Application Manual and Product Information for NorthStar Battery Company
Table of Contents Introduction...3 NSB Blue Series Benefits...4 ISO Certifications...5 NSB Blue Product Specifications...6 Leak Free Terminations...7 Open Circuit Voltage and State of Charge...8 Important Definitions...9 Unstable AC Mains...10 Charging...11 Ambient Temperature and Battery Performance...13 Battery Longevity...14 Low Voltage Disconnect...18 Optimizing Battery Life and Performance...19 Contact Information...20 NorthStar Battery Company 2
Introduction I n certain emergent countries there is an opportunity for standby batteries that perform well in applications with unstable mains. If the main power is unstable, intermittent and random outages are commonplace. These outages can last for a few seconds, or for many hours. During these outages, the batteries may never be fully discharged, or fully recharged. This results in repeated shallow discharges, often with the battery in a partially charged condition, also known as PSOC (Partial State-of-Charge) cycling. Under these harsh conditions, a standard AGM can quickly lose capacity and reach the end of its useful life. To meet this demand, the NorthStar Battery team has developed the Blue Technology line of lead-acid batteries. These are electrochemically and metallurgically engineered to operate in the harsh conditions associated with unstable mains. This allows them to withstand extended periods of PSOC cycling. NorthStar Battery Company 3
NSB Blue Series Benefits I n addition to the benefits offered by its valve regulated technology the NSB Blue battery offers a long list of features that serve to increase the reliability and overall performance of your system. Specifically designed for indoor/outdoor telecom cabinet applications 2 year shelf life 3 step terminal seal ensuring leak-free operation Industrial standard footprints assure mechanical interchangeability Non-halogenated flame retardant (UL94-V0) PPO case and cover Container is resistant to degradation even after reaching end of life High conductivity female terminals Can be installed in any orientation (inverted is not recommended) Exceptional recharge efficiency Exceptional charge acceptance Less dependent on complete recharge following an outage Operates in PSOC mode for longer durations Patented alloy composition increases useful life Optimized positive and negative paste additives NorthStar Battery Company 4
ISO Certifications N orthstar Battery Company has been fully tested and approved to ISO 9001 and 14001 standards. This, along with the recent addition of a second manufacturing facility in Springfield MO, makes NorthStar Battery Company one of the most reliable and environmentally friendly lead-acid battery OEMs in the world today. NorthStar Battery Company 5
NSB Blue Product Specifications Front Terminal Range NSB100 Blue NSB170 Blue Height Length Width Weight 287mm 11.30 396mm 15.59 108mm 4.24 36.0kg 79.4lbs 320mm 12.60 560mm 22.05 125mm 4.92 59.1kg 130.3lbs Terminal M8 x 1.25 M8 x 1.25 C/2 Power 430 Watts per 12 Volt Monoblock 700 Watts per 12 Volt Monoblock Impedance (1kHz) 3.5mΩ 2.2mΩ Conductance@ 25 C (77 F) 1355S 2316S Short-circuit Current 3,500A 5,000A NorthStar Battery Company 6
Leak Free Terminations N orthstar batteries are produced with rugged, highly conductive, brass terminals. To take advantage of the design and insure a long life low resistance connection, the battery terminals should be coated with NO-OXID or similar material. Stainless steel hardware, with a minimum of 8 mm engagement, torqued to 8.0 N-m/71 inlbs is recommended. In portable applications, or installations where periodic retorquing of terminals is limited, a spring washer is recommended. This will reduce the loosening effects of material creep, temperature expansion and vibration. NorthStar Battery Company 7
Open Circuit Voltage and State of Charge M easuring the open-circuit voltage is an excellent way of estimating the %SOC of NSB Blue batteries, since the open-circuit voltage is a direct function of the concentration of electrolyte within the battery. As the concentration of electrolyte decreases so too does the %SOC. The relationship can be linearly approximated by the following equation: %SOC @ C/20 = OCV x 67.8 763.2 In order to be accurate the open-circuit voltage should not be measured within a minimum of 4-hours of being discharged or recharged. NorthStar Battery Company 8
