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How to check a used BYD Dolphin battery: size, warranty and health (UK)

Published 2026-11-06 · Last updated 2026-11-06 · based on 14 sourced Dolphin data points and 18 sources

The BYD Dolphin is a small LFP "Blade" hatchback sold in the UK with either about 44.9 or 60.5 kWh usable. On the 4 UK dealer AVILOO certificates we found, results ranged from 97.7%–98.8%. The bigger questions on a used Dolphin are which pack it has, BYD's warranty mileage conflict (250,000 km in the manual vs 200,000 km on the UK web page), and how an independent test compares with other Dolphins. This guide covers each check.

All figures with method and date: used BYD Dolphin battery data. Going to a viewing? Make a printable list of questions for the seller. Sister BYD guides: Atto 3 · Seal. More Chinese-brand EVs: Chinese EVs battery guide.

1. Battery size: 44.9 or 60.5 kWh LFP Blade

EV Database UK listings, checked 2026-11-06. Test certificates usually print 60.48 kWh for the larger pack. All 4 of our UK dealer certificates are for that 60.48 kWh pack.

• Do not confuse the Dolphin with the smaller Dolphin Surf (2025-on) – a different car with different battery sizes (EV Database).
• AVILOO lists FLASH-test support for Dolphin packs including 44.9, 58.56 and 60.48 kWh (AVILOO GmbH).
• Compare a test result only with the same pack. We have no UK independent results yet for the 44.9 kWh Active.

2. Check for recalls

When we checked DVSA's recall file (DVSA; Dolphin rows re-checked 2026-11-06 against the 2026-10-31 download), it listed no recall under the Dolphin passenger-car name and no high-voltage battery recall for the Dolphin. The BYD rows in that file are for buses and coaches, not the Dolphin hatchback. The file can lag behind new campaigns, so this isn't proof that a car is clear. Run the free GOV.UK recall check on the registration (GOV.UK) and ask a BYD dealer to check the VIN for open campaigns and software updates.

3. Check the battery warranty (and which mileage applies)

BYD's sources don't agree on the mileage, so here is what each says (same conflict as on the Atto 3 and Seal):

• The manual and the newer press release both say 250,000 km. As the web page still says 200,000 km, ask a BYD dealer or BYD UK to confirm the cover for the car's VIN in writing, especially on a high-mileage car.
• Count the 8 years from the first registration date. EV Database lists UK Dolphin orders from September 2023, so even the oldest cars on that listing stay inside the 8 years until about 2031 – check the date on the V5C.
• The cover is for capacity falling below 70%. Gradual loss above that isn't covered. If the battery is repaired under warranty, BYD may use a new, reconditioned or remanufactured part (BYD).
• Our battery warranty checker works out the time and mileage left from the registration date.

4. Get a battery reading you can trust

• Don't trust the car's own figure alone. On the 4 AVILOO certificates that also print the car's own BMS figure, the car's own reading was higher on 3, the same on 1 and lower on 0, by up to about 1.3 points.
• AVILOO lists FLASH-test support for the Dolphin (AVILOO GmbH). An independent test (AVILOO GmbH) gives a figure you can compare with the table below. UK options and prices: UK battery test comparison. To read the result: certificate guide.

5. Compare the result with other Dolphins

• No AVILOO median is published for the Dolphin itself. Every figure below is a single car (n=1).
• The 4 UK dealer AVILOO certificates (all 60.48 kWh; 12,498–24,126 km, ≈7,766–14,991 miles) read 97.7%–98.8%. The lowest, 97.7%, was at 10,548 miles; the highest-mileage UK car (14,991 miles) had 98.8%.
• 1 Australian dealer AVILOO certificate (hot climate – not UK conditions) read 96.6%–96.6% at 7,902–7,902 km.
• 9 other single-car results (owner forums and a Brazilian press report) ranged 87.0%–99.0%. Most are Brazilian owner OBD/app readings – useful examples, not UK averages. One ride-hailing Dolphin GS was reported at 87.0% after 307,000 km of mostly DC fast charging in a hot climate (Estadão – Jornal do Carro).
• A UK independent result clearly below about 97.7% at similar low mileage is worth questioning. Get the car tested again or ask BYD to check it.
• As a rule of thumb for all EVs, ADAC expects at least 92% at 50,000 km, 88% at 100,000 km, 84% at 150,000 km, 80% at 200,000 km (ADAC).
• Compare the Dolphin with other Chinese-brand EVs on the battery degradation chart, or get a quick estimate with the battery health estimator.

Every Dolphin single-car result we have (n=1 each)

4 UK and 1 Australian dealer AVILOO certificates and 9 other single-car readings. Single cars show the spread, not an average. Owner-app and car-reported rows are not independent tests. Every row is also on the Dolphin data page.

6. Battery replacement cost (UK)

We have not found a verifiable, dated UK price for a new Dolphin battery from BYD, so we don't quote one. Inside 8 years and the warranty mileage, a battery below 70% capacity is covered by BYD (BYD). For a car near the end of its cover, get a written quote from a BYD dealer before you buy. General UK figures are in our EV battery replacement cost guide.

Also see: BYD Atto 3 battery check · BYD Seal battery check · Chinese EVs battery guide (MG, BYD, Polestar…) · general used-EV battery checklist · battery problem after buying: your rights (UK) · all models compared.

We are not paid by the battery-test providers mentioned on this page. Links marked "paid link" in the "Useful products and services" box are affiliate links. See our disclosure.

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