Stock XJ uses Group 58 / 34. Group 34 fits factory tray with 750-880 CCA. Group 65 needs a different tray but offers ~850 CCA. Group 24 AGM (Optima D34) is common upgrade.
The factory XJ battery tray accepts Group 58 (1984-1990) or Group 34 (1991-2001). Standard Group 34 is 10.25 x 6.8 x 7.875 inches with ~750-880 CCA. Optima YellowTop D34 (deep-cycle/dual-purpose AGM) is the gold-standard upgrade — handles winch loads, vibration, and deep discharge cycles.
Group 65 (12.0 x 7.5 x 7.6) is taller and longer; it does NOT fit the stock tray without modification but is what some Ford trucks use. Don't bother — Group 34 fits and is enough.
For heavy use: Odyssey 34-PC1500 (850 CCA, 68 Ah) is the toughest AGM commonly recommended. Northstar NSB-AGM34M is another premium choice. Avoid el cheapo flooded batteries if you wheel — vibration kills them and acid spilling in a rollover is a nightmare.
Aux battery sizing: Group 24 AGM (75-85 Ah) is the typical second battery for fridge + lights duty cycle. A 100 Ah lithium (Battle Born, Renogy) gives 2x the usable capacity at half the weight but needs a DC-DC charger.
| Part | Vendor | Est. price |
|---|---|---|
| Optima YellowTop D34 | Optima | ~$290 |
| Odyssey 34-PC1500 | Odyssey | ~$350 |
| Northstar NSB-AGM34M | Northstar | ~$380 |
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.