What is a battery?

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Does size matter? Yes and No Yes and No –Yes The larger the battery the more capacity it has The larger the battery the more capacity it has –That is, more amp hours –NO Batteries of all sizes can supply the same voltage Batteries of all sizes can supply the same voltage Which size? Which size? –What is your voltage (do you need to make a string?)? –Which will give you the most power per $$ or power per cm 3 ?

4 Battery Terminology Primary battery: not rechargeable Primary battery: not rechargeable Charge: The conversion of electrical into chemical energy. Charge: The conversion of electrical into chemical energy. Cycle: One complete discharge and charge or vice-versa. Cycle: One complete discharge and charge or vice-versa. Capacity: The battery’s ability to provide a sustained current for a given amount of time. Units: Ampere-hours (Ah). Capacity: The battery’s ability to provide a sustained current for a given amount of time. Units: Ampere-hours (Ah).

5 Power: The rate of doing work. Power (Watts) = E(Volts) x I(Amps). Power: The rate of doing work. Power (Watts) = E(Volts) x I(Amps). Self Discharge: The process by which a battery discharges without an external load due to internal chemical reactions. Self Discharge: The process by which a battery discharges without an external load due to internal chemical reactions. Shelf life: the amount of time a battery can remain in storage before its capacity has reduced to a specified level. Shelf life: the amount of time a battery can remain in storage before its capacity has reduced to a specified level.

6 Types of batteries Lead Acid Lead Acid – Wet Cell (2 types): Serviceable (flooded) Serviceable (flooded) Maintenance free (sealed) Maintenance free (sealed) – Gel Cell – Absorbed Glass Mat (AGM) – Valve-regulated (VRLA) for UPS, emergency lights, and security systems

Types of batteries Carbon-zinc: These are the plain, old-fashioned batteries: 1.5V Carbon-zinc: These are the plain, old-fashioned batteries: 1.5V –power of 950mAh (AA) –sloping discharge curve (voltage drops as capacity is used. –Operating range down to 20 ⁰ F They perform very poorly at low temperature They perform very poorly at low temperature at -5 ⁰ F their service life is decreased by 75% and output drops quickly as the temperature drops below room temperature at -5 ⁰ F their service life is decreased by 75% and output drops quickly as the temperature drops below room temperature –shelf life is 1/3 to 1/10th of other types - about 3.5 years.. –On the plus side, they're cheap. Alkaline Alkaline Lithium-ion Lithium-ion Nickel Metal Hydride Nickel Metal Hydride Nickel Cadmium Nickel Cadmium

Types of batteries Alkaline (Duracell, Energizer etc): 1.5V Alkaline (Duracell, Energizer etc): 1.5V –Capacity: about 2850mAh Depends on discharge rate Depends on discharge rate More in lithium section More in lithium section –sloping discharge curve. –Operating range is down to 0 ⁰ F at -5 ⁰ F their service life is decreased by 60% and output drops quickly as the temperature drops below room temperature. at -5 ⁰ F their service life is decreased by 60% and output drops quickly as the temperature drops below room temperature. –shelf life is 10+ years. –Although they're more expensive, they're comparable to carbon-zinc in terms of cost per hour of use.

Types of batteries Lithium: 3V (but newer chemistries are 1.5) Lithium: 3V (but newer chemistries are 1.5) –About the same capacity as alkaline, ~2900mAh –flat discharge curve: voltage stays high until nearly all capacity is gone and then drops. –Operating range down to -40 ⁰ F; at -5 ⁰ F their service life only is decreased by 20% and output decreases slowly as the temperature drops at -5 ⁰ F their service life only is decreased by 20% and output decreases slowly as the temperature drops –Shelf life is 10+ years. –They're also much more expensive –Also can be dangerous; may explode if “shorted”

Caveats Useable capacity depends on discharge rate Useable capacity depends on discharge rate –Especially in alkaline batteries

Consider temperature effects Alkalines lose a lot of capacity at deep sea temperatures Alkalines lose a lot of capacity at deep sea temperatures Data.energizer.com

Discharge Curves Digital electronics shut down when a minimum voltage is reached. Digital electronics shut down when a minimum voltage is reached. Data.energizer.com

