Every truck on our repair bench has a story, and a surprising number of them start with the battery. A pack that sat full in a hot garage for a month. A charger set to the wrong cell count. A "150C" bargain pack that puffed on its third run. The battery is the fuel tank, the gas pedal and, if you get careless, the biggest hazard in the hobby.
The good news is that batteries are not complicated. Learn a handful of numbers, build four or five habits, and your packs will last longer, hit harder and stay boring in the best way. Here is everything we explain at the counter, minus the waiting in line.
The Short Answer
For most RC drivers and pilots, LiPo is the performance choice and NiMH is the easy choice. A LiPo cell is 3.7 V nominal and 4.20 V full. Balance charge it at 1C unless the maker says otherwise, store it near 3.8 V per cell, never charge it unattended, and recycle it properly when it is done.
- Read the label: S is cell count (voltage and speed), mAh is runtime, C is the maker's discharge rating.
- Charge smart: right chemistry, right cell count, 1C, balance lead connected, in a LiPo bag, with you in the room.
- Store and retire safely: storage-charge idle packs, and take dead or puffed packs to a battery recycler, not the trash.
1. Know Your Battery: Chemistries, Labels and Plugs
Before you can charge a pack correctly, you need to know what it is. The label tells you almost everything.
LiPo, NiMH, LiHV and LiFe compared
| Chemistry | Volts per cell | Best for | Watch out for |
|---|---|---|---|
| NiMH (nickel-metal hydride) | 1.2 V nominal (6 cells = 7.2 V, 7 cells = 8.4 V) | First RTR trucks, kids' cars, simple ownership | Heavier, and power fades as the pack runs down |
| LiPo (lithium polymer) | 3.7 V nominal, 4.20 V full | Brushless cars, planes, drones, anything fast | Needs a balance charger, storage charging and careful handling |
| LiHV (high-voltage LiPo) | 3.8 V nominal, 4.35 V full | Racers chasing a little extra punch | Only charge to 4.35 V if the pack is labeled LiHV |
| LiFe (lithium iron phosphate) | 3.3 V nominal | Receiver and transmitter packs | Needs the LiFe setting on your charger, never LiPo |
If you are new and just want to drive, a NiMH pack like the Traxxas 7-cell 3000mAh NiMH with iD is hard to mess up. Once you go brushless, you will want LiPo. Browse both in our LiPo battery collection and NiMH packs.
Decoding a LiPo label: S, mAh and C
| Label | What it means | Example |
|---|---|---|
| S (cell count) | Cells in series. Each adds 3.7 V nominal. More S means more speed. | 3S = 11.1 V nominal, 12.6 V full |
| mAh (capacity) | How much energy is in the tank. More mAh means longer runs. | 5000mAh = 5.0 amp-hours |
| C (discharge rating) | The maker's rating for how fast current can come out. | 50C x 5.0 Ah = 250 A on paper |
Connectors and "smart" packs
- Spektrum IC3 and IC5 (ARRMA, Losi, Axial, E-flite) add a data pin for Smart batteries and also accept older EC3 and EC5 plugs. Smart G2 packs like the Spektrum 3S 5000mAh 50C Smart G2 balance through that single plug when used with a Smart G2 charger.
- Traxxas iD builds the balance wiring into the main plug. An iD charger like the Traxxas EZ-Peak Plus reads the pack and sets itself up automatically. See the Traxxas 3S 5000mAh iD pack.
- XT60, XT90 and Deans (T-plug) show up on drones, planes and custom builds. Mismatched plugs are what adapters are for, but a clean, correct connector is always better than a stack of adapters. We stock connectors and charge leads.
2. Charge It Right: Balance Charging and the 1C Rule
Charging a LiPo is not like plugging in a phone. The charger only knows what you tell it, so tell it the truth.
The 1C rule, in plain math
Horizon Hobby's LiPo safety guide says never to charge faster than 1C unless another rate is specified for that battery. 1C in amps is just the capacity divided by 1000:
| Pack capacity | 1C charge current |
|---|---|
| 2200mAh | 2.2 A |
| 3000mAh | 3.0 A |
| 5000mAh | 5.0 A |
| 8000mAh | 8.0 A |
From empty, a 1C charge takes a little over an hour, because the charger slows down near the top. Some packs are rated for faster charging, and the label or manual will say so. If it does not say so, use 1C.
Always balance charge
Each cell in a LiPo needs to finish at the same 4.20 V. Balance mode lets the charger watch every cell and even them out. Without it, one cell can end up overcharged while another is low, which is how packs swell and fail. Plug in the small balance lead every time, unless your pack is a Smart G2 or Traxxas iD that balances through the main plug.
Safe charging, step by step
- Inspect the pack. Check for swelling, dents, torn wrap or damaged wires. If you find any, do not charge it.
- Set up a safe spot. Put the pack in a LiPo bag or case on a non-flammable surface, away from anything that can burn.
- Connect both leads. Plug in the main lead and the balance lead (Spektrum Smart G2 and Traxxas iD packs balance through the main plug).
- Check the settings. Confirm chemistry (LiPo, not LiHV unless the pack says so), cell count and a 1C charge rate unless the maker approves more.
- Stay with it. Stay in the room while it charges and stop if the pack gets hot, swells or smells.
