A battery is a collection of voltaic cells connected together (literally, a battery of cells) in an arrangement to give a particular voltage difference between its terminals, and allow electrons to flow through a conductive load applied to them.
Cells come in a number of different chemistries, each with different properties.
- Dry cell
- Covers a number of non-rechargeable chemistries, typically with a nominal voltage of 1.5V. Dry cell technologies include Zinc-Carbon, Alkaline, Lithium, and Silver Oxide.
- Lead Acid battery (Pb)
- Cheap robust battery technology, but poor energy density. Nominal voltage of 2.1V. Usually grouped into 3 cells (6V) or 6 cells (12V) and used in the flight box for running the starter motor, battery chargers, etc.
- Nickel Cadmium (NiCd)
- Older form of rechargeable battery with a nominal voltage of 1.2V, used as a dry cell substitute. Largely superseded by NiMH cells, NiCd cells were typically either trickle charged at 1/10C for 14 hours, or delta peak fast charged.
- Nickel Metal Hydride (NiMH)
- Newer form of rechargeable battery with a nominal voltage of 1.2V, these have similar recharging characteristics to NiCd but are more sensitive to poor delta peak charging.
- A variation of lithium ion cells with a nominal voltage of 3.8V and maximum voltage of 4.2V; have very good capacity to weight, but are intolerant of abuse.
- Lithium Iron (LiFe)
- A variation of lithium ion cells; much more tolerant of abuse, but with lower energy density. Often sold under the name A123 or M1 cells, they are often obtained by cannibalizing DeWalt 36V power tool packs. LiFe cells have a nominal voltage of 3.3V and a normal charged voltage of 3.6V
- Lithium Phosphate
- Another variation of lithium ion cell, more tolerant of abuse. Charge voltage 4.2V, nominal voltage 3.2V. Sold under the name Saphion.
In this table, energy density is given as milliwatt-hour (capacity * voltage) per gram or cubic centimetre. Max charge is aggressive charge and may not be practical. Discharge is continuous, and given as C (equivalent to watts per watt-hour) and watts per gram. Lipo values are for 80% discharge. Values are illustrative.
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Buying new batteries and making connections
If you buy batteries for your helicopter, sometimes they might not have connectors on them (see image on right). In this case, please see this instructional video for a general method on how to do this.
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