RC Battery Parallel Pack Calculator
Calculate combined capacity, C-rating, and discharge current when connecting RC LiPo batteries in parallel.
How RC Battery Parallel Packs Work
Connecting LiPo batteries in parallel increases total capacity and maximum discharge current while keeping the voltage the same. This is commonly done in large RC planes, boats, and heavy-lift drones that need more energy than a single pack provides.
Parallel Connection Rules
Voltage stays the same:
V_total = V_single (all packs must be the same cell count / voltage)
Capacity adds up:
Capacity_total_mAh = Capacity_per_pack × Number_of_packs
Maximum continuous discharge adds up:
Max_Amps_total = Max_Amps_per_pack × Number_of_packs
Where Max_Amps_per_pack = (Capacity_mAh / 1000) × C_Rating
C-Rating Explained
The C-rating indicates how fast a battery can safely discharge relative to its capacity:
- A 2200 mAh battery with a 25C rating can deliver: (2200/1000) × 25 = 55 amps continuous
- Two of these in parallel: 110 amps continuous, 4400 mAh total
Worked Example
Three 5000 mAh 4S (14.8V) 30C packs in parallel:
- Voltage: 14.8V (unchanged)
- Total capacity: 5,000 × 3 = 15,000 mAh (15 Ah)
- Max discharge per pack: (5000/1000) × 30 = 150A
- Total max discharge: 150 × 3 = 450A
- Total energy: 14.8V × 15Ah = 222 Wh
Important Safety Rules
| Rule | Why |
|---|---|
| Same cell count (S) | Different voltages cause dangerous current flow |
| Same or similar capacity | Unmatched packs cause uneven load |
| Match voltage before connecting | Even 0.1V difference causes a large inrush current |
| Same C-rating preferred | Weaker pack gets stressed during high-draw maneuvers |
Charge Time Estimation
Charge_Time_hrs = Total_Capacity_mAh / (Charge_Rate_mA)
At 1C charge rate: Charge_Time = Total_mAh / Total_mAh = 1 hour (theoretical). In practice, charging takes about 1.2 hours at 1C due to the balance and CV (constant voltage) phase at the end of the charge cycle.
Weight Consideration
Total pack weight = Single_Pack_Weight × Number_of_Packs. In RC aircraft, every gram matters for flight time and handling. Parallel packs are most common in boats and ground vehicles where weight is less critical.