Rechargeable VS One-time use Rechargeable Rechargeable –Pro Multiple uses Multiple uses –Saves money Saves having to open the instrument Saves having to open the instrument –Cons Usually have less amp hours / cell Usually have less amp hours / cell Sometimes can cost a lot Sometimes can cost a lot –But should be made up for in uses Often have higher self-discharge rates Often have higher self-discharge rates

Types of rechargeable batteries Nickel Cadmium (NiCd) (1.2V) Nickel Cadmium (NiCd) (1.2V) –Previous standard, now obsolete –Serious memory issues Nickel Metal Hydride (NiMH) (1.2V) Nickel Metal Hydride (NiMH) (1.2V) –Now the standard –Less memory but still require special care Lithium ion (3.6V) Lithium ion (3.6V) –No memory; low self discharge rate –Extreme energy density –Require very specific charging circuits

Wikipedia.com

16 Battery Charging; general rules Recharge batteries immediately after they are discharged. Recharge batteries immediately after they are discharged. Li ion should be stored at ½ charge Li ion should be stored at ½ charge Do not discharge them more than 80% of their normal capacity. Do not discharge them more than 80% of their normal capacity. NiMH can be very hard to bring back NiMH can be very hard to bring back Recharge them at the rate recommended by manufacturer Recharge them at the rate recommended by manufacturer Control by varying voltage and monitoring Amps Control by varying voltage and monitoring Amps Have the positive and negative terminals clearly marked. Have the positive and negative terminals clearly marked.

17 Battery Life and Performance Batteries sit too long between charges. Batteries sit too long between charges. Batteries are stored without some type of energy input like a trickle charge. Batteries are stored without some type of energy input like a trickle charge. “Deep cycling” a battery designed to start an engine reduces its life. “Deep cycling” a battery designed to start an engine reduces its life. Undercharging a battery reduces performance. Undercharging a battery reduces performance. Heat > 100 o Fahrenheit increases internal discharge. Heat > 100 o Fahrenheit increases internal discharge.

18 Cold weather reduces the internal chemical activity and less energy is produced. Cold weather reduces the internal chemical activity and less energy is produced. Low electrolyte level in the cells. Low electrolyte level in the cells. Incorrect charging levels from inexpensive battery chargers. Incorrect charging levels from inexpensive battery chargers.

Myths About Batteries A battery will discharge if it is in contact with concrete. Modern battery cases are made of polypropylene or hard rubber. A battery will discharge if it is in contact with concrete. Modern battery cases are made of polypropylene or hard rubber. A battery will not lose its charge while sitting in storage. Batteries have a normal self- discharge of 1% to 25% a month. A battery will not lose its charge while sitting in storage. Batteries have a normal self- discharge of 1% to 25% a month. A battery will not explode. Hydrogen and oxygen gasses are produced during recharging. A battery will not explode. Hydrogen and oxygen gasses are produced during recharging. 19

This battery was part of an emergency generator This battery was part of an emergency generator It exploded while being charged during a routine test. It exploded while being charged during a routine test. 20

Providing batteries to your instrument: buy or build? Most oceanographic sensor companies will sell you the battery packs needed for their sensor. Most oceanographic sensor companies will sell you the battery packs needed for their sensor. –They will also replace that battery pack at a some cost when the pack dies May be cheaper to build your own pack May be cheaper to build your own pack –Only time it is not cheaper is when it becomes too specialized Configuration is complicated Configuration is complicated –i.e. glider batteries or ADCP –Possibly turn it into a rechargeable If amp hours requirements will allow If amp hours requirements will allow

Oceanographic Battery Depth problems Depth problems – Need to oil compensate for depth Temperature at depth can affect performance Temperature at depth can affect performance

How many batteries do I need? Total voltage for sensor(s) Total voltage for sensor(s) – Series V total = V1+V2+V3... V total = V1+V2+V3... – 12v car battery is nothing but 6 – 2v cells

How many batteries do I need? How long do you want it to last!? How long do you want it to last!? –Batteries in Parallel Only put batteries of the same voltage in parallel!! Only put batteries of the same voltage in parallel!! Add up Amp hours Add up Amp hours

How many batteries do I need? Use a combination on series and Parallel Use a combination on series and Parallel How big is your pressure housing How big is your pressure housing – i.e. How much space do you have?

