Quick Answer
A 4S2P battery uses eight cells: four series groups set the voltage, while two cells in each group double capacity. This Flywoo pack is listed at 9000mAh, 573.5g and 45A continuous. It suits efficient, 4S-compatible aircraft that can carry its mass; it is not a sensible battery for a small Explorer LR 4.
What 4S2P Actually Changes
Inside the Flywoo Explorer Molicell P45B 4S2P pack are eight 21700 cells. Four groups connected in series make it a 4S pack. Pairing two cells in parallel in every group raises capacity from 4500mAh to 9000mAh.
| Marking | What it controls | Listed value |
|---|---|---|
| 4S | Series count and pack voltage | 14.8V on the Flywoo listing; 16.8V fully charged |
| 2P | Parallel cells per group | Two |
| 9000mAh | Stored charge | Two 4500mAh cells in parallel |
| 45A | Finished-pack continuous limit | Use this, not a theoretical doubled cell rating |
The naming hides two useful details. Molicel rates the individual P45B 21700 cell at 3.6V nominal and 4.2V charged, although the finished pack is marketed as 14.8V. More importantly, two 45A cells in parallel do not give permission to pull 90A: our finished-pack listing specifies 45A continuous, so that is the limit we would design around.
The Revision Trap We Would Check First
Flywoo's current manufacturer page at the same product URL now describes a BAK P45D version rated at 60A, while our product record identifies Molicel P45B cells and a 45A pack limit. Those are different revisions, not interchangeable numbers. Check the label on the pack you receive and use its lower published limit rather than copying a current web specification onto older stock.
At 573.5g, this pack weighs more than twice the complete sub-250g limit. The “Explorer” name describes Flywoo's battery range; it does not make this pack suitable for the 4-inch Explorer LR. Our Explorer LR 4 guide uses far smaller 4S packs. We would reserve this 4S2P battery for a larger endurance platform whose motors, ESC, connector and payload calculation all work below 45A continuous.
Charging Without Guessing
Use a charger with a Li-Ion programme, select 4S, connect both XT60 and the five-pin JST-XH balance lead, and confirm a 16.8V final voltage. Do not choose 18.0V LiHV mode. Set charge current from the finished pack's label or Flywoo's instructions; do not infer it by multiplying the bare-cell maximum.
Balance-charge on a non-flammable surface and stop if a parallel group drifts, the wrapper is damaged or the pack becomes unusually warm. For chemistry and flight-style trade-offs, read our Li-Ion versus LiPo guide, then browse current battery and power options by aircraft voltage and current requirement, not capacity alone.
FAQ
Q: Does 4S2P mean eight cells?
A: Yes. It contains four series groups, each made from two parallel cells: 4 × 2 = eight cells.
Q: Can I charge it as a 4S LiPo?
A: Only if the charger programme terminates at 4.2V per cell and the pack maker permits it. A dedicated Li-Ion mode is clearer. Never use a 4.35V-per-cell LiHV setting.
Q: Is 9000mAh automatically better than 4500mAh?
A: No. The extra parallel cells double capacity but also add mass. The aircraft must gain enough endurance to justify carrying a 573.5g pack while remaining inside its current and weight limits.