3.7V Timbertech RSSR01 Hedge Trimmer Compatible Battery 2900mAh

My Timbertech hedge trimmer cuts fine for a bit then suddenly stops mid-trim — is that the battery dying or something else?

That's thermal cutoff triggering, not a dead battery. The 3.6V Li-ion cell in the RSSR01 is small, and switching between the hedge trimmer and shear attachments without rest periods builds heat faster than most users expect. Let the tool sit for a few minutes after it cuts out, then try again — if it restarts normally, heat was the cause, not a failed cell. If it won't restart even when cool, put the battery on charge and check that the indicator shows it's actually accepting charge rather than sitting at a fault state.

I put a new battery in my RSSR01 and the blades feel slower and weaker than they used to — what's wrong?

A replacement battery that measures below 3.5V resting voltage will run the motor under-powered even if it's fully charged by the indicator light. The RSSR01's motor draws enough current that a cell with high internal resistance — common in batteries that sat in a warehouse — will sag under load and never spin the blades at full speed. We've seen this on the bench with cells that show "full" but drop hard the moment load hits them. Charge the new battery for a full uninterrupted cycle, then test resting voltage with a multimeter — you're looking for 4.1–4.2V at full charge before it goes into the tool.

My Timbertech grass shear won't hold a charge anymore even after leaving it on the charger overnight — is there any way to fix it?

Overnight charging on a small 1300mAh Li-ion cell with a basic trickle charger often does nothing if the cell has dropped below the charger's detection threshold — the charger sees it as absent or shorted and never enters charge mode. This is common with Li-ion tools that get stored partially discharged for more than a month, which is the typical shelf pattern for seasonal garden tools. There's no reliable way to recover a cell that's gone below roughly 2.5V — that's why a replacement makes sense here rather than a longer charge attempt. Before fitting the new battery, check that the charger contacts on the tool are clean and making solid contact, since corroded pins are the other reason a known-good charger appears to do nothing.