The Battery Tender Charge N Start 4120 combines a 4-amp ISM smart charger with a 1200 peak-amp lithium jump starter in one portable unit, so a dead battery and routine maintenance no longer require two separate tools. The manufacturer calls it the most capable Charge N Start model, with four times the charging output of the 1100 and 1120 and the same jump power as the 1120. It charges and maintains 12V lead-acid, AGM, GEL, flooded, sealed, and lithium batteries. The jump function runs independently of the AC charging circuit, so the starter stays ready while the charger works. Per the manufacturer's charging table, a 40 Ah small car battery takes about 7 hours and a 100 Ah truck battery about 17 hours.
Fitment is rated by engine size: the manufacturer specifies jump-starting for gas engines up to 6.0L and diesel engines up to 4.0L, and its blog points to trucks, SUVs, and larger vehicles as the best match. Owners who want a garage battery maintainer for a seasonal truck, a boat, or a powersports machine can keep one unit for both jobs. Search terms like "4 amp lithium battery maintainer with 1200 amp jump starter," "jump start 6.0L gas truck portable," and "AGM and lithium battery tender with jump pack" describe what this unit does.
Yes, within limits. The manufacturer rates the 4120 for diesel engines up to 4.0L. Larger diesels fall outside that specified range.
No. The manufacturer provides two separate clamp sets, one for smart charging and maintenance and one for jump starting. The manufacturer lists using the charger cables for jump starting as a common misconception.
Yes. The manufacturer states the 4120 charges and maintains lithium batteries alongside lead-acid, AGM, and GEL types.
No installation is required because this is a portable unit that connects directly to the battery. To jump-start, connect the jump starting clamps to the battery and activate the integrated lithium jump starter, which runs separately from the charging circuit. Keep the charging clamps and jump clamps apart, since they are not interchangeable. The manufacturer notes the unit is not waterproof, so keep it dry, and it recommends preventing corrosion on battery connections. Expect reduced capacity in cold weather, and store the unit on a regular charge maintenance schedule.
