82V GreenWorks Cordless Lawn Mower Replacement Battery G82B25

My GC82LM46 cuts fine for the first pass then bogs down and loses power on the second — is the battery dying or is something else wrong?

On high-draw brushless mowers, this pattern almost always points to thermal throttling rather than a failing cell — the pack heats up during the first pass and the BMS reduces output to protect it. Check whether the battery feels hot to the touch when the power drops; if it does, the fix is a 10–15 minute rest between passes to let the pack cool below 40°C. If the battery stays cool and the bog still happens, measure resting voltage after the second pass — a healthy 82V pack should read above 78V under no load. Consistently dropping below that points to cell imbalance, not heat.

Replaced the battery and now the mower deck judders and vibrates more than it did with the old pack — could a new battery cause that?

A new battery doesn't cause vibration directly, but a higher resting voltage from a fresh pack can briefly drive the brushless motor faster than the old worn-down pack did, which makes existing blade imbalance or a bent blade more obvious. Remove the blade and check it for nicks, uneven wear, or a slight curve along the cutting edge — any asymmetry that was masked before will be amplified with a fully charged 82V supply. Reinstall the blade and torque the center bolt to spec before assuming the battery or motor is the problem. If the judder disappears once the pack drops to mid-charge, an unbalanced blade is almost certainly the cause.

The 82V charger stopped mid-cycle and the LED is solid red — pulled the battery out and put it back in and nothing changed

A solid red fault light that persists after reseating the battery usually means the BMS detected a cell voltage that was either too low to safely charge or outside the temperature window when you plugged in. Leave the battery at room temperature (15–25°C) for 30 minutes, then try the charger again — cold packs pulled from a garage in winter trigger this constantly on 82V Greenworks hardware. If the fault clears and charging starts, you're fine; if it stays red after the pack has warmed up, measure the battery's output terminals with a multimeter — a reading below roughly 70V means one or more cells have discharged past recovery and the pack won't accept a charge cycle.