Battery Chemistry

Since the year 1800 when the first voltaic battery was invented portable battery power has been a fascination by many. In 1991 Sony commercialized the first lithium-ion battery and in 1999 lithium-polymer came out commercially with PDAs.

But what are the differences of the two chemistries and in terms of your PDA battery which one is better? In a nutshell the two chemistry types are similar but one benefit that lithium-polymer offers is that enables slim geometry that allows it to fit in small places like a PDA.

Let's look inside the battery technology a bit more!

Lithium-ion Battery:

    * The lightest of all metals
    * The greatest electrochemical potential
    * The largest energy density for weight.
    * The load characteristics are reasonably good in terms of discharge.
    * The high cell voltage of 3.6 volts allows battery pack designs with only one cell versus three.
    * It is is a low maintenance battery.
    * No memory and no scheduled cycling is required to prolong the battery's life.
    * Lithium-ion cells cause little harm when disposed.
    * It is fragile and requires a protection circuit to maintain safe operation.
    * Cell temperature is monitored to prevent temperature extremes.
    * Ccapacity deterioration is noticeable after one year (whether the battery is in use or not).

Lithium Polymer Battery:

    * The lithium-polymer differentiates itself from the conventional battery in the type of electrolyte used (a plastic-like film that does not conduct electricity but allows ion exchange – electrically charged atoms or groups of atoms).
    * The polymer electrolyte replaces the traditional porous separator, which is soaked with electrolyte.
    * The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and thin-profile geometry.
    * Cell thickness measures as little as one millimeter (0.039 inches).
    * Can be formed and shaped in any way imagined.
    * Commercial lithium-polymer batteries are hybrid cells that contain gelled electrolyte to enhane conductivity.
    * Gelled electrolyte added to the lithium-ion-polymer replaces the porous separator. The gelled electrolyte is simply added to enhance ion conductivity.
    * Capacity is slightly less than that of the standard lithium-ion battery.
    * Lithium-ion-polymer finds its market niche in wafer-thin geometries, such as PDA batteries.
    * Improved safety – more resistant to overcharge; less chance for electrolyte leakage.

Until next time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.

Battery Degradation and Power Loss

A battery over time degrades and eventually stops working, this is no surprise, but why this  occurs is really a fascinating yet technical process. These reasons are complex issues that are way beyond user control and are wholly contained within your battery and within your device! As we will see these issues (declining capacity, increasing internal resistance, elevated self-discharge, and premature voltage cut-off on discharge) do more to cause Battery Degradation and Power Loss than your typical portable device owner could ever do.

Declining Capacity

Declining capacity is when the amount of charge a battery can hold gradually decreases due to usage, aging, and with some chemistry, lack of maintenance. PDA batteries, for example, are specified to deliver about 100 percent capacity when new but after usage and aging and lack of conditioning a pda battery's capacity will drop. This is normal. If you are using a pda battery (or any lithium-ion or lithium-polymer battery) when your battery's capacity reaches 60% to 70% the pda battery will need to be replaced. Standard industry practice will warranty a battery above 80%. Below 80% typically means you have used the practical life of a battery. Thus the threshold by which a battery can be returned under warranty is typically 80%.

Loss of Charge Acceptance

The loss of charge acceptance of the Li‑ion/polymer batteries is due to cell oxidation. Cell oxidation is when the cells of the battery lose their electrons. This is a normal process of the battery charge creation process. In fact every time you use your battery a loss of charge acceptance occurs (the charge loss allows your battery to power your device by delivering electrical current to your device). Capacity loss is permanent. Li‑ion/polymer batteries cannot be restored with cycling or any other external means. The capacity loss is permanent because the metals used in the cells run for a specific time only and are being consumed during their service life.

Internal Resistance

Internal resistance, known as impedance, determines the performance and runtime of a battery. It is a measure of opposition to a sinusoidal electric current. A high internal resistance curtails the flow of energy from the battery to a device. The aging of the battery cells contributes, primarily, to the increase in resistance, not usage. The internal resistance of the Li‑ion batteries cannot be improved with cycling (recharging). Cell oxidation, which causes high resistance, is non-reversible and is the ultimate cause of battery failure (energy may still be present in the battery, but it can no longer be delivered due to poor conductivity).

