# Battery Terms

### What is a "1C" rating?  What does 2s2p mean?  Some common battery pack definitions.

"C" Rating:

"C" stands for the capacity of the battery pack.  For instance, a 2600mA-h Relion has a "1C" charge rating of 2600 milliamps, or 2.6 amps.  If you charge it at 1/2C, your rate would therefore be 1300 milliamps; 1.3 amps.  Our batteries are rated for up to a 1C charge rate, but they will last a little longer if you charge them at our recommended rate of 1/2 to 3/4C...and you will likely not notice the difference in the charging time.

mA-h (milliamp-hour):

mA-h stands for milliamp-hour, which is a unit of electrical storage.  For instance, a 2600 milliamp-hour pack could put out 2600 milliamps (2.6 amps) for one hour...or twice that for half an hour, or half of that for two hours...  It is the standard unit of battery capacity in the same way that 'gallon' refers to the storage capacity of a gas tank.  The Relion unit cell nominally has 2600 milliamp-hours in it; our Iron Corps A123(tm) cells have 2300mA-h per cell.

Amp:

An amp is a unit for electrical flow.  If you have a servo that is using 1 amp (or 1000 milliamps - same thing), it will take 2.6 hours to completely drain the nominal capacity of a 2600mA-h battery.  Please note that we recommend a substantial safety margin - think reserve capacity - when sizing your packs.

Volt:

A volt is a unit for elecrical pressure.  If you have a servo operating at a higher voltage, it will be quicker to move (and wear out), as the higher voltage will be trying to stuff electrons (current) through it at a faster rate.  A Relion has a unit cell voltage of 4.2 volts fully charged and 3.7 volts nominal (average voltage over a test discharge).  An A123 has a unit cell voltage of 3.6 volts fully charged and 3.3 volts nominal (average).

Pack Cell Count Dimensioning:

You sometimes hear packs referred to as "2s2p" or "3s1p", etc.  The packs are defined by how many cells are in them, and how they are electrically connected together.  For instance, the "s" number in 2s2p means the number of series cells in the pack...which determine the pack's voltage.  Each Relion series cell has 4.2 volts fully charged such that two of them in series (2s) equals a fully charged pack voltage of 8.4 volts.  A "2s" therefore refers to twice the voltage of a unit cell, 3s would be triple, etc.  The "p" number means the number of cells hooked up inparallel...which determines the pack's capacity.  In a 2s2p Relion pack, the "2p" means there are dual parallel cells - the pack is a 5200mA-h (double the capacity of a 2s1p which is a 2600mA-h pack).  Each parallel cell has a fully charged nominal capacity of 2600mA-h

Revised 10/17/2010 mf