🔋 Why This 6,000-Mile Kia EV6 Is an Absolute Death Trap | OGS & Mechanics

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)