Gardena AP12 12V 3000mAh Replacement Battery

My Gardena hedge shears start strong then suddenly cut out halfway through the hedge — is the battery dying or is something else going on?

That cutout pattern is classic Ni-MH voltage sag under load — the pack still has charge but can't sustain the current draw when the blades hit thick stems, so the tool's protection circuit reads it as a dead battery and shuts down. It gets worse as cells age because individual cells lose capacity unevenly and the weakest one drags the whole pack down. Before replacing anything, fully charge the battery, let it cool to room temperature, then run it on light growth first to see if the cutout only happens under hard load. If it shuts off within the first few cuts on thin material too, the pack has degraded beyond recovery and needs replacing.

I charged my Gardena battery overnight and the tool still feels sluggish and weak — the charger showed it was done but something's off

Ni-MH packs can develop voltage depression — sometimes called the memory effect — after repeated shallow charges, where the cells accept a full charge on paper but deliver less usable power under load. This is common on the Accu-System V12 tools if the battery was regularly topped up before it was fully depleted. The fix is a full discharge cycle: run the tool until it stops completely, then put it on a full charge from flat. If sluggishness persists after two full discharge-recharge cycles, check the terminal voltage under load with a multimeter — a healthy 12V Ni-MH should hold above 10.8V while the blades are running.

My replacement AP12 battery sits in the charger for hours but never seems to get warm — is it actually charging?

Ni-MH packs should get noticeably warm toward the end of a charge cycle — if it stays cold the entire time, the charger may not be detecting the pack correctly, which usually means a contact or handshake issue rather than a faulty cell. Check that the battery connector is fully seated and that the terminal contacts on both the battery and charger are clean and free of green oxidation or debris. The Gardena Accu-System chargers use a temperature and delta-V detection method to terminate charge, so a pack that never warms up may never trigger proper charge current. Wipe the contacts with a dry cloth, reseat the battery firmly, and check whether the charge indicator light changes behavior within the first 15 minutes.