30.9. Battery care and maintenance

Different types of batteries have different requirements for care and maintenance. In order to ensure maximum battery usability, you should carefully follow the recommendations for each battery type.

30.9.1. Nickel-cadmium (NiCad) batteries

Nickel-cadmium batteries are generally the most robust of all the battery types. They're the oldest and most reliable battery type, (often over 200 charge/discharge cycles) and are fairly resistant to overcharging, vibration, and other forms of abuse.

NiCad batteries can be charged at a maximum rate of 2C.

NiCad batteries should be left discharged at the end of the flying day. When stored long-term (over two months) they should be stored in a cool storage area. After storage, you should do a formatting charge (which overcharges the pack slightly) to ensure the battery pack is properly balanced.

[Warning]Warning

NiCad batteries contain cadmium which is toxic and can cause lung and kidney damage. Be sure to wash your hands after handling nicad batteries. Also, nicad batteries MUST be disposed of properly. See Section 30.9.4, “NiCad/NiMH/LiPo Battery disposal”.

30.9.2. Nickel-metal-hydride (NiMH) batteries

Nickel-metal-hydride batteries are a newer battery type than nickel-cadmium. They have a higher energy capacity than nicad, but have a much shorter life (about 100 charge/discharge cycles), and they are more easily damaged by overcharging and vibration.

NiMH batteries can be charged at a maximum rate of 1C, however, some people claim the Sanyo HR2600SC can be charged at 2C rates. This warms up the cell for maximum performance prior to flying. Chargers will fail to properly terminate the charge when NiMH cells are charged at rates less than 0.4C, so slow charges must be carefully timed to avoid overcharging the cells.

NiMH batteries can be left either charged or discharged at the end of a flying day. When stored long-term they should be stored in a cool storage area. After storage, they should be cycled a few times to restore capacity.

30.9.3. Lithium-Polymer (LiPo) batteries

Lithium polymer is the newest battery type. They have up to four times the battery capacity of nicad batteries, but they are very fragile. They contain lithium which is a metal which ignites on contact with air, so if the battery balloons and the covering pops or the covering of the battery is punctured, it will ignite and explode.

LiPo batteries can be charged at a maximum rate of 1C.

LiPo batteries are very sensitive to overcharging. They should NEVER be overcharged, and ALWAYS be charged in a fireproof container and should ALWAYS be attended because they have been known to ignite in some circumstances.

LiPo batteries should not be discharged below 3 volts per cell because they can be damaged by overdischarging. A LiPo battery should not be discharged below 80% capacity if possible because this stresses the cell and reduces the cell lifetime (number of charge/discharge cycles before cell capacity degrades significantly). They should not be fully discharged at the end of the day; you should leave some charge in them. Thunder Power recommends long-term storage with about a 40% charge left in the cell; this minimizes cell deterioration and prevents the cell's voltage from dropping too low. They should be stored in a cool place in a fireproof container.

LiPo batteries are fairly fragile. You should avoid dropping them (especially onto concrete or asphalt) because this can cause cell damage. LiPo batteries have beeen damaged in a crash and have spontaneously ignited up to 30 minutes later. Any LiPo batteries which have been in a helicopter that has crashed should be kept in a fireproof container for a few hours for observation.

Do not attempt to charge or discharge a ballooned battery pack. The proper way to dispose of a bad lipo cell is to take a container and fill it with water, then keep adding salt and stirring until no more salt will dissolve (reached saturation). Drop in the cell and leave for at least TWO WEEKS. Also, please search for "lipo disposal" in the RC Groups forums for the latest safety information on this technique.

30.9.4. NiCad/NiMH/LiPo Battery disposal

All battery types, especially NiCad and LiPo battery packs, must be disposed of properly. In the US, go to www.rbrc.org to find the nearest battery disposal site.

More information on R/C batteries can be found at Red Scholefield's R/C battery clinic at www.rcbatteryclinic.com and also at www.batteryuniversity.com..

30.9.5. Solderless power tube (SPT) battery packs

The endcaps of the solderless power tubes can be damaged in hard crashes when the battery pack is ejected from the helicopter. These endcaps can be purchased separately from MEC.

My experience with the SPT battery packs is the battery terminals tend to oxidize as the batteries are heated and cooled. This oxidation results in increased resistance and the battery pack may appear to be weak.

I recommend disassembling the SPT battery packs about once a year and inspecting the battery terminals. If the positive terminal has a thin film of white residue on it, then this is a sign the cell has vented. This indicates the cell is probably weak. You should clean the terminal and write a mark on the cell to indicate it has been cleaned. If this cell requires cleaning more than once, it should probably be replaced.