Oceanographic Battery Safety Test all batteries for voltage before plugging them into you sensor Test all batteries for voltage before plugging them into you sensor –Especially ones you have made!! –Wrong voltage or polarity could mean dead sensors! Salt Water and Batteries do not mix Salt Water and Batteries do not mix –Corrodes batteries and then they leak Lithium batteries and water Lithium batteries and water –Releases gases –Dissolves quickly If happens in your pressure housing you have a bomb!!! If happens in your pressure housing you have a bomb!!! Be careful when opening any pressure housing with batteries after any deployment Be careful when opening any pressure housing with batteries after any deployment –You don't know the state of the batteries Open any pressure housing when recharging batteries Open any pressure housing when recharging batteries –Gases released during charging

Computers

Computer numeric systems Different ways computer store data Different ways computer store data –Numbers Binary Binary Hexadecimal Hexadecimal Octal Octal Decimal Decimal –Text ASCII ASCII

Binary Base 2 system Base 2 system –0 and 1 0=0 0=0 1=1 1=1 10=2 10=2 11=3 11=3 100=4 100=4 101=5 101=5 110=6 110=6 111=7 111=7 etc etc

Octal Base 8 system Base 8 system –Use 0-7 –Binary numbers grouped into 3 Decimal 112 Decimal 112 –Binary – or –Octal = 160  (1*8 2 )+(6*8 1 )+(0*8) = = 112

Hexadecimal Base 16 Base 16 –0-9 and A-F –A=10 –F=15 Example – 8AC7 = (8*16 3 )+(10*16 2 )+(12*16 1 )+(7*16 0 )

Data storage Bit – binary digit Bit – binary digit –0 or 1 –So small usually worked with in groups of 8 Byte = 8 bits Byte = 8 bits –Numeric values Kilobyte = 1024 bytes Kilobyte = 1024 bytes Megabye =1024 KB or (1024*1024) bytes Megabye =1024 KB or (1024*1024) bytes

Flashback to last week A/D converters A/D converters –0-5v analog signal through a 12-bit A/D converter – What is the resolution of the signal? –16bit – resolution?

Memories Computers, by definition, have memories Computers, by definition, have memories – hold the program a program is what makes a computer a computer a program is what makes a computer a computer – hold data Requirements of memory: Requirements of memory: –enter data –save data –retrieve data What is memory? What is memory? –recording of a series of binary numbers (that's all) –in the case of data, these are actually numbers – in thee case of a program, these may be numbers or may be a truth table showing the computer how to respond to a given circumstance.

Memory types Non-Volatile (mass storage device) Non-Volatile (mass storage device) –- used for long-term storage – magnetic core = magnetized donuts which store bits isn't used very much any more isn't used very much any more takes up quite a bit of space takes up quite a bit of space random access random access don't sweat the details of how this works don't sweat the details of how this works – tape drives data stored in tracks (bits plus parity) data stored in tracks (bits plus parity) prone to errors prone to errors very cheap very cheap slow sequential access slow sequential access –disks (floppy, hard, laser etched) data stored in tracks and sectors data stored in tracks and sectors may or may not be exchangeable may or may not be exchangeable – ROM's read only read only simplest form is a series of diodes which select a current path simplest form is a series of diodes which select a current path in more complicated form, they are semiconductor memories which are programmed using high voltages in more complicated form, they are semiconductor memories which are programmed using high voltages some are erasable using light or another voltage some are erasable using light or another voltage act like a big truth table act like a big truth table

Memory 3. types of ROMS 3. types of ROMS – mask programmed mass produced mass produced not field changeable not field changeable –Programmable ROMS (PROMs) programmed by burning away a fusible link programmed by burning away a fusible link not changeable unless you change ones to zeros not changeable unless you change ones to zeros –Erasable PROMs (EPROMs) written by using high voltage written by using high voltage erased by UV or electrically (EEPROMs) erased by UV or electrically (EEPROMs)