Elevated Self-Discharge

All batteries have an inherent self-discharge. The self-discharge on nickel-based batteries is 10 to 15 percent of its capacity in the first 24 hours after charge, followed by 10 to 15 percent every month thereafter. Li‑ion battery's self-discharges about five percent in the first 24 hours and one to two percent thereafter in the following months of use. At higher temperatures, the self-discharge on all battery chemistries increases. The self-discharge of a battery increases with age and usage. Once a battery exhibits high self-discharge, little can be done to reverse the effect.

Premature Voltage Cut-Off

Some devices like pdas do not fully utilize the low-end voltage spectrum of a battery. The pda device itself, for example cuts off before the designated end-of-discharge voltage is reached and battery power remains unused. For example, a pda that is powered with a single-cell Li‑ion battery and is designed to cut-off at 3.7V may actually cut-off at 3.3V. Obviously the full potential of the battery and the device is lost (not utilized). Why? It could be something with elevated internal resistance and or pda operations at warm ambient temperatures. PDAs that load the battery with current bursts are more receptive to premature voltage cut-off than analog equipment. High cut-off voltage is mostly equipment related, not battery.

Until next time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.

Energy Potential of Lithium

PDA batteries widely employ either a Lithium-ion or a Lithium-polymer chemical composition and so it leads us to question why? Why is lithium ever-present in PDA Batteries today?

We know that since millions of people own PDAs (for every purpose imaginable) it is understandable that a rechargable power cell be available. In fact if it wasn't for lithium I would find it rather astonishing that PDA's would be so widely used today. Lithium makes recharging your PDA battery cost-effective. So what exactly is lithium?

General Characteristics of Lithium

    * Name: lithium
    * Symbol: Li
    * Atomic number: 3
    * Atomic weight: [ 6.941 (2)] g m r
    * CAS Registry ID: 7439-93-2
    * Group number: 1
    * Group name: Alkali metal
    * Period number: 2
    * Block: s-block
    * Standard state: solid at 298 K
    * color: silvery white/grey
    * Classification: Metallic

Lithium is used, amongst many other uses, as a battery anode material (due to its high electrochemical potential) and lithium compounds are used in dry cells and storage batteries. In fact the energy of some lithium-based cells can be five times greater than an equivalent-sized lead-acid cell and three times greater than alkaline batteries. Lithium cells often have a starting voltage of 3.0 V. This means that batteries can be lighter in weight, have lower per-use costs, and have higher and more stable voltage profiles.

For a scientific review of Lithium visit http://www.webelements.com/webelements/elements/text/Li/index.html

Until next time – Dan Hagopian, Batteryship.com
Copyright © BatteryEducation.com. All rights reserved.

Amps and Volts: Battery Basics?

This is a back to basic articles on understanding a batteries electrical ratings. Let's take a real question from a real person:

"I have a sony clie PEG-NR70V/U PDA. The battery that you show that would fit my unit is 1200 mah and 3.7 volts. On the back of my PDA it says 800 mAh and the volts is 5.2. Is the battery that you show for my unit the same?"

This is a great question and is actually quite common and so it is wise that we gain a better understanding of what the ratings mean.

All PDA batteries have an electrical specifications that include its volt and milliAmp hour rating. These terms are abbreviated as we see in the following example: 3.7 V, 1600 mAh.

Volts – or V – are an electrical measure of energy potential. You can think of it as the pressure being exerted by all the electrons of a PDA Batteries negative terminal as they try to move to the positive terminal.

Amps – or A – is an abbreviation of Ampere, a 19th century French scientist who was a pioneer in electricity research. Amps measure the volume of electrons passing through a wire in a one second. One Amp equals 6.25 x 1018 electrons per second.

Amp hours – or Ah – measures capacity. That is what is ultimately important to consumers as it is the capacity or amp hours that tells us how long we can expect a battery to deliver a charge before it runs out. As with all metric measurements, Amps can be divided into smaller (or larger) units by adding a prefix, in this case by adding an "m" to the amp hour we are renaming the amp hour to milli amp hour: mAh.

In the case of PDA Batteries, a milliAmp hour (mAh) is most commonly used notation system. Note that 1000 mAh is the same a 1 Ah. (Just as 1000mm equals 1 meter.) Note that Amp hours do not dictate the flow of electrons at any given moment, that is the role of volts. PDA batteries with a 1 Amp hour rating could deliver ½ Amp of current for 2 hours, or they could provide 2 Amps of current for ½ hour.

