Within the past fifteen years there has been a revolution in both types and capabilities of rc model batteries. During this blog, we will attempt to analyze current types of batteries on the market and their best uses.
The NICAD or nickel cadium battery was the first battery in use for rc models and has served the radio control pilot for decades. NICAD batteries were first developed in Sweden, with the first practical batteries produced in 1906. Nickel cadium batteries were first produced in the United States in 1946 and radio control enthusiasts began to use them in the 1950s. They were popular because they had a higher power to weight ratio than gasoline engines in use on rc models of the time, although they had a limited endurance. Nickel cadium batteries offer the advantages of a low internal charge resistance, producing high currents. These batteries also have a relatively low self discharge (retaining its charge while stored) and their performance is not drastically affected by fluctuations in temperature. Some of the disadvantages of NICADS are they are both heavier and bulkier than newer technology batteries, are not environmentally friendly, as well as gradually losing their charge capacity if not periodically drained and recharged. Despite the availability of newer battery types, some rc hobbyists continue to use them when extremely fast performance Is required.
Nickel-metal hydride (NIMH) batteries are chemically similar to nickel cadium cells while utilizing a hydrogen-absorbing alloy instead of cadium. An NIMH battery has two to three times the capacity of an NICAD battery. Nickel-metal hydride batteries were first tested in 1967 using a lanthanum alloy, which was both expensive to produce in addition to having a limited charge life. After extensive testing in the 1970s and 1980s a practical battery using a mischmetal alloy was developed in 1987. NIMH batteries have the advantages of a higher capacity than NICAD batteries, in addition to retaining more of their charge capacity over time and being more environmentally friendly. Nickel-hydride batteries can lose their charge faster than other types, and require an outside charger for peak efficiency, unlike NICAD batteries. NIMH batteries are lighter than nickel-cadium units and more subject to breakage with imported batteries often running below stated capacity. NIMH batteries are most often used in transmitter and receiver packs of rc model units.
A lithium polymer or LIPO battery is a rechargeable battery of lithium-ion in a soft pouch type structure, unlike NICAD or NIMH batteries. The cells of the LIPO batteries contain liquid electrolytes with the polymer barriers used to separate the battery cells. The electrolytes may also be gelled by a polymer additive to conduct current. Lithium polymer batteries have been in use since the mid 1990s and have a very high power to weight ratio. They retain much of their charge in storage and are resistant to temperature changes. However, they are sensitive to overcharging and rapidly discharging, posing a fire hazard due to the polymer chemicals. RC models such as quadcopters now routinely use LIPO batteries attaining performance and endurance greater than many gas powered units. There are two recent variations of LIPO technology which overcome some of the basic LIPO battery limitations. The LifePO4 is more resistant to overcharging and discharging than the basic LIPO battery, as well as being less flammable . The LifePO4 has an ever higher power to weight ratio than a regular lithium polymer battery. The A123 battery, a modified LifePO4 utilizing nano technology, is able to deliver current at an even faster rate than the LifePO4 with greater safety. Such batteries give the rc pilot revolutionary advantages of weight, performance and safety.