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Glossary of battery (Part two)
Jan 18, 2017


Cell (battery) 

 A single unit of an electrochemical device capable of producing direct voltage by converting chemical energy into electrical energy. A battery usually consists of several cells electrically connected together to produce higher voltages. (Sometimes the terms cell and battery are used interchangeably). Also see photovoltaic (PV) cell.


Charge Factor 

 A number representing the time in hours during which a battery can be charged at a constant current without damage to the battery. Usually expressed in relation to the total battery capacity, i.e., C/5 indicates a charge factor of 5 hours. Related to charge rate.


Charge Rate 

 The current applied to a cell or battery to restore its available capacity. This rate is commonly normalized by a charge control device with respect to the rated capacity of the cell or battery.

Battery charging takes place in 3 basic stages: Bulk, Absorption, and Float.


Bulk Charge 

 The first stage of 3-stage battery charging. Current is sent to batteries at the maximum safe rate  until voltage rises to near (80-90%) full charge level. Voltages at this stage typically range from 10.5 volts to 15 volts. There is no "correct" voltage for bulk charging, but there are limits on the maximum current that the battery and/or wiring can take.

Absorption Charge

 The second stage of 3-stage battery charging. Voltage remains constant and current gradually tapers off as internal resistance increases during charging. It is during this stage that the charger puts out maximum voltage. Voltages at this stage are typically around 14.2 to 15.5 volts.

Float Charge

 The third stage of 3-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level (typically 12.8 to 13.2) to reduce gassing and prolong battery life. This is often referred to as a maintenance or trickle charge, since it's main purpose is to keep an already charged battery from discharging. PWM, or "pulse width modulation" accomplishes the same thing. In PWM, the controller or charger senses tiny voltage drops in the battery and sends very short charging cycles (pulses) to the battery. This may occur several hundred times per minute. It is called "pulse width" because the width of the pulses may vary from a few microseconds to several seconds. Note that for long term float service, such as backup power systems that are seldom discharged, the float voltage should be around 13.02 to 13.20 volts.


Conductance 

 It is the ability of a battery to conduct current. It is a measurement of the plate surface available in a battery for chemical reaction, which determines how much power the battery can supply.  Conductance can be used to detect cell defects, shorts, and open circuits which can cause the battery to fail.

Conversion Efficiency - is how well a battery converts an electrical charge into chemical energy and back again. The higher this factor, the less energy is converted into heat and the faster a battery can be charged without overheating.


Current

 It is the rate at which electricity flows through a conductor; measured in amps (A).  Current flow over time is defined as ampere-hours (a.k.a. amp-hours or Ah), a product of the average current and the amount of time it flowed.


Cycles (Battery)

 A period of discharge and recharge is called one cycle. A battery cycle is one complete discharge and recharge cycle. It is usually considered to be discharging from 100% to 20% DOD, and then back to 100%. Battery performance may be measured by the expected number of cycles it may deliver at varying depths of discharge.


Cycle Life 

 is the measure of how many charge and discharge cycles a battery can take before its lead-plate grids/plates are expected to collapse and short out. The greater the average depth-of-discharge, the shorter the cycle life. Be careful when looking at ratings that list how many cycles a battery is rated for unless it also states how far down it is being discharged. A battery that is rated for a 20 year life expectancy if discharged by only 5% may have a 5 year life expectancy if discharged to 50%.  A battery that is continually cycled 5% or less will usually not last as long as one cycled down 10%. At shallow discharge cycles Lead Dioxide builds up on the the positive plates rather in an even film.  Calculate based on an average DOD of around 50% for the best storage vs. cost factor.


Deep-Cycle Battery 

 A battery with large plates that can withstand many discharges to a low state-of-charge.  Deep Cycle batteries have thicker lead plates that make them tolerate deep discharges better. They cannot dispense charge as quickly as a starter battery but can also be used to start combustion engines. Thicker lead plates lead to a  longer the life span.  Battery weight is a simple indicator for the thickness of the lead plates used in a battery. The heavier a battery for a given group size, the thicker the plates, and the better the battery will tolerate deep discharges.


Deep Cycling

 This is a battery restoration technique employing the repeated to deep discharge and recharge of most of the battery's total storage capacity.


Deep Discharge 

 Discharging a battery to 20% or less of its full charge capacity.


Deficit Cycling  

 When a battery is not being fully charged on a regular basis


Depth of Discharge (DOD) 

 is a measure of how deeply a battery is discharged. When a battery is 100% full, then the DOD is 0%. The ampere-hours removed from a fully charged cell or battery, expressed as a percentage of rated capacity. For example 25 Ah are removed from a 100 Ah battery, thus it's depth of discharge is 25% and the battery is at a 75% state of charge.


Direct current ( DC )

 electric current which flows in only one direction in a wire. Solar voltaic panels and batteries are DC.


Discharge 

 The withdrawal of electrical energy from a battery.


Discharge Cycle 

 When connected to a load, the chemical reaction within the battery between sulfuric acid and the lead plates releases releases electrons from the electrolyte. The chemical reaction coats both positive and negative plates with a substance called lead sulfate also known as sulfation during during discharge. If immediately recharged the lead sulfate a soft material is easily back into lead and sulfuric acidduring the recharge cycle.


Discharge Factor 

 A number equivalent to the time in hours during which a battery is discharged at constant current usually expressed as a percentage of the total battery capacity, i.e., C/5 indicates a discharge factor of 5 hours.( see discharge rate and amp hour rating).


Discharge Rate 

 The rate, usually expressed in amperes or time, at which electrical current is taken from the battery.


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