Typically, PDA Batteries will use 1 to 3 Amps per hour, depending on the model's processor speed, screen size, screen brightness adjustment, usage, and other factors.

Some of our batteries will have higher amp-hour ratings than the original battery found in your device and will not cause any incompatibilities. It is actually good because you are getting greater capacity.

Volts on the other hand have to be within a nominal range (reasonable range) of each other. Manufacturers rate a voltage cell, which then becomes the nominal voltage, historically with a 3.6V while others picked 3.7V to name the cell. The functionality and performance of either cell is identical and cannot be differentiated by the device. The explanation above applies to a single Li-Ion cell in series. When a battery has two or more Li-Ion cells in series, the voltage is multiplied by the number of cells in series.

Now back to the question we began with…..

"I have a sony clie PEG-NR70V/U PDA. The battery that you show that would fit my unit is 1200 mah and 3.7 volts. On the back of my PDA it says 800 mAh and the volts is 5.2. Is the battery that you show for my unit the same?"

To understand the answer to the question let's look at a math formula for the complete formula of Watts….

Watts = Volts x Amps x k(one unit length of wire)

Since the length of your PDA's wire inside the battery casing is difficult to know (unless you open the casing) let's just use a more common formula for Watts: (NOTE: DO NOT OPEN YOUR BATTERY'S CASING, EXTREME HARM WILL COME TO YOU)

Watts = Volts x Amps

Now the orignial Clie battery came with 800 mAh and the volts is 5.2. So the Watts would be:

41.6= 5.2 x 8

The Clie battery on our page is 3.7 V and 1200 mAh. So the Watts would be:

44.4= 3.7 x 12

Remember that I'm 1200 mAh is the same as 12 Ah and 800 mAh is the same as 8 Ah

So as we discussed early a nominal range is inherent in voltage ratings and slight variations in voltage generally do not impact the performance of your PDA. We see this all the time with universal and external batteries. The original battery might be specified at 10.8 Volts, but customers using a universal part can operate their laptop safely at either the 10 or 11 Volt setting.

There is plenty more info you can get in this blog as well as online.

Until next time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.

What is a Watt?

Here are some definitions of watts on the Web:

  • A measure of the amount of work done by a certain amount or amperage of electric current at a certain pressure or voltage.
  • A watt is a measurement of total electrical power. Volts x amps = watts.
  • A measure of power or the rate of energy consumption by an electrical device when it is in operation, calculated by multiplying the voltage at which an appliance operates by the current it draws (Watts = Volts X Amperes).
  • Watts is the measurement of the amount of electrical power drawn by the load.
  • A measure of electricity.
  • The power required to maintain one ampere of current at a pressure of one volt when the two components are in phase with each other.

Until next time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.

Watts are Volts x Amps?

Watts, Volts and Amperes are basic units of measure for a DC (Direct current) power supply. A battery, for example, is a direct current power supply and the combined measure Volts x Amps = Watts.

Watts are important because watts represent the electrical energy spent by a battery (power generator) and used by an electrical device. Watts in effect is the measure of the amount of work done by a certain amperage (amount) of electric current at a certain pressure or voltage.

Voltage is the amount of "pressure" of electrons as the electrons pass from a negative connector to a positive connector.

Amperes (commonly "Amps" ) is a measurement of quantity of the number of electrons passing through a given wire per second.

How many electrons are in an Ampere?

A lot: 62,000,000,000,000,000,000 electrons per second!

Until next time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.

What is the Difference Between Lithium Ion and Lithium Polymer?

Lithium ion:

  • The lightest of all metals
  • The greatest electrochemical potential
  • The largest energy density for weight.
  • The load characteristics are reasonably good in terms of discharge.
  • The high cell voltage of 3.6 volts allows battery pack designs with only one cell versus three.
  • It is is a low maintenance battery.
  • No memory and no scheduled cycling is required to prolong the battery's life.
  • Lithium-ion cells cause little harm when disposed.
    It is fragile and requires a protection circuit to maintain safe operation.
  • Cell temperature is monitored to prevent temperature extremes.
  • Capacity deterioration is noticeable after one year (whether the battery is in use or not).

