Lights again

[mfj197]

Anything with an XM-L will almost certainly be running at 2.8 or 3 amps (the emitter will take 3A but there's a few cheap drivers at 2.8A). On a single, good quality 18650 cell of let's say 2,800 mAh capacity they will run for one hour max, and will be getting pretty dim towards the end. Two cells, two hours etc.

The white XP-G LEDs are normally driven at half that current - 1.4A, so one cell gives 2 hours runtime, 2 cells gives 4 hours etc.

Michael

 

[derf]

Anything with an XM-L will almost certainly be running at 2.8 or 3 amps (the emitter will take 3A but there's a few cheap drivers at 2.8A). On a single, good quality 18650 cell of let's say 2,800 mAh capacity they will run for one hour max, and will be getting pretty dim towards the end. Two cells, two hours etc.

The white XP-G LEDs are normally driven at half that current - 1.4A, so one cell gives 2 hours runtime, 2 cells gives 4 hours etc.

Michael

I must be the only one who regularly nearly gets driven over, and feel I survive because of some bright Busch and Muller's and a dynohub. seriously, if you fit these (under hundred quid if you settle for (low price shimano hub dynamo), you will never again think about lights or light batteries and it will always be on, day and night for safety/visibility..

 

[KirstinS]

Anything with an XM-L will almost certainly be running at 2.8 or 3 amps (the emitter will take 3A but there's a few cheap drivers at 2.8A). On a single, good quality 18650 cell of let's say 2,800 mAh capacity they will run for one hour max, and will be getting pretty dim towards the end. Two cells, two hours etc.

The white XP-G LEDs are normally driven at half that current - 1.4A, so one cell gives 2 hours runtime, 2 cells gives 4 hours etc.

Michael

Hi Michael

Would you be able to explain to me how the bangood light can take 8v to 85v ? Does it have an internal dc dc convertor ?

It says it's 10w , which at 3a means about 3.3v (volts x amps is watts)

If you run a high voltage like I will be (48v nominal, 54v hot off charger) what prevents it going pop ?

I know it will work and I've ordered a switch to go with it. And am plenty capable of soldering/testing

I just don't understand why it works !

Thanks

 

[mfj197]

Hi Michael

Would you be able to explain to me how the bangood light can take 8v to 85v ? Does it have an internal dc dc convertor ?

That's it exactly. Many LED drivers have voltage conversion in, either up (for driving multiple LEDs from one cell - known as a boost driver) or down as here (known as a buck driver). There are also linear drivers which don't do any voltage conversion.

In fact the drivers are actually a constant current source rather than a constant voltage source. With LEDs it is current you are trying to regulate carefully, and a 3A driver connected to a large voltage supply like your battery could drive one, two, or more XM-L LEDs all wired in series.

Michael

 

[Deleted member 4366]

One frustrating thing with these eBay lights is that hardly any of them specify the burn time on a fresh set of batteries. To be useful to me, any bike light needs to run for a minimum two hours at full power - ideally more like 3 hours in case of any problems en route. I have my doubts that many of them will.

Anyone actually bought one and timed how long it stays lit?

The single Cree XMLs do an easy 2 hours on maximum with the 4 cell battery pack. They go for longer if you use it on flash or low-beam. You can work back from there. A Torch with a single cell will be 1/2 hour, etc.

Or you can calculate. They take about 2.5A at maximum with their supply voltage of about 3v (converted from 7.2v) so that makes 7.5W. If you allow for inefficiency in the driver, say 10w max. A 4 cell pack of 2200mah 18650s has 2.2 x 4 x 3.6 watt-hours = 32.5wh if they're in good nick and you don't mind running them to their minimum.. That works out at a maximum of 3 hours at maximum brightness if you have a 4-cell pack. A single cell will last about 45 minutes, or a 3 emitter light on maximum with four cells will last one hour.

The only question is, how good are the cells in the Chinese packs? Most of mine are pretty good. They're 2 years old and still going strong. I've repaired a couple of packs for other people, and they both had wires broken off, so an easy repair. There's a type of BMS (LVC) under the shrink-wrap.

 

[axolotl]

Thanks, folks. The technical knowledge on this forum is great!

I must be the only one who regularly nearly gets driven over, and feel I survive because of some bright Busch and Muller's and a dynohub

For being seen, I couldn't agree more, derf. I've got a dynohub already and Hermann lights that run all the time, night and day. However, the front lamp just isn't that beefy because it has to share the 1.5w nominal power from the hub with the rear lamp. There's not really enough light for seeing where I'm going on unlit routes, travelling at speed.

The single Cree XMLs do an easy 2 hours on maximum with the 4 cell battery pack

That sounds like what I need then, d8veh. I've found this kit on eBay which looks suitable:

http://www.ebay.co.uk/itm/2000-Lumen-CREE-XML-T6-LED-BICYCLE-BIKE-CYCLING-FRONT-HEAD-LIGHT-TORCH-HEADLIGHT-/321484671361?pt=UK_SportGoods_CyclAcces_RL&hash=item4ad9fac981

Any thoughts?

