June '18

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rv-pro.com June 2018 • RV PRO • 57 Table 1 (on page 56) compares the amount of power (watt hours) per kilogram these various battery types can store. Note that the standard lead/acid battery only stores 40 watt hours, while the most efficient lithium battery, the NCA (nickel, cobalt, and aluminum) battery, can produce 250 watt hours – or more than six times more than a current RV battery. If it weren't for the cost and possible hazards, this would be a great RV battery. For safety and cost reasons, Progressive Dynamics has decided to design its lithium chargers to provide the proper CCCV (constant current constant voltage) charge profile for the safer lithium-iron phosphate (LFP) batteries. As you can see in Table 1, the LFP battery provides about three times the power of lead/acid at about half the weight, and many units are UL-listed. One of the requirements for a lithium battery to acquire this UL-listing is a built-in battery management system (BMS). This electronic package performs several functions to ensure safety and long battery life. Safety features of the BMS include constant monitoring of each of the four (3.2-volt) lithium cells connected in series required to produce a 12.8-volt lithium battery. This monitoring includes the voltage of each cell for high or low voltage limits and disconnects the battery from the load or charger, to prevent damage. Each cell is monitored for temperature and excess current drain, and again, the battery is disconnected from the load if these limits are exceeded. The BMS also monitors the state of charge for each of the four cells and automatically balances their voltages during the recharge cycle to bring all cells to full charge at the same time. This balancing ensures a safe full charge and long battery life. Based on these features, lithium-iron phosphate batteries are very safe and reliable. Since 2015, Progressive Dynamics has been monitoring more than 1,500 lithium battery systems installed in RVs in the field without any reported lithium battery or charger failures. How long will an expensive lithium battery last? Lithium battery life is based on the number of charge and dis- charge cycles it is subjected to. A cycle requires bringing the battery to full charge and then fully discharging before fully charging it again. Lithium batteries typically are rated for 3,000 to 5,000 cycles. In contrast, lead/acid batteries typically last for only 300 to 400 cycles. This is true provided they are recharged as soon as possible after discharge and kept on a trickle charge with periodic equalization charges during winter storage to prevent battery sulfation. Lithium batteries can be stored without having to be trickle charged and will maintain more than 90 percent of their charge for a year or more. For increased battery life, lithium batteries should not be stored with a full charge. Around a 50 percent to 60 percent charge is recommended. Assuming a life of 300 cycles for a lead/acid battery, and it is charged and discharged, 100 cycles per year would equal a three- year battery life. Assuming 100 cycles per year for a lithium battery with a 3,000-cycle life, it could theoretically equal 30 years of life. Again, this is a theoretical figure and there are many fac- tors that can increase or decrease battery life, including depth of rv.steelerubber.com Quality Seals for Slide-Outs, Doors Compartments & More 800-230-6378 Catalog FREE Weatherstripping steelerubber.com/rv 800-230-6378 R SLIDE-OUTS SEALS HATCH COMPARTMENTS GATE RAILS FOR YOUR CATALOG R Check out the NEW Battery Doctor® Gauges/USB Ports! Always know the condition of your battery, and be able to charge or run your electronic devices with the handy USB ports. #20600 DC Digital Voltage Meter • Range 6V-30V DC • Illuminated Red Read-out #20602 Dual USB with Voltage Meter • Dual USB with Weatherproof Cover • Total: 4.2A (2.1A + 2.1A) • Range 5V-30V DC #20601 Dual USB Port • Dual USB with Weatherproof Cover • Total: 3.1A (1A + 2.1A) • Indicator Light #20603 Dual USB Port • Dual USB with Weatherproof Cover • Total: 3.1A (1A + 2.1A)

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