Every rc helicopter is a fascinating universe. Learn about batteries to make the top choice. As main advantages, NiMH batteries have a higher charge density (capacity / weight ratio exceeding approx. 40% -70% more capacity) do not contain Cd (toxic) effects apparently have no capacity loss due to mishandling, or formation of dendrites. As disadvantages, they have a higher internal resistance that limits its use in high power applications. It is true that there are new types on the market (Sanyo RC 3000 HV, HV RC330) practically equal in discharging capacity to the cells of the same size NiCd, RC2400. Another drawback is that do not support a load as fast as NiCd, under risk of deterioration. It is a good measure to charge them higher rates C: HV is a cell RC3000 can be loaded without problems 3 A. Even more than in the case of NiCd, NiMH elements are sensitive to heat, can cause overheating and internal rc helicopter gas overpressure leading to leakage and leakage losses, reducing the lifetime of the cells. The total charge state is also more difficult to detect on NiMH, so it is recommended to specify their fitness chargers to charge NiMH batteries, thus preventing unwanted overheating. Smart charger A rc helicopter smart charger is called so because it has full control of the state of the battery to charge. The same is scheduled to run checks on the voltage, current and temperature of the battery pack attached, making the security is the most important factor to keep. When a battery is charged, there are many factors involved, from the materials of its manufacture to room temperature. Each of these factors should be considered so that the loader performs the best load and load shedding.The main problem with an intelligent charger is that the "smart" is provided by the operator, i.e., us. The person who gets to charge the batteries that controls the time under load, temperature, and hopefully another parameter such as voltage and / or current. This is very dangerous because any neglect, omission or any other factor that makes us distracted from the control can result from simply losing the battery to fire. On the other hand, a smart rc helicopter charger has the great disadvantage of the price as it is much more expensive in relation to one made with 3 transistors or a single dedicated IC. As far as I'm concerned, the value is covered by the life span of the first packs you have.