LiPo is lighter, punchier and runs longer if you'll storage-charge it; NiMH forgives mistakes. Weights, cell counts, C ratings, connectors and the charger to buy.
LiPo, if you'll build one habit: storage-charge the packs when you're done for the day. It's lighter, holds its power to the end of the run and lasts longer per charge. NiMH is the right call if the car is going to a kid, or you want to drive without learning any battery rules yet. Both run the same car. Pick by how much looking-after you want to do, not by speed.
What's the difference on the track?
Punch. LiPo holds its voltage almost flat until it's nearly empty. NiMH fades, so the car gets slower through the whole pack.
Weight. A 2S 5000mAh LiPo is around 250–300 g. A 7.2V NiMH stick of similar capacity is around 400–450 g. In a 1/10 buggy you feel that in jumps and steering.
Runtime. More usable energy per gram, so more minutes per pack at the same weight.
Lifespan. A NiMH pack usually survives more charge cycles, and a LiPo loses less charge sitting on the shelf. Published cycle counts disagree widely (anywhere from 150 to 1,000), because how you treat a pack matters more than its chemistry: a LiPo run flat or stored full dies early, and a well-kept one lasts years.
Forgiveness. NiMH doesn't care if you run it flat, leave it half charged for a month, or charge it on the basic wall charger from the box. LiPo cares about all three.
Is NiMH still worth buying?
For a first car that gets handed around, yes. It's the pack a lot of RTRs still ship with, and it survives abuse that would ruin a LiPo. It isn't fireproof (a shorted or badly overcharged NiMH pack can vent and burn), but it's far more tolerant of mistakes.
The downside shows up after a few weekends: the car is noticeably slower at the end of each pack, and the pack is heavy. That's usually when people move to LiPo.
What does LiPo ask of you?
Three rules:
Don't run it flat. Below about 3.0V per cell the cells are damaged. Turn on the low-voltage cutoff in your ESC (every modern Hobbywing, Castle, Spektrum or Traxxas brushless ESC has one) and stop when the car goes soft.
Balance charge it. Plug in the small white balance lead every time, on a charger that balances.
Don't store it full. A LiPo left at 4.2V per cell for weeks swells and loses capacity. Storage charge (about 3.8V per cell) if it won't run within a couple of days.
The full routine, including where to charge and how to retire a puffed pack, is in LiPo battery care and safety.
Will a LiPo work in a car that came with NiMH?
Usually, yes. A 2S LiPo (7.4V) sits in the same voltage range as the 6 or 7 cell NiMH stick most 1/10 RTRs ship with. Before the first run, check four things:
The ESC has a LiPo setting. Most current ESCs have a low-voltage cutoff that you switch on with a jumper, a button sequence or a program card; on many Traxxas ESCs it's called Low-Voltage Detection. That cutoff is what stops the car before the pack drops below 3.0V per cell.
No cutoff, no LiPo. An older or bargain ESC with no LiPo mode will happily drain a pack to ruin. Replace the ESC, or at least plug a cheap LiPo voltage alarm into the balance lead and stop the moment it beeps.
The cell count is allowed. Read the ESC's rating. "2S LiPo / 6 to 7 cell NiMH" means a 3S pack will burn it out.
The charger can balance. A NiMH wall charger can't charge a LiPo safely. This is where the dual-chemistry charger below pays for itself.
Then check the plug and the tray: a hard-case 2S stick fits most trays built for a NiMH stick, but the connector often doesn't match (see below).
Which LiPo should I buy?
Cell count first. 2S is 7.4V nominal, 3S is 11.1V. Only go to 3S if your ESC and motor are rated for it. Most brushed RTRs are 2S only, and 3S into a 2S system burns something out.
Capacity: 5000mAh 2S is the default for a 1/10 truck or buggy. More capacity means more minutes and more weight.
C rating: mostly marketing. A cheap "120C" pack often delivers less than an honest 50C pack from a brand people trust. For a normal 1/10 car, anything 40C or up from a known name is plenty.
Size: measure the battery tray. Hard-case "stick" packs fit most 1/10 trucks; "shorty" packs are for race buggies with a battery slot to match.
XT60 / XT90: very common on aftermarket packs and chargers.
Deans (T-plug): older race standard.
Either buy packs with your car's plug or pick one standard and solder it across the fleet. Adapters work, but every adapter is another joint that can get loose or hot.
Buy the charger before the second battery. The wall charger in an RTR box usually can't balance a LiPo. A $40–70 dual-chemistry balance charger (ISDT, SkyRC, ToolkitRC and similar) charges both NiMH and LiPo, has a storage mode, and will outlast several cars.
How fast should I charge?
1C to start: a 5000mAh pack at 5 amps. It's gentle on the pack, and an hour is fine at home. Charge LiPos on a non-flammable surface or in a LiPo bag, and stay in the room.
A good starting kit for most people is one good balance charger and two 2S 5000mAh LiPos with the car's connector. Batteries go on sale constantly, so check RC deals before paying full price. A used car from the listings often comes with a pack or two.
