NiMH Battery

Nickel-metal hydride cells run at 1.2V each, so a NiMH pack needs many more cells stacked in series than a LiPo to reach the same voltage, making them noticeably heavier and bulkier for the same capacity. They tolerate rougher charging and storage without the fire risk LiPo carries, which is why they remain common in beginner and rental packages.

Voltage sags more under load than LiPo, so a heavily upgraded gearbox with a strong spring can bog a NiMH pack down noticeably by the end of a magazine. Most players upgrade to LiPo or LiFe as soon as they start tuning internals, keeping a NiMH pack only as a rugged backup.

A "memory effect" reputation follows NiMH from older nickel-cadmium chemistry, but modern NiMH cells are largely free of it — the real reason packs seem to lose capacity over time is usually ordinary cell aging, not incomplete discharge cycles.