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The Care and Feeding of Batteries

Explore the history, types, characteristics, and advancements in battery technology. Learn about internal resistance, discharge, charge methods, service life, and precautions for various battery types. Discover the future trends and conclusions in battery technology.

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The Care and Feeding of Batteries

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  1. The Care and Feeding of Batteries Ham Perspective February 13, 2003

  2. OUTLINE • History • Battery Types • Characteristics • Internal Resistance • Discharge • Charge • Pulse Charging • Termination Methods • Service Life • Precautions • Trends • Conclusion

  3. Time Event Name Time Event Name 1791 Frog leg experiment Galvani 1792 Voltaic piles Volta 1891 Thermodynamics of dry cells Nernst 1802 Mass produced battery Cruickshank 1899 Nickel cadmium battery Nernst 1813 Giant battery (2,000 cells) Davy 1900 Ni Storage batteries Edison 1820 Electricity from magnetism Ampere 1905 Ni ironbatteries Edison 1827 Ohm's law Ohm 1911 Automobile self-starter Kettering 1833 Ionic mobility in Ag2S Faraday 1927 Silver zinc Andre 1836 Cu/CuSO4, ZnSO4/Zn Daniell 1930 Nickel-zinc battery Drumm 1839 Principle of the air cell Grove 1943 Cuprous chloride battery Adams 1859 Lead acid battery Planté 1945 Mercury cell Ruben 1868 Zn/NH4Cl/C wet battery Leclanché 1950 Sealed mercury Cell Ruben 1874 Telegraph Edison 1956 Alkaline fuel cell Bacon 1878 Air Cell Maiche 1959 Alkaline primary cell Urry 1880 High capacity lead/acid Faure 1983 Lithium metal rechargeable Moli 1881 Zn/NH4Cl/C encapsulated Thiebault 1991 Commercial lithium ion Sony 1885 Zinc-bromine Bradley 1992 Reusable alkaline Kordesch 1887 Zn/NH4Cl/C dry battery Gassner 1995+ Recent developments .. History If you would not be forgotten as soon as you are dead & rotten, either write things worth reading, or do things worth the writing." Benjamin Franklin

  4. Secondary Cells Zinc Air Lithium Nickel Metal Hydride Nickel Cadmium Gel Cell Lead Acid Primary Cells Lithium Alkaline Carbon Zinc General Types

  5. Evolution of Cell Technologies Rechargeable cell technology has made dramatic strides in the past twenty years, offering new product design options while increasing energy density

  6. Energy Density Comparison Lithium-ion/polymer cells offer higher energy density versus Ni-MH and Ni-Cd. Lithium-polymer is typically a thinner cell than the equivalent capacity lithium-ion, which may be a key consideration.  Pb

  7. Internal Resistance • Internal Resistance is an important characteristic for applications that require periods of high current • Handhelds or any receive/transmit situation are examples of intermittent high drain applications. • This characteristic is the factor that favors the use of NiCad or NiMH AA cells over alkaline cells even though the alkaline cells have a higher rated capacity. • General preference • NiCad, SLA, Li-Ion, NiMH, and Alkaline • Internal resistance increases as cell discharges • More so for SLA and Alkaline • Specific Application is the determinant

  8. Discharge Comparison NIMH Alkaline The device operational voltage limits are important factors in battery charge utilization 0.8 Volt is considered full discharge

