Headlight trouble cbf125

Newbie here, recently had trouble with my headlight. To begin with it wasnt working at all. Got quoted over 400 quid to fix it at a garage for a new CDI an wiring loom. Instead I had my partners dad have a look and we ended up changing the alternator and rectifier as this is what he diagnosed and for the past couple weeks it has been fine and working no problems!

Now my head light is flashing dim and bright, cars keep thinking I'm flashing them and is quit annoying and dangerous! Just noticed it on the way home last night. My full beam light is flashing in tandem with the headlight when the beam is on but the tail and brake light are fine. Giving revs in neutral affects the way it behaves slightly. Does anyone have any idea as to where to begin? I have a Haynes manual but electrics is not my forte! Any help would be much appreciated as I've spent way more than this bike is worth and garage is not an option realistically. I have a video of it which il upload to youtube if needed. Thanks!

Josh

Here's the link to the video if it helps anyone

http://youtu.be/9ZHsFm0cRy8

lucky escape from the rip-off garage!!

Why did it need a new CDI and loom???

What state is the battery in? how bright is the headlight with the engine not running?

Cold weather kills batteries so might just be a dead battery - it happens

Thanks for the reply joeman! Rip off garage indeed, they said the connection to the wiring loom had rusted and damaged the connections to the CDI unit so needed both replacing, I bought a CDI online for a tenth of the price they quoted and went to replace it myself but no sign of rust at all. My partners dad got a multimeter out and diagnosed it in seconds so was a lucky escape indeed!! PGH in Torquay Devon were the culprits!!

My model of bike the lights are fed off the alternator and turn on only when the engine is running. I had the battery replaced last month and had it charged up when we swapped the alternator coils and rectifier so I can't see it being that :/ if you watch the video I posted you can see when I rev it the light goes dim and stops flashing as much but I am at a loose end!

Update: my alternator casing is too hot to touch! What could be causing my alternator to fail??

Alternators do not like that!

The cause could be many things tho. Hard to say over the web unless its a common fault. Wiring faults can be hard to find when I am 200 miles away or I'd be happy to lend a hand.

Its consistently doing it from the video! Not even changing much when theres revving.

Id first just go over connections and make sure everything is ok. Then get a multimeter on the rec/reg and check its giving out a steady output.

Then check the battery. If any are unsteady then replace.

When reg/rec goes it can cook the battery with AC voltage from the alternator. The alternator as it was the last thing newly installed seems suspect to me as well so again check all connections there too.

When you do work and stuff like this happens its usually something has gone iffy with the work itself. You need to go over it and make sure everything is in correctly. Take it apart and put it back together and see what happens is usually what I do. I usually find the problem that way.

Cold weather kills batteries so might just be a dead battery - it happens

Not true

I always thought it was the cold that kills them until recently

its actually the heat that kills the battery but you don't notice until it gets cold and the battery cant deliver the required amps

The cold actually stops a battery discharging quickly

but yeah it could be a dead battery if you have cooked it with a duff reg/rec or charging components

although the charging system should be putting out a steady charge all the time most voltages rise when you rev them but you should have atleast a constant 12.5 ideally 14.4

check all wiring as suggested make sure you have a good connection on everything

Cold weather kills batteries so might just be a dead battery - it happens

 

Not true

I always thought it was the cold that kills them until recently

its actually the heat that kills the battery but you don't notice until it gets cold and the battery cant deliver the required amps

The cold actually stops a battery discharging quickly

Cold temperatures slow down the chemical reaction that goes on inside a battery to produce current, so at colder temperatures, the battery is less able to provide the required current.

Also cold batteries don't charge as well, so in cold weather you end up in a situation where you have the same demand on the battery (if not more demand from lights and heaters etc) but the battery is less able to produce current and also less able to replenish its charge.. Its the reason lots of industrial applications have battery heaters to keep the battery at optimum operating temperature.

Back on topic though... if Stuff's getting hot, then something's not right!! do you have a short circuit somewhere?? the way the light dips at higher revs almost suggest the higher charge produced from the higher RPM is actually working against the battery to light the lights! no idea how that would happen though...

got anything to back it up??

http://batteryuniversity.com/learn/arti ... ttery_life

Heat is a killer of all batteries and high temperatures cannot always be avoided. This is the case with a battery inside a laptop, a starter battery under the hood of a car and stationary batteries in a tin shelter under the hot sun. As a guideline, each 8°C (15°F) rise in temperature cuts the life of a sealed lead acid battery in half. A VRLA battery for stationary applications that would last 10 years at 25°C (77°F) would only live for five years if operated at 33°C (92°F). The same battery would desist after 2½ years if kept at a constant desert temperature of 41°C (106°F). Once the battery is damaged by heat, the capacity cannot be restored. The life of a battery also depends on the activity and is shortened if the battery is stressed with frequent discharge

http://batteryuniversity.com/learn/arti ... mperatures

Like humans, batteries function best at room temperature, and any deviation towards hot and cold changes the performance and/or longevity. Operating a battery at elevated temperatures momentarily improves performance by lowering the internal resistance and speeding up the chemical metabolism, but such a condition shortens service life if allowed to continue for a long period of time. Some manufacturers of lead acid batteries make use of the improved performance at warmer temperatures and specify the batteries at a toasty 27°C (80°F).

