Security Business

MAR 2019

Find news and information for the executive corporate security director, CSO, facility manager and assets protection manager on issues of policy, products, incidents, risk management, threat assessments and preparedness.

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18 Security Business / / March 2019 I recently had the chance to visit the Altronix headquarters and factory deep in the heart of Brooklyn, N.Y. When I asked what's new, I was told about a new battery charger they had developed for lithium-based batteries. Naturally, I thought they were talking about lithium ion batteries, used in untold applica- tions – but also the source of some spontaneous fires. I was puzzled about their motiva- tion since, for eons, lead acid batteries have been the workhorse of the secu- rity industry. us began my education on lithium iron phosphate – LiFePO4 (aka lithium ferrophosphate) or "LFP" batteries. Comparing Battery Types Before we can get into the specifics of LFP batteries, let's take a closer look at the various types of batteries and how to compare them, with the help of a guide I found at Battery University ( First, some parameters used to com- pare and evaluate batteries: • Gravimetric energy density (Wh/ kg): e amount of energy stored in a defined weight volume. ink of this as how much power a battery of a cer- tain weight has the capability to deliver. ere is also a parameter known as volumetric energy density, i.e., power per unit volume. • Internal resistance: Determines how much power can (or can't) be deliv- ered to the external load as a result of internal resistive losses, creating some amount of heat from the voltage drop. • Cycle life: e number of complete charge-discharge cycles the battery can undergo until its capacity falls to 80 percent of its original. Changing Batteries Half the weight of its traditional counterparts, lithium ferrophosphate (LFP) batteries can be recharged quickly and repeatedly Tech Trends BY RAY COULOMBE ■ At more than 2,000 cycles, the per-cycle cost for LiFePO4 or "LFP" batteries is 2.5 times less than a typical lead acid battery and half that of lithium ion. • C-rate: Also referred to as dis- charge rate, it is the amount of the battery's charge that can be dissipated – referenced to one hour – when dis- charged at its stated rate. For example, a 1C rate for a 10 Ah-rated battery, will source 10 A and fully discharge in one hour. A .5C rate for the 10 Ah battery will source 5 A for 2 hours to full dis- charge, while a 2C rate for that battery will provide 20 A for 30 minutes to discharge. C, known as the coulometric (had to get that in here) capacity, is 10 Ah in this example. • Self-discharge: e amount of capacity a battery loses sitting on the shelf or not connected to a load. • Cell voltage: A typical battery is a collection of cells in series, with the total voltage being the voltage of an individual cell multiplied by the num- ber of cells. A lead acid battery has a cell voltage of 2 V, so a 12 V battery has 6 cells. Here is Battery University's sam- pling of battery types: • Nickel cadmium (NiCd): ese are used in two-way radios, biomedical equipment, professional video cameras and power tools. ey feature a mod- est energy density (~ 50 Wh/kg), high cycle life (~1500), 20-percent self- dis- charge, and cell voltage of 1.25 V. • Lead acid: Extensively used in back-up power systems and start- ing applications, these have a density slightly lower than NiCd, modest cycle life (200 – 300), 5-percent self-dis- charge, and 2 V cell voltage. • Lithium ion: Common in laptop computers and mobile devices, they feature energy density double that of NiCd, reasonable cycle life (500 – 1000), 10-percent self-discharge, and ~3.6 V/cell. Interestingly, LFP batteries were not described on the list, but it appears that they began to gain acceptance in certain applications about 10 years ago and have gained acceptance in vehicle use, utility scale stationary applica- tions, and backup power. How do they compare? Energy density for LFP is significantly better than lead acid and NiCd, around 100 Wh/kg; cycle life significantly higher than lithium ion and lead acid (2000 -7000); and lower self-discharge than lead acid with the ability to be dis- charged more deeply without adverse effect (almost 100 percent vs. ~70-per- cent max discharge for lead acid). ey have been shown to be safer than lithium ion and more environmen- tally friendly than lead acid; also, the working cell voltage of 3.2 V can allow a single cell to power an LED.

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