NorthStar Pure Lead AGM - MD Application Manual 05-14-12

NorthStarPure Lead AGMAutomotive and Marine Application Manual1NorthStar Pure Lead AGM - Confidential

21ChargeIntroduction2.1The NorthStar (NSB) range of automotive andmarine batteries are made with Valve RegulatedLead-Acid (VRLA) Absorbed Glass Mat (AGM)technology. Consequently, one package canprovide an excellent cycle life, as well asextreme power capability in a wide range ofapplications. Utilizing NSB technology, we cannow combine engine start, truck and RV power,marine, auto-audio and deep cycle applicationsinto the one package. This has been achievedby using advanced designs, highest qualitymaterials, and highly automated manufacturingprocesses.NSB automotive and marine batteries excel atproviding both short duration high amperagepulses, low rate long duration deep dischargesand high cyclic capabilities.1.1Flooded vs. NSB AGMDetermining State of Charge (SOC)For batteries in storage for long periods, or priorto being employed in a marine application, it isdesirable to fully recharge the battery. Refer tosection 3.1 for details. The SOC of a fullyrecharged battery is 100%. An estimate of theSOC can be obtained by measuring the OpenCircuit Voltage (OCV) of the battery. The OCV ofa battery is the voltage measured between itspositive and negative terminals without thebattery connected to an external circuit (load). Itis very important to take OCV reading at least 3hours after a charge period, or at least 10 minafter a discharge event. Measurements will beinaccurate if these rest times are too short. Agood quality voltmeter is all that is required tomeasure the OCV.The chart below shows the relationship betweenOCV and SOC for the NSB automotive andmarine batteries.Flooded batteries can generate and ventexplosive gases and must be vented to theoutside world. These batteries can also acid"mist" during charging leading to corrosion ofterminals and cables.In NSB AGM technology the electrolyte is fullyabsorbed in a very fine glass mat which allowsfor the recombination of any gas generatedduring the charging process. Furthermorebecause the electrolyte is fully absorbed thebatteries under normal operation cannot leakthereby eliminating any corrosion concerns atthe terminal and connecting links.1.2Discharge RateIn this document, the charge and dischargerates (amps) are expressed as multiples of I10,where I10 is the current for a 10-hour dischargeto 100% depth-of-discharge (DOD). Thesevalues serve to normalize data across a range ofbattery sizes. Consider the following example:10-h discharge capacity NSB 100FT 100 Ah(EODV 1.80 VPC @ 25 C).1 x I10 1 x (10-h discharge current)1 x I10 (NSB 100FT) 1 x 10A 10 A2 x I10 (NSB 100FT) 2 x 10A 20 A2NorthStar Pure Lead AGM - ConfidentialThe graph shows that a healthy, fully chargedNSB automotive and marine battery will have anOCV of approximately 13.0 V.2.2Thermal CompensationThe optimum level for float charging the NSBautomotive and marine batteries is 2.27 volts/cellat 25 C ( 77 F). If the battery temperatureincreases above this level, a thermalcompensation of -4 mV/cell/ C is recommended.Conversely, if the temperature decreases below25 C, the voltage should be increased by 4mV/cell/ C. The graph below shows values foran individual cell.

depending on the maximum charge currentavailable. If the DOD is less than 100%, thetotal recharge time will be less. To preventovercharge, the duration from T1 to T2 (i.e. thetime at 2.41 Volts/Cell) should always be limitedto 4 hours, and then the rectifier voltage returnedto the recommended float voltage.2.3Fast ChargingIf the charging system is properly sized, a fastcharging regime will serve to minimize the timeneeded to recharge NSB automotive and marinebatteries. This can be beneficial, for maximizingthe cycle life of the product.If the battery temperature increases above 25 C ( 77 F), a thermal compensation of -4mV/cell/ C to boost voltage is recommended.Conversely, if the temperature decreases below25 C, the boost voltage should be increased by4 mV/cell/ C. The graph below shows values foran individual cell:In a fast charging regime, the charging system isassumed to be adequately sized to provide thepower needed (see Section 2.4). Chargevoltage is increased which results in increasedcharge current. This in turn causes adischarged battery bank to fully recharge in ashorter time.The increased voltage setting is known as boostvoltage. In a fast charging regime the boostvoltage shall be 2.41 Volts/Cell provided that thetemperature is a nominal 25 C ( 77 F). Thefollowing graph shows the recommendedcharging profile following a 100% DOD cycle:2.4Recharge PowerDepending on the charging system, rechargetimes can vary greatly following an outage. Ifthe recharge power is relatively low, it will takelonger to fully recharge a battery. It isrecommended to provide a regular overchargefactor of between 103% and 106% SOC after adischarge.The following chart shows the time required tofully recharge an NSB automotive and marinebattery from a complete 100% DOD discharge,as a function of rectifier voltage and availablecurrent.The table above shows the time needed torecharge following a 100% DOD cycle,3NorthStar Pure Lead AGM - Confidential