Cold temperature increases the internal resistance and diminishes the capacity. Batteries that would provide 100 percent capacity at 27°C (80°F) will typically deliver only 50 percent at –18°C (0°F). The capacity decrease is linear with temperature.

Like I said heat kills them but when you need the power when its cold it cant deliver it as it hasn't got it any more

batteries are kept at room temp to keep them at their best so they don't work too hard and deliver all available power

My GCSE Chemistry Teacher??

But a quick search of the same site you found reveled this:

http://batteryuniversity.com/learn/arti ... mperatures

Low-temperature Charge

Fast charging of most batteries is limited to a temperature of 5 to 45°C (41 to 113°F); for best results consider narrowing the temperature bandwidth to between 10°C and 30°C (50°F and 86°F). Nickel-based batteries are most forgiving in accepting charge at low temperatures, however, when charging below 5°C (41°F), the ability to recombine oxygen and hydrogen diminishes. If NiCd and NiMH are charged too rapidly, pressure builds up in the cell that will lead to venting. Not only do escaping gases deplete the electrolyte, the hydrogen released is highly flammable. The charge current of all nickel-based batteries should be reduced to 0.1C below freezing.

Nickel-based chargers with NDV full-charge detection offer some protection when fast-charging at low temperatures. The resulting poor charge acceptance mimics a fully charged battery. This is in part due to the pressure buildup caused by gas recombination problems. Pressure rise and a voltage drop at full charge appear to be synonymous.

To enable fast-charging at all temperatures, some industrial batteries include a thermal blanket that heats the battery to an acceptable temperature; other chargers adjust the charge rate to prevailing temperatures. Consumer chargers do not have these provisions and users should make all attempts to only charge batteries at room temperatures.

And a google search for "Cold Soaked Batteries" found this... (good reason we should stick to Petrol )

http://gm-volt.com/2011/08/24/the-volt-in-cold-weather/

First, let’s consider battery performance as a function of temperature. If you charge any battery in a heated garage and then take it outside into freezing weather, the temperature of the battery will quickly be reduced to the ambient outside temperature and the electrochemical reactions that provide the current will occur at a slower rate. Thus the battery will seem to have lost capacity since as it is used the current will decline from a lower starting point and the battery will quickly fail to provide enough current at a given voltage to perform its function.

Batteries work best at "Optimum temperature"... they dont like cold and they dont like Hot!! but in the UK they are more likely to get too Cold than too Hot!

thats basically what I posted above! baring the charging bit!

once they get hot and damaged they wont perform as they should when cold which give the impression that the cold has killed them

I also see it on my car when the temp drops my battery is on the way out and when its below about 4 degrees when I start my car I get a brake warning on the dash which is because the voltage has dropped at my ABS module when starting once running all is fine when its warmer all is fine too

the battery is on its way out and cant deliver the power when cold hence the low voltage warning

all it takes for a battery to get too hot is a nice hot day and a lot of charge from starting it can soon take its toll on little bike batteries not to mention how close they can be to the engine...well mine is with it been a V twin I have a big arse cylinder right next to it

Its probably a mixture of both killing batteries hot starts it cold finishes it off plus most bikers dont ride or charge their battery in winter which isnt good for them and the sulphate

anyway as you said earlier lets keep on topic

Thanks for the replies everyone, I've got to the bottom of the problem, not 100% what it was but it definately wasn't my alternator. I noticed wiggling my starter relay connections stopped the flickering so I dissambled it cleaned all the connections and double checked them all and now it seems to be fine!! I did take the alternator coils out and checked nothing was shorting And it seemed fine but that didn't solve it. I had a pattern relay installed a few months ago as I couldn't find the official part for less than £100!! So that must of been playing up for some reason! Appreciate everyone's input though and I now have a good knowledge of battery's

Sounds like all the power goes through your starter relay like mine does

They can be a pain when they furr up they can overheat and melt

Yeah that is the case, probably why they're so expensive for my bike!! Might have to fork out for it though if what I've done is only a temporary fix. Fingers crossed it stays ok!

There is ways and means to bypass it to reduce the load

Strange. I've noticed my headlight flickers quite bad at idle after the engine has warmed up. Doesn't dim but I guess this thread is something to keep in mind.

Wanted to put a h4 60/55 bulb in like I had on my xr 125.

wow googled my problem and this popped up. My relay has furred up with white alloy rust.

Problem of overheating alternator caused more than likely to a high resistive joint - joints between alternator and battery. The voltage regulator is sensing low voltage at your battery due to the corroded connection, so it then compensates and produces excessive power from the alternator making it run hot. Same rule applies if your battery is duff don't ignore it, it could end up trashing your charging system. Good to hear you have found your problem

Would that point to my over revving too? showing warm 1.9k at idle when it should be 1.5k +/- 100rpm

ordered a second hand one off eBay for £9 as I can't be bothered riding all the way to abingdon then getting picked up then doing it all again. also replacing spark cap as it's torn.

Would that point to my over revving too? showing warm 1.9k at idle when it should be 1.5k +/- 100rpm

That would be hard to tell, l think your bike is fuel injected. So with lambda sensors and all the rest of the electronics' that needed to make the thing run. I would start by just checking that your throttle cable is adjusted properly and not to tight.