the car is a battery-electric or range-extender version. Keep the battery-energy calculation separate from any fuel available to a range extender. Do not infer usable kWh from a badge or an amp-hour figure without the matching technical reference.
Confirm the fitted charging hardware, compatible connectors and included cables on the individual car. An equipment list for a different year or market is not evidence of what is installed. Request repair documentation for any pack or charging-system work.
When a diagnostic screen reports capacity, record its field name and method. An isolated service-menu value should not be relabelled as a certified SoH percentage. Use consistent recent evidence when comparing changes over time.
Turn the evidence into a useful estimate
Use a documented usable capacity and consumption from conditions matching your trip. Keep original specifications separate from the seller’s current battery-health evidence.
EVVerity estimates are informational and are not a substitute for a professional battery diagnostic or pre-purchase vehicle inspection.
Manufacturer sources & scope
- BMW — 2019 i3 120 Ah specifications
2018-09 · checked 2026-10-04
Source verification means the cited statement was reviewed. It does not extend a historical specification to other years or markets. Missing values are intentionally not inferred.
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Research another used EV
If you are considering more than one model, use its own guide to check the battery reference, charging equipment and seller evidence. Specifications and warranty terms must be verified separately for each car.