Bosch AHS 18 7.2V Replacement Battery 3600mAh Ni-MH

My Bosch AHS 18 hedge trimmer cuts fine for a bit then loses power halfway through the hedge — is the battery dying or is something else wrong?

With Ni-MH at this voltage class, the most likely cause is voltage sag under blade load — the pack drops below the trimmer's cutoff threshold before the cells are actually empty, especially if the battery is more than two or three seasons old. Cold pack temperature makes this worse; Ni-MH cells lose headroom fast below 10°C. Charge the battery fully, let it reach room temperature, then check resting voltage with a multimeter — a healthy 7.2V Ni-MH should read between 8.4V and 8.6V fully charged. If it reads below 7.8V at rest after a full charge, the pack has lost significant capacity and won't recover.

The replacement battery charged up fine but my AHS 18 trimmer blades are moving slower than they did with the original — what's wrong?

A fresh Ni-MH pack often needs two or three full charge-discharge cycles before it delivers full rated capacity — this is a known conditioning behaviour for this chemistry, not a fault. If the blades are sluggish on cycle one, run the trimmer until it stops, charge it fully, and repeat twice before drawing any conclusions. Also check the blade gap and lubrication on the AHS 18 cutter bar — increased mechanical resistance will pull more current and make even a good battery appear weak. If sluggishness persists after three cycles, measure pack voltage under load; a drop below 6.0V during cutting points to a cell imbalance inside the pack.

I left my Bosch hedge trimmer in the shed all winter with the battery in it and now it won't power on at all — can it be recovered?

Ni-MH cells self-discharge significantly over months of storage, and a pack left fully or partially discharged in cold conditions can drop into a deep-discharge state that most chargers won't recognise as a valid battery. The charger may show no activity or a fault signal because the pack voltage is too low to trigger the charge cycle. Try leaving the battery at room temperature for 24 hours, then attempt a charge again — some chargers will initiate a recovery charge once the pack warms up. If the charger still won't engage, measure pack voltage directly; anything below 4.5V on a 7.2V Ni-MH pack usually means one or more cells have reversed and the pack will not recover safely.