ASUS C42N1728 Replacement Laptop Battery | 15.4V 71Wh 4-Cell for ZenBook Pro 15 UX534FT UX534FD UX580GD UX580GE Series

Q1: Does C42N1728 fit both UX534FT and UX580GD — are these the same chassis?
No, they are different chassis generations but use the same battery. UX580GD/GE is the original ZenBook Pro 15 (2018) with first-generation ScreenPad. UX534FT/FD is the 2019 refresh with updated processors and GPU options. ASUS maintained battery platform continuity between these two generations — same connector, same bay dimensions, same C42N1728 specification. A single stock position covers both the 2018 and 2019 ZenBook Pro 15 repair market. Verify the original battery label shows C42N1728 or 0B200-03150000 before ordering.

Q2: Why does my ZenBook Pro 15 shut down at 20–25% battery even with a new C42N1728 installed?
This is almost always a cell matching issue in the replacement pack. In a 4-cell series configuration, a single cell with higher internal resistance hits its minimum voltage threshold before the others, triggering BMS cutoff for the entire pack. The other three cells still have remaining capacity, but the laptop shuts down anyway. The shutdown-at-20% pattern is the field indicator. On a properly assembled C42N1728 with cells matched to within ±1.5% capacity tolerance, this failure does not occur within the first 500 cycles. If you see this symptom on a new replacement battery, request cell matching documentation from your supplier — that is the root cause.

Q3: The ScreenPad seems to drain the battery faster. Is this a battery defect or expected behavior?
Expected behavior. The ScreenPad secondary display adds approximately 3–5W to system power draw when active. On a new C42N1728, runtime with ScreenPad enabled will be 5–6 hours versus 7–8 hours with it disabled under comparable workloads. This is not a defect — it reflects the additional power budget the secondary display consumes. For repair shops advising customers after battery replacement: set this expectation clearly before the customer picks up the device. A customer expecting 8 hours who gets 5–6 hours with ScreenPad active will generate an unnecessary warranty complaint.

Q4: How do I verify a C42N1728 replacement battery is genuine spec and not underspecced?
Two checks. First, discharge a sample unit at 0.5C with a lab charger — a genuine 71Wh pack returns 67–75Wh at room temperature. Units consistently returning below 64Wh are underspecced. Second, after a full charge, check cell balance via the BMS balance port: all four cells should read within 20mV of each other. A spread greater than 50mV on a new battery indicates either mismatched cells or a BMS calibration fault — both will produce early shutdown behavior in the field. Request cell lot traceability and matching data from your supplier before accepting bulk stock on this platform.

Q5: What is the typical repair demand profile for ZenBook Pro 15 battery replacements?
Different from high-volume consumer platforms. ZenBook Pro 15 owners are professional users — designers, video editors, developers — who paid $1,500–$2,000 for these machines in 2018–2019 and maintain strong loyalty to their hardware. Repair intent is high and price sensitivity is lower than consumer VivoBook platforms. Repair shops see C42N1728 requests from customers 5–7 years into ownership with specific professional workflows invested in that hardware. Demand is lower volume but higher per-unit margin than B31N1842 or B31N1912. For distributors building an ASUS catalog, C42N1728 is a margin SKU rather than a volume SKU.

Q6: What documentation comes with bulk C42N1728 orders and how are warranty claims handled?
Each bulk shipment includes a Certificate of Conformance specifying cell lot number, production date, capacity QC results, and cell matching tolerance data. Warranty is 12 months from shipment date covering manufacturing defects including capacity degradation below 70% of rated 71Wh and cell balancing failures. For DOA or early-failure claims, submit a photo of the defective battery label and a brief description of the failure symptom — return shipment is not required below our defined batch replacement threshold. Replacements dispatch within 5 business days of claim confirmation. Mixed-SKU orders combining C42N1728 with other ASUS ZenBook batteries are supported in a single purchase order with consolidated CoC documentation.