Stihl HSA 25 Cordless Shears 10.8V Replacement Battery

My HSA 25 shears start cutting then slow down and stop after a few passes — why does it keep cutting out?

At 10.8V, this chemistry is sensitive to voltage sag under load — when the blade hits dense stems or wet growth, current draw spikes and the protection circuit trips to prevent cell damage. The battery hasn't failed; it's doing its job. Let the pack sit for two minutes, then try again on lighter material to confirm the pattern. If it cuts out even on thin grass, check the resting voltage with a multimeter — a healthy 10.8V Li-ion pack should read above 11V off the charger.

Replaced the battery on my HSA 25 and now it won't hold a charge — drains sitting in the shed without even using it.

Li-ion cells at this capacity class self-discharge faster when stored in a discharged state, and a new pack that sat in a warehouse can arrive with cells slightly out of balance. If the pack drops to near-empty and sits that way for weeks, one or more cells can drift below recovery threshold. Charge it fully as soon as it arrives and store it at roughly half charge in a cool, dry place — not in a hot shed or car. If it's losing significant charge within a week of a full charge without use, run a full charge-discharge-charge cycle and check whether the pattern repeats.

Charger light goes green but my HSA 25 shears still feel weak and stop halfway through trimming the hedge — is the battery actually charged?

A green charge light means the charger stopped pushing current, but it doesn't confirm all cells are balanced — one weak cell can pull the pack voltage down under load even after a full charge reads complete. This is a common issue with Li-ion packs that have been deeply discharged or left flat for an extended period. Put the pack on charge for a full uninterrupted cycle, then test it immediately on the shears — don't let it sit overnight before testing, as surface charge can mask a weak cell. If it still fades quickly, check the pack voltage under load with a multimeter; a reading that drops below 9V during cutting points to a cell that's no longer holding capacity.