3.7V Steinel Neo 1 Cordless Glue Gun Replacement Battery

My Steinel Neo 1 glue gun stopped heating mid-project and now it just won't turn on — is the battery dead or did something else happen?

At 3.7V, Li-ion cells at this capacity will trigger an undervoltage lockout if they're discharged too far, and the gun's protection circuit cuts power completely — it doesn't just run slow, it goes dark. This usually happens when the gun sat unused for several months and the cell self-discharged below the recovery threshold. Plug it in via micro USB and leave it for at least 20 minutes before trying to power it on, since a fully depleted cell often won't respond in the first few seconds of charge. Check that the charging indicator is actually active — no light at all after plugging in usually means the cell is below 2.5V and needs a slow recovery charge or replacement.

The glue keeps dripping from the nozzle even though I'm not pressing the feed button — did something happen to the battery or is this a mechanical fault?

The anti-drip system on the Neo 1 is motor-driven and depends on the battery holding enough voltage to retract the adhesive when you release the trigger. When a Li-ion cell starts aging and voltage sags under load, the retraction mechanism doesn't pull back with enough force, so adhesive continues to creep forward. This is one of the first signs the cell is losing capacity — the heater still works, but the motor doesn't get clean power. Check resting voltage after a full charge with a multimeter; a healthy 3.7V cell should read between 4.1V and 4.2V fully charged, and anything under 3.9V at rest points to a degraded cell that needs replacing.

My Neo 1 charges fine and the light goes green, but it barely gets through a few glue sticks before dying — brand new replacement battery did the same thing, what's going on?

If a replacement cell shows the same symptom, the most likely cause is an incomplete first charge cycle — Li-ion cells shipped in storage mode sometimes only partially initialize on the first charge and report full when they aren't. Run the gun until it shuts off from low voltage, then do a full uninterrupted charge via micro USB until the indicator goes green without interruption. If the problem persists across two full charge-discharge cycles, check the USB charging cable — the Neo 1's micro USB port is current-sensitive, and a worn or low-quality cable can cap the charge current low enough that the cell never reaches full capacity. Swap to a known-good cable and repeat the full cycle before concluding the replacement cell is faulty.