AC/DC

[nashdm2]

Hi, I have recently ordered a KTM Sport which should be with me in October. I have been looking at this model for some while and back in June this year I was so confident that I was going to order one, I purchased a B&M front light to go on it (there was one supplied on the bike, but mine would have been an upgrade to one supplied) I went to order the bike to be told that 2014 models were now out of stock, so, I ordered a 2015 (which is better in any case)
When the spec of the new 2015 model came out I noticed that the light supplied was still a B&M unit, but now it was DC fed from the battery instead of AC fed from the 2014 model Shimano front hub dynamo!!!
So, the bike will be with me soon and I now have an AC light which will not fit it.
Is there any way I can alter the AC light to fit the DC output of the battery?
Many thanks in anticipation, if I cannot do this, I will just sell it.
Dave

 

[Deleted member 4366]

I don't quite understand. If the bike is already fitted with a B&M light, why do you want to fit yours?

Although I've not looked inside one of those lights, I'm pretty sure that it wouldn't be possible to run an A/C one from a battery without some complicated electronics. What's the point though when you can get really good lights that run direct from the battery from Banggood for only a few quid. They'll be much brighter than your B&M one.

http://www.banggood.com/LED10-U_S-CREE-U2-Chip-10W-Motorcycle-Headlight-Motor-Lamps-HiLo-Beam-p-936965.html

 

[danielrlee]

Hi. I don't have the exact answer you are looking for, but I think it would be possible. After all, I imagine the AC power from a hub dynamo would have to be rectified to DC for the light to function. You might even find that it works straight from a DC source if it is within the correct operating voltage range.

To be honest though, fantastically bright lights can now be had for a few quid, so you might be better off selling it and getting something else if it looks like it's going to be too much trouble.

 

[nashdm2]

Thanks for the replies chaps, appreciated. I did look into the rectifier element. Either way, it looks like the best bet is to sell what I have and see if the one that comes with the bike is good enough, if not, buy one of the ones being mentioned on here as I do not want to connect my AC B&M light if there is any danger of causing issues to either the battery or controller.
Thanks again,

Dave

 

[RobF]

How confusing.

One tends to think the B&M upgraded light runs on the same type of power as the lower range one.

But I agree the electronics of a new ebike is not a suitable test bed.

Worth pointing out modern hub dynamos can run powerful beams at very low ground speeds.

There's an American cycle shop owner who has written a great deal on this topic.

http://www.peterwhitecycles.com/plight.asp

 

[nashdm2]

Thanks Rob, yes, I read his site with interest, great pages of information.

 

[Deleted member 4366]

For us, no dynamos make sense. Why would you want to use power from the battery to propel the bike to turn a dynamo to make electricity for a light when you can take electricity directly from the battery.

 

[nashdm2]

Correct which is why I guess KTM dropped the dynamo in 2014 to main battery fed in 2015 model

 

[RobF]

Hard to make a case for dynamos on an ebike, but the advantages, such as they are:

Always available - I'm guessing once the controller shuts down the battery to prevent over discharge, that's it, no lights, even though there's plenty of juice in the battery.

Standard bulbs - hard wired lights will probably use 36V bulbs, so may not be easy to replace.

 

[Alan Quay]

For us, no dynamos make sense. Why would you want to use power from the battery to propel the bike to turn a dynamo to make electricity for a light when you can take electricity directly from the battery.

Things may have changed, but I thought there was a law/regulation (poss EU) that states that the bike should have a separate supply for the lights. I'm guessing that's why the terrible solution of a dynamo has been used.

To my mind, the best way would be to have a small battery for lights, charged from the main battery.

On my bikes though, I just carry a little rear light and a good Cree torch, all battery powered. Never had to use them, but some of the places I ride if my lights went tits up I'd be knackered. The street lights go out a midnight in my village.

 

[Croxden]

My Grace MX came with a bottle dynamo, however the Delite has the usual Bosch built in system, much better although the Grace lights were dammed good if a little noisy.
Where I ride there are no lights at all and under the canopy of the trees it goes dark much sooner. And very creepy.

 

[Geebee]

Hard to make a case for dynamos on an ebike, but the advantages, such as they are:

Always available - I'm guessing once the controller shuts down the battery to prevent over discharge, that's it, no lights, even though there's plenty of juice in the battery.

Standard bulbs - hard wired lights will probably use 36V bulbs, so may not be easy to replace.

Pick up the power connection at the power input to your controller or direct from the battery and as long as the battery is above your BMS cut off you will have light, if your BMS cutt off due to motor load once it is removed your battery will recover and run your lights for hours.