• ETT Level 3.18: Direct-Current Systems

    Learn how to identify, service, and test various types direct-current systems and components.

    1. Servicing and testing - Identify and record, type, construction, characteristics, and ratings. Inspect connections, conductors, mounting, housing, ventilation and general conditions. Measure and/or perform connection resistance, specific gravity, liquid level, impedance, load, voltage, and discharge test, as applicable. Inspect and test battery chargers with regard to charging rates, float and equalize voltages, and operations.
      • Battery Testing Guide by Megger [PDF] Batteries are used to ensure that critical electrical equipment is always on. There are so many places where batteries are used it is nearly impossible to list them all.
      • Maintenance and Testing of Battery Systems [PDF] At a minimum, annual testing verification, and inspection of a battery system should be performed. The annual preventive maintenance, which should be performed for both wet and sealed battery systems.
      • Essential Battery Charger Knowledge [PDF] The correct charging system means everything to the performance and service life of the station battery system. Under normal operating conditions, the battery provides very little current. The battery charger provides the continuous load current (i.e. relay/meter power supplies, indication lights, etc) and maintains a charge on the battery bank.
      • The Truth About Battery Impedance Testing [PDF] Through routine maintenance, gradual loss of capacity be avoided and is easily found by impedance testing.
      • Battery Testing - Then and Now [PDF] During the last ten years much has changed in our understanding of batteries and how they can be tested more effectively and effi ciently at less cost and higher reliability.
      • Electrical Theory as it Pertains to Internal Ohmic Testing of Stationary Batteries [PDF] Internal ohmic testing is both efficient and extremely cost-effective.
      • Battery Work Safety [PDF] Battery work requires a heightened awareness of a number of safety issues unique to this technology. Becoming familiar with the procedures and equipment appropriate for this work will minimize the likelihood of you or a member of your crew getting injured on these jobs.
      • The Truth About Battery Impedance Testing [PDF] Floating effects are the gradual loss of capacity due to long periods on float without being cycled. This can also cause a catastrophic failure of the supported load. However, through routine maintenance, this can be avoided and is easily found by impedance testing.
      • Storage Battery Maintenance and Principles [PDF] This guide outline the duties and responsibilities for routine operation and care of vented lead-acid batteries.
      • Glossary of Battery Terms Quick reference of over 250 battery terms and acronyms.
      • DC System Grounds: Can You Afford to Live with Them? [PDF] This paper discusses the many causes of unintentional grounds on floating dc power systems in switchgear and control applications and the effects these grounds can have on the operations of the dc system, personnel safety issues that can arise as the result of unintentional dc system grounds, and ground detection systems designed to identify the existence of unintentional dc grounds.

    External links are provided by our community of test technicians. Please submit any resources that you feel may be helpful to this topic.

    Recommended: Study tips for the NETA exam

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