This article was written by Jerry Hastings & appears on www.helium.com, www.diggs.com, www.del.icio.us.com & www.hastprotrucks.com/forum
There are several things to consider and be aware of when jump starting a car for both safety's sake as well as the well being of the car that provides the jump start. Proper jumping techniques should be followed to reduce the strain on the starter of the car being jumped too.
Here are two very important things one should be aware of beforehand. The possibility exists that the car with the dead battery has an internal short in it's battery. The possibility of a spark while hooking the cables to a discharged battery can cause an explosion.
In the first mentioned scenario, a shorted battery can fry the "jumper's" alternator in seconds as well as pose the problem of a potential explosion. If the dead battery obviously wasn't caused by an electrical device or lights being left on without the engine running, jump starting may not be the best solution. If the dead battery does not even click the starter relay, further diagnosis will be in order BEFORE hooking up the jumper cables!
In the first and second scenarios, a discharged battery emits very explosive gases that could be ignited by the spark from the jumper cables while connecting them. There are alternate means to connect the jumper cables that greatly lessens the chance of an explosion.
First, hook up the cables to the car providing the jump start (red to the positive terminal and black or stripped to the negative terminal) while at the same time keeping the opposite ends of the jumper cables separated from each other. Next, hook up the red cable to the positive terminal on the car's battery that needs the jump start, BUT, DO NOT hook up the negative battery jumper cable to the dead battery. Instead, hook it to a good ground (void of paint or rust) as far away from the dead battery as possible (ground - meaning an engine bolt head or metal bracket etc.).
Allow several minutes to pass with the running car charging up the dead battery some BEFORE trying to start the dead car. Bringing up the jumping car's RPM a little will speed up this charging time. After 5-10 minutes of recharge time, try momentarily to start the dead car. If it starts right up, great. If not, stop trying to start it and continue to allow more recharge time.
Starters will burn up from low voltage quickly! Absolutely do not crank the starter over for more than 30 seconds at a time (allow 3-5 minutes cooling time between times too). Also, on board engine controlling computers will not function correctly until the voltage during the starting process is adequate enough, therefore preventing the spark plugs from firing.
For safety's sake, unhook the jumper cables by removing the ground connection on the jumped car first, then the negative cable on the jumper's battery, that eliminates the temporary circuit formed by the jumper cables (and the possibility of shorting one jumper cable end against the other before final disconnection).
Despite popular belief, batteries will not recharge in 30 minutes or so. They require several hours to fully recharge at the amperage most car alternators are capable of. Also with today's cars that have constant drains on the battery by clocks etc., the battery really should be hooked to a charger at least overnight at first opportunity, unless the car is driven for quite a distance before killing the engine.
Suspected shorted batteries should be checked out using the proper equipment. Some battery chargers are so equipped, others are not. Make sure you heed any tool's instructions in regards to hooking and unhooking a discharged battery as well as instructions on how to properly check a battery's condition.
Treat an automotive battery with the respect you would an open container of gasoline when connecting or disconnecting one, or hooking up jumper cables. They can be just as deadly
Thursday, January 24, 2008
Monday, January 21, 2008
Basic anatomy of an electrical relay-automotive
An post written by Jerry Hastings which also appears on www.hastprotrucks.com/forum
People are often confused by a relay and most importantly it's function and intended purpose. A relay is simply a switch like a toggle switch, but instead of manually toggling the switch, a relay uses electrical connections other than the "load" circuit to do the switching.
The 5 prong relay is a simple example. On one prong is the load's supply wire from either a positive electrical source or it could simply be to a good ground (providing a ground or negative connection instead of a positive connection). The corresponding prong is connected to the load (ie electrical motor, solenoid or other loads).
An entirely different circuit is then used to accomplish the switching action. This circuit is electrically separated from the load circuit. It consists of a good ground from the appropriate prong on the relay to the actual grounding location. The opposite prong on the relay is then connected to an electrical supply that is either a key operated positive supply or may be a supply generated by the action of another switching action of a related accessory. For simplicity we will call that positive and negative connection the "trigger" supply.
This "trigger" circuit can be negatively controlled if desired, but most of the time it is positively controlled. For simplicity we will use the positively controlled relay for further explanation.
When electrical current flows to the "trigger" prong on the relay (which necessitates utilization of the ground or negative connection), it causes a switching action to occur inside the relay which turns on the "load" circuit. This "trigger" circuit is a low amperage circuit meaning it is more friendly to actual connecting or activating items like the key switch or switch associated with another accessory than the "load" circuit. The "load" circuit is a relatively high amperage circuit.
The "trigger" circuit can also use smaller wires since it is a low amperage circuit unlike the "load" circuit which must use larger wires and larger amperage requirements. Smaller wires and low amperage are imperative in computer connections, wiper switches, light switches, etc.
If you find two fuses in the fuse panel that have the same label, the one with the smallest amperage rated fuse is on the "trigger" circuit and the high amperage fuse is on the "load" circuit.
Of course, larger vehicles like class 8 trucks often have their left and right headlamp circuits isolated from each other. That is primarily for safety reasons since one circuit can fail but the other stays functional. In that case, the fuses (or breakers) and relays are labeled "left headlamp" and "right headlamp".
More complicated relays are often found in todays cars and trucks which are capable of performing multiple tasks and/or controlling more than one load. These relays still function by the same principles as the simple 5 prong relay but can be configured to work on both the positive "triggering" and negative "triggering" circuits in the same relay.
People are often confused by a relay and most importantly it's function and intended purpose. A relay is simply a switch like a toggle switch, but instead of manually toggling the switch, a relay uses electrical connections other than the "load" circuit to do the switching.
The 5 prong relay is a simple example. On one prong is the load's supply wire from either a positive electrical source or it could simply be to a good ground (providing a ground or negative connection instead of a positive connection). The corresponding prong is connected to the load (ie electrical motor, solenoid or other loads).
An entirely different circuit is then used to accomplish the switching action. This circuit is electrically separated from the load circuit. It consists of a good ground from the appropriate prong on the relay to the actual grounding location. The opposite prong on the relay is then connected to an electrical supply that is either a key operated positive supply or may be a supply generated by the action of another switching action of a related accessory. For simplicity we will call that positive and negative connection the "trigger" supply.
This "trigger" circuit can be negatively controlled if desired, but most of the time it is positively controlled. For simplicity we will use the positively controlled relay for further explanation.
When electrical current flows to the "trigger" prong on the relay (which necessitates utilization of the ground or negative connection), it causes a switching action to occur inside the relay which turns on the "load" circuit. This "trigger" circuit is a low amperage circuit meaning it is more friendly to actual connecting or activating items like the key switch or switch associated with another accessory than the "load" circuit. The "load" circuit is a relatively high amperage circuit.
The "trigger" circuit can also use smaller wires since it is a low amperage circuit unlike the "load" circuit which must use larger wires and larger amperage requirements. Smaller wires and low amperage are imperative in computer connections, wiper switches, light switches, etc.
If you find two fuses in the fuse panel that have the same label, the one with the smallest amperage rated fuse is on the "trigger" circuit and the high amperage fuse is on the "load" circuit.
Of course, larger vehicles like class 8 trucks often have their left and right headlamp circuits isolated from each other. That is primarily for safety reasons since one circuit can fail but the other stays functional. In that case, the fuses (or breakers) and relays are labeled "left headlamp" and "right headlamp".
More complicated relays are often found in todays cars and trucks which are capable of performing multiple tasks and/or controlling more than one load. These relays still function by the same principles as the simple 5 prong relay but can be configured to work on both the positive "triggering" and negative "triggering" circuits in the same relay.
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