Wolf Garten 7.4V 2500mAh Li-ion Replacement Battery 8803

My Wolf Garten grass shears cut fine for a bit then slow right down before the battery is even close to empty — what's happening?

At 7.4V, Li-ion cells in light cutting tools drop voltage faster under blade resistance than the charge indicator reflects, so the tool's protection circuit reads an acceptable state of charge but the actual cell voltage sags below the motor's efficient operating threshold mid-job. This is often worse with a new replacement battery on its first two or three cycles before the cells have balanced. Run two or three full discharge-and-charge cycles before assuming the battery is faulty. If the slowdown keeps happening after that, check resting voltage with a multimeter — a healthy 7.4V pack should read between 8.2V and 8.4V fully charged.

Charged the replacement battery overnight and the shears won't even turn on — no lights, nothing

A 7.4V Li-ion pack that's been stored or shipped in a deeply discharged state can sit below the threshold the charger needs to recognise it and begin charging, so it never actually took a charge. This is called a sleep state, and the pack looks dead even though it isn't necessarily failed. Try leaving it on the charger for a full 24 hours — some chargers will trickle enough current to wake the cells. If there's still no response after that, measure voltage directly across the battery terminals; anything below 5.5V means the cells have dropped too far to recover safely.

Blade is spinning but feels weak and it's struggling through grass it used to handle easily — replaced battery and it's worse than the old one

Counterintuitively, a brand-new Li-ion replacement can perform worse than an old partially degraded pack for the first few cycles because the cells haven't gone through enough charge-discharge passes to reach full capacity. The 2500mAh rating is the cell's rated capacity at formation, not what it delivers out of the box. Check that the battery is clicking fully into the tool's contact bay — a partially seated pack on the BS80 Plus or 8824 body creates enough contact resistance to rob power at the motor. Fully seat it, run it to cutoff twice, and recharge completely before judging performance.