LiPo Batteries in FPV Drones: A Beginner’s Guide

Lithium Polymer (LiPo) batteries are the ideal power source for FPV drones, delivering exceptional energy storage and delivery. However, improper handling can pose safety risks. This guide covers the fundamentals of LiPo batteries for FPV drones, including safe charging practices and proper storage techniques when not in use.

Battery Recommendations

When selecting LiPo batteries, always choose reputable brands to ensure performance and quality. For a lighter, more agile drone, opt for smaller packs; for longer flight times over maneuverability, choose larger packs. Note that larger packs can supply higher currents but add weight, requiring a trade-off.

5-Inch Freestyle and Racing Drones

The most common LiPo batteries for 5-inch freestyle and racing FPV drones are 4S and 6S configurations. If unsure, I recommend 6S—it’s practically the industry standard in 2025. Typical capacity for 4S 5-inch drones is around 1500mAh, while 6S ranges from 1000mAh to 1300mAh.

Are LiPo Batteries Safe?

When handled correctly, LiPo batteries are perfectly safe. However, misuse or physical damage can lead to fire. Treat batteries with care and always store and charge them in fire-resistant locations to minimize risk.

Understanding LiPo Battery Basics

Lithium Polymer (LiPo) batteries offer an outstanding power-to-weight ratio, making them ideal for FPV drones. To choose the right LiPo, learn to read the label and understand key terminology—explained in the sections below.

LiPo Battery Voltage

LiPo batteries consist of individual cells, each operating within a specific voltage range:

• Fully charged: 4.2V per cell
• Fully discharged: 3.0V per cell

“Empty” does not mean 0V! Discharging below 3.0V can cause irreversible performance loss or damage. Overcharging above 4.2V per cell is extremely dangerous and may cause fire.

To extend battery life, land when cell voltage reaches ~3.5V. Exceptions exist—e.g., 1S pilots sometimes discharge below 3.2V to maximize flight time, as replacement cost is low.

Cell Count

LiPo batteries may contain multiple cells. The “S” rating indicates cells in series, increasing total voltage. Each cell has a nominal voltage of 3.7V, so labels show total nominal voltage:

• 1S = 1 cell = 3.7V
• 2S = 2 cells = 7.4V
• 3S = 3 cells = 11.1V
• 4S = 4 cells = 14.8V
• 5S = 5 cells = 18.5V
• 6S = 6 cells = 22.2V

Examples:

• A 4S battery has a nominal voltage of 14.8V (4 × 3.7V), with a minimum voltage of 12.0V and a maximum voltage of 16.8V (4 × 4.2V)
• A 6S battery has a nominal voltage of 22.2V, with a minimum voltage of 18.0V and a maximum voltage of 25.2V.

Higher cell counts increase motor RPM and drone power—if the drone supports the voltage. However, higher-S packs are heavier and more expensive.

Fun Fact:

• To calculate energy capacity, consider both voltage and capacity.
• Series: Two identical batteries in series double voltage, capacity stays the same (e.g., two 2S 1000mAh → one 4S 1000mAh).
• Parallel: Capacity doubles, voltage stays the same (→ one 2S 2000mAh).

Labels may include “P” (e.g., 4S2P or 6S2P), where “P” means parallel cell groups. 6S1P = “6 cells in series, 1 group in parallel” (usually just labeled 6S). 6S2P = 12 cells total.

Capacity

Capacity is measured in mAh (milliamp-hours), indicating how much current a battery can deliver over one hour until depleted. Note: 1000mAh = 1Ah.

Example: A 1300mAh (1.3Ah) battery at 1.3A constant draw lasts 1 hour. At 2.6A, it lasts 30 minutes. At 39A, only 2 minutes (1.3/39 = 1/30 hour).

Higher capacity extends flight time but increases weight and size. Weight significantly affects flight time and agility, so balance capacity and weight for optimal efficiency and performance.

Higher-capacity batteries can also deliver higher discharge currents.

C Rating

The C rating specifies the maximum safe current draw without damage. Theoretically: Max current = Capacity × C rating

Exceeding the C rating risks overheating, increased internal resistance, reduced lifespan, or thermal runaway (fire).

