Battery

[Rumieus]

car and motocycle use what type of current? Dc or Ac?

 

[Nigel Goodwin]

All batteries are DC.

 

[rezer]

All autos and motorcycles use DC systems.

 

[Hero999]

That's not 100% true, some use AC or even both.

My old 125 used AC to power the headlight and DC to charge the battery.

 

[silvarblade]

well all the cars and motorcycles that i know of have a dc battery. but the car alternator produces ac rite?

 

[Willbe]

I think they went to batteries as soon as people wanted starter motors. When hand-crank car engines backfire they break the radius or the ulna or both. If I were there, I'm sure I would have disliked this.

Speaking of AC, I think LED taillights use/will be using a DC-DC convertor.

 

[arrie]

well all the cars and motorcycles that i know of have a dc battery. but the car alternator produces ac rite?

True, but the AC in modern car alternators are immediately rectified. The alternator then ends up charging the battery using DC, surprise surprise.
The battery and alternator thus supplies all electrical components of the car with DC.

 

[Nigel Goodwin]

well all the cars and motorcycles that i know of have a dc battery. but the car alternator produces ac rite?

Not entirely true - the alternator produces AC inside, but most car alternators have an internal rectifier and provide a DC output.

Motorcycles normally have a rectifier mounted external to the alternator. which again converts it to DC.

 

[arrie]

I think most motorcycles makes use of a magneto, rather than an alternator.
Not sure what the tech behind the magneto is though.

 

[Mickster]

Inductive components, such as some ABS sensors & Crank/Camshaft speed sensors produce AC...

 

[Nigel Goodwin]

I think most motorcycles makes use of a magneto, rather than an alternator.
Not sure what the tech behind the magneto is though.

No, magneto's were use LONGGGGG! ago for the ignition, on all engines, before coil ignition was used - nothing to do with the electrical system. My 1954 Velocette 350cc used a Magento and a dynamo.

Motorcycles used alternators long before cars ever did though, which still used dynamos (which output DC) for many years.

The reason was simple, cars needed much higher powers - motorbikes needed very little, and a crude alternator is very simple and cheap (fixed coil, spinning permanent magnet).

My Velocette looked something like this:



The magneto is the gray circle at the front of the engine, if I remember correctly the points were under there?.

 

[Mickster]

The magneto is the gray circle at the front of the engine, if I remember correctly the points were under there?.

A little before my time there Nigel, but I had a couple of field bikes that had magnetos. The magneto was driven from the flywheel, attached directly to the crankshaft. The point set was operated from a cam on the inside of the flywheel and thus, was a bit of a bugger to set the gap through the flywheel window.

Ahhh... happy days.

 

[Nigel Goodwin]

A little before my time there Nigel, but I had a couple of field bikes that had magnetos. The magneto was driven from the flywheel, attached directly to the crankshaft. The point set was operated from a cam on the inside of the flywheel and thus, was a bit of a bugger to set the gap through the flywheel window.

The alternator coils are under the flywheel as well, usually two, one for charging the battery, and the other for directly feeding the headlights.

 

[ecerfoglio]

The alternator coils are under the flywheel as well, usually two, one for charging the battery, and the other for directly feeding the headlights.

In that case the headlight circuit is also AC

The same happens (or used to happen some 40 years ago) in some bicycles: the generator had a rotating permanent magnet and a fixed coil. It fed the headlight and a small taillight.

It was known as the bicycle "dinamo", but in fact it was an alternator and not a dinamo as dinamo means DC generator.

 

[Nigel Goodwin]

In that case the headlight circuit is also AC

Yes, that's why I said 'directly feeding the headlight'.

The same happens (or used to happen some 40 years ago) in some bicycles: the generator had a rotating permanent magnet and a fixed coil. It fed the headlight and a small taillight.

It was known as the bicycle "dinamo", but in fact it was an alternator and not a dinamo as dinamo means DC generator.

Yes, they were generally alternators, and I beleive often still are?.

 

[arrie]

Just goes to show how out of touch I am with motorbikes, I used to have a Kawasaki with a magneto. Air cooled the lot.
I ended up driving it into the back of a Saphire in 1992, ended up on the car's roof. hehehe.
That was the end of my oll kawalski.
Good old days, I would not mind having a bike again, but the wife will be very angry if I do.

 

[Diver300]

A lot of small engines, especially small motorbikes, lawnmowers and outboards, use alternators and magnetos. They often use the same permanent magnets on the flywheel to generate current for the spark with one set of coils and for battery charging (via diodes) or lighting on another set of coils.

The modern magnetos don't have contacts and they use some electronic switching instead to cut the current and generate the big voltages needed for the spark, but they are still magnetos in the fact that they generate enough power for a spark from only the engine rotation in less than one turn.

Magnetos have the advantage that no battery is needed. For small engines like lawnmowers and small outboards, that is often the only electrical system fitted. On large outboards it means that even 115 hp engines can be pull started if needed (I've done that) when the battery has totally failed. On some small engines it lets the manufacturer get away with no battery regulation.

The alternators with permanent magnets have to have regulation built into the rectifiers. Car and lorry alternators have electromagnets for the field and the field current is varied to regulate the voltage.