  9. NiCd NiCd NiCd NiMH NiMH NiMH Lead Acid Lead Acid Lead Acid Li-ion Li-ion Li-ion Li-ion polymer Li-ion polymer Li-ion polymer ReusableAlkaline ReusableAlkaline ReusableAlkaline Gravimetric Energy Density (Wh/kg) Gravimetric Energy Density (Wh/kg) Gravimetric Energy Density (Wh/kg) 45-80 45-80 45-80 60-120 60-120 60-120 30-50 30-50 30-50 110-160 110-160 110-160 100-130 100-130 100-130 80 (initial) 80 (initial) 80 (initial) Internal Resistance(includes peripheral circuits) in mW Internal Resistance(includes peripheral circuits) in mW Internal Resistance(includes peripheral circuits) in mohms 100 to 20016V pack 100 to 20016V pack 100 to 20016V pack 200 to 30016V pack 200 to 30016V pack 200 to 30016V pack <100112V pack <100112V pack <100112V pack 150 to 25017.2V pack 150 to 25017.2V pack 150 to 25017.2V pack 200 to 30017.2V pack 200 to 30017.2V pack 200 to 30017.2V pack 200 to 200016V pack 200 to 200016V pack 200 to 200016V pack Cycle Life (to 80% of initial capacity) Cycle Life (to 80% of initial capacity) Cycle Life (to 80% of initial capacity) 15002 15002 15002 300 to 5002,3 300 to 5002,3 300 to 5002,3 200 to 3002 200 to 3002 200 to 3002 500 to 10003 500 to 10003 500 to 10003 300 to 500 300 to 500 300 to 500 503(to 50%) 503(to 50%) 503(to 50%) Fast Charge Time Fast Charge Time Fast Charge Time 1h typical 1h typical 1h typical 2-4h 2-4h 2-4h 8-16h 8-16h 8-16h 2-4h 2-4h 2-4h 2-4h 2-4h 2-4h 2-3h 2-3h 2-3h Overcharge Tolerance Overcharge Tolerance Overcharge Tolerance moderate moderate moderate low low low high high high very low very low very low low low low moderate moderate moderate Self-discharge / Month (room temperature) Self-discharge / Month (room temperature) Self-discharge / Month (room temperature) 20%4 20%4 20%4 30%4 30%4 30%4 5% 5% 5% 10%5 10%5 10%5 ~10%5 ~10%5 ~10%5 0.3% 0.3% 0.3% Cell Voltage (nominal) Cell Voltage (nominal) Cell Voltage (nominal) 1.25V6 1.25V6 1.25V6 1.25V6 1.25V6 1.25V6 2V 2V 2V 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 1.5V 1.5V 1.5V Load Current-    peak-    best result Load Current-    peak-    best result Load Current-    peak-    best result 20C1C 20C1C 20C1C 5C0.5C or lower 5C0.5C or lower 5C0.5C or lower 5C7 0.2C 5C7 0.2C 5C7 0.2C >2C1C or lower >2C1C or lower >2C1C or lower >2C1C or lower >2C1C or lower >2C1C or lower 0.5C0.2C or lower 0.5C0.2C or lower 0.5C0.2C or lower Operating Temperature (discharge only) Operating Temperature (discharge only) Operating Temperature (discharge only) -40 to 60°C -40 to 60°C -40 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C 0 to 60°C 0 to 60°C 0 to 60°C 0 to 65°C 0 to 65°C 0 to 65°C Maintenance Requirement Maintenance Requirement Maintenance Requirement 30 to 60 days 30 to 60 days 30 to 60 days 60 to 90 days 60 to 90 days 60 to 90 days 3 to 6 months9 3 to 6 months9 3 to 6 months9 not req. not req. not req. not req. not req. not req. not req. not req. not req. Typical Battery Cost(US$, reference only) Typical Battery Cost(US$, reference only) Typical Battery Cost(US$, reference only) $50(7.2V) $50(7.2V) $50(7.2V) $60(7.2V) $60(7.2V) $60(7.2V) $25(6V) $25(6V) $25(6V) $100(7.2V) $100(7.2V) $100(7.2V) $100(7.2V) $100(7.2V) $100(7.2V) $5(9V) $5(9V) $5(9V) Cost per Cycle (US$)11 Cost per Cycle (US$)11 Cost per Cycle (US$)11 $0.04 $0.04 $0.04 $0.12 $0.12 $0.12 $0.10 $0.10 $0.10 $0.14 $0.14 $0.14 $0.29 $0.29 $0.29 $0.10-0.50 $0.10-0.50 $0.10-0.50 Commercial use since Commercial use since Commercial use since 1950 1950 1950 1990 1990 1990 1970 1970 1970 1991 1991 1991 1999 1999 1999 1992 1992 1992 Characteristic

  10. Pros Cons Technology Comparisons Ni-Cd • Long cycle life (500+) • Environmental concerns due to   cadmium • Excellent low temp capacity (up to   -30ºC) • Low energy density and high self  discharge • High rate capability • Memory effect Ni-MH • Medium cycle life (400+) • Lower charge efficiency • 30% more energy density than NiCd • High self discharge • Environmentally friendly • Poor rate capability Li-ion • Medium cycle life (400+) • Lowest shelf life • Highest energy density • Complex charge controls required • Very low self discharge Li-ion Polymer • Same as Li-ion • Same as Li-ion • No metal "can" • Difficult to handle • Broad and thin design capability • Lower charge rate capability • Lack of field history • Cost