 

[Deleted member 4366]

That's the one. The price is coming down all the time. I think I paid about £25 for mine from China.

 

[steve.c]

Hi axolotl.I have not timed mine But they will easely last me for my 10 mile comute through lanes to my work and back but that is on low power which belive me with a full power of 5000 lumens low power is plenty good enough and if I put the power up people complain !!!!!! and when I get home its still showing 3 lights of battery left so OK for me and of coarse on flashing it will last even longer and I have forgotten to charge it sometimes and it will still do the job for the 2 days.I don't believe in spending stupid money on a light ( I bought a Cateye front light a while ago for 25 quid and you cant see anything in the dark at all !!)

 

[Gubbins]

The most sensible way with lights is to buy one that takes std rechargeables rather than a rechargeable pack. My Hopes take 4 X 2800's which are cheap as chips and 2 spare battery cages for a couple of quid. 3 hours on full power for each set.

 

[jackhandy]

The most sensible way with lights is to buy one that takes std rechargeables

Or 18650 cells, if you've disassembled a knackered bike battery

 

[Alan Quay]

Or 18650 cells, if you've disassembled a knackered bike battery

Www.fasttech.com have loads of high power Cree torches. most of them use 18650's.

They also sell adapters to fit to bars, chargers, etc.

I have an ultra fire WF-502b that I use as a backup light. I cannot imagine you would need anything brighter. It cost less than £10 delivered.

 

[Geebee]

The most sensible way with lights is to buy one that takes std rechargeables rather than a rechargeable pack. My Hopes take 4 X 2800's which are cheap as chips and 2 spare battery cages for a couple of quid. 3 hours on full power for each set.

The most sensible way on an e-bike is to run it off the main battery, job done.

 

[axolotl]

The most sensible way on an e-bike is to run it off the main battery, job done.

I disagree. Lights are too safety-critical. If your main battery runs out of juice you're riding in the dark which is dangerous and illegal. I think you need some kind of backup, be it lights with separate batteries or a dynohub.

 

[Geebee]

I disagree. Lights are too safety-critical. If your main battery runs out of juice you're riding in the dark which is dangerous and illegal. I think you need some kind of backup, be it lights with separate batteries or a dynohub.

Your main battery will recover enough once you shut down the motor to run the lights for ages.
My bike does still have its original battery lights for emergency use and my being to lazy to take them off.
If you are worried throw a couple of spare cheapies (red and white) in your pannier, short of a catastrophic failure (battery explosion, wiring harness melt down) they will not be used.

 

[Alan Quay]

Your main battery will recover enough once you shut down the motor to run the lights for ages.
My bike does still have its original battery lights for emergency use and my being to lazy to take them off.
If you are worried throw a couple of spare cheapies (red and white) in your pannier, short of a catastrophic failure (battery explosion, wiring harness melt down) they will not be used.

That's pretty much what I do, run main lights from he battery and carry battery powered spares.

 

[Deleted member 4366]

Those little lights that you get in Aldi are really good. They're surprisingly bright. The back one is bright enough on its own. I use the front one for when I'm on a lit cyclepath and other times when brightness isn't too important. My main light works direct from the battery with a switch, so it's a bit like running on side-lights and headlights.

While I think about it, I noticed something interesting when I was in Japan. All the vehicles switch to side-lights when they get below a certain speed. I think it's automatic. They have all sorts of creative devices to show when their side-lights are on, like mirrors and perspex rods.

 

[EddiePJ]

Spotted a bit of 'light' reading earlier today. http://reviews.mtbr.com/2014-mtbr-bike-lights-shootout

 

[Deleted member 4366]

Spotted a bit of 'light' reading earlier today. http://reviews.mtbr.com/2014-mtbr-bike-lights-shootout

I couldn't find the Banggood or Ebay ones in there anywhere!

The best one was 9 lumens per dollar. This one gives 173 lumens per dollar. Even allowing for a bit of Chinese exaggeration, it's still got to be ten times as much for the money.:

http://www.ebay.co.uk/itm/like/400554413825?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0

 

[mfj197]

I couldn't find the Banggood or Ebay ones in there anywhere!

The best one was 9 lumens per dollar. This one gives 173 lumens per dollar. Even allowing for a bit of Chinese exaggeration, it's still got to be ten times as much for the money.:

http://www.ebay.co.uk/itm/like/400554413825?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108&ff19=0

Or there's even one with 7 XM-Ls. However I'm not so sure of the longevity of those lamps, but for that money is maybe not so much of an issue! Heatsinking is a concern as the lamp head would have to dissipate over 40 watts of heat at full chat for 4 LEDs.

However they are dangerous for use on road as even the one with 4 XM-Ls will be pumping out just under 4,000 lumens in the face of oncoming traffic. That is brighter than a car with main beams on.

Michael

 

[jackhandy]

Is the perceived glare dependent just on the emitter output, or does the large reflector of a car headlamp ramp it up?