LED vs normal lights - power consumption question.

LED vs normal lights - power consumption question.

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Colin 1985

Original Poster:

1,899 posts

125 months

Thursday 11th November 2010
quotequote all
I understand the alternator in my BEC (hayabusa) produces 400W @ 5000rpm.

Since electrical power is at a premium, and I am wanting to install a more power draining electric water pump I was wondering if anyone knew how much power can be saved by using LED bulbs rather than standard ones (break lights, indicators), and are they a direct replacement?

Edited by Colin 1985 on Thursday 11th November 21:50

singlecoil

28,742 posts

201 months

Thursday 11th November 2010
quotequote all
They are a direct replacement as long as they have the necessary resistors built in. They will save some power but I would have thought it would be negligible, unless you spend a lot of the time turning and braking.

See my reply on the other thread re the pump, and bear in mind that a bigger pump won't necessarily draw more power unless it it working under a restriction, and the motor slows down.

Defcon5

5,544 posts

146 months

Thursday 11th November 2010
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How many bulbs do you currently have and what wattage are they?

Huff

2,560 posts

146 months

Thursday 11th November 2010
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Also - rememeber that the generator on a bike is regulated differently to that on a car. Basically, bike generators work flat-out and the voltage regulator shorts the excess current to ground (shunt regulation of a delta-wound 3phase generator).

You can add loads until the genny runs out of steam, all that happens is that the voltage regulator/ rectifer runs cooler! Beyond the c.400w limit(slightly dependant on engine speed) any excess loading is picked- up by the battery of course. So the best way to check is to monitor battery voltage and ensure it remains above say 13.2 to 13.5v at idle (a slight positives charge); if so, all will be well.

If the car is only run on a track, you could run the battery total-loss of course.

Edited by Huff on Thursday 11th November 22:25

Colin 1985

Original Poster:

1,899 posts

125 months

Thursday 11th November 2010
quotequote all
Defcon5 said:
How many bulbs do you currently have and what wattage are they?
Not sure about wattage but I will check, I thought they might just be a standard wattage(I posted this as an after thought in another thread so haven't looked at the properly). There is just two break lights, two rear lights and the indicators. The fronts are HID so can't do anything with them.
One of the reasons I asked though is because at tick over with all the lights on and the fan running if I indicate the warning light on the digi dash blinks to say low voltage.

If the LED light have a resister in them wouldn't that mean they consume the same amount of power overall because the resistor 'waists' the saving between the LED lights and the standard ones? Or am I being stupid?

Edited by Colin 1985 on Thursday 11th November 22:32

Defcon5

5,544 posts

146 months

Thursday 11th November 2010
quotequote all
Colin 1985 said:
Not sure about wattage but I will check, I thought they might just be a standard wattage(I posted this as an after thought in another thread so haven't looked at the properly). There is just two break lights, two rear lights and the indicators. The fronts are HID so can't do anything with them.

Edited by Colin 1985 on Thursday 11th November 22:32
I reckon the LEDs will sort it tbh, dont they draw single figures? Im not sure about the resistor

Your HIDs will be 35w, so lower than halogens anyway.

gtmdriver

328 posts

128 months

Friday 12th November 2010
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I have a 1989 Moto Guzzi which has a very marginal charging system.

I have replaced all the filament bulbs except the headlamp with LED equivalents. I have fitted an HID headlamp system as this also uses less power than a filament bulb, about 36 watts (3 amps current) rather than the normal 55 watts (5 amps).

The LED bulbs uses a fraction of the power of filament bulbs. H3 filament light bulbs are rated at 55w and draw about 4.5 amps each. The LED equivalents draw 0.11 amps each so their power requirement is only 1.3w.

The downside, however, is the actual light output. LED bulbs look a lot brighter when viewed directly, making them fine for most uses, but they do not actually project much light so they are no good for headlights or spotlights.

All the automotive LED replacement bulbs are rated at 12v so no resistors are needed. If you use LED's for your warning lights make sure you get 12v versions. The normal 5v LED's will need a current limiting resistor to prevent them failing.

If you use LED bulbs in your indicators they may not draw enough current to trigger a standard bi-metal flasher unit. One solution is to use high power resistors in parallel with the bulbs but this pushes the current draw back up to the level of a standard bulb so there is no advantage. A better solution is to use an electronic flasher unit which does not depend on current flowing through it to trigger the flashing function. It has a timer circuit instead.

When choosing LED replacement bulbs make sure the bulb output colour matches the lens colour. e.g. orange bulbs for indicators, red bulbs for rear lights etc. The plastic lenses are basically filters. A red lens takes the white light from a bulb, allows the red component to pass through and blocks all the rest. If you use a white LED a coloured lens will filter out a lot of the output. If you use a red LED behind a red lens almost all the light output will pass straight through giving you the maximum light output.

blitzracing

5,940 posts

175 months

Friday 12th November 2010
quotequote all
Huff said:
Also - rememeber that the generator on a bike is regulated differently to that on a car. Basically, bike generators work flat-out and the voltage regulator shorts the excess current to ground (shunt regulation of a delta-wound 3phase generator).

