Lights. CREE XML XM-L T6 / U2 etc Thread

[Custom24]

How do people deal with the power cable being too long if you want to locate the battery pack at the front of the bike?
I'm cautious of having loops in the cable, in the same way as you are supposed to fully unwind an extension lead?
But on the other hand, I couldn't be bothered fiddling around with the soldering iron and risking wrecking the light...

 

[tincaman]

Don't worry about loops, just do it, try and keep it tidy. There is no electrical reason not to do it

 

[Origamist]

This might be ok, Halfords own brand but the battery pack could be a good one.
http://www.ebay.co.uk/itm/141212215493
1200 lumens for £20 delivered
The same seller also has the lower rated Bikehut front lights as well, the 450 lumen one is only £12.99

A good find, cheers.

I have just taken a punt on the above. The cut-off looks v good and the foreground illumination is wide and bright. The trade off appears to be a serious lack of throw. I can't imagine it's anywhere near 1200 lumens, but with a Cree XM-L it will have punch as long as its driven reasonably hard. The pulse mode looks good for lit urban situations.

@tincaman how are you finding it? Will it light up the road 30-40 metres ahead on full power? Have you had any probs with the battery pack failing? What's the run time like on high and medium? Sorry for all the questions!

If it's any good, I might buy two and carry a spare battery pack.

Will report back when I've tested it.

 

[tincaman]

@tincaman how are you finding it? Will it light up the road 30-40 metres ahead on full power? Have you had any probs with the battery pack failing? What's the run time like on high and medium? Sorry for all the questions!

If it's any good, I might buy two and carry a spare battery pack.

Will let you know.

 

[fossyant]

Most 4 cell packs are 8.4v 2S2P (2 series 2 parallel) I could make a 4P to get me 4.2v, but I would like a suitable battery holder instead of soldering the pack together. Alternatively source another of the 2 cell 4.2v packs and wire them in parallel with a splitter cable

You should be OK to use the pack but remember the cells will need to be orientated in the SAME direction. I run two of my packs at 8.4v with two batteries, but in parallel - one +ve up, one -ve up.

Now the packs are designed for two +ve, two -ve at the top, if you ran with 4 cells all the same way, you'd end up with 4.2v but at 10,400 mah 4 x 2600.

Test it with a volt meter first though. Don't run the light at 8.4v, you will blow it.

 

[Lanzecki]

Now the packs are designed for two +ve, two -ve at the top, if you ran with 4 cells all the same way, you'd end up with 4.2v but at 10,400 mah 4 x 2600.

Test it with a volt meter first though. Don't run the light at 8.4v, you will blow it.

Sticking batteries (cells) in the wrong way is gonna be bad.

Most likely the pack isn't going to work because of the internal wiring of the pack. It's hard to explain but it's designed to have 2 terminals Positive down and 2 up. Depending on the case you'll end up with the cells being negative to negative (in a wiring sense) and so not giving any voltage.

My worry that without checking the way the pack is wired could result in the cells being linked short circuit. You'd want to run away if that happened. I'm looking for a previous post I made about battery safety. The modern batterys we use now can be dangerous. Treat with care please.

Here's a little graphic I made to try and show what's being discussed when people talk about series and parallel. I realise that most people understand it, but anything to help the unsure : (No attempt here to teach Mother to suck eggs)

 

[Lanzecki]

I got to grips with the search engine (very nice).
http://www.cyclechat.net/threads/lights-cree-xml-xm-l-t6-u2-etc-thread.117285/post-2872955

To add to that post:

Damaged should be safely disposed of even if they still work. I'n the early days dropped batterys were known to self combust minutes/hours after damage.
Use a control circuit. This will stop over charging, and stop the battery draining. Both if these will kill the battery.
Don't Short them out. If you do, Li-ion batteries may suffer thermal runaway and cell rupture in seconds. In extreme cases this can lead to combustion AKA a big bang.

Remember kids, Li-ion cells contain (unlike ni-cad) a flammable electrolyte and are also kept pressurized.