3Discharge3.1EODV (Volts/Cell)201.85101.8051.7511.70Storage and Self DischargeLead-acid batteries experience self-dischargeduring storage. The rate of this process isrelated to several factors, with the two mostimportant being (i) the purity of the materialsused during construction, and (ii) the storagetemperature. As NSB batteries aremanufactured from the highest puritycomponents, they have one of the lowest selfdischarge rates in the industry. As the rate ofself discharge increases with temperature, it isrecommended that batteries be stored at as lowa temperature as possible above freezing.Approximatley every 10 C (18 F) increase intemperature, increases the self discharge by afactor of 2 and cuts the storage time in half.Thus at low temperatures (below 25 C), thebattery may be stored for up to two years,although it is recommended that a conditioningcharge be delivered if the battery drops below50% SOC any time during storage. The chartbelow shows how the self discharge changeswith time and temperature for the NSBautomotive and marine batteries.3.2Discharge Rate(hours)End of Discharge Voltage (EODV)In the event of a deep discharge, arecommended minimum end-of-dischargevoltage (EODV) should be used to avoid overdischarge. A value of 1.80 Volts/cell is common,but this value should be adjusted based on thedischarge rate. The following table provides aguide for EODVs at various discharge rates.4NorthStar Pure Lead AGM - ConfidentialEODV can be controlled using a Low VoltageDisconnect (LVD) as part of the load circuit.3.3Cold Temperature PerformanceColder temperatures can prolong battery lifebecause corrosion processes within the positiveplates of the battery slow down as thetemperature decreases. Unfortunately, lowertemperatures also lower the capacity of leadacid batteries. As battery temperature dropsbelow the recommended operating temperatureof 25 C ( 77 F), the battery capacitydecreases. However, the NSB automotive andmarine battery was designed and built to have avery low internal resistance. As a result, itsperformance at low temperatures and highcurrent loads is still relatively high. Coldtemperatures affect NSB automotive and marinebattery capacity according to the following chart:3.4Quiescent DischargeQuiescent discharge occurs if the batteries areconsidered at rest or otherwise not in use, butsmall amounts of power are still required byparasitic accessories in the application. Anexample of this situation would be clocks andother electrical equipment in the vehicle whilstthe vehicle is dormant. Also, batteries poweringsecurity systems experience low but consistentloads, as do trucks and vans which have to sit atrest for months between uses. A current of 10

mA is quite common in such situations, andwhilst it does not sound like much, it can fullydischarge a 20 Ah battery in approximately 80days.These low level consistent loads on batteriescan result in the total discharge of batterysystems over time. This results in a total lack ofpower necessary for the required task (e.g.starting the vehicle or boat engine.)Overdischarge, as a result of a parasitic load,can also damage the battery if severe enough.4Useful Life4.1Shelf LifeNSB automotive and marine batteries may bestored for up to 2 years, provided that the SOCis maintained above 50%. Failure to provide therequired maintenance charging (see Section 3.1)may lead to irreversible capacity loss.4.2Cycle Life vs. Depth of DischargeOne factor which influences the cycle life of abattery is the depth-of-discharge (DOD). DOD isexpressed as a percentage of rated capacitydelivered during discharge. For example, if a100 Ah battery delivers 10 Ah, the DOD wouldbe 10%. As the DOD per cycle increases, thecycle life of the battery will decrease. Thefollowing chart can be used to estimate the cyclelife of a NSB automotive and marine battery ifthe DOD per cycle is known.5Frequently Asked Questions5.1Is the NSB a gel battery?No, the NSB battery is AGM technology whichmeans the electrolyte is held within glass matseparators wedged between the plates. In gelbatteries, the acid is thickened into a paste bythe addition of very fine silica. This paste is thenviscous enough to remain between the plates,even when the battery is placed on its side.AGM designs typically provide a betterperformance at higher rates of discharge thangel equivalent, because AGM designs havethinner plates and a far lower gap (pitch)between the positive and negative plates.5.2What is the Ah rating?The ampere-hour (Ah) rating defines thecapacity of a battery. A battery rated at 100Ah atthe 10-hour rate of discharge will deliver 10A for10 hours before the terminal voltage drops to astandard value such as 10.02 volts for a 12Vbattery.5.3Does mishandling the battery voidthe warranty?The warranty applies to manufacturing defectsand workmanship issues and does not coverdamages as a result of mishandling by thecustomer.5.4What is a CCA rating?The cold cranking ampere (CCA) rating refers tothe number of amperes a battery can deliver for30 seconds at a temperature of 18 C (0 F)before the voltage drops to 1.20 volts per cell, or7.20 volts for a 12V battery. A 12V battery thathas a rating of 550 CCA means that the batterywill provide 550 amps for 30 seconds at 18 C(0 F) before the voltage falls to 7.20V.5.5What is impedance?The impedance of a battery is a measure of itsinternal resistance. The lower the batteryimpedance the more power is available. The5NorthStar Pure Lead AGM - Confidential