Electrical experts pls advise

[arthur_chan]

hi, i need some advise regarding fuse.

 

if say my equipment is 48w and in a pair (2pc), what amp of fuse should i get? the recommended is 16A, which is twice the current of the equipment. is it safe or should i get a lower fuse. i'm not intending to add more items to the circuit. the supplied is 12v.

 

my calculation:

48w*2=96w

96w/12v=8A

thus 16A will supply twice the current of my equipment b4 it breaks. do correct me if i'm wrong. i'm a noob in these stuff. similarly using a lower amp fuse will break the circuit b4 powering up anything right?

[kinwei]

Yes, using a lower amp fuse than the operating current will cause the fuse to fused when you first start the equipment. However if you put a much higher amp fuse, incase of electricity short circuit, the fuse may not break in time and the equipment or wire may burn first. By right, you should use a fuse that is slightly higher than the operating current. Normally I will go for 50% more. So you need 12A.

 

You installing the Hella 0902 horn? I also thought it need 8 ohms but according to the CMO thread, it stated 3.5 ohms MAX.

Edited December 31, 2010 by kinwei

[Refugee]

i'm not electrical expert.... but anyway, you should take into consideration your 12V source.

 

what ampere is it able to pump out? more then 16A?

 

wiring in series and parallel also plays a part.

[ezzyoiler]

it is normal...

the 16amp..is to protect your system...

 

yes it may be 100% above the intended amps..this is normal..

any equipment that draws more than operation amps...the fuse size have to provide for the surge in start up..so this 16 amp is nothing to worry about..

[arthur_chan]

Yes, using a lower amp fuse than the operating current will cause the fuse to fused when you first start the equipment. However if you put a much higher amp fuse, incase of electricity short circuit, the fuse may not break in time and the equipment or wire may burn first. By right, you should use a fuse that is slightly higher than the operating current. Normally I will go for 50% more. So you need 12A.

 

You installing the Hella 0902 horn? I also thought it need 8 ohms but according to the CMO thread, it stated 3.5 ohms MAX.

 

yes. what's the 3.5ohm u were talking about, wiring?

 

what ampere is it able to pump out? more then 16A?

 

wiring in series and parallel also plays a part.

not sure, it's from motocycle battery direct, tapped to a relay.

 

yes it may be 100% above the intended amps..this is normal..

any equipment that draws more than operation amps...the fuse size have to provide for the surge in start up..so this 16 amp is nothing to worry about..

 

however i'm worried if there's a surge, the equipment blow out 1st b4 the fuse.

[kinwei]

yes. what's the 3.5ohm u were talking about, wiring?

 

 

not sure, it's from motocycle battery direct, tapped to a relay.

 

 

 

however i'm worried if there's a surge, the equipment blow out 1st b4 the fuse.

 

Opssss. I made a mistake. It should be 3.5A, not ohms (resistance). According to the CMO thread, the TS stated the specification in the 1st thread. It says maximum drawing current is only 3.5A. Seems abit low against the calculation.

 

The wiring should be in parallel according to the circuit diagram. I don't think electric horn require a higher starting power. Anyway just follow the manufacturer recommendation and install a 16A fuse. Like what Ezzyoiler mentioned, it is normal to put a higher rating fuse. I don't think they will screw themselves.

[Demon]

hi, i need some advise regarding fuse.

 

if say my equipment is 48w and in a pair (2pc), what amp of fuse should i get? the recommended is 16A, which is twice the current of the equipment. is it safe or should i get a lower fuse. i'm not intending to add more items to the circuit. the supplied is 12v.

 

my calculation:

48w*2=96w

96w/12v=8A

thus 16A will supply twice the current of my equipment b4 it breaks. do correct me if i'm wrong. i'm a noob in these stuff. similarly using a lower amp fuse will break the circuit b4 powering up anything right?

 

It also depends on equipment.

 

Sometimes you have sized the fuse to accommodate the initial surge, such as for HID.

 

Besides the correct fuse rating, what is equally important is the wiring must be able to handle the new load, otherwise wire and connectors will melt, and may even cause fire.

 

Electrical stuff, don't play play

[BodilyPartsOnTheRoad]

It also depends on equipment.

 

Sometimes you have sized the fuse to accommodate the initial surge, such as for HID.

 

Besides the correct fuse rating, what is equally important is the wiring must be able to handle the new load, otherwise wire and connectors will melt, and may even cause fire.

 

Electrical stuff, don't play play

 

i am no elect expert but i agreed with demon, your switch may even melt too if the rating is not right.

 

Do take into consideration if your bike alternator is can handle the additional output?? To me, my logic is put in some electrical component, take out some( ie, installing foglights (60 watts) = cut off head lights (55/60w) ). i dunno if it will cause any damage or not but i guess this suits me well ~

[chris 525]

If your brain need surgery, then you go visit the brain surgeon, and get the expert treatment, do you DIY the surgery yourself..