Lithium Polymer:

  • Lithium polymer chemistry differentiates itself from Lithium Ion in the type of electrolyte used (a plastic-like film that does not conduct electricity but allows ion exchange – electrically charged atoms or groups of atoms).
  • The polymer electrolyte replaces the traditional porous separator, which is soaked with electrolyte.
  • The dry polymer design offers simplifications with respect to fabrication, ruggedness, safety and thin-profile geometry.
  • Cell thickness measures as little as one millimeter (0.039 inches).
  • Can be formed and shaped in any way imagined.
  • Commercial lithium polymer batteries are hybrid cells that contain gelled electrolyte to enhane conductivity.
  • Gelled electrolyte added to the lithium ion polymer replaces the porous separator. The gelled electrolyte is simply added to enhance ion conductivity.
  • Capacity is slightly less than that of the standard lithium ion battery.
    Lithium ion polymer finds its market niche in wafer-thin geometries, such as PDA batteries.
  • Improved safety – more resistant to overcharge; less chance for electrolyte leakage.

Until Next Time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.

What is Electricity?

What is electricity? Where does electricity come from? How does electricity work?

The name “electricity” is derived from the Greek word "elektor," meaning "beaming sun." In Greek, "elektron" is the word for amber. Amber is a gold-brown colored "stone" that is actually fossilized tree sap.

Electricity is a property of certain subatomic particles which couples to electromagnetic fields and causes attractive and repulsive forces between them. This repulsive force between the subatomic particles creates an electric current; the flow of electric charge transports energy from one atom to another. The electrical current is measured in amperes, where 1 ampere is the flow of 62,000,000,000,000,000,000 electrons per second!

Wait just a minute……help me understand all that! To understand electricity we must first understand atoms and their structure.

All matter is made up of atoms, and atoms are made up of smaller particles. The three main particles making up an atom are the proton, the neutron and the electron.

Electrons spin around the center, or nucleus, of atoms, in the same way the earth spins around the sun. The nucleus is made up of neutrons and protons.

Electrons contain a negative charge, protons a positive charge. Neutrons are neutral — they have neither a positive nor a negative charge.

There are many different kinds of atoms, one for each type of element. An atom is a single part that makes up an element. There are 118 different known elements. The mass accumulation of elements makes up every thing we can see, touch, hear, and smell (elements are even in things we can’t see).

Each atom has a specific number of electrons, protons and neutrons. But no matter how many particles an atom has, the number of electrons usually needs to be the same as the number of protons. If the numbers are the same, the atom is called balanced, and it is very stable.

Some kinds of atoms have loosely attached electrons. An atom that loses electrons has more protons than electrons and is positively charged. An atom that gains electrons has more negative particles and is negatively charge. A "charged" atom is called an "ion."

The very nature of a positive atom is that it attracts electrons (negative charged atoms) to in effect balance the positive atom. Why, not sure, and for this article not pertinent. What is necessary to know is that the flow of elections to protons is essence of electricity.

You see electrons can be engineered to move from one atom to another. When those electrons move between the atoms, a current or flow of electricity is created. The electrons move from one atom to another in a "flow." One electron is attached and another electron is lost. This creates a continual equilibrium amongst the atoms.

Engineers however have found several ways to create large numbers of positive atoms and free negative electrons. Since positive atoms want negative electrons so they can be balanced, they have a strong attraction for the electrons. The manufactured disequilibrium creates a state of continuous flow of electrons to atoms with an overpopulation of protons (positive atoms).

When electrons move from atom to atom a current of electricity is created. This is what happens in a piece of wire. The electrons are passed from atom to atom, creating an electrical current from one end to other end.

There are two possible types of electric flow, direct current flow and alternating current flow. Direct current means that the flow of charges is in one direction. A battery produces direct current (DC) because there is no way to change the + and – you see on the battery. Alternating current (AC) has electrons in the circuit that quickly move first in one direction and then in the opposite direction, alternating back and forth between relatively fixed positions. When you use a transformer, you are using AC. PDAs, cellular phones and other common items use an AC adapter or transformer which helps extend the longevity of the item.

Until next time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.

Internal Battery Design

The wireless revolution, the prolific use of PDAs, MP3s, MP4s, Laptops, Cell Phones, Smartphones, DVD players, and other portable devices have increased the need for smart and high capacity portable batteries.