  11. Application Feature Comparison of Nickel-Metal Hydride to Nickel-Cadmium Batteries Nominal Voltage Same (1.25V) Discharge Capacity NiMH up to 40% greater than NiCd Discharge Profile Equivalent Discharge Cutoff Voltages Equivalent High Rate Discharge Capability Effectively the same rates High Temperature (>35oC) Discharge Capability NiMH slightly better than standard NiCd cells Charging Process Generally similar; multiple-step constant current with overcharge control recommended for fast charging NiMH Charge Termination Techniques Generally similar but NiMH transitions are more subtle. Backup temperature termination recommended. Operating Temperature Limits Similar, but with NiMH, cold temperature charge limit is 15oC. Self-Discharge Rate NiMH slightly higher than NiCd Cycle Life Generally similar, but NiMH is more application dependent. Mechanical Fit Equivalent Mechanical Properties Equivalent Selection of Sizes/Shapes/Capacities NiMH product line more limited Handling Issues Similar Memory and Depression? Environmental Issues Reduced with NiMH because of elimination of cadmium toxicity concerns

  12. Lithium-ion vs. Lithium-ion Polymer Pros Cons Li-ion Technology • State-of-the-art • Cell material in rigid metal can • Mechanically robust construction • Tolerant to mild pressure build up • No manufacturing flexibility • Loses (20%) energy efficiency with thin cells Li-ion Polymer Technology • Next level of improvement • Soft plastic package • "Soft" construction • Maintains energy efficiency with thin cells • Limited manufacturing flexibility • Cells easily bulge upon pressure build up

  13. Li –Ion vs. Li Polymer The Li-ion polymer offers little or no energy gain over conventional Li‑ion systems; neither do the slim profile Li-ion systems meet the cycle life of the rugged 18560 cell. The cost-to-energy ration increases as the cell size decreases in thickness. Cost increases in the multiple of three to four compared to the 18650 cell are common on exotic slim battery designs. If space permitted, the 18650 cell offers the most economical choice, both in terms of energy per weight and longevity. Applications for this cell are mobile computing and video cameras. Slimming down means thinner batteries. This, in turn, will make the cost of the portable power more expensive. *Note- The 18560 is probably the only Li battery that would be feasible for to attempt to use in a general purpose (ham) setting. Even then, the charger would need be carefully fit to the application.

  14. Note: An inexpensive source for Alkaline AA’s is Costco. The Kirkland’s are about $0.25 each AlkalineCells

  15. Primary Alkaline vs. Rechargeable

  16. NiCad vs. NiMH NiMH NiCad

  17. VoltageWhen Lithium-ion batteries are charged, the voltage will continue to rise. Therefore, the charger must manage the battery voltage to define charge termination and optimize battery life. • TemperatureLithium-ion batteries are not exothermic until they overcharge. • Charge Control • Constant current-constant voltage limit (4.2 V maximum) • Typical charge time is 2.5 hours with host turned off at 25º C • Temperature cut off is typically not used (Temperature is fairly constant with this method.) • Safety: Overcharge can cause failure. Charging Lithium-ion Chemistries

