Used BMW i3 Alternator

The BMW i3 ran from 2013 to 2022 in the UK, with a notable update in 2017 that introduced the 120Ah battery pack alongside the existing 94Ah cars, and a further refresh around 2018. Because the i3 is primarily an electric vehicle, it does not use a conventional alternator in the way a petrol or diesel car does; what it does have is a DC-DC converter that performs a similar role of charging the 12V auxiliary battery. Always confirm with the breaker exactly which component you need by supplying your registration, as the terminology and part numbers can differ from traditional alternator listings.

The 2014 car sits in the pre-2017 specification and the 2017 car represents the updated 120Ah generation, so there is a production boundary between these two vehicles that may affect ancillary electrical components including the DC-DC converter. Engine code and electrical architecture are the deciding factors here, not the year alone, so confirm with the breaker against both registrations before purchasing. Never assume fitment across that 2017 boundary without the breaker verifying part numbers directly.

The i3s is a higher-performance trim of the i3 with a more powerful electric motor, but the DC-DC converter and 12V charging system are not affected by trim level in the way a mechanical alternator would be on a combustion car. Trim level does not drive fitment for this component, so an i3 and an i3s of the same production year are very likely to share the same part; however, confirm with the breaker against your specific registration to be certain. You may also notice cosmetic differences between donor and receiver cars, but those are irrelevant to whether the part itself works.

The REX model carries a small two-cylinder petrol generator which does charge the main battery pack, but it is a separate generator unit rather than a conventional belt-driven alternator, and the 12V DC-DC converter serving the auxiliary battery is a different item again. If you are sourcing either the REX generator or the DC-DC converter, make sure you tell the breaker which variant you have, as the REX and non-REX cars are mechanically quite different in this area. Supply your full registration or VIN to the breaker so they can pull the correct part.

The 60Ah, 94Ah, and 120Ah designations refer to the traction battery capacity and correspond broadly to different production periods, meaning the underlying electrical architecture can differ between them. The DC-DC converter that charges the 12V auxiliary battery may or may not be interchangeable across these variants, and whether ancillary components changed between battery generations is something you should confirm with the breaker against your registration rather than assume. Providing your VIN or registration to the breaker is the safest way to ensure the correct part is identified.

ECU pairing and whether any control module needs coding to your specific vehicle after fitting are topics you must confirm with the breaker or your fitting garage, as this can vary and we cannot state it as fact here. What is clear is that modern BMW electrical systems can require coding when components are replaced, so budget for that possibility. Ask the breaker whether the unit they supply has any pairing or immobiliser implications before you commit to the purchase.