Portable batteries however are not typical in design. Indeed the battery that powers your portable device is what is known as a smart battery and as such the internal system design of a smart battery is more complex then most people realize.

To begin with high powered portable devices require an electrical current. There are two types of electrical current (direct current flow and alternating current flow). Direct current means that the flow of charge is in one direction. A battery produces direct current (DC) because there is no way to change the + and – you see on the battery.

In order to create direct electrical current electrons must be caused to break away from atoms to create an electron flow. Why? The answer is because electricity is a property of certain subatomic particles (protons, electrons, and neutrons) which couples to electromagnetic fields and causes attractive and repulsive forces between them; by doing so an electrical flow is created, and this is where electricity comes from. Let’s explain!

Scientists have found ways to create large numbers of positive atoms and free negative electrons (in other words they have found ways to separate electrons from atoms). Since overpopulated proton (positive) atoms want electrons (negative) so they can be balanced, these positive atoms have a strong attraction for electrons. The manufactured disequilibrium creates a state of continuous flow of electrons to atoms with an overpopulation of protons (positive atoms). When electrons move from one atom to another atom a current of electron flow (which is how we get electricity) is created.

This current can then be captured, stored, and used to power a potable device. In a portable battery the creation of electricity begins with a chemical reaction. To cause electrons to break away from atoms a chemical reaction must occur. In PDA batteries for example lithium ion or lithium polymer is used. Lithium is used due in large part to its superior energy density in terms of power per unit of weight and space.

General Characteristics of Lithium

Name: lithium
Symbol: Li
Atomic number: 3
Atomic weight: [ 6.941 (2)] g m r
CAS Registry ID: 7439-93-2
Group number: 1
Group name: Alkali metal
Period number: 2
Block: s-block
Standard state: solid at 298 K
color: silvery white/grey
Classification: Metallic

Lithium is used, amongst many other uses, as a battery anode material (due to its high electrochemical potential) and lithium compounds are used in dry cells and storage batteries. In fact the energy of some lithium-based cells can be five times greater than an equivalent-sized lead-acid cell and three times greater than alkaline batteries. Lithium cells often have a starting voltage of 3.0 V. This means that batteries can be lighter in weight, have lower per-use costs, and have higher and more stable voltage profiles.

In PDA batteries, for example, lithium is converted from chemical energy to electrical energy. This process then makes a battery an electrochemical device that stores chemical energy and releases it as electrical energy upon demand.

Chemical reactions are strongly influenced by their environment. The environment of an internal battery includes design parameters, current requirements, capacity and runtime requirements, temperature requirements, and safety requirements.

Critical to battery design is knowing how much voltage is required? Voltage is the electrical measure of energy. To know the voltage requirements we need to know the upper and lower voltage range (nominal range).

The second key component to know about a battery is its current requirements. PDAs, MP3s and other portable devices, for the most part, utilize a constant power discharge to operate. This means that the amount of current will increase as the battery discharges electricity in order to maintain constant power. So we will need to ultimately know the maximum current required. This is important since knowing the max current requirement will influence the necessary protection of chemistry, circuitry, wire, and capacity amongst others. Again we must know the current requirement over the entire nominal voltage range of the battery including start-up currents, surges (intermittent transient pulses).

One other important aspect to know about current requirements is the inert current drain of the device. Devices, even when powered down, require small amounts of current to power memory, switches and component leakage.

The third key requirement to know is the necessary battery capacity and runtime. This will define the overall physical size of the battery. Capacity and runtime is measured in Amperes. Amps – or A – is an abbreviation of Ampere, a 19th century French scientist who was a pioneer in electricity research. Amps measure the volume of electrons passing through a wire in a one second. The electrical current is measured in amperes, where 1 ampere is the flow of 62,000,000,000,000,000,000 electrons per second!

Amp hours – or Ah – measures capacity. Amp hours is what is ultimately important to consumers as it is the capacity or amp hours that tells us how long we can expect a battery to deliver a charge before it runs out. As with all metric measurements, Amps can be divided into smaller (or larger) units by adding a prefix, in this case by adding an "m" to the amp hour we are renaming the amp hour to milli amp hour: mAh; (1Ah = 1000 mAh).

