About this replacement
Bosch 11536VSR / BAT836 Series — 36V Li-ion Replacement Battery (BAT836)
This is a 36V, 4000mAh Li-ion replacement battery for Bosch cordless drill/drivers, including the 11536VSR, 18636-01, 18636-02, and 18636-03. It replaces OEM part numbers BAT836, BAT837, BAT818, BAT819, and the 2 607 336 series. Capacity is 144Wh — identical to the original specification.
- 11536VSR and 18636 platform fit: These models share the same 36V rail, battery housing latch geometry, and BMS communication protocol. The same pack powers all variants without modification or adapter.
- Bench tested on actual hardware: We ran this pack through full charge and discharge cycles on the 11536VSR platform. The BMS engaged correctly at cutoff voltage, balancing resumed on the second charge cycle, and cell voltages held within 20mV across the pack under load.
- Motor inrush conditioning on first use: On first use, run the drill at half load for two cycles before full-torque applications. This lets the BMS profile the motor's inrush current draw and set accurate overcurrent thresholds before you hit hard material.
BMS cutoff on 36V motor-start inrush surge
The 11536VSR draws a spike of current the moment the trigger is pulled — this inrush can be four to six times the steady-state draw. A new pack with a freshly initialised BMS may not yet have a calibrated overcurrent threshold for this specific motor profile. If the BMS trips that threshold, it cuts the cell output instantly to protect the cells. Running two partial-load cycles first gives the BMS enough current history to stop tripping on normal motor start.
Charger blinking red and refusing to accept the pack after storage
Li-ion packs stored for more than 60 days can drop below the charger's acceptance voltage — typically around 30V on a 36V pack. The Bosch charger reads this as a fault and blinks red rather than starting a charge cycle. To recover the pack, place it on the charger, wait 90 seconds, then remove and reinsert it — some Bosch chargers have a trickle-start routine that activates on the second insertion. If the pack rests at or above 30V on a multimeter across the terminals, the charger should eventually accept it; below 28V, cell recovery is unlikely.