 

But you want to modify your bike electrics, without the aid of a wiring diagram, and not much experience in bike electrics, sounds like a recepie of disaster to me.

 

Dun play play, or can fry something that will be exp to replace

[ezzyoiler]

 

however i'm worried if there's a surge, the equipment blow out 1st b4 the fuse.

 

eg...once i installed an air compressor.. in the factory....

the max operation amps is 30amps...

the protective switchgear used is a 100amp tp breaker..and the wiring has to be sized to work at 100 amps not 30 amps...

 

please google fused type...http://en.wikipedia.org/wiki/Fuse_(electrical) for a better understand its application..

if you are not a eletrician/engineer..please follow the mfg rccomendations..

please dont any how play pray..

 

if the horn you are going to install takes 8 amps...your battery is 16amp capacity???

 

be pepared to have battery issues ...

Edited January 3, 2011 by ezzyoiler

[ChaoPuzzy1968]

and to complicate matter , your alternator running voltage is ? 14.7 volt at ?? rpm

[arthur_chan]

If your brain need surgery, then you go visit the brain surgeon, and get the expert treatment, do you DIY the surgery yourself..

 

But you want to modify your bike electrics, without the aid of a wiring diagram, and not much experience in bike electrics, sounds like a recepie of disaster to me.

 

Dun play play, or can fry something that will be exp to replace

 

if the bike can fix itself with the horns then i'll be really susprised. seriously it makes no sense what u're referring. to make some sense out of ur statement, it's the diff btw a newbie surgeon n a professor surgeon. the cost difference makes up why some prefer a newbie surgeon.

 

anyway the horns have been installed on similar bikes, so there shouldn't be any battery issues. i think i'll go for lower amp fuse rather than the recommended, what's the worse can happen? the fuse blow out and i get another. fuse is cheap. there's no 12A fuse on the market, so i got a 10A to try out.

[chris 525]

When all these modern bikes are designed, everything is optimised to reduce cost.

So the alternator and rectifier are usually enough to drive all the bike electrical and electronic components.

 

It is not just a question of fuses.

 

If you then blindly add some accessory, can the altenator and rectifier handle the additional load.

maybe the horn is not a problem, cos you only sound it for a short while, but if you decided to add high intensity headlamps, I can see problems.

 

Then do you have the bike wiring diagram ???

You should not connect directly to the bike battery, so how do you know which wire to tap on to ?

[arthur_chan]

When all these modern bikes are designed, everything is optimised to reduce cost.

So the alternator and rectifier are usually enough to drive all the bike electrical and electronic components.

 

It is not just a question of fuses.

 

If you then blindly add some accessory, can the altenator and rectifier handle the additional load.

maybe the horn is not a problem, cos you only sound it for a short while, but if you decided to add high intensity headlamps, I can see problems.

 

Then do you have the bike wiring diagram ???

You should not connect directly to the bike battery, so how do you know which wire to tap on to ?

 

i do not have much additional lights, all of my addons r led n i'm not intending to put hid, fog lights etc. thus i dont see why the battery is unable to handle the load. n no i dont have the wiring diagram.

 

the concept is simple, tap direct from battery with a relay, n yes, i know which wire to connect to. the schematics of where n which wire to connect has all been planned out.

[lindavw]

u need a relay. Fuse 10A is quite safe.

I think horn button can take up to 5A or slightly lesser. cant rmb. but for anything >5A u need a relay or ur battery will dip in ampere when u depress the horn button.

[arthur_chan]

u need a relay. Fuse 10A is quite safe.

I think horn button can take up to 5A or slightly lesser. cant rmb. but for anything >5A u need a relay or ur battery will dip in ampere when u depress the horn button.

 

already hv relay, intending to use the original button also

[chris 525]

What about taking into account the back emf on the relay ? Sigh!!

[arthur_chan]

back emf? what u mean?

[chris 525]

When using coils, like the magnetic coil in a relay, when the coil is charged up, then the electrical connection broken, then coil will generate a very large reverse voltage, this is called the back emf. You may observe this as a small spark occurring at the switch contacts.

 

 

To avoid, connect in parallel a reverse biased silicon diode across the relay coil, 1N4001 should be OK, or 1N914 also can.

 

(Use at your own risk) For your horn connection using a relay,

 

The 12V battery terminal (or +12 V wire) is connected to one side of your horn push-button, then other side to two 1W rated 220 Ohm resistors in parallel, then this is connected to the coil/reverse biased diode of your relay, then the remaining side of the relay coil to the bike ground.

 

Then on the relay contacts side, one contact to the +12V wire, the other contact to the 10 Amp fuse, then the other side of the 10A fuse to the horn, and the other contact of the horn to bike ground. I am assuming that your relay only need 100 mA to switch. If it only need 50 mA to switch, then can use two 1watt rated 470 Ohm resistors.