LiPo Batteries
LiPo Battery Basics (What They Are)
LiPo = Lithium Polymer rechargeable battery packs commonly used in RC cars, trucks, planes, and drones.
Common Pack Types
- 2S = 2 cells = 7.4V nominal
- 3S = 3 cells = 11.1V nominal
- 4S = 4 cells = 14.8V nominal
- 6S = 6 cells = 22.2V nominal
“S” means cells in series. Higher S = more voltage = more power.
What “mAh” Means
mAh (capacity) = how long it runs. Example: 5000mAh usually runs longer than 3000mAh (same setup).
What “C Rating” Means
C rating = how fast it can safely deliver power (ratings are often optimistic).
Don’t rely heavily on C ratings—real-world performance varies by brand and pack condition.
LiPo Voltage Chart (Most Important Numbers)
These are per cell values:
Normal / Safe Range
- 4.20V = Full charge (absolute max)
- 3.85V = Storage voltage (ideal)
- 3.70V = Nominal
- 3.50V = Getting low (stop soon)
- 3.30V = Low / damage risk begins
- 3.00V or lower = Danger zone (permanent damage likely)
Pack Voltage Example (3S)
- Full: 12.6V
- Storage: 11.55V
- Nominal: 11.1V
- Low-ish: 10.5V
- Too low: 9.9V or less
Charging a LiPo (Proper Settings)
Use a LiPo balance charger. Do not use a “dumb charger.”
Always Use BALANCE CHARGE
Balance charging keeps each cell equal and helps prevent overcharging a single cell.
Charge Rate (Amps)
Standard safe charge rate is 1C unless the battery specifically supports higher.
For maximum battery life, charging at 0.5C is easier on the pack.
Correct Cell Count Matters
Confirm your charger is set to the correct S count (2S, 3S, 4S, etc.). Never force charge if the charger detects the wrong cell count.
Battery Checker / Alarm (Highly Recommended)
There is a small inexpensive device called a battery checker. For less than $10, this device will show you the pack voltage and each individual cell so you can quickly confirm if your battery is charged or needs attention.
It also has a programmable alarm that will beep when your battery voltage starts getting low. You can leave this plugged into your battery when you fly and place it inside the aircraft next to the battery. When the battery is starting to get low, it will emit an extremely loud beeping sound to notify you it’s time to think about landing. It will continue to beep until the pack voltage recovers above the set threshold or you unplug it.
This is a must-have for anyone without an advanced radio system. We recommend keeping one in your flight pack and one near your charger if you’re not using a digital smart charger.
Recommended: FMS LiPo Battery Voltage Checker
Storage Voltage (How to Store LiPos Correctly)
If you’re not using the battery within a day or two, store it at:
Most chargers have a Storage Mode that automatically charges/discharges to the correct level.
Why Storage Voltage Matters
- Storing a LiPo fully charged long-term can cause swelling and faster wear.
- Storing a LiPo empty can kill it.
Best Storage Conditions
- Cool, dry place
- Avoid heat (like inside a car)
- Use a LiPo safe bag or ammo can (with venting)
Discharging / Using LiPos Safely
Don’t Over-Discharge
Over-discharging is the #1 killer of LiPos. Most ESCs have LVC (low voltage cutoff), but don’t rely on it too much. A good rule: stop driving/flying when performance drops noticeably.
Recommended Minimum Voltage Under Load
Try to stop before cells drop below 3.4V–3.5V per cell under load. After the pack rests, voltage will bounce back higher.
Notes by Use Case
- RC Cars/Trucks: Easy to run too low because you’ll keep driving until it crawls. A voltage alarm helps.
- RC Planes: If you have telemetry, set warnings. If not, use flight timers and land early.
Charger Recommendations
1) Beginner “Set It and Forget It” Charger
This is best for beginners who want an easy, “set it and forget it” operation. Simply plug in the battery plugs as shown and press and hold the charge button until it beeps. It will beep again once fully charged.
It also has a simple one-button Storage Charge function for when you return from the field, which helps keep your batteries in optimum condition. It will charge 2S–4S batteries with an XT-60 plug with no adapters needed for Ranger 1220 batteries. No charger programming needed.
Link: Gens Ace Beginner Smart Charger
2) Programmable Dual Charger (Charge 2 Batteries at Once)
This is a fully programmable dual charger that’s still intuitive. Charge up to two batteries at once and adjust the cell voltage and charge rate to optimize your charging.
It has default settings for voltage for charging, balancing, and storage modes, making it easy to use (and you can adjust these voltages if needed).
To use the charger: insert the two battery plugs as shown, choose your charge mode (charge, storage, etc.), set your charge rate (amps—1300mAh = 1.3A, 2200mAh = 2.2A), and press start. If you’re charging a second battery, it will carry over the same settings to the next screen, so if the batteries are the same you usually just press start again.
This charger supports 2S–6S, comes standard with XT-60, and includes adapters for T, EC5 and EC3 plug types (other adapters can be purchased).
Link: Gens Ace Dual Smart Charger
Do’s and Don’ts (Straight to the Point)
DO
- Balance charge every time
- Charge at 1C or less for longest life
- Store at 3.85V/cell if not using soon
- Use a LiPo bag or fire-resistant container while charging
- Check packs regularly for swelling or damage
- Secure the pack so it can’t bounce around
- Let the pack cool before recharging
DON’T
- Don’t charge unattended
- Don’t charge a damaged or swollen pack
- Don’t puncture, crush, or bend packs
- Don’t store fully charged for long periods
- Don’t run a pack until the vehicle stops moving
- Don’t charge above 4.20V/cell
- Don’t use NiMH mode on a LiPo
- Don’t short the leads (even for a second)
What Happens If a LiPo Swells?
A swollen LiPo usually means:
- It was over-discharged
- Overcharged
- Overheated
- Or it’s simply worn out
Connectors and Balance Plugs
A LiPo has:
- Main power connector (XT60, EC3/EC5, Deans, etc.)
- Balance plug (2S/3S/4S multi-pin plug)
The balance plug is required for balance charging and checking individual cell voltage. If a balance plug is damaged, don’t charge until it’s repaired.
LiPo FAQ
Q: Can I leave my LiPo plugged into my RC?
No. Even with the vehicle off, many ESCs draw a small amount of power and can over-discharge the pack.
Q: Can I charge a warm LiPo?
Better not. Let it cool to room temperature first. Heat = stress = shorter life.
Q: My pack is at 3.2V per cell. Is it ruined?
Maybe not, but it’s not good. Charge it immediately with balance charge and watch cell behavior. If it won’t balance or one cell stays low, replace it.
Q: What’s a “balanced pack”?
A healthy pack has cells close together, usually within 0.01V–0.05V of each other.
Q: Can I fast charge at 2C or 3C?
Only if the battery specifically supports it, and even then it shortens life. 1C is the safe standard.
Q: What voltage should a LiPo be after driving/flying?
If you stop at a good time, it should usually rest around 3.7V–3.85V per cell. If it rests around 3.4V or lower, you probably went too far.
Q: Is it normal for LiPos to puff slightly?
A tiny amount of puffing over time can happen, but any noticeable swelling means it’s nearing end of life and shouldn’t be trusted.
Q: Can I put LiPos in the fridge?
Not recommended (condensation risk). Cool room-temperature storage is fine.
How to Dispose of LiPo Batteries
Do not throw LiPos in the regular trash. Use a local battery recycling drop-off (hardware stores or recycling centers). If the pack is damaged, follow local guidelines and treat it as hazardous.