  18. Figure 1: Characteristics of commonly used rechargeable batteries Figure 1: Characteristics of commonly used rechargeable batteries NiCd NiCd NiCd NiCd NiMH NiMH NiMH NiMH Lead Acid Lead Acid Lead Acid Lead Acid Li-ion Li-ion Li-ion Li-ion Li-ion polymer Li-ion polymer Li-ion polymer Li-ion polymer ReusableAlkaline ReusableAlkaline ReusableAlkaline ReusableAlkaline Gravimetric Energy Density (Wh/kg) Gravimetric Energy Density (Wh/kg) Gravimetric Energy Density (Wh/kg) Gravimetric Energy Density (Wh/kg) 45-80 45-80 45-80 45-80 60-120 60-120 60-120 60-120 30-50 30-50 30-50 30-50 110-160 110-160 110-160 110-160 100-130 100-130 100-130 100-130 80 (initial) 80 (initial) 80 (initial) 80 (initial) Internal Resistance(includes peripheral circuits) in mW Internal Resistance(includes peripheral circuits) in mW Internal Resistance(includes peripheral circuits) in mW Internal Resistance(includes peripheral circuits) in mW 100 to 20016V pack 100 to 20016V pack 100 to 20016V pack 100 to 20016V pack 200 to 30016V pack 200 to 30016V pack 200 to 30016V pack 200 to 30016V pack <100112V pack <100112V pack <100112V pack <100112V pack 150 to 25017.2V pack 150 to 25017.2V pack 150 to 25017.2V pack 150 to 25017.2V pack 200 to 30017.2V pack 200 to 30017.2V pack 200 to 30017.2V pack 200 to 30017.2V pack 200 to 200016V pack 200 to 200016V pack 200 to 200016V pack 200 to 200016V pack Cycle Life (to 80% of initial capacity) Cycle Life (to 80% of initial capacity) Cycle Life (to 80% of initial capacity) Cycle Life (to 80% of initial capacity) 15002 15002 15002 15002 300 to 5002,3 300 to 5002,3 300 to 5002,3 300 to 5002,3 200 to 3002 200 to 3002 200 to 3002 200 to 3002 500 to 10003 500 to 10003 500 to 10003 500 to 10003 300 to 500 300 to 500 300 to 500 300 to 500 503(to 50%) 503(to 50%) 503(to 50%) 503(to 50%) Fast Charge Time Fast Charge Time Fast Charge Time Fast Charge Time 1h typical 1h typical 1h typical 1h typical 2-4h 2-4h 2-4h 2-4h 8-16h 8-16h 8-16h 8-16h 2-4h 2-4h 2-4h 2-4h 2-4h 2-4h 2-4h 2-4h 2-3h 2-3h 2-3h 2-3h Overcharge Tolerance Overcharge Tolerance Overcharge Tolerance Overcharge Tolerance moderate moderate moderate moderate low low low low high high high high very low very low very low very low low low low low moderate moderate moderate moderate Self-discharge / Month (room temperature) Self-discharge / Month (room temperature) Self-discharge / Month (room temperature) Self-discharge / Month (room temperature) 20%4 20%4 20%4 20%4 30%4 30%4 30%4 30%4 5% 5% 5% 5% 10%5 10%5 10%5 10%5 ~10%5 ~10%5 ~10%5 ~10%5 0.3% 0.3% 0.3% 0.3% Cell Voltage (nominal) Cell Voltage (nominal) Cell Voltage (nominal) Cell Voltage (nominal) 1.25V6 1.25V6 1.25V6 1.25V6 1.25V6 1.25V6 1.25V6 1.25V6 2V 2V 2V 2V 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 3.6V 1.5V 1.5V 1.5V 1.5V Load Current-    peak-    best result Load Current-    peak-    best result Load Current-    peak-    best result Load Current-    peak-    best result 20C1C 20C1C 20C1C 20C1C 5C0.5C or lower 5C0.5C or lower 5C0.5C or lower 5C0.5C or lower 5C7 0.2C 5C7 0.2C 5C7 0.2C 5C7 0.2C >2C1C or lower >2C1C or lower >2C1C or lower >2C1C or lower >2C1C or lower >2C1C or lower >2C1C or lower >2C1C or lower 0.5C0.2C or lower 0.5C0.2C or lower 0.5C0.2C or lower 0.5C0.2C or lower Operating Temperature (discharge only) Operating Temperature (discharge only) Operating Temperature (discharge only) Operating Temperature (discharge only) -40 to 60°C -40 to 60°C -40 to 60°C -40 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C -20 to 60°C 0 to 60°C 0 to 60°C 0 to 60°C 0 to 60°C 0 to 65°C 0 to 65°C 0 to 65°C 0 to 65°C Maintenance Requirement Maintenance Requirement Maintenance Requirement Maintenance Requirement 30 to 60 days 30 to 60 days 30 to 60 days 30 to 60 days 60 to 90 days 60 to 90 days 60 to 90 days 60 to 90 days 3 to 6 months9 3 to 6 months9 3 to 6 months9 3 to 6 months9 not req. not req. not req. not req. not req. not req. not req. not req. not req. not req. not req. not req. Typical Battery Cost(US$, reference only) Typical Battery Cost(US$, reference only) Typical Battery Cost(US$, reference only) Typical Battery Cost(US$, reference only) $50(7.2V) $50(7.2V) $50(7.2V) $50(7.2V) $60(7.2V) $60(7.2V) $60(7.2V) $60(7.2V) $25(6V) $25(6V) $25(6V) $25(6V) $100(7.2V) $100(7.2V) $100(7.2V) $100(7.2V) $100(7.2V) $100(7.2V) $100(7.2V) $100(7.2V) $5(9V) $5(9V) $5(9V) $5(9V) Cost per Cycle (US$)11 Cost per Cycle (US$)11 Cost per Cycle (US$)11 Cost per Cycle (US$)11 $0.04 $0.04 $0.04 $0.04 $0.12 $0.12 $0.12 $0.12 $0.10 $0.10 $0.10 $0.10 $0.14 $0.14 $0.14 $0.14 $0.29 $0.29 $0.29 $0.29 $0.10-0.50 $0.10-0.50 $0.10-0.50 $0.10-0.50 Commercial use since Commercial use since Commercial use since Commercial use since 1950 1950 1950 1950 1990 1990 1990 1990 1970 1970 1970 1970 1991 1991 1991 1991 1999 1999 1999 1999 1992 1992 1992 1992 Typical 7AH Gel Cell

