About this replacement
TomTom Spark 3 / Spark Cardio 2 — 3.7V Li-Polymer Replacement Battery (SP322826PA)
This is a 3.7V, 150mAh Li-Polymer cell that replaces the original SP322826PA battery in the TomTom Spark 3, Spark Cardio 2, and Spark 3 GPS watches. It fits directly into the same 28.35 × 28.40 × 3.70mm cavity as the factory cell. Voltage and protection circuit pinout match the original spec.
- Spark 3 and Spark Cardio 2 compatibility: Both models share the same chassis dimensions, connector orientation, and BMS handshake protocol — that is why one cell covers all three variants. The protection circuit on this cell responds to the same charge termination signal the watch sends at 4.2V.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Spark 3 platform and confirmed the BMS accepted charge, terminated correctly at 4.2V, and did not trip on GPS acquisition current draw. The fuel gauge IC re-initialised after a full charge cycle from near-zero.
- Post-swap charging requirement: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before turning it on. The Spark 3 fuel gauge IC loses its voltage reference during a cell swap and cannot report accurate capacity until it completes one full charge cycle from near-zero.
Why the Spark 3 GPS and continuous heart rate monitoring drain a new cell faster in the first week
A new Li-Polymer cell has a slightly different internal impedance compared to the aged cell it replaces. The Spark 3's optical heart rate sensor and GPS radio adjust their drive current based on signal return strength — on a new cell, that process can take several charge cycles to settle. You may notice the battery percentage dropping faster than expected during the first three to five days. This is not a fault with the cell; it normalises once the firmware's power management routine adapts to the new impedance profile.
Watch not pairing to phone after battery replacement
Removing the battery clears the active Bluetooth Low Energy session stored in the watch's volatile memory. The phone still shows the watch as a saved device, but the watch no longer recognises the session token. Go into your phone's Bluetooth settings, forget the TomTom Spark 3 device entirely, then re-pair it from scratch through the MySports app. Do not attempt to pair while the battery is below 20% — the BLE radio on this platform can drop the pairing handshake under low-voltage conditions.