Your battery limits every flight. S-ratings, C-ratings, mAh capacity, balance charging, storage voltage, and safety rules — for RC planes, cars, helicopters, and FPV drones.
LiPo batteries power most modern RC aircraft, cars, and drones. Every pack is defined by three numbers: S-rating (cell count = voltage), mAh (capacity = runtime), and C-rating (discharge rate = power headroom). For a beginner RC plane trainer, a 3S 1800–2200mAh 30–40C pack covers most needs. Always charge with a balance charger, store at 3.75–3.85V per cell, and retire any puffed or swollen pack immediately.
Every LiPo label carries the same three pieces of information. Understanding them removes the guesswork from every purchase and lets you match a pack to any aircraft on spec alone.
S-rating — cell count and voltage. Each lithium polymer cell has a nominal voltage of 3.7V. Cells connected in series add their voltages: a 3S pack is 3 × 3.7V = 11.1V nominal, 12.6V fully charged, 9.0V minimum safe cutoff. The S-rating is the first number to check when matching a pack to an aircraft.
| S-Rating | Nominal | Full Charge | Common Use |
|---|---|---|---|
| 1S | 3.7V | 4.2V | Micro FPV, indoor park flyers |
| 2S | 7.4V | 8.4V | Small planes, beginner FPV, micro cars |
| 3S | 11.1V | 12.6V | Trainer planes, small helis, 1/10 RC cars |
| 4S | 14.8V | 16.8V | Sport planes, FPV 5" quads, 1/8 cars |
| 6S | 22.2V | 25.2V | Large aerobatics, large helis, FPV racing |
mAh — capacity and runtime. Milliamp-hours measure how much charge the pack stores. A 2200mAh pack can deliver 2.2 amps for one hour, or higher currents for shorter periods. A trainer aircraft drawing 15–20A cruise will get roughly 6–8 minutes from a 3S 2200mAh pack. Higher capacity = longer runtime, heavier pack. Never exceed the aircraft's rated maximum pack weight.
C-rating — how fast you can pull power. The C-rating × mAh capacity = maximum safe continuous current. A 40C 2200mAh pack: 40 × 2.2A = 88A continuous. For a trainer drawing 25A peak, a 40C pack has plenty of headroom. C-ratings above 65C are relevant for RC cars, FPV racers, and aerobatic aircraft — not for beginner trainers.
For beginner planes: 30–40C is sufficient. For RC cars and FPV racing: 65–100C. A higher C-rating than needed does no harm — the pack simply won't be stressed near its limit.
The connector on your battery must match your aircraft's ESC. The four connectors you will encounter most often:
NiMH (Nickel Metal Hydride) — heavier per unit of energy than LiPo but more mechanically robust. A punctured NiMH pack vents and heats — it does not ignite the way a LiPo can. Some older and budget aircraft are designed for NiMH specifically. For any modern aircraft, LiPo's superior energy density and discharge rate make it the correct choice — a LiPo of equivalent capacity is typically 30–50% lighter.
LiFe (Lithium Iron Phosphate) — considerably more thermally stable than LiPo, with a lower cell voltage (3.3V nominal vs 3.7V). Used primarily in RC transmitters and receiver battery packs where safety and longevity matter more than peak power output. Not interchangeable with LiPo packs without ESC reprogramming.
RC planes — trainers. Most beginner trainers use 3S packs in the 1800–2200mAh range. The AeroScout S2 uses a 3S 1800mAh pack; the Apprentice STS uses a 3S 3200mAh. Always follow the manufacturer's voltage recommendation — installing a 4S pack in a 3S-rated aircraft overspins the motor and ESC.
RC cars. Beginner 1/10 scale electric cars typically use 2S 5000–6000mAh packs. C-ratings for cars run higher than aircraft (65–100C) due to high burst current during acceleration. Physical dimensions matter: verify the pack fits the battery tray before purchasing.
RC helicopters. Size determines chemistry. Micro helis: 1S–2S. 450-class: typically 3S 2200mAh. 550–700 class: 6S packs with 4000–6000mAh. Consistent voltage under load is critical — insufficient C-rating causes rotor speed variation and loss of control authority.
FPV racing quads (5"). The current standard: 6S 1100–1500mAh at 100C+. The shift from 4S to 6S provides higher efficiency at lower current draw. Freestyle pilots preferring longer flight time commonly use 6S 2000mAh packs.
Every LiPo pack must be charged with a balance charger. Individual cells within a multi-cell pack drift in capacity over time. A balance charger monitors each cell individually through the balance lead and equalizes them to within a few millivolts on every charge cycle. This prevents cell imbalance, the most common cause of premature LiPo degradation.
⚠️ Never charge a LiPo with a simple wall charger or any charger not rated for LiPo. Overcharging beyond 4.2V per cell causes thermal runaway — the reaction that leads to fire. Only use a balance charger with dedicated LiPo mode.
The 1C rule: charge at a rate in amps equal to the pack's capacity in amp-hours. A 2200mAh pack charges at 2.2A. This balances charge time with cell stress and maximizes pack longevity. A 3S 2200mAh pack charged at 1C from storage voltage reaches full charge in approximately 45–60 minutes.
If not flying for more than 48–72 hours, store packs at storage voltage: 3.75–3.85V per cell. For a 3S pack, that is 11.25–11.55V total. Storing fully charged degrades cells through oxidative stress. Storing deeply discharged causes irreversible capacity loss. Most modern balance chargers include a Storage mode that handles the charge or discharge automatically.
After every flying session, put unused full packs into Storage mode before storing. This single habit extends pack life from 50 cycles to 200+ cycles.
Three signs indicate immediate retirement: visible puffing or swelling (gas from internal reactions — a safety risk, not cosmetic damage); significant voltage sag under load that reduces flight performance vs a new pack of the same spec; and persistent cell imbalance that cannot be corrected by repeated balance charging.
A well-maintained pack — charged at 1C, stored at storage voltage, never deep-discharged — lasts 150–300 cycles. To dispose: fully discharge using the salt-water method, then take to an electronics recycling drop-off. Never put a LiPo in household trash or curbside recycling.
The post-crash inspection guide covers how to assess a battery after an impact before deciding whether it is safe to charge.
10-page PDF covering the equipment checklist, pre-flight routine, LiPo handling, and what to do after a crash — formatted for the field, not the browser.