Safety Reference

LiPo Battery Safety & Charging Guide

LiPo batteries deliver high power at low weight — perfect for RC. They also demand careful handling. This guide covers the practices we require and recommend at Marlow Anderson Field.

Golden Rules Charging Calculator Storage Emergency FAQ

Overview

LiPo (lithium polymer) packs are safe when treated correctly. Most incidents are caused by over-charging, physical damage, short circuits, or improper storage. Follow the procedures below and use proper charging gear to minimize risk.

⚠️ Never charge LiPos unattended.

If you must step away, stop the charge and disconnect the pack first.

The Golden Rules

Balance-charge every time (use the main leads and the balance lead).

Verify correct chemistry (LiPo) and cell count (S-count) on the charger.

Default to 1C charge rate unless the pack label explicitly allows higher.

Use a LiPo-safe bag or fire-resistant container while charging.

Keep dry sand within reach; know where the ABC extinguisher is.

Inspect packs before and after each flight (puffing, damage, heat).

Stop using any pack that is puffed, leaking, hot, or has been crashed.

Store at ~3.85V per cell (storage mode) — cool, dry, in a metal box.

Do not exceed the pack C-rating or your ESC/current limits.

Label your packs with name, capacity, S-count, and purchase date.

Charging: Step-by-Step

1
Place the pack in a LiPo-safe bag on a non-flammable surface (concrete, tile, or metal tray).
2
Set charger to Balance Charge → LiPo → correct S-count (e.g., 3S/4S).
3
Set current (amps) to pack capacity × C-rate (1C is the default — see calculator below).
4
Connect main leads and balance lead; check polarity and tight connections.
5
Start the charge and monitor it. The pack should stay cool to mildly warm.
6
Completion voltage is 4.20V per cell (e.g., 12.6V for 3S, 16.8V for 4S).
7
Let the pack rest a few minutes before installation or storage.

Charge Rates & Quick Calculator

1C = pack capacity in amps. For a 2200 mAh (2.2 Ah) pack, 1C = 2.2 A. Some packs support 2C+ charging — only use that if the label or manual explicitly allows it.

Typical Settings

Pack	1C Current	Full Voltage
2S 2200 mAh	2.2 A	8.40 V
3S 2200 mAh	2.2 A	12.60 V
4S 1500 mAh	1.5 A	16.80 V
6S 5000 mAh	5.0 A	25.20 V

Calculator

Capacity (mAh)

C-Rate

Cell Count (S)

Note: If your charger reads cell voltages significantly imbalanced (>0.05–0.10V spread), stop and balance-charge at a lower current, or retire the pack.

Storage & Transport

Voltage Targets

State	Per Cell	Notes
Storage	3.75–3.85 V	Use charger's `Storage` mode
Min (avoid)	≤ 3.0 V	Permanent damage risk
Max (full)	4.20 V	Never above 4.25 V (non-HV)

During flight: land before any cell sags below ~3.5V under load.

Transport

Use LiPo-safe bags or a vented metal container — no airtight lids.
Keep packs separated to prevent lead contact and shorts.
Never leave packs in a hot car. Heat accelerates puffing and risk.
Bring sand or a metal tray for field charging; clear combustibles first.

Inspection & When to Retire a Pack

Before Each Use

· No swelling/puffing beyond very slight softness.
· No cuts, dents, or punctures in the pouch or heat-shrink.
· Leads and balance plug secure; no exposed copper.
· Cells within ~0.02–0.05V of each other at rest.

Retire If You See

· Visible swelling, hissing, or chemical odor.
· Pack gets hot at low loads or during a gentle charge.
· Severe imbalance that won't correct with balance charge.
· Any crash with suspected physical damage.

Field Charging Setup

✓ Do

· Charge on concrete, asphalt, or a metal tray.
· Use a LiPo bag and quality balance charger.
· Keep dry sand and an ABC extinguisher nearby.
· Stay within arm's reach while charging.

✗ Don't

· Charge on grass, wood, or car interiors.
· Leave packs on full charge for days.
· Use damaged, puffy, or hot packs.
· Daisy-chain sketchy adapters or connectors.

Power Sources

· Use regulated AC/DC supplies or a healthy deep-cycle battery.
· Fuse DC leads; avoid alligator-clip chaos.
· Keep chargers shaded/cool for accurate temp sensing.
· Inspect leads & connectors for wear before each session.

🔥 Fire / Emergency Response

1
If a pack smokes or vents: Unplug if safe to reach. Move people back at least 25 feet.
2
Smother with dry sand to contain the pack. An ABC extinguisher handles the surrounding fire (grass, wood, gear) but won't stop thermal runaway inside the cell.
3
If it's only heating without flame, move the pack outdoors onto concrete or a metal tray and monitor — packs commonly flare more than once.
4
After it has fully cooled, treat the pack as hazardous waste and take it to a battery recycler.

A note on water

RC LiPos contain liquid electrolytes — water tends to scatter burning material rather than extinguish it. Our field standard is dry sand first , with water used only at a distance to keep surrounding fuel from igniting. Class D extinguishers are designed for lithium- metal fires and are not specifically required for LiPo packs.

Disposal & Recycling

Discharge the pack fully with a resistor/discharger or your charger's "Discharge" function (low current, supervised). Do not puncture the pack.
Tape over exposed terminals to prevent shorts during transport.
Bring to a battery recycling center — Home Depot, Lowes, and Best Buy all accept rechargeables. Avoid the outdated "saltwater soak" method.

Find a battery drop-off near you

Where to Buy LiPos

RCBattery.com

Hawks Pick

Our recommended source for low-cost, high-quality LiPo packs. Solid C-rating accuracy, fast US shipping, and a wide range of capacities and connectors. Great value for trainers, sport flyers, and bigger sport models alike.

Shop RCBattery.com

Other reputable shops include Horizon Hobby (Spektrum Smart packs), Pulse Battery, and SMC. Buy from a known seller — no-name Amazon listings often misstate capacity or C-rating.

FAQ

What voltage is "empty" for a LiPo?

Under load, try to land before any cell sags below ~3.5V. At rest after the flight, you'll usually read 3.7–3.8V per cell. Consistently going below 3.0V per cell damages packs and shortens cycle life.

Can I parallel-charge?

Yes, but only packs of the same cell count and similar state of charge (within ~0.1V per cell). Use a quality parallel board with fuses; total current = sum of individual 1C rates.

My pack is slightly puffy — is it safe?

Minor soft puffing is a warning sign. Reduce loads and monitor closely; if it grows, retire the pack. Visible ballooning, heat at rest, or a chemical smell means retire immediately.

Do I need to "break in" new packs?

Not strictly, but the first few cycles at modest discharge and 1C charges generally improve longevity.

How long should LiPos last?

A well-maintained LiPo typically delivers 200–300 useful cycles before capacity drops to ~80%. Heavy abuse (hot, full-charge storage; deep discharges; high-C charging) can cut that in half.

What does "HV" or "LiHV" mean?

High-voltage LiPos are designed to charge to 4.35V per cell (vs 4.20V standard). Only charge to that voltage if the label specifically says HV/LiHV — overcharging a standard pack is dangerous.

This page is hobby guidance for our field. Always follow your charger's manual and pack manufacturer instructions — they take precedence over anything written here.