To diagnose, I need more details. **Please tell me:**
| Model | Common Issues | Fixes |
|---|---|---|
| DS Phat / Lite | Bent charger port pins, dead battery, broken charger wire | Gently straighten pins (toothpick), replace battery (cheap, easy), try known-good charger |
| DSi / DSi XL | Proprietary charger failure, battery swelling, port wear | Test with USB charger cable (if port works), replace battery, check port solder |
| 3DS / 2DS / New 3DS | USB port lint, battery degradation, charging circuit failure | Clean port (compressed air, plastic pick), replace battery, try dock/cradle |
Reply with your model + symptoms for a precise fix.