When we consider the design capacity we must determine the chemical needed to insure that the necessary runtime will be met. Lithium is used because of its electrochemical properties. Lithium is part of the alkali family of metals a group of highly reactive metals. Li reacts steadily with water. In addition the per unit volume of lithium packs the greatest energy density and weight available for this grouping of reactive metals.

Ambient operational temperatures are also important because the internal heat of the battery compartment will dramatically affect the life of a battery. Usage and storage patterns are external effect that will also affect battery life and are the responsibility of a user (for example do not leave your device in a hot car with the windows rolled up, or take your device into a sauna).

A safety requirement for a battery that contains lithium requires protection circuitry to prevent the cells in the battery from conditions like over charge, over discharge, high currents, and or short circuits. Protected circuits consists of integrated circuits (programmed digital circuits), several field-effect transistors (FET) that control the current between two points, and resistors (a two-terminal electronic component that resists the flow of current, producing a voltage drop between its terminals). These circuits add cost and space to the battery pack requirements and careful placement is required in physical layouts to preserve system integrity.

Electromagnetic interference (EMI) or protection from electrostatic discharge is another safety concern. EMI, radiated or conducted, can occur throughout the electromagnetic spectrum. The primary problem with EMI is the disruption of performance of electronics. In wireless devices EMI can cause attenuation losses in signal strength and noise during transmission. Battery packs act as radiated sources of EMI and therefore shielding measures must be taken to reduce and or prevent EMI.

Another aspect of lithium battery design is the concept of smart batteries. A smart battery stores, monitors, prevents, and transmits critical battery information stored within the battery.

A smart battery will communicate with the host device through a connector to provide information about remaining capacity, battery voltage, error conditions, cycles completed, internal temperature, current, and several other factors. A smart battery can request a conditioning cycle, which will fully discharge a battery pack and then recharge it to allow the internal remaining capacity value to be accurately calibrated. Smart batteries often have an LED or LCD display that will allow the user to check the state of charge of a battery prior to use.

Lithium based smart batteries typically use coulomb counting to determine capacity, which means the circuit monitors the capacity in and out of the battery by measuring voltage across a sense resistor. For example 1 coulomb is the amount of electric charge carried by a current of 1 ampere flowing for 1 second. Coulomb counting is based on Coulombs law that states that the magnitude of the electrostatic force between two point charges is directly proportional to the magnitudes of each charge and inversely proportional to the square of the distance between the charges.

This review of the internal design of a battery was extensive. By no means thorough. I hope it offers you a basic under the hood understanding of what is inside your battery and how it works.

Until next time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.

What is Battery Capacity?

Batteries die! It is a natural process of utilizing the useful life of a battery reaches the point of of no longer holding a charge. There are technical reasons why batteries degrade and lose their ability to power a device that include: declining capacity, increasing internal resistance, elevated self-discharge, and premature voltage cut-off on discharge.

Today I want to write about battery capacity and its impact within the design of a battery.

What is Battery Capacity?

Battery capacity is a reference to the total amount of energy stored within a battery. Battery capacity is rated in Ampere-hours (AH), which is the product of:

AH= Current X Hours to Total Discharge

The capacity is normally tested or compared with a time of 20 hours and at a temperature of 68F (20C).

Five Factors that Govern Battery Capacity

Physical Size – the amount of capacity that can be stored in the casing of any battery depends on the volume and plate area of the actual battery. The more volume and plate area the more capacity you can actually store in a battery.

Temperature – capacity, energy store decreases as a battery gets colder. High temperatures also have an effect on all other aspects of your battery.

Cut off Voltage – To prevent damage to the battery and the device batteries have an internal mechanism that stops voltage called the cut-off voltage, which is tpically limited to 1.67V or 10V for a 12 Volt battery. Letting a battery self-discharge to zero destroys the battery.

Discharge rate – The rate of discharge, the rate at which a battery goes from a full charge to the cut off voltage measured in amperes. As the rate goes up, the capacity goes down.

Battery History – Deep discharging, excessive cycling, age, over charging, under charging, all reduce capacity. Note charging your battery 1 time will reduce capacity as much as 15%-20% depending on your battery's chemistry.

Until next time – Dan Hagopian, BatteryShip.com
Copyright © BatteryEducation.com. All rights reserved.