LiPo vs NiMH vs Lead-Acid: Choosing Batteries for RC Model Boats

The short answer

There’s no single best battery for every RC model boat. As a general guide:

• Large, heavy scale models (tugs, trawlers, cargo ships) often run well on sealed lead-acid (SLA) batteries, which are cheap and robust, and whose weight doubles as ballast.
• Small and mid-sized scale models, and plastic kit conversions, often suit NiMH packs: forgiving, reasonably light, and with a simple charging routine.
• Fast electric boats, racing yachts and weight-sensitive models usually use LiPo for its high energy and power for its weight — with more care needed in charging and handling.

The rest of this guide explains why, and how to match the battery to the rest of your setup.

Battery basics: voltage, capacity and discharge rating

• Voltage sets how fast the motor will spin. Each chemistry has a nominal voltage per cell, and packs are made by putting cells in series.
• Capacity (mAh or Ah) is how much energy the pack stores. More capacity generally means longer run time, but also more weight and size.
• Discharge rating is how much current the pack can safely deliver. For LiPo, this is given as a C rating: a 5000 mAh pack rated at 20C can, in principle, deliver 100 A continuously. Scale boats usually draw modest currents; fast boats draw much more.

Your ESC and motor set the voltage range you can use, so check them first. Our guide to choosing a brushed or brushless ESC covers ESC voltage and current ratings.

Lead-acid (SLA)

Sealed lead-acid batteries, the kind used in alarm systems and emergency lighting, are a long-standing choice for scale model boats.

• Voltage: about 2 V per cell nominal; commonly sold as 6 V and 12 V blocks.
• Pros: inexpensive, tough, widely available, and their weight is useful ballast in big models.
• Cons: heavy for the energy stored, and they don’t like being left discharged — storing them flat can permanently reduce capacity.
• Charging: use a charger designed for sealed lead-acid batteries.

If a large model needs several kilograms of ballast anyway, an SLA battery lets that weight do useful work. See our guide to ballasting an RC model boat.

NiMH

Nickel-metal hydride packs are made from cells of about 1.2 V nominal each, so you’ll see packs such as 7.2 V (6 cells) or 8.4 V (7 cells).

• Pros: robust, tolerant of being used and stored without much attention, and generally considered lower-risk than LiPo. Good current delivery for most scale and sport boats.
• Cons: heavier and bulkier than LiPo for the same energy; they slowly self-discharge in storage (low self-discharge types reduce this).
• Charging: use a charger with NiMH termination (commonly peak detection), at the rate the pack maker recommends.

LiPo

Lithium polymer packs are the default for fast electric boats and weight-sensitive models.

• Voltage: about 3.7 V nominal per cell, around 4.2 V fully charged. Packs are described by cell count, such as 2S (7.4 V) or 3S (11.1 V).
• Pros: the most energy and power for the weight, holding voltage well through the run. Ideal where every gram counts.
• Cons: need more care. Over-discharging, over-charging, physical damage or water damage can ruin a pack and, in some cases, cause it to catch fire.
• Charging: use a LiPo-compatible balance charger, and follow the pack maker’s charge rate.
• Discharge: don’t run cells too low. Many ESCs offer a LiPo low-voltage cutoff; make sure it’s enabled and set for your cell count.
• Storage: many makers recommend storing at a partial charge (around 3.8 V per cell is a common figure) rather than full or empty.

For a scale boat, LiPo is perfectly usable, but you may need extra ballast to make up for the weight saved.

A note on LiFePO4

Lithium iron phosphate (LiFePO4 or LFP) packs, at around 3.2–3.3 V nominal per cell, are sometimes used as an alternative. They are generally regarded as more tolerant than LiPo, though less energy-dense. They need a charger with a LiFePO4 setting, and your ESC’s cutoff should suit the chemistry. Check compatibility before swapping.

Comparison at a glance

Choosing by type of boat

• Large scale models (1 m and up): SLA or large NiMH packs. Weight is rarely a problem and the model may need ballast anyway. A 1:16 Tamar class lifeboat is a typical example.
• Mid-sized scale models: NiMH is a common, forgiving choice; LiPo if you want longer runs or to free up space.
• Plastic kit conversions and small models: NiMH or small LiPo packs, depending on the weight budget. Our guide to converting a plastic model boat to RC discusses the trade-offs.
• Fast electric boats: LiPo, with an ESC and motor rated for the current. Take care with vintage balsa hulls such as the classic power boat kits, which can be overstressed by too much power.
• RC sailing yachts: a small receiver pack (NiMH or LiPo with a suitable regulator) powers the rudder servo and sail winch; check the winch’s voltage rating. See RC model sailing yachts.

Matching the battery to your ESC and motor

• Voltage: the battery must be within the ESC’s input range and suit the motor. A higher-voltage pack makes the motor spin faster and draw more current.
• Current: the pack must deliver the current the motor draws without strain. If a pack gets very hot in use, it’s being overworked.
• Connectors: use connectors rated for the current. Our RC setup guide covers connectors and fusing.
• BEC: if the ESC powers the receiver, it must be rated for the battery voltage you’re using.

Charging, storage and safety

General good practice for all types:

• Use a charger designed for the battery’s chemistry, and follow the battery maker’s instructions on charge rate.
• Charge on a non-flammable surface, away from anything that could burn, and don’t leave charging batteries unattended.
• Many modellers charge and store LiPo packs in a fire-resistant LiPo bag or container.
• Stop using any pack that is swollen, damaged, or has been soaked. Dispose of it as the maker or your local recycling rules advise.
• Disconnect the battery from the boat after each session.
• Keep batteries secured in the hull so they can’t shift or rub through their insulation.
• Recycle old batteries through appropriate collection points rather than household waste.