Presentation on theme: "Battery Basics A guide to battery use in engineering projects"— Presentation transcript:
1 Battery Basics A guide to battery use in engineering projects Thomas G. Cleaver University of Louisville Department of Electrical and Computer Engineering Jan. 28, 2013
2 ReferencesThis presentation was developed using the following sources:T.E. Bell, “Choosing the Best Battery for Portable Equipment,” IEEE Spectrum, March, 1988, ppWalt Kester, Joe Buxton, “SECTION 5, BATTERY CHARGERS,” available atCustom Power Solutions, available atNew Technology Batteries Guide (1998), available atGreen Batteries, available atSteve Garland, Kyle Jamieson, “Battery Overview,” available at:Harding energy Inc, available atBatteryUniversity.com, available at
3 Battery Terms 1Capacity: The charge a battery can hold in ampere-hours (Ah) or milliampere-hours (mAh) or the energy the battery can hold in watt-hours.C: Charge or discharge rate. Battery capacity in Ah or mAh divided by 1 hour. Also know as C rate.Charge life: The total capacity over the life of the battery (capacity x cycles).Discharge rate: The maximum allowable load or discharge current.End voltage: The voltage below which a battery will not operate satisfactorily. Also know as “final voltage.”Energy density: The energy storage capacity of a battery compared to its mass or volume. The higher the energy density, the better.Memory effect: The tendency of some rechargeable batteries to lose capacity when not periodically totally drained – a particular problem in NiCd batteries.
4 Battery Terms 2 Primary battery: A disposable battery. Polarity reversal: The reversal of the polarity of an over-discharged cell of a rechargeable battery in a series connection. If one cell in a series string discharges before the others, the discharged cell may reverse polarity. If the current is maintained, the reversed cell may be permanently damaged.Secondary battery: A rechargeable (storage) battery.Self-discharge: The loss of charge over time of a battery when it is unused.Service life: The length of time a battery is expected to be usable.Shelf life: The length of time a battery will retain useful charge when stored.
5 Primary (Disposable) Battery Types Zinc-carbon:“Ordinary” batteryVoltage decreases steadily during dischargeZinc-alkaline:“Alkaline” batteryBetter than zinc-carbonZinc-air:Button cell hearing aid batteriesVoltage almost constant over useful lifeLithium ion:High energy density
6 Secondary (rechargeable) Battery Types Sealed Lead-Acid (SLA):Automobile batteriesLow costLead is toxic; sulfuric acid is corrosive.Nickel-Cadmium (NiCd):InexpensiveMemory effectCadmium is toxic.Nickel-metal-hydride (NiMH):Moderately expensiveVoltage almost constant over useful lifeLithium ion (Li-ion):ExpensiveHigh energy densityDangerous if overcharged
7 Standard SizesButton – used in hearing aids and in other applications that require small sizeCylindrical – like AAA, AA, C, D – all usually 1.2 to 1.5 VPrismatic – like 9 V batteriesRechargeable Li-ion does not typically come in standard cylindrical sizes.
8 Discharge and VoltageThe voltage of some batteries doesn’t change much as the battery is discharged, for example, NiCD and NiMH.The voltage of others drops off as the battery is discharged, for example, zinc-carbon, and alkaline.
10 Discharge and CurrentBattery capacity, usually expressed in mAh, is measured under specific conditions.The higher the current, the less the effective capacity.Example: A battery rated at 1500 mAh may be able to deliver 150 mA for 10 hours, but it may not be able to actually deliver 1500 mA for 1 hour.
12 C Rate Calculations C = Rated capacity/ 1 hour Example: A 2800 mAh NiMH battery has a C of 2800 mA.Batteries can be tested at various multiples of C.Example: For the 2800 mAh battery, C/4 would be 700 mA; 3C would be 8400 mA.
13 Voltage Dependence on Current Batteries are not ideal devices – They have internal resistance.Vloss = IRinternalBattery TypeTypical Internal Resistance (milliohms)NiCd 1.2 V AA30NiMH 1.2 V AA150Li-ion 3.6 V320Alkaline 1.5 V AA
14 Maximum and Suggested Drain Battery TypeMax DrainSuggested DrainAlkaline.5 C< .2 CSLA.2-5 C.2 CNiCd2-20 C< .5 CNiMH.5-5 CLi-ion1-2 C< 1 C
15 Batteries in Series Batteries should be identical. Total voltage = Voltage of each cell x number of cellsWhen using rechargeable batteries in series, beware of deep discharge because of polarity reversal.
16 Batteries in Parallel Batteries should be identical. Total current = Current of each cell x number of cellsUsually a bad ideaGood batteries may discharge through bad battery.
17 Illumination Economics Incandescent, Compact Fluorescent (CFL), and LED lighting characteristicsTypeCost of bulbLumensEfficiencyLifetime60 W Incandescent$18402%1K hours(~ 1 Month)13 W CFL$28259%10k hours(~ 1 year)10 W LED$1681012 %50k hours(~ 5 years)
18 Total Cost by Bulb TypeCost for purchase of bulb(s) and for electrical 10 ₵/kWh.But this assumes you turn the light on and never turn it off until it blows out and you replace it.Type1 month1 year5 years60 WIncandescent$7$70$35013 W CFL$3$15$7510 W LED$17$26$65
19 What’s so Bad about CFLs? On/off cycling shortens lifetime.They are sensitive to physical shock and breakage.Most CFLs are not dimmable.Some people don’t like the quality of the light (too harsh).Some CFLs take time (~ 30 seconds) to achieve maximum light output.CFLs contain a small amount of mercury (a disposal issue).Low temperature reduces CFL light output (an outdoor use issue).High temperature shortens CFL light (a luminaire issue).