Important Definitions B elow is a list of important definitions of terms used in this document. Capacity The amount of energy, measured in amp hours (Ah), stored in a lead-acid battery. AGM Absorbent Glass Mat. A specific configuration of lead-acid battery in which the electrolyte is absorbed in matted glass fiber separator material. State-of-Charge (SOC) A measure of total energy stored in a lead-acid battery, expressed as a percentage of rated capacity. If 20% of the rated capacity of a fully charged battery is consumed, it is said to be at 80% SOC. Partial State-of-Charge (PSOC) Cycle When a battery is partially discharged while subsequently never being fully recharged (reaching 100% SOC). Deep Cycle When a lead-acid battery discharged to 20% SOC or below and then completely recharged. PSOC Window A value that represents the total change in SOC NorthStar Battery Company 9
Unstable AC Mains If the main AC power is routinely unavailable, it can be considered unstable. Batteries must discharge in order to supply power needed by the application. As the stored chemical energy in the batteries is consumed, the SOC decreases. The length of an outage and the discharge rate determine the depth of the discharge, and consequently the % drop in SOC. Figure 1 shows a Blue battery string operating in an unstable main power grid over a one week period. Note that the chart shows extended periods of PSOC cycling, as well as intermittent deep cycles. 100 80 % SOC 60 40 20 0 0 2 4 6 8 10 Days Figure 1: Unstable AC main application NorthStar Battery Company 10
Charging C harging is one of the most critical factors that determine the life expectancy of a valve regulated lead acid (VRLA) battery and the NSB Blue series from NorthStar Battery is no exception. There are two broad categories of charging, constant current (CC) charging or constant voltage (CV) charging. Constant current (CC) charging As the name implies, in CC charging a current of constant magnitude is forced into the battery, regardless of the state of charge of the battery. While CC charging rapidly replaces the ampere-hours lost by the battery, it is very easy to dangerously overcharge the battery with this method of charge. This is the main reason why CC charging on a regular basis is not recommended for the NSB battery. Since a CC charge provides each battery in the series string with exactly the same amount of ampere-hours this charge technique is well suited to equalize a series string that comprises cells in various states of charge. As the battery charges, its terminal voltage increases. Since the CC charger is designed to provide the same current throughout the charge cycle, its voltage must increase in order to overcome the rising battery voltage and push a constant current into the battery. Constant voltage (CV) charging I n contrast to CC charging it is the charge voltage rather than the charge current that remains constant during the charge cycle. As the battery charges its terminal voltage increases, the charge current drops as the charger s output voltage NorthStar Battery Company 11
remains constant. This automatic regulation of the charge current makes CV charging the preferred charge technique for VRLA batteries. Minimum Float Voltage /VPC Nominal Float Voltage /VPC Maximum Float Voltage /VPC Temp / C 0 (32 F) 2.35 2.37 2.39 5 (41 F) 2.33 2.35 2.37 10 (50 F) 2.31 2.33 2.35 15 (59 F) 2.29 2.31 2.33 20 (68 F) 2.27 2.29 2.31 25 (77 F) 2.25 2.27 2.29 30 (86 F) 2.23 2.25 2.27 35 (95 F) 2.21 2.23 2.25 40 (104 F) 2.19 2.21 2.23 42 (107.6 F) 2.18 2.20 2.22 45 (113 F) 2.17 2.19 2.21 50 (122 F) 2.17 2.17 2.19 Figure 2: Charge voltage compensation for NSB Blue batteries NorthStar Battery Company 12
Ambient Temperature and Battery Performance H eat is the number one killer of batteries it accelerates the failure mechanisms such as corrosion and dry-out. A good rule of thumb to use is that for every 10ºC (18 F) increase in ambient temperature the float life of the battery is cut in half. Note: When mounted in a rack, it is recommended that all NorthStar products should have a space of approximately 10mm between the batteries to allow for heat convection. In addition, it is also recommended that the supporting shelf should have air circulation holes positioned directly below the gaps between the batteries. NorthStar Battery Company 13
Battery Longevity T he longevity of a battery is dependent upon two discharge factors. The first factor is the Depth of Discharge (DOD) while the second is the amount of stored energy consumed per day. The following figures show how these two factors can affect the number of cycles, and the useful life you may expect from an optimally charged NSB Blue battery. Figure 3 shows cycle life curves for both a traditional cycling and PSOC cycling. Number of Cycles 10,000 9,000 8,000 7,000 6,000 5,000 4,000 3,000 2,000 1,000 0 NSB Blue PSOC Cycling 10% 20% 30% 40% 50% 60% 70% 80% Depth of Discharge NSB Standard Traditional Cycling Figure 3: Effect of DOD on cycle life NorthStar Battery Company 14