Even with identical capacity, higher C-rated batteries are often heavier and larger. For example, two 4S 650mAh batteries with different C ratings vary in weight and size.

Higher C-rated batteries perform better in high-power drones but may be overkill for low-power cruising—added weight can reduce flight time. Choose based on your needs; no one-size-fits-all.

Note: C ratings have become marketing-heavy. Brands may inflate specs, making cross-brand comparisons unreliable. Within the same brand, it’s useful. With our recommended batteries, C rating shouldn’t be a primary concern.

Internal Resistance (IR)

All electronics have resistance; in batteries, it’s internal resistance (IR)—a measure of opposition to current flow. Lower IR means more efficient power delivery to your FPV drone.

Monitoring IR helps assess battery health and know when to retire it. IR increases slowly with age and use—an irreversible process. Accelerating factors include:

• Over-discharge/overcharge
• Prolonged high-current draw
• Overheating

High IR causes greater voltage sag under throttle, reducing motor RPM, power, and responsiveness.

Some batteries (e.g., for radios or goggles) are designed for low current and naturally have higher IR—this is normal. 18650 Li-ion cells also have higher IR than typical LiPos.

Battery Connectors

All LiPo batteries (except 1S) have two connectors:

• Main discharge connector
• Balance connector

Discharge leads: Two thick red/black wires for powering the drone. Balance leads: Smaller wires to a white connector—number of wires depends on cell count.

Common discharge connectors:

• XT60: Standard for 5-inch+ FPV drones
• XT30: Smaller version for micro drones (same shape, lower current rating)

Balance Connector

Multi-cell LiPos include a JST-XH balance connector for monitoring and equalizing cell voltages during charging.

Wire count = cell count + 1:

• 2S → 3 wires
• 3S → 4 wires
• 4S → 5 wires
• 5S → 6 wires
• 6S → 7 wires

Long balance leads can be bundled with a rubber band to reduce vibration.

Keep Batteries Balanced

Before use, ensure cell voltages are close. Unbalanced packs risk over-discharging weaker cells. Persistent imbalance may indicate high IR in one cell—inspect carefully.

Dead Cell

If one cell shows 0V, the battery has a dead cell. Confirm with a multimeter—do not use.

Battery Types

Lithium Polymer (LiPo)

Standard for racing and freestyle FPV drones. Full charge: 4.2V/cell. Storage: ~3.85V/cell.

Lithium Ion (Li-Ion)

Higher capacity per weight than LiPo—ideal for long-range. Lower discharge performance; not suited for high-intensity flight.

How Many Packs Should a Beginner Buy?

Four packs are ideal for beginners. With 5–10 minute flights (including crash retrieval, setup, and breaks), four packs provide ~40 minutes of flight time. Field charging extends this significantly.

Weight

Battery weight should be ~half the drone’s dry weight (without battery/GoPro). Example: 600g drone → 300g battery for agile freestyle. For cinematic/slow flight, 1:1 ratio is acceptable.

For long-range/cinematic FPV, larger batteries maximize flight time—weight can equal or exceed drone weight when responsiveness isn’t priority.

Determine Drone Current Draw

After selecting motors and props, find thrust data and current draw. Example: One motor + 5040×3 prop at full throttle = 36.74A. Quad (4 motors) max draw = 36.74 × 4 = 146.96A.

For safety, reduce by 30–40%:

• Rarely full throttle > few seconds
• In-flight draw lower than static bench tests

Other components draw negligible current.

Choose Optimal Battery Capacity

General guidelines for freestyle/racing drones:

4S LiPo:

• 7-inch: 1500–2200mAh
• 5-inch: 1300–1800mAh
• 4-inch: 850–1300mAh
• 3-inch: 650–1000mAh

6S LiPo:

• 7-inch: 1200–1500mAh
• 5-inch: 900–1300mAh
• 4-inch: 550–900mAh
• 3-inch: 400–650mAh

Formula for C rating: C rating = Current draw / Capacity

Rule of thumb: Battery weight ≈ half drone weight. Not perfect, but works for most setups.

