Voltage per cell, weight, discharge rate, and charging — what each chemistry actually delivers and which one belongs in your RC setup.
For performance RC flying, LiPo wins on every metric that matters — weight, energy density, and discharge rate. NiMH is heavier, lower voltage per cell (1.2V vs 3.7V), and limited to roughly 5–10C discharge. The trade-off is simplicity and safety: NiMH tolerates incorrect storage, needs no balance charger, and carries no fire risk. For beginners with entry-level RTF aircraft, NiMH is fine. For anything requiring real power output, LiPo is the standard upgrade path.
The most important structural difference between NiMH and LiPo is cell voltage. NiMH cells operate at 1.2V nominal — fully charged around 1.4V, discharged around 1.0V. LiPo cells operate at 3.7V nominal — fully charged at 4.2V, with a discharge cutoff of approximately 3.5V under load.
To reach the same pack voltage, NiMH requires more cells in series. A 7.2V NiMH pack — the most common RC stick pack format — uses six cells. A 2S LiPo reaches 7.4V with only two cells, saving both weight and internal resistance losses. The higher voltage per cell also means LiPo can deliver the same power through fewer connections and less wiring resistance.
When upgrading from NiMH to LiPo, match total pack voltage to the ESC's design specification. A 6-cell NiMH (7.2V) is electrically closest to a 2S LiPo (7.4V). Never exceed the ESC's rated input voltage.
LiPo packs deliver approximately 150–200 Wh/kg of energy density. NiMH packs sit at roughly 60–100 Wh/kg — less than half. In practical terms, a LiPo pack stores significantly more energy for the same weight, or delivers the same energy at roughly half the weight of a NiMH equivalent.
For a concrete comparison: a 2S 2200mAh LiPo pack weighs approximately 130–150g and stores around 16Wh of energy. A 7.2V 2000mAh NiMH stick pack at equivalent run capacity weighs roughly 250–300g. On a small trainer aircraft, that 100–150g difference has a direct, noticeable effect on flight time and climb performance.
The NiMH weight penalty accumulates with cell count. Higher voltage setups using NiMH require proportionally more cells and proportionally more weight — the disadvantage grows as voltage requirements increase.
RC-grade NiMH packs are typically rated at 5–10C continuous discharge. A 2000mAh NiMH at 10C can deliver 20A — adequate for low-power motors in slow trainers, insufficient for anything performance-oriented. At higher current demands, NiMH packs heat significantly, voltage sags, and available capacity drops.
LiPo packs for RC use are rated from 25C to 100C+. A 2200mAh LiPo at 45C delivers 99A continuously without stress — far beyond what any trainer aircraft requires, and well within the range of sport and performance setups. The discharge rate headroom also means the pack runs cooler and degrades more slowly under typical loads.
Voltage sag under load: NiMH packs sag voltage noticeably when drawing high current. At 10A+ from a 7.2V NiMH, effective voltage can drop to 6V or lower — reducing motor performance and potentially triggering ESC low-voltage cutoffs. LiPo voltage sag is significantly lower at comparable C-ratings.
NiMH charging uses peak detection (ΔV) — the charger monitors for the voltage drop that signals full charge. No balance lead is required. NiMH chargers are inexpensive, widely compatible, and forgiving of mild overcharge. Storage at full charge causes no significant degradation — a fully charged NiMH left for several weeks will lose some capacity but suffers no damage.
LiPo charging requires a chemistry-specific balance charger. Every charge cycle should balance individual cell voltages via the balance lead. Storage at full charge (4.2V per cell) causes measurable degradation — packs left at full charge for more than a few days should be discharged to storage voltage (approximately 3.85V per cell). LiPo also carries a thermal runaway risk under abuse conditions, making fireproof storage bags and supervised charging standard practice.
For beginners, NiMH's charging simplicity is a genuine advantage. Incorrect LiPo handling — wrong cell count setting, missing balance lead, full-charge storage — degrades packs quickly and carries safety implications. NiMH eliminates these failure modes at the cost of performance.
| Spec | LiPo ★ Performance | NiMH |
|---|---|---|
| Nominal cell voltage | 3.7V | 1.2V |
| Discharge rate | 25–100C+ | 5–10C |
| Energy density | ~150–200 Wh/kg | ~60–100 Wh/kg |
| Weight (equiv. capacity) | ~140g (2S 2200mAh) | ~280g (7.2V 2000mAh) |
| Cycle life | 150–300 cycles | 500–1,000 cycles ★ |
| Charging | Balance charger required | Simple ΔV charger ★ |
| Storage tolerance | Strict (3.85V/cell) | Forgiving ★ |
| Fire risk | Higher | Very low ★ |
| Best use | Aircraft, FPV, performance | RTF entry, receiver packs ★ |
For the full LiPo reference including safe charging and storage protocol, see the RC Batteries Guide.
Ready to upgrade to LiPo? The RC Batteries Guide covers everything — cell counts, C-ratings, balance charging, and storage voltage.
10-page PDF covering the equipment checklist, LiPo handling, pre-flight routine, and the 5 most common beginner mistakes — formatted for the field.