Husqvarna 18V 1500mAh Lithium-Ion Gardening Tool Battery

My Husqvarna tool cuts fine for a minute then suddenly stops like it hit a wall — is the battery dying or is something else wrong?

That hard cutoff mid-use is almost always thermal protection triggering, not a dead cell — 18V Li-ion packs at 1500mAh have limited heat headroom under sustained load, and dense vegetation or a dull blade forces the draw high enough to trip the protection circuit. Let the battery cool for 15 minutes completely away from the tool, then check the resting voltage with a multimeter — it should read between 19.8V and 20V when fully charged. If the voltage is fine but the cutoff keeps happening at the same point in the job, the blade or cutting head is the real culprit, not the battery. Clean the cutting head, check for drag, and see if the cutoff moves later into the task.

Replaced the battery and now my Husqvarna runs noticeably weaker than the old one — same cuts feel harder than before

A new 1500mAh Li-ion pack can behave sluggishly for the first several charge cycles because the cells haven't reached full electrochemical conditioning yet. Run the battery through three full discharge-and-charge cycles under real working load before drawing any conclusions about capacity. Also confirm the terminals on both the battery and tool are clean and making full contact — even a thin layer of oxidation on an 18V connection creates enough resistance to drop perceived power noticeably. If it still feels weak after conditioning, put a multimeter on the pack under load and watch for voltage sagging below 15V, which would indicate a cell mismatch.

Charged the battery overnight and it's already dead after barely using it — wasn't storing it empty was I?

Li-ion cells self-discharge faster when stored fully depleted, and if this battery sat in that state for more than a few weeks before first use, one or more cells may have dropped below the recovery threshold — typically around 2.5V per cell. Charge it fully, leave it 24 hours without use, then measure resting voltage at the terminals — a healthy 18V Li-ion pack should hold above 18V at rest. If the voltage has already dropped to 15V or lower after sitting idle, the pack has an unrecovered cell and won't regain normal behavior through regular cycling. For future storage, keep the pack at roughly half charge in a dry location away from temperature extremes.