Wolf Garten 7084889 3.6V Grass Trimmer Replacement Battery

My grass shears cut fine for a few passes then the blades slow down and feel like they're dragging — is that the battery dying or something else?

That symptom — full speed at first, then progressive blade drag without a full shutoff — points to voltage sag under load, which is characteristic of an aging or degraded Ni-MH pack losing its ability to sustain current draw during the cutting stroke. A fresh Ni-MH cell at 3.6V holds steady under light loads like this trimmer, but a worn pack drops below the tool's minimum operating threshold within a few cycles of use. Charge the battery fully, then measure the terminal voltage under load with a multimeter — a healthy pack should hold above 3.2V while the blades are running. If it's reading below that within the first minute of cutting, the pack is the problem, not the blades or motor.

The replacement battery won't hold a charge after sitting in the shed all winter — it charges, shows full, then dies almost immediately when I turn the shears on.

Ni-MH cells self-discharge significantly faster than lithium, and a pack left uncharged in cold storage over winter can develop voltage depression — sometimes called "lazy battery" — where individual cells drop so low they partially reverse-polarity during charging, leaving the pack appearing full but with almost no usable capacity. The charger sees enough voltage to stop charging, but the actual energy stored is near zero. Run two or three full charge-discharge cycles deliberately: charge completely, run the shears until they stop, then recharge immediately. If the pack doesn't recover usable runtime by the third cycle, the cells have not recovered and the pack needs replacement.

The blades on my Wolf Garten 7084889 are spinning but cutting grass is taking way more passes than it used to — blade dulling or is the new battery putting out less power than the original?

A 3000mAh Ni-MH replacement versus the original 2.2Ah pack is a capacity upgrade, not a voltage change, so the motor isn't getting less power — rule out the battery as the cause of reduced cutting performance. What actually happens with cordless grass shears is that the fixed-blade comb and the moving blade wear unevenly, and the gap between them widens enough to fold grass instead of shear it. Check the blade alignment first: the moving blade should travel the full 8cm stroke and seat flush against the comb with no visible gap along the cutting edge. If the blades look fine and the tool recently had a new battery installed after long storage, run the shears unloaded for a few seconds and listen — a sluggish or uneven stroke cadence points back to a cell not yet at full capacity, which resolves after a full conditioning cycle.