RC Batteries & Chargers: What You Actually Need to Know

I used to think of batteries as magic pixies in a box. Plug in the box, pixies wake up, motor goes. That was good enough for teenage me — charge for 45 minutes, run for 15, hope you brought enough packs.

That was the NiMH era. Nickel-metal hydride batteries powered just about everything in RC for a long time, and they still work. I still run NiMH in a couple of my bashers. But for crawlers — and honestly for most modern RC — the world has moved to LiPo, and for good reason.

If you’re just getting into crawling, here’s what you actually need to know without the chemistry lecture.

NiMH vs. LiPo: The Short Version

NiMH batteries are the old standard. They’re forgiving, relatively cheap, and hard to damage if you leave them on the charger a little too long. A lot of entry-level trucks still ship with them.

LiPo (lithium polymer) batteries store more energy in a smaller, lighter package. They hold voltage better through a run, so your truck doesn’t start feeling sluggish as the pack drains. The tradeoff is that they require a little more attention — more on that in a minute.

If you’re buying a crawler today, you’re almost certainly buying into LiPo. That’s a good thing. Just go in knowing what you’re working with.

Understanding the Numbers

When you look at a LiPo pack, you’ll see a few numbers that actually matter:

Voltage / Cell Count (S rating) — A 2S battery has two cells in series and runs around 7.4 volts nominal. A 3S has three cells and runs around 11.1 volts. More cells means more voltage, which means more speed and power. Most micro and compact crawlers run 2S or 3S. Bigger 10th scale rigs can handle 3S sometimes more.

Capacity (mAh) — Milliamp hours. Higher number means more runtime. A 5000mAh pack will run significantly longer than a 1200mAh pack of the same voltage. For crawling — where you’re moving slowly and deliberately — capacity matters more than it does for bashing.

C Rating — This is a discharge rating. Without going deep into the math: for crawling, you don’t need a high C rating. A 25C or 35C pack is plenty. High C ratings matter more for high-draw applications like racing or bashing.

What I Actually Run

To make this concrete, here’s what’s in my garage right now:

TRX4M fleet — All running stock Traxxas 750mAh 2S packs. I’ve picked up a couple of extra packs so I can keep running on trail days without waiting for a charge. The stock batteries work great for this platform, and staying in the Traxxas ecosystem keeps charging simple.

SCX24s — Still on the stock 350mAh 2S packs that came with them. They work, they fit, and for a truck this size the capacity is appropriate. There’s not a lot of room to upgrade here without some modifications, even if you wanted to.

SCX10 III Gladiator — This is a bigger truck that can take a bigger battery. I’m running a pair of 5000mAh 3S 50C packs and swapping between them. At this scale, capacity really makes a difference in how long you can stay on the trail.

Arrma Mojave Grom — I keep two packs for this one: a 1400mAh 2S for normal running and a 1300mAh 3S for when you really have to go fast. The 3S wakes that truck up in a way that makes you grin and question your decisions simultaneously.

Brand-wise — I stick with Traxxas and Spektrum for my packs. GensAce is another name worth trusting. There are cheaper brands out there, and some of them are fine, but with batteries specifically I lean toward names that have a reputation to protect. A bad battery isn’t just a bad day — it’s a potential fire hazard. Spend the few extra dollars.

The Charger Situation

This is where I’d encourage you not to skip out. The charger that comes with most RTR trucks — including the TRX4M and the SCX24 — is a USB charger. It works. It will charge your battery. It will just do it slowly. Really slowly.

For occasional running, the stock USB charger is fine. But if you plan to run regularly, or you have multiple packs, a standalone charger is worth having.

I run two chargers:

Traxxas EZ-Peak Plus 2970 — Handles all my Traxxas packs. Straightforward, reliable, fits the Traxxas ecosystem cleanly. If you’re building a Traxxas-heavy garage like mine, this is the obvious choice. Point of note, you will need an adapter for the TRX4M packs. The connected is much smaller than the standard Traxxas batteries.

Spektrum Smart S155 — This one came with a used SCX10 I bought from someone getting out of the hobby, along with a pile of Spektrum batteries. I would have ended up with this charger or the S1200 anyway — the S1200 has higher wattage and handles multiple chemistry out of the box, which is appealing. The S155 can charge NiMH with a firmware update if that matters to you.

The honest advice: match your charger to your battery ecosystem. Traxxas batteries and the Traxxas charger speak the same language. Spektrum Smart batteries and a Spektrum Smart charger communicate charge data back and forth. You can mix and match with adapters, but it’s easier to just stay in one world where you can.

A good local hobby shop will point you toward the right charger for whatever batteries you’re running. That’s exactly what mine did when I bought my first TRX4M, and it saved me from making a dumb purchase.

LiPo Safety: The Stuff That Actually Matters

LiPos have gotten a reputation for being scary. That reputation isn’t totally unearned — an improperly handled LiPo can swell, vent, or in bad cases catch fire. But in practice, if you follow a few basic rules, they’re not something to be afraid of.

Don’t leave them unattended while charging. This is the big one. Plug in the charger, stay nearby, check on it. When the charge is done, disconnect. Don’t charge overnight, don’t charge and leave the house.

Get a LiPo safe bag. These are fireproof charging and storage bags that contain a problem if one ever develops. They’re inexpensive, available at any hobby shop or on Amazon, and give you real peace of mind. I use one every time.

Don’t over-discharge. Running a LiPo down to nothing damages it and can make it unstable. Most ESCs have a low-voltage cutoff that will reduce power or cut the motor before the pack gets critically low. Respect that warning — when the truck starts feeling weak, it’s time to stop.

Storage charge for longer breaks. This one took me a while to build into my routine, but it matters. If a battery is going to sit unused for 48 hours or more, I put it on a storage charge. Both of my chargers have this mode built in. A storage charge brings the pack to roughly 50% — a stable middle voltage that LiPos prefer to sit at long-term. Leaving a LiPo fully charged or fully depleted for extended periods shortens its life. Storage charging is easy, takes a few minutes to set up, and keeps your packs healthy for the long haul.

The Simple Starting Point

If you’re buying your first crawler and feeling overwhelmed by batteries, here’s the short version:

Your RTR truck will come with a battery and charger that work. Use them, get some runs in, learn how the truck behaves. When you find yourself wishing your runs were longer or your charge times were shorter, that’s the right moment to look at upgrading your charger and picking up an extra pack.

Buy from a brand with a real reputation. Get a LiPo safe bag. Stay nearby while charging and disconnect when it’s done. Storage charge if you’re not running for a while.

That’s genuinely most of it. The pixies are pretty cooperative as long as you treat them right.

---

See also: Best LiPo Batteries for the SCX24 and TRX4M · Everything You Need to Buy With Your First Crawler · Recommended Gear

This page contains affiliate links. If you purchase through these links, I may earn a small commission at no additional cost to you. I only recommend gear I actually use.