- Unplug and cool down. Unplug when finished. Let packs cool before charging again, and storage charge any pack you will not use soon.
Picking a charger
Match the charger to your packs. A Spektrum S155 G2 or the dual-port Spektrum S250 Smart Charger handles Smart packs and most others up to 4S. Traxxas owners get the easiest setup with an iD charger like the EZ-Peak Plus, which handles 2S-3S LiPo and NiMH. Running 6S? Bring your setup to the counter and we will help you size a charger.
3. Store, Protect and Retire Packs Safely
Most dead packs we see were not killed on the track. They were killed on a shelf.
Storage voltage: about 3.8 V per cell
A LiPo left fully charged ages faster, and one left empty can drop too low to recover. If a pack will sit more than a couple of days, use your charger's storage mode to bring it to about 3.8 V per cell, roughly half full. Spektrum Smart G2 packs do this for you: they come set to discharge to 3.90 V per cell after 72 hours of inactivity. NiMH is more forgiving and can sit far longer without harm.
Don't run it flat
Set your ESC's low-voltage cutoff for LiPo and stop when the truck slows down. Running a pack below the maker's rated minimum voltage under load damages it. Let hot packs cool before you charge them again.
Signs a pack is done
- Swelling or a "puffy" feel
- Dents, punctures or torn wrap after a crash
- Unusual heat, a strange odor, popping sounds or discoloration
The NFPA says to stop using a battery that shows any of these signs. Horizon Hobby's guide adds: if a pack swells or gets hot while charging, stop charging, move it to a LiPo bag in a safe place and watch it, then remove it from service.
Recycling a dead pack
The EPA says lithium batteries do not belong in household trash or curbside recycling bins, because they can start fires in trucks and at recycling plants. Tape the connector terminals or put the pack in its own plastic bag, then take it to a battery recycling or household hazardous waste drop-off. Call2Recycle has a ZIP code locator. Store drop-off bins often will not take swollen or damaged packs, so call ahead or ask your county's household hazardous waste program. Follow your battery maker's disposal instructions too. And skip the old salt-water bucket trick; it is not an approved disposal method.
Conclusion
Batteries reward good habits. Read the label, charge at 1C with the balance lead connected, stay in the room, storage-charge packs that will sit, and retire puffed packs the right way. Do that and your batteries will be the least exciting part of your RC weekend, which is exactly the goal.
Shop LiPo batteries and chargers, LiPo safety bags and cases and NiMH packs online, or bring your truck or plane to our Cumming, GA showroom and we will match the right pack, plug and charger to it.
Gear Mentioned in This Guide
Spektrum S155 G2 1x55W AC Smart Charger
Smart charging and one-plug balancing for packs up to 4S.
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Traxxas EZ-Peak Plus 4A Charger with iD
Plug in a Traxxas iD pack and it sets itself up. 2S-3S LiPo, NiMH.
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Spektrum 3S 5000mAh 50C Smart G2 LiPo (IC5)
Auto-storage after 72 hours idle and one-plug balancing.
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Traxxas 7-Cell 3000mAh 8.4V NiMH with iD (2926X)
The simple, forgiving choice for a first Traxxas.
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LiPo Voltage Checker (1S-8S) with Buzzer
Read every cell in seconds through the balance plug.
Shop nowFrequently Asked Questions
What is the difference between LiPo and NiMH RC batteries?
NiMH packs use 1.2 V cells, are heavier and are very forgiving to charge and store. LiPo packs use 3.7 V nominal cells, are lighter and hit harder, but they need a balance charger, the right storage voltage and careful handling.
What does 3S 5000mAh 50C mean on a LiPo?
3S means three cells in series, or 11.1 V nominal and 12.6 V full. 5000mAh is capacity, which sets runtime. 50C is the maker's discharge rating: 50 times 5 amps, or 250 amps on paper. Treat the C number as a rough guide, not a lab result.
How many amps should I charge my LiPo at?
Charge at 1C unless the battery maker says otherwise. 1C in amps is the capacity in mAh divided by 1000, so a 5000mAh pack charges at 5.0 amps and a 2200mAh pack at 2.2 amps.
What is LiPo storage voltage?
About 3.8 V per cell, roughly half charged. Use your charger's storage mode if a pack will sit for more than a couple of days. Spektrum Smart G2 packs drop to 3.90 V per cell on their own after 72 hours idle.
Is it safe to charge LiPo batteries overnight?
No. Never leave a charging battery unattended. Charge on a non-flammable surface, away from anything that can burn, ideally in a LiPo bag or case, and stop charging if a pack gets hot, swells or smells odd.
How do I dispose of a dead or puffed LiPo?
Do not put it in the trash or curbside recycling. Tape the connector terminals, bag it, and take it to a battery recycler or household hazardous waste site. A damaged or swollen pack may not be accepted in store drop-off bins, so call ahead.
Sources and Further Reading
- U.S. CPSC: Fire hazard with remote-controlled helicopters and airplanes (charging safety tips)
- NFPA: Lithium-ion battery safety
- U.S. EPA: Used lithium-ion batteries (disposal and recycling)
- Horizon Hobby: LiPo battery safety, warnings and guidelines (PDF)
- Battery University: Cell voltages for NiMH, Li-ion and LiFePO4
- Battery University: How to store batteries
- Call2Recycle: battery drop-off locator
