Batteries updates

To test the battery you can do a hydrometer test and a reading on a 12.25 is an alright battery. check every cell on the battery if one cell is buggered then you have to replace the battery, or you can do a load test by hooking up the load tester to the positive and negitave termianls and crank the tester to half the cold cranking amps of the battery and do this for upto 15 seconds and a good battery would hold more than 9.5volts under load to be in good working order. to maintain the battery you can also check the level of fluids and the condcition of the fluids.

Alternators

Alternators have a lot of parts in them and are one of the main parts is is the rotor, the rotor is the electromagnet takes power from the starter and the resistor controls where the power goes. Another part of the alternator is the brushes, the have to be at least 4mm long and on the alternator that we tested in practical they were 7mm long so they still had plenty of life in them. You can also box test the alternator for short circuits, if the short circuit light comes on then there is a short circuit in the alternator, if the light comes on but is very dim then it means the circuit is fine. In a rotor winding ground test it should show infinite on the ohms setting of the millimetre to be in good condition. The main job of the alternator it to keep the battery charged so that when you accessories are on the car doesn’t go flat. If your alternator blelt snaps then your car will still run but your battery will evently go flat, this can also happen if you belt is old it can get worn down and start slipping. The alternator is very important part of the car and is always good to make sure it is in good shape

 

Above I have attached a picture of a common alternator attached to an engine with arrows pointing the direcdtion of the alternator belt and some of the exterior parts

This is a labeled diagram on the parts inside and out of a common alternator

Batteries.

The battery is on of the most important components of the car with out the battery the car cannot function. The battery voltage when the battery is fully charged is 12.6V but when the battery is only half charged it is at 12.4V. The minimum voltage a battery could be at while under load (having one of the accessories on, headlights etc.) is 9.5V. One of the main hazards when around a battery is it could explode in your face and cause serious injury, batteries realise the flammable gas called hydrogen and if the fumes come in contact with a naked flame then it will explode. Inside the battery there are 6 things called ‘cells’ and they are in a parallel line, each cell when the battery is fully charged produces 2.1V. If the car doesn’t crank/start then there is only two things it could be, power and fuel. The first thing to check is that if the car is getting power so you start at the battery, the most important thing is that there is a battery in the engine bay!! Then you can move on to checking the voltage etc. if the battery has been on charge and is now over charged (12.75V) then you can remove the surface charge buy putting it under load for approx. 2 minutes then you can check the available voltage with a multimeter and keep putting it under load until it reached 12.6 VOLTS

 

Above is the inside of a better and the 6 cells that produce 2.1 volts each.

Safety Blog

At Unitec the safety of the staff and the students is taken very seriously. Two main things that are followed up on in the workshop are that all persons must be wearing steel caped work boots and long armed and long legged overalls, you also have to follow all of the normal safety regulations like in every other workshop like no running, no alcohol on the premices and no drugs e.t.c. you have to be careful when using mechanery and wear safety classes and also ear muffs. If using a lathe or a drill it is very important to wear safety glasses because ther is little pieces that can fly into an eye and could cause serious injury and even blindness and also ear muffs if the equipment is loud. While operating equipment that is spinning it is also very important to tie up long hair and loose clothes and jewellery are taken off or moved to avoid getting pulled off or broken. If you are studying a trade at Unitec it is compulsory to have a valid level one first aid certificate and are able to talk to the emergency services and so you can give them a good idea of the seriousness of the injurys of the person need medical attention..

Circuit Blog

Parallel and Series Circuits

There are three different kinds of circuits: Series, Parallel & Compound. Firstly series, a series circuit is when all the components are in a series to each other. For example,

In a series circuit the voltage is shared between everything in the circuit. Foe example if you made a two bulb series circuit then each bulb would be using approximately just under 6 volts, the amperage in the circuit stays the same and the resistance increases

Parallel Circuits

A parallel circuit consists of a battery input and the output that goes directly to the earth, a parallel circuit is when all of the component are in a parallel form. For example a three bulb circuit,

Compound circuit

A compound circuit is when there are bulbs in parallel and series, for example if you where to make a compound circuit with two bulbs in parallel and two bulbs in series it would look something like this. E.g.