  19. Typical Gel Cell(Power-Sonic 1270) Measuring the open circuit voltage of a gel cell can provide a good indicator of its state of charge. This is especially true if you have the specifications for the particular battery. An approximation is – 12.8 - 13 V – Full charge 11.5 - 11.8 V - 10% charge

  20. NiCd Charge vs. Temp, Pressure The profiles for NiCD and NiMH are similar but note that it is difficult, if not impossible, to slow-charge a NiMH battery on the basis of these characteristics. At a C rate of 0.1C and 0.3C, the voltage and temperature profiles fail to exhibit defined characteristics to measure the full charge state accurately and the charger must rely on a timer. Harmful overcharge can occur if a partially or fully charged battery is charged with a fixed timer. The same occurs if the battery has aged and can only hold 50 instead of 100 percent charge. Overcharge could occur even though the NiMH battery feels cool to the touch.Lower-priced chargers may not apply a fully saturated charge. The full-charge detection may occur immediately after a given voltage peak is reached or a temperature threshold is detected. These chargers are commonly promoted on the merit of short charge time and moderate price. Some ultra-fast chargers also fail to deliver full charge.

  21. Charge Termination Methods • Constant voltage with current termination • Suitable for Li-ion, Li-ion polymer and Lead Acid • Terminate based on set current value • Simple in implementation but requires better accuracy for safety and performance • Time-based termination • Suitable for all chemistries (Li-ion with constant voltage charging • Low cost and simple design • Applicable for low current and slow chargers only • Temperature termination (not applicable for Li-ion chemistries) • Delta temperature/delta time: Suitable for nickel chemistries • 85-90% complete charging (100% with trickle charging) • Absolute temperature cut off (TCO) • Delta voltage termination (not applicable for Li-ion chemistries) • Suitable for nickel chemistries (best for Ni-Cd) • Less accurate method Commercial fast-chargers are often not designed in the best interests of the battery. The two common battery killers are high temperature during charge and incorrect trickle charge after charge. Choosing a quality charger makes common sense. This is especially true when considering the high cost of battery replacements and the frustration poorly performing batteries create. In most cases, the extra money invested in a more advanced charger is returned in longer lasting and better performing batteries. The selection of the ‘best’ method, is closely coupled to whether the method is being applied to a cell or battery (multiple cells in series), what the charge rate will be, and the chemistry involved. Some say that the ‘best’ method is to employ delta temperature, delta voltage or voltage inflection, with time and max temp as backups. Li is class unto its own.

  22. Power Sonic Charging (7 AH) Cycle Applications: Limit initial current to 1500mA. Charge until battery voltage (under charge) reaches 14.40 to 14.70 volts at 68 F (20 C). Hold at 14.40 to 14.70 volts until current drops to approximately 70mA. Battery is fully charged under these conditions, and charger should either be disconnected or switched to “float” voltage. “Float” or “Stand-By” Service: Hold battery across constant voltage source of 13.50 to 13.80 volts continuously. When held at this voltage, the battery will seek its own current level and maintain itself in a fully charged condition. NOTE: Due to the self-discharge characteristics of this type of battery, it is imperative that they be charged after 6-9 months of storage, otherwise permanent loss of capacity might occur as a result of sulfation.

