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Manufacturer: Dell Last updated: 2026-09-29
Dell WY9DX Replacement Battery Review
Dell WY9DX replacement battery, the 42Wh 3-cell 11.4V pack for the Dell Latitude 5420, Latitude 5520 and Precision 3560.
Dell's Latitude 5420 spec sheet lists this 3-cell 42Wh pack as the smaller of two battery options, at 207.9 mm long versus 238 mm for the 4-cell 63Wh pack (Dell RJ40G). Parts-People sells it as the Dell OEM WY9DX and lists M3KCN, WK3F1, R89GC and 05R42 as older codes for the same part.
Our verdict
Reviewed by Burooj Alam. Rated by us, not by users.
Best for
- Latitude 5420 and 5520 owners with the original 42Wh battery
Not for
- Owners who want the longer-running 63Wh RJ40G
Specifications
What these specs mean| Brand | Dell |
|---|---|
| Battery Model Code | WY9DX |
| OEM Spare Part Number | WY9DX, 0WY9DX |
| Nominal Voltage | 11.4 V |
| Cell Count | 3 |
| Series Configuration | 3S |
| Capacity Wh | 42 Wh |
| Capacity Basis | OEM Label |
| Length | 207.9 mm |
| Width | 95.9 mm |
| Thickness | 5.7 mm |
| Compatible Models | Dell Latitude 5420, Latitude 5520, Precision 3560 |
| Replaces Part Numbers | M3KCN, WK3F1, R89GC, 05R42 |