1 100 199 Application Manual & Product Information for Traditional Cycling Regime In a traditional cycling regime the battery is fully charged every cycle. The inefficiency of the recharge process necessitates a small amount of overcharge, typically 4%. This consistent overcharging results in life-limiting processes such as dry-out and positive grid corrosion, which ultimately cause the battery to reach end of life. 120 Overcharged every cycle. 100 2.0V %Capacity 80 60 40 20 Continuous overcharge eventually leads to EOL. 1.9V 1.8V End of Discharge Voltage 0 Cycles Figure 4: Traditional Cycling Regime PSOC Cycling Regime In a PSOC cycling regime the battery is allowed to cycle in a partially charged state, e.g. 80% to 50%. The recharge exactly balances the capacity removed from the battery during the discharge. In this way, overcharge problems are avoided. Unfortunately the NorthStar Battery Company 15
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 Application Manual & Product Information for battery plates progressively discharge during this strategy, and a standard AGM battery can quickly reach EOL. Several battery manufacturers clearly state that their product is incapable of withstanding such a PSOC cycling regime. With specially modified AGM products, like the NSB Blue Technology, the battery is capable of withstanding this PSOC cycling without any detrimental effect. Apart from occasional equalization charges, the Blue can operate in this manner for a greatly extended lifetime when compared to standard products. 120 Overcharge only when needed. 100 2.0V %Capacity 80 60 40 20 0 Negative electrode runs down, but can be recovered Cycles 1.9V 1.8V End of Discharge Voltage Figure 5: PSOC Cycling Regime NorthStar Battery Company 16
PSOC Window The total amount of stored energy consumed and replenished per day, expressed as a percentage of rated capacity (Ah). For example, if we consume 10 Ah of a 100 Ah battery over the course of one day, regardless of the number of cycles, the PSOC Window would be 10%. Figure 6 shows the relationship between PSOC cycles per day, PSOC Window, and useful PSOC life. Number of PSOC cycles per day 15 14 13 12 11 10 9 8 7 6 5 4 3 2 20% PSOC Window 30% PSOC Window 40% PSOC Window 15% PSOC Window 12% PSOC Window 10% PSOC Window 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Years 8% PSOC Window Figure 6: Effect of PSOC cycles per day, and PSOC window on useful life NorthStar Battery Company 17
Low Voltage Disconnect A nother key to optimizing battery performance is to ensure that it is not subjected to an overdischarged condition, particularly for any appreciable length of time. The only practical way to prevent this condition from occurring is to employ a low voltage disconnect (LVD) in the load circuit that prevents the battery from discharging to a level below the designed end of discharge voltage (EODV) value. Although 10.02V is a typical EODV for a 12V battery, the following chart may be used to set the LVD. Discharge in amps EODV per 12V battery 0.05C 10 (C 10 /20) 10.5V 0.1C 10 (C 10 /10) 10.2V 0.2C 10 (C 10 /5) 10.02V 0.4C 10 (C 10 /2.5) 9.9V 1C 10 9.6V 2C 10 9.3V > 5C10 9.0V Figure 7: Recommended EODV as a function of discharge rate NorthStar Battery Company 18
Optimizing Battery Life and Performance T o obtain maximum performance from your battery and get the longest life out of it is simply a matter of providing the right environment for the battery. The following checklist is designed to help you optimize your battery s overall performance. The checklist assumes that the battery is properly sized for the application. Temperature Battery ambient temperature of 25ºC (77ºF) is ideal. A cooler temperature will extend battery life but may degrade capacity If battery temperature varies significantly from 25ºC (77ºF), compensating the battery charge voltage is necessary Charging Correct charge parameters are critical to battery longevity Charge method must be matched to the application; check with the Technical Support department if you are unsure about the parameters for your application Overdischarge Repeated over-discharge is harmful to the battery Use of a low voltage disconnect is recommended NorthStar Battery Company 19
Contact Information Mailing address: NorthStar Battery Company 4000 Continental Way Springfield, MO 65803 Tel: +1 (417) 575-8200 Fax: +1 (417) 575-8250 Email: info@northstarbattery.com Functional area Telephone number Customer Service +1 (417) 575-8201 Technical and Quality +1 (417) 575-8205 Sales and Marketing +1 (417) 575-8203 NorthStar Battery Company 20