⚡ 2025 KIA EV6 | 84kWh | WRITTEN OFF AT 6,000 MILES ⚡

A botched backstreet battery repair, and a design flaw nobody talks about.

This 2025 Kia EV6 drove in with NO warning lights. Underneath it had a punctured traction battery, a leaking cooling plate, metal swarf inside the pack, a dead cell, and a module shorting to the casing. Someone had already "repaired" it. We stripped the whole pack to show you what was hiding inside, and how we made it safe again.

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🚗 VEHICLE

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▸ Make / Model: Kia EV6

▸ Year: 2025

▸ Mileage: ~6,000 miles

▸ Battery: 84kWh (earlier EV6s use 77.4kWh, which are NOT interchangeable)

▸ Status: Insurance write-off, sold at auction, previously "repaired"

▸ Complaint: Coolant loss, no dash warnings

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🔍 DIAGNOSTICS & READINGS

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▸ DTC: BMS HV isolation fault (high-voltage circuit not isolated from the chassis)

▸ Isolation resistance: 340kΩ (expected -1,000kΩ)

▸ Pack voltage: 649.4V

▸ Cell delta: 3.4V (should be close to 0V)

▸ Cell 79: 0V, dead cell

▸ Module readings: 20.54V healthy vs 17.11V faulty

▸ New module supplied at 22.88V, matched down to ~20.52V before fitting

▸ Final pack delta after rebuild: 20mV ✅

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⚠️ WHAT WE FOUND INSIDE

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❌ Silicone/filler used to "seal" a punctured battery casing

❌ Missing and mismatched casing bolts

❌ Module securing bolts not fitted

❌ Grinding and welding swarf left throughout the pack

❌ Welded cooling plate, distorted and no longer flat

❌ NO thermal paste under the modules

❌ Coolant ingress into a module, exposing electrolyte

❌ Punctured module shorting to the casing (the source of the isolation fault)

❌ Footprint-style dents on the module pouches

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🧠 THE DESIGN QUESTION

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▸ The underbody battery protection is a thin, flexible fibre panel

▸ The cooling plate sits directly under the modules

▸ The LOWER cooling layer is much thinner than the upper layer, so one impact punctures the coolant circuit

▸ Compare this with packs that route cooling along the sides (e.g. Tesla)

▸ The replacement casing comes with the SAME thin protection

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🔧 THE REPAIR

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✅ New battery casing (sold separately by Kia)

✅ 2x new modules

✅ All modules cleaned, inspected and transferred

✅ New 2-part thermal paste (~15 packs used)

✅ Voltage matching of the new modules

✅ Historic isolation DTC cleared

✅ Full coolant bleed procedure (~30 mins)

✅ 200+ mile road test

💷 Approx. total: ~£10,000 (vs ~£20,000 for a new battery)

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⏱️ TIMESTAMPS

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0:00 What we found inside 😱

0:24 Why EV battery repair needs regulating

1:00 2025 EV6, written off at 6,000 miles

1:50 First clue: empty coolant tank

2:20 Diagnostic scan, isolation fault

3:00 On the ramp: filler on the battery

3:50 Missing and mismatched bolts

4:40 Cooling damage, a silicone "repair"

5:20 How the EV6 cooling floor works

7:00 Pack readings: 649.4V, 3.4V delta, 0V cell

8:20 Isolation: 340kΩ

9:30 Opening the pack: metal swarf everywhere

10:45 Hunting the faulty module

12:10 Module bolts NOT fitted

13:25 Broken module put back in

14:20 Welded cooling channel, no thermal paste

16:30 Coolant inside the cells

17:30 Module isolation test: the punctured module

19:40 Casing no longer flat

20:45 Is this real battery protection?

22:40 Cooling under the modules vs on the sides

23:55 3V delta: Kia drives, Mercedes EQS won't?!

25:30 Cutting the cooling jacket

27:15 The bottom layer is MUCH thinner 😳

31:30 Is the casing even sealed?

34:00 84kWh vs 77kWh, a dead end

34:50 New battery £20k = car value

35:20 The solution: a new casing

36:30 Transferring the modules

38:30 Damaged module pouches

40:15 Did someone STAND in this battery?

42:20 Should EV repairers be regulated?

44:50 Thermal paste explained

45:25 Fitting the new modules

47:20 Voltage matching new modules

49:05 How much paste? (it's expensive)

50:30 How 2-part thermal paste works

51:45 Last module in

52:15 Final balance: 20mV

53:40 Pack refitted to the car

54:20 Clearing the historic isolation fault

55:00 Coolant bleeding procedure

56:30 200-mile road test

57:00 Full recap

58:30 Cost breakdown

1:00:12 Final verdict

Music from #InAudio: https://inaudio.org/

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Music from #InAudio: https://inaudio.org/

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