You can add loads until the genny runs out of steam, all that happens is that the voltage regulator/ rectifer runs cooler! Beyond the c.400w limit(slightly dependant on engine speed) any excess loading is picked- up by the battery of course. So the best way to check is to monitor battery voltage and ensure it remains above say 13.2 to 13.5v at idle (a slight positives charge); if so, all will be well.

If the car is only run on a track, you could run the battery total-loss of course.

Edited by Huff on Thursday 11th November 22:25
I thought that was in the days of the early Triumphs and Nortons with those huge Zener diodes and heat sinks mounted in the airflow. Dont they now have current controlled field coils in the alternators? Things must have move on from that surely?

Kiwi XTR2

2,693 posts

187 months

Friday 12th November 2010
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If you're running a hayabusa in a mid-engined config be careful about the placement of the voltage regulator. It's hard to get the same amount of cooling on it as when it's out in the breeze on a bike.

I fried a couple of them before relocating it frown

gtmdriver

328 posts

128 months

Friday 12th November 2010
quotequote all
As a rough guide you can tell how the charging system is regulated by looking at the alternator rotor (magnet).

If the rotor is a simple cylindrical permanent magnet type then regulation is done by bleeding off the excess voltage, although the system is a little more sophisticated than the old Lucas Zener nowadays.

If the rotor has coils, slip rings and carbon brushes then output regulation is done be varying the field coils in the rotor.

Huff

2,560 posts

146 months

Friday 12th November 2010
quotequote all
Things have moved on a bit - motorbike regs now use switched SCRs to clip peak voltage by shorting windings at high frequency, but it's still basically a shunt reg and things do get hot.

The point made above about mounting the regulator/rectifier in airstream is a very good one!

XTR2Turbo

1,528 posts

186 months

Friday 12th November 2010
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Cooling fans will draw a lot of current. Check that the fan is not coming on unless really needed. These engines are generally designed to run quite hot.

mikeveal

3,577 posts

205 months

Friday 12th November 2010
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As as been hinted at by other posters - you can save power by changing to LED bulbs, but the amount you save will be peanuts.

In order of things to look at :
Headlights.
Standard bulbs are 55W, HID are around 35W. You're already doing hte right thing.
Petrol pump.
Some electric petrol pumps will draw 9A. That's 108W. A properly spec'd fuel pump for a 200ish bhp setup can be had for around 4A. Speak to these guys: http://www.fuelsystem.co.uk/ (no connection, just a happy customer) They always used to have graphs of flow/Pressure/Current for their pumps available on the web. Unfortunately it looks like the graphs have gone, but they may be able to help.
So potential saving of 5A (60W).

Cooling fan.
Cooling fans from cars can be power hungry too. Usually those from the bike are more conservative. Without knowing what you're using, it's difficult to say how much power could be saved.


Brake / Tail Bulbs.
I think a brake / tail bulb is 21/5W. So the normal draw of this part is 5W, 21W when braking and 26W when braking at night. You can ignore the braking current, since this is an intermittent demand and will be backfilled by the battery. Your total POTENTIAL for saving on the bulbs is 10W (assuming your LEDs draw nothing at all.) Frankly this is such a small saving that you shouldn't bother looking here until you have exhausted the other options first.

Indicator bulbs are an intermittent draw. So don't worry about them unless you're popping fuses (regulators,generators) when you're indicating.

Kiwi XTR2

2,693 posts

187 months

Friday 12th November 2010
quotequote all
Also be sure to use a smart/float/trickle charger or similar to keep the battery topped up when in the garage.

Depending on which year of Hayabusa you have then any "unstarts" (cranking but failing to start) can cause serious damage to the starter. I can't remember which years this problem applied to but I think it was fixed around 2004 or 2005 ???

Colin 1985

Original Poster:

1,899 posts

125 months

Friday 12th November 2010
quotequote all
Thanks for your replys, in answer to some points:

The regulator is mounted on the passenger bulkhead, the wires were getting hot, but I reconnected them and think they are ok.

I'm not sure what rating the fan is. It only comes on when stationary though, when driving (when the cooling system is working as it should) the car tended to over cool slightly if anything. Haven't had it on a track day yet though.

Fuel pump hadn't occurred to me, if I fit the new water pump and do experience problems I will look into that.

With respect to starting, it is a 2003 motor, but the first idler gear has been replaced with a clutch which protects the starter from it kicking back (I think that was the problem?).