Importance of Balance Charging

Always plug in the balance lead before charging. The charger monitors and balances each cell.

Cells have slightly different IR; post-flight, some may be higher than others. Within reason, this is normal. Charging without balance risks overcharging some cells (>4.2V) while others remain undercharged—dangerous.

Most modern chargers require balance leads for safety. If yours doesn’t—discard it and buy a smart charger.

Charging Speed: How Fast Should You Charge?

Charge at 1C or slower to minimize stress. 1C = charging current = battery capacity

• 1500mAh → 1.5A
• 900mAh → 0.9A

Fun fact: 1C charging takes ~1 hour from empty to full, regardless of pack size.

Some new batteries support 3C or 5C fast charging—check specs. When in doubt, use 1C. Faster charging increases heat/fire risk.

Batteries should not get warm during charging. Stop immediately if they do—could indicate fast charging or battery fault.

Choose a Safe Charging Location

Charge away from flammable materials. Indoors: near a window/door for quick removal in case of fire.

Never Leave Charging LiPos Unattended

Stay in the room. Many LiPo fires occur from unattended charging. Monitor temperature regularly. Stop if batteries get hot or swell—could indicate failure, overcharge, or excessive rate.

How to Safely Use LiPo Batteries

Storage Charge

If not using for >2 weeks:

1. Charge/discharge to 3.80–3.85V per cell (~40–50% capacity)
2. Store in a fireproof container (LiPo bag, ammo can)
3. Keep at room temperature—extreme cold/heat harms lifespan and safety

This is the most stable state. New batteries ship at storage voltage. Most chargers have a “Storage” mode.

How Long Can Fully Charged LiPos Be Stored?

Charging the day before flying is fine. Personally, I return to storage voltage (3.8V/cell) if not flying for days.

Avoid prolonged full or empty storage. Most agree a few days is acceptable. For weeks without flying, use storage mode. Most chargers handle this easily (discharge is slower).

Operating Temperature

LiPos perform best at 30°C to 60°C. Cold weather increases voltage sag and reduces flight time.

When to Land

Land at 3.5–3.6V per cell. Flying lower stresses the battery, generates heat, and shortens life. Voltage drops faster below 3.5V—risk of over-discharge before safe landing.

Exception: 1S Whoop batteries often land at 3.2V or 3.0V due to extreme sag (voltage rebounds post-flight). Maximizes flight time; 1S packs are cheap.

How Long Do LiPo Batteries Last?

No expiration date. With care, they last years. I have 6–7-year-old packs still performing. Performance degrades over time—most replace every 2–3 years for peak performance.

Summary:

• Gradual decline: No shelf life
• Performance loss: ~3.8% in first 100 cycles (5.4% for LiHV)
• Replacement: I replace every 200–300 cycles or 2–3 years
• Extended use: Safe to continue, but higher IR → more sag, less capacity, shorter flights

When to Retire a LiPo Battery

Limited cycle life—one full charge/discharge = one cycle. Well-maintained RC LiPos last >300 cycles. Physical damage often ends them sooner.

No strict rule, but rising IR reduces punch and capacity. Discard if dented or puffed like a balloon.

FAQs

Q: Are puffed LiPos dangerous?

A: Yes—unsafe to use or store.

Q: What causes puffing?

A: Gas buildup inside. Natural over time; accelerated by damage, overheat, over-discharge.

Q: Can I fix a puffed LiPo?

A: No. Dispose properly immediately.

Q: How to prevent puffing?

A:

• Avoid over-discharge (use voltage alarm)
• Avoid overheating (no sun/heat sources, don’t overload)
• Never overcharge (proper charger settings, monitor)
• Store correctly (as above)

Q: Do new batteries need break-in?

A: Controversial. Some advocate slow charge/discharge cycles. I’ve tried—no noticeable difference.

Technical Terms

• Cut-off voltage: Fully discharged voltage; 3.0V for LiPo
• Cycle life: Total charge/discharge cycles before significant degradation
• State of charge: Energy level 0–100%
• Burst C rating: Max discharge for short bursts (~10 sec)