ARK 9 #1 Posted January 19, 2014 Things electrical 12 V DC battery and alternator charging things and devices that may help you to understand what takes place with the electrical parts of your wheeled vehicle. This will be as non-technical as I can get it. First off, a wet battery is a storage tank, not a producer of current, voltage, power. In today’s world wet acid batteries can be charged, discharged, hold that charge or be completely useless when dead. The state of charge is dependent on the complete system. The system includes: the battery, the alternator (AC Generator), starter, relay, the wires, cables, terminations, devices, ground and you. Battery---a wet cell battery consisting of 6 wet cells, walls, rigid container, cell covers, electrolyte, terminations and lead in compound form, so the electrolyte interacts with the lead portion of the compound. The bigger the battery the more power is stored, delivered and taken on. The electrolyte (1.25-1.3 S.G.) is a liquid conductor, tested with a hydrometer measuring specific gravity (S.G.) as compared to pure water (1 S.G.). Water freezes at 0C, 32F, electrolyte with a full charge is good to about -40 C, F at least. Battery must be clean, secure with terminations clean and tight. The electrolyte level must be maintained at the proper level and at a S.G. that allows power to come in and go out. Alternator---as used in vehicles is a machine that rotates and this rotation cuts lines of magnetic force from permanent magnets or electromagnets. The more magnets, the slower the RPM, THE MORE LINES OF FORCE ARE CUT, the more power. Alternators can use carbon brushes to transport the generated current to the end use. Cars, trucks and tractors have their end use as the battery. The primary purpose of the alternator is to keep the battery charged. But alternators produce AC (Alternating Current) not DC (Direct Current). Since AC and DC react differently and the battery is DC this rotational AC current must be changed from AC to DC and this is done by the rectifier set (rectifier). The rectifier set in newer equipment is a 3-phase device that is 3 lines of power, all forming into DC current to feed the battery. A single phase set up would have but 1 power line. A regulator if used may be part of the rectifier or alternator and is used to keep the highest voltage around 15 V. As a note there are many types of regulators but they are doing the same job. Wires and cables---are the roadways that carry the DC current to and from the battery and to and from ground and to and from all electrical devices. When new the wires and cables are clean but age makes them old, dirty, corroded or loss of insulation. Time makes it important to maintain these wires or cables. Cables are bigger than wires so they can carry a greater amount of current. Motor starter---the biggest consumer of energy because it takes a lot of amps to start a cold internal combustion engine. To get power to the starter motor which usually is a series wound DC motor that has the ability of using 300% of normal power to produce a great deal of spinning torque, is the starter relay. It is a contactor that can handle all the current that the starter motor needs. Since it operates at the same current as the starter motor, it should be as robust as the starter motor. Also it is these 2 things that take the most current, but the starter contactor, relay, and solenoid, (terminology) does not consume this power. The starter contactor directs all the power that the battery holds and the starter motor needs and releases this power when the auxiliary starting switch is turned on (key ignition). The starter contactor has smaller control wire(s) to turn on/off the contactor and in many cases to monitor. Depending on how it is wired and /or designed there could be 1 or more control wires. Control wires are small compared to power wires because of the amount of current. Often the mounting bolts are grounded and used as the return, so it looks as if only 1 wire is used. Terminations---joints of wires, cables, battery, starter. Every time a wire or cable is used that wire or cable must be joined to the device or terminated. The termination varies with size via the wire size, the device size and the amount of current and time. Battery terminals get dirty, corroded, rusty, loose, covered with atmosphere. All these things make it difficult for electrons to move. Clean tight terminations are needed and it takes intervention by you. Every joint over time will become bad and needs to be opened, cleaned and then put back together. You---are needed to make all maintenance whether you do it yourself or have somebody else do the work. Without PM (Preventive Maintenance) things electrical and mechanical break down. Usually mechanical breaks sooner and more frequent than electrical. Since electrical things break down in stages a conductor can become a semi-conductor and then an insulator, which is one of the reasons for gremlins. Ground is a pathway to save on wires and is a common carrier for all 12V –(Neg) ground systems. Because most grounds are the steel frameworks, joining steel with copper, use of dissimilar metals, cause bad interactions with the joint over time and must be maintained. This applies to every joint that is a ground, even if bolts, nuts, washers. The best ground joint is a weld. By the way there are compounds to help with conductivity with dissimilar metals, but maintenance is still needed. When things are built brand new, manufacturers use dielectric grease properly to seal electrical joints. These joints will last longer than warranty time, but as time moves on everything has a lifespan. When that time is over things electrical start to break down and need PM. If you use dielectric grease learn how to apply it. Applied incorrectly will cause greater problems, remember that it is a non conductor. To troubleshoot electrical problems, tools are needed to see and verify electron movement. Get a multi-meter (many meters in one) and learn the basic laws that govern DC electricity and learn how to use that meter. Learn to be safe. Some basic numbers: A 12 V wet lead acid battery has a normal range from 10-15 VDC A 12 V battery reading at 9V is dying A 12 V battery at higher than 15V is over charged Alternators deliver a range of voltage with RPM, LOAD, belt tension, weak field, worn brushes, dirty armature or commutator, worn bearings or loose magnets. Simple test with machine running and alternator spinning higher than mid range and battery hooked up all devices off except engine, battery reading at 13-15 VDC. Engine off all dead but charged battery at least 12.6-12.9 Remember battery voltage has a range. Bad voltage less than 10V Checking the starter amp draw, try the voltage drop no less than 10 V Exact voltage is hard to give because of battery age, condition, all internal conditions of all devices, but with PM on a regular basis the answers become clearer and electrical phantoms are non-existent. Always start to check the electrical system with a fully charged battery at float voltage. Formulae: E=I x R, voltage = current x resistance Transpose the formula to get all 3 equations There is a circle chart on Google with more formulae that may assist you. 1 Share this post Link to post Share on other sites
can whlvr 991 #2 Posted January 21, 2014 very informative Share this post Link to post Share on other sites
