7.2V Wolf Garten Grasschere Replacement Battery 3600mAh

My Wolf Garten grass shears cut fine for a while then suddenly stop mid-session — why does it keep dying with battery still showing charge?

This is a classic Ni-MH voltage sag under load. At 7.2V the pack has very little headroom, and once a few cells drop below the tool's cutoff threshold, the electronics shut it down even though the resting voltage reads fine. Ni-MH cells also lose capacity faster than the fuel gauge tracks, especially if the battery has been stored discharged or has gone through shallow charge cycles repeatedly. Let the pack cool for ten minutes, then try again — if it resumes immediately, thermal cutoff isn't the culprit and cell imbalance is. Charge the battery fully, run it completely flat twice to help recondition the cells, and check whether it holds a full session after that.

Charged the replacement battery overnight and the shears feel weaker than the old one — blades moving slower than they should be

Ni-MH batteries ship in a partially discharged, low-activity state and often need two or three full charge-discharge cycles before they deliver rated capacity. If the blades feel sluggish straight out of the box, the cells haven't yet reached their working voltage curve. We see this consistently on bench when a fresh 7.2V Ni-MH pack is tested on day one versus after three cycles — the difference in sustained current delivery is measurable. Run a full charge, use the shears until they stop on their own, charge fully again, and repeat once more before deciding the battery is underperforming.

Charger light goes solid green after only an hour — is the battery actually full or did it just stop charging early?

Most fast chargers for 7.2V Ni-MH packs use a delta-V detection cutoff, which measures the tiny voltage drop that signals full charge. On a new or deeply discharged Ni-MH pack, the cells can warm up unevenly and trigger a false cutoff before the pack is genuinely full. Pull the battery off the charger, wait fifteen minutes for it to cool, then reseat it — if the light goes back to charging mode, the first cycle was a false stop. If it immediately returns to green, charge the pack on a slower trickle setting if your charger supports it, as trickle charging is more reliable for detecting true full charge on Ni-MH chemistry.