How many bulbs does it take....

25-08-2006, 01:08 PM

... to blow up a bike?

Not the start of a bad joke but a serious question here.
I've been reading PD's recent thread on making a headlight and decided its the way I have to go.
My question is thus, if I run 5 55W bulbs will it melt me bike. I'll be running a direct feed from the battery via a couple of relays but am worried about frying my regulator and/or alternator and maybe even the battery. By my gusses all 5 running at once would be drawing 22.9A.
Any ideas if the stock electrics will cope?
The other option is to run either 2 or 3 lights at a time for low/high beam drawing a more modest 13.75A with 3 bulbs, but still a breif spike to the 22.9A if I hit the flash switch.

Anybody got any ideas?

Thanks

25-08-2006, 01:38 PM

As long as the relay and the main wiring to it and to the lights is rated for the higher current you won't have any problems with that.

Where you might get a problem is the power your bike can supply this may put undue strain or overload the altenator/generator if this exceeds it's rating. On my bike things go a touch dimmer at tick over with standard lights!!

I don't think the battery is a problem as in theory when the bikes running all its doing is being charged by the altenator/generator when theres spare electric as the altenator/generator is powering everything.

I think you can get uprated altenator/generators for this type of thing to increase the current capacity.

Not sure about the regulator though

Sorry it's a bit vauge but i'm at work and don't have anything to look at to check, hopefully someone will confirm if what i've said is right or if i'm just an idiot that shoulsd shut up

Ill check when i get home and have the stuff in front of me.

Cheers,

Andy

25-08-2006, 01:58 PM

a quick flick through the s4 manual says the generator is a 12v 520W

and the electronic voltage regulator is protected by a 40 A fuse

if thats of any use

25-08-2006, 02:24 PM

Cheers for that.
I think the alternator on my lil 600 is about 320W if I remember rightly.
Even with all 5 bulbs running at once which is unlikely they would be 275W. Problem is I've no idea how much the rest of the bike takes for ignition etc.

hmmm, might get away with running 2 for low beam and 3 for high. Just have to hope it doesn't go pop if I hit the flash switch.....

manwithredbike · 25-08-2006, 10:01 PM

remember if you're running a new circuit off the battery to protect the new wires with an in line fuse which i don't think you've mentioned.
275w running full time along with ignition, tail light etc would not be ideal on a 320w alternator, that would be close to full load and could damage it over a period of time. if you split them to dip/main the odd spike for flashing lights etc would be less harmful providing your relay etc were rated apt.

ps 5 lights !? what's that not going to look like!!?? you're more likely to fry the paint off the bonnet of an oncoming car.

25-08-2006, 01:08 PM	#1
Lost Again Guest Posts: n/a	How many bulbs does it take.... ... to blow up a bike? Not the start of a bad joke but a serious question here. I've been reading PD's recent thread on making a headlight and decided its the way I have to go. My question is thus, if I run 5 55W bulbs will it melt me bike. I'll be running a direct feed from the battery via a couple of relays but am worried about frying my regulator and/or alternator and maybe even the battery. By my gusses all 5 running at once would be drawing 22.9A. Any ideas if the stock electrics will cope? The other option is to run either 2 or 3 lights at a time for low/high beam drawing a more modest 13.75A with 3 bulbs, but still a breif spike to the 22.9A if I hit the flash switch. Anybody got any ideas? Thanks

25-08-2006, 01:38 PM	#2
Shandy Guest Posts: n/a	As long as the relay and the main wiring to it and to the lights is rated for the higher current you won't have any problems with that. Where you might get a problem is the power your bike can supply this may put undue strain or overload the altenator/generator if this exceeds it's rating. On my bike things go a touch dimmer at tick over with standard lights!! I don't think the battery is a problem as in theory when the bikes running all its doing is being charged by the altenator/generator when theres spare electric as the altenator/generator is powering everything. I think you can get uprated altenator/generators for this type of thing to increase the current capacity. Not sure about the regulator though Sorry it's a bit vauge but i'm at work and don't have anything to look at to check, hopefully someone will confirm if what i've said is right or if i'm just an idiot that shoulsd shut up Ill check when i get home and have the stuff in front of me. Cheers, Andy

25-08-2006, 01:58 PM	#3
Scotty Guest Posts: n/a	a quick flick through the s4 manual says the generator is a 12v 520W and the electronic voltage regulator is protected by a 40 A fuse if thats of any use

25-08-2006, 02:24 PM	#4
Lost Again Guest Posts: n/a	Cheers for that. I think the alternator on my lil 600 is about 320W if I remember rightly. Even with all 5 bulbs running at once which is unlikely they would be 275W. Problem is I've no idea how much the rest of the bike takes for ignition etc. hmmm, might get away with running 2 for low beam and 3 for high. Just have to hope it doesn't go pop if I hit the flash switch.....

25-08-2006, 10:01 PM	#5
manwithredbike aka Phil Join Date: Nov 2005 Location: derry Bike: M900 Posts: 376	remember if you're running a new circuit off the battery to protect the new wires with an in line fuse which i don't think you've mentioned. 275w running full time along with ignition, tail light etc would not be ideal on a 320w alternator, that would be close to full load and could damage it over a period of time. if you split them to dip/main the odd spike for flashing lights etc would be less harmful providing your relay etc were rated apt. ps 5 lights !? what's that not going to look like!!?? you're more likely to fry the paint off the bonnet of an oncoming car.