About this replacement
Bayco SLR-2120 — 7.4V Li-ion Replacement Battery (2ICR)
This 7.4V 2600mAh Li-ion battery fits the Bayco SLR-2120 portable LED work light. It replaces the original pack when the cell can no longer hold a charge or fails to power the light through a full work session. Capacity is 19.24Wh, matching the original cell specification.
- SLR-2120 platform fit: The SLR-2120 uses a two-cell 7.4V Li-ion pack with a specific connector and BMS handshake that controls current to the LED driver board. This replacement uses the same 2ICR cell configuration and connector, so the driver board recognises the pack without a fault state.
- Bench tested on actual hardware: We cycled this battery through charge and discharge on the SLR-2120 driver board. The BMS engaged thermal cutoff correctly under load and the LED driver stepped through its brightness tiers without undervoltage trips.
- First-cycle LED driver calibration: Run the light on medium brightness for the entire first charge cycle. The LED driver uses that cycle to calibrate current output against the new cell's internal resistance before you push maximum brightness — skipping this can cause early dimming on the first few uses.
Why the SLR-2120 dims before the low-battery indicator triggers
The LED driver in the SLR-2120 monitors cell voltage independently from the battery's own fuel gauge. When the driver detects voltage dropping under sustained draw, it reduces current to the LED array before the BMS low-battery signal fires. This protects the LED from current spikes during the final discharge phase. The result is visible dimming while the indicator still shows adequate charge — this is normal driver behaviour, not a faulty battery.
Light not reaching full brightness after installing a new battery
A new Li-ion pack straight from storage often sits at a resting voltage of 3.5–3.6V per cell — below the threshold the SLR-2120 driver needs to push full current to the LED array. The driver clamps output to protect the LEDs until both cells read above approximately 3.7V each. A full charge cycle before first use brings the pack to 4.2V per cell and resolves this. If the light still won't hit full brightness after a complete charge, check the charger output voltage — it should read 8.4V at the terminals.