  23. Sealed Lead Acid Considerations Finding the ideal charge voltage limit for a sealed lead acid system is critical. Any voltage level is a compromise. A high voltage limit produces good battery performance, but shortens the service life due to grid corrosion on the positive plate. The corrosion is permanent and cannot be reversed. A low voltage preserves the electrolyte and allows charging under a wide temperature range, but is subject to sulfation on the negative plate. Once the SLA battery has lost capacity due to sulfation regaining its performance is often difficult and time consuming. Reasonably good results in regaining lost capacity are achieved by applying a charge on top of a charge. This is done by fully charging an SLA battery, then removing it for a 24 to 48 hour rest period and applying a charge again. This is repeated several times, and then the capacity of the battery is checked with a full discharge. The SLA is able to accept some overcharge, however, too long an overcharge could harm the battery due to corrosion and loss of electrolyte. Applying an over-voltage charge of up to 2.50V/cell for one to two hours can reverse the effect of sulfation of the plastic SLA. During that time, the battery must be kept cool and careful observation is necessary. Extreme caution is required not to raise the cell pressure to venting point. Cell venting causes the membrane on some SLA to rupture permanently. Not only do the escaping gases deplete the electrolyte, they are also highly flammable! There are a number of other approaches advertised that use various pulsing, reflex charging and ‘resonant frequencies’ to prevent or recover batteries from the effects of sulfation. The is some evidence that these approaches are effective, at least in the short term, but the major battery producers have not endorsed or discouraged the approaches.

  24. Pulse Charging, Sulphation and Conjecture • Why • Rapid Charging • Conditioning • Discharge Pulse • Reduce Bubbles • Reduce Capacitance • Stir Electrolyte • Contrasting Opinion • Negative Pulse Charge - "Burp" Charging - Fact or Fiction? • http://www.rcbatteryclinic.com/menu.htm Equivalent Circuit SULFATION Removal What Frequency/duty cycle is best? Swept, PbSO4 Resonant Frequency? See the Internet for details but be aware that there are contrasting opinions about the effectiveness and long term benefits of some of the sulfation removal removal approaches. Wallwarts can be a cheap front end to a homebrew charger or de-sulfator. http://www.flex.com/~kalepa/desulf.htm Pulser circuit & info http://www.uoguelph.ca/~antoon/circ/bcgla.htm Gel cell charger http://users.pandora.be/vandenberghe.jef/battery/ Pulser circuit & info http://acs.comcen.com.au/batterypulser.html Pulser circuit & info http://www.vdcelectronics.com/desulphation.htm Sulphation info http://www.rcbatteryclinic.com/menu.htm RC Battery charging info

  25. Service Life - Capacity vs Use for Common Batteries Life ?

  26. Trends in Cell Technology Product Life Cycles Newer rechargeable technologies are gaining share in the marketplace as older technologies have reached maturity and are being used in fewer new product designs. Knowledge of the marketplace trends helps in selecting the proper cell technology for the optimum cost-benefit scenario. It is important to consider the energy system components' life cycle and compare it to the life cycle of the end product.

  27. CONCLUSION • Observe recommended precautions for use and disposal of all battery types. • Discard “sealed” cells that show definite signs of leakage. • For Ham purposes NiCad, Lead Acid (GelCell), NiMH and Alkaline, are most practical. Lithium batteries require a matched smart charger and all chemistries benefit from a smart charger. • Battery Life (rechargeable) is directly related to temperature, and discharge/charge patterns. • The most economical operation results from selecting quality batteries and following recommend usage guidelines and charging procedures. • Occasional “refreshing” (discharging to nominal discharge level and recharging) and finishing off the charge cycle with a trickle charge can enhance the life of NiCad and NiMH batteries. (Not SLA) • Batteries within the same family can have important differences. • Don’ts: • Do not short • Do not solder unless solder tabs are available • Do not over charge • Do not allow an SLA to remain in a discharged state • Do not believe everything you hear or read on the Internet.

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