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 Can I use Lithium batteries for electric flight?

Q. Can I use Lithium batteries for electric flight?
A. RC Groups Forums

First a warning. There are a number of different types of batteries with Lithium in the name. Of these, rechargeable Lithium Metal cells are the most practical for use in electric flight at the time of writing (Aug 2000). The most other types of lithium battery technology are either too fragile, unable to deliver high currents or not easily rechargeable though some people are apparently successfully using rechargeable Lithium Ion cells despite the fact that they need very special charging conditions. Be careful what you are buying. You should check that you are getting RECHARGEABLE Lithium Metal cells, some Lithium Metal cells are primary cells, i.e. non-rechargeable.

Rechargeable Lithium Metal cells, made by Tadiran, have a very high energy density i.e. high Watt-Hours for very low weight. When reading the mAH rating for these cells remember that they deliver 3V per cell rather than the 1.2V of NiCad/NiMH. However they can only deliver low currents (up to about 3A) and they require specialized chargers. They cannot be charged with standard NiCad chargers and are very easily destroyed if charged incorrectly. They also have a shorter life, typically 100 charge/discharge cycles rather than 500/1000 for NiCad's. Their main use is for very lightweight indoor models typically using the small coreless motors sold for that purpose.

Some people have indicated that rechargeable Lithium Ion cells can also be used with care. They deliver around 3.6V per cell. Since they will not deliver very high currents they are sometimes used in series/parallel configuration e.g. 2 series sets of 3 parallel cells will give 7.2V and current draw up to about 10A, enough for very long durations with a Speed 400 size motor. Like Lithium Metal cells these must not be charged using a standard NiCad charger. They have an extremely poisonous organic electrolyte and can explode if charged incorrectly. They require a constant voltage charge up to about 80% capacity followed by a tapering current charge for the remaining 20%. Because they are so difficult to handle they are never sold as individual cells only in ready made packs for laptops, camcorders etc with the necessary safety devices built into the pack. You should not pull these packs apart unless you are confident that you understand the likely problems and are willing to take responsibility for any accidents.