 

[Custom24]

I got to grips with the search engine (very nice).
http://www.cyclechat.net/threads/lights-cree-xml-xm-l-t6-u2-etc-thread.117285/post-2872955

To add to that post:

Damaged should be safely disposed of even if they still work. I'n the early days dropped batterys were known to self combust minutes/hours after damage.
Use a control circuit. This will stop over charging, and stop the battery draining. Both if these will kill the battery.
Don't Short them out. If you do, Li-ion batteries may suffer thermal runaway and cell rupture in seconds. In extreme cases this can lead to combustion AKA a big bang.

Remember kids, Li-ion cells contain (unlike ni-cad) a flammable electrolyte and are also kept pressurized.

Is your opinion that the battery packs that come with these Chinese XML T6 lights safe? Do you know if there is a control circuit in the battery pack?

 

[fossyant]

there is usually a circuit in the cheap ones, but make sure you tape them up to make more waterproof.

 

[Lanzecki]

Is your opinion that the battery packs that come with these Chinese XML T6 lights safe? Do you know if there is a control circuit in the battery pack?

The ones I have (came with the lights) do. Generally in the plastic heat shrink packs the control circuit is down the side of the pack. A small bulge if any. The power connector is connected to this not directly to the cells themselves.

Here is a pack I have that's not working (lasts a few mins. Don't know why yet). Unopened on the left showing the cable connected to the circuit on the side. Right showing the opened pack and what the average circuit looks like. It can be felt through the heat shrink.

It's worth noting and as mentioned previously the advertised mah ratings of these cheap chinese battery packs are often .. shall we say exaggerated. Spending a few € more will get a much better rated pack. I don't yet know why this pack doesn't hold a charge, but once I get my charger back I can cycle each battery and see what's up and what the rating is.

 

[Lanzecki]

Also you can get the circuits separately from the web. So it's possible to make your own safe packs with control circuits.

Don't solder directly the the battery, get cells with tabs fitted.

 

[tincaman]

A good find, cheers.

I have just taken a punt on the above. The cut-off looks v good and the foreground illumination is wide and bright. The trade off appears to be a serious lack of throw. I can't imagine it's anywhere near 1200 lumens, but with a Cree XM-L it will have punch as long as its driven reasonably hard. The pulse mode looks good for lit urban situations.

@tincaman how are you finding it? Will it light up the road 30-40 metres ahead on full power? Have you had any probs with the battery pack failing? What's the run time like on high and medium? Sorry for all the questions!

If it's any good, I might buy two and carry a spare battery pack.

Will report back when I've tested it.

Actually used for the first time this morning, so not sure about run times yet. My commute is pitch dark for about 8 miles before street lights kick in, so what I can can say is that even on the low setting there is plenty of light. You are right that there is not any throw down the road but the design precludes that, what you get is a squarish beam which provides good light for about 20 metres and which probably wont dazzle oncomers. Its a bit weak down by the wheel area but better when you run on med or high. The high will probably be more useful for wet road when there is less light reflection.
I have a T6 torch on the bars as well so that one comes on when I need to throw further down the road, I have fast descents through forest so I need to be able to spot deer in the distance

 

[Origamist]

Actually used for the first time this morning, so not sure about run times yet. My commute is pitch dark for about 8 miles before street lights kick in, so what I can can say is that even on the low setting there is plenty of light. You are right that there is not any throw down the road but the design precludes that, what you get is a squarish beam which provides good light for about 20 metres and which probably wont dazzle oncomers. Its a bit weak down by the wheel area but better when you run on med or high. The high will probably be more useful for wet road when there is less light reflection.
I have a T6 torch on the bars as well so that one comes on when I need to throw further down the road, I have fast descents through forest so I need to be able to spot deer in the distance

Thanks for the update. Mine should be arriving today and I will report back with my findings this week! Stay tuned light/torch fiends...

 

[Lanzecki]

Charge every 3 months for optimum care.

That said some say every Month, others say don't fully charge, but don't allow them to drop below 40%..

Rule of thump, Keep out of sunlight and extreme temps. Don't let them go flat. Personally I'll drop them in a charger every 3 months.

That said they are a consumable, at best you'll get 3 years out of them.

 

[Origamist]

Thanks for the update. Mine should be arriving today and I will report back with my findings this week! Stay tuned light/torch fiends...

First impressions are v positive... The cut off is clearly defined and I'd be happy on unlit lanes using the medium setting. Will take some pics at the weekend.

20 quid well spent.