Hardwiring a Torch light

[Scottyf]

Hello all,
Quick query really. More of a confirmation.
I have a UltraFire Torch 502b which uses a Cree T6 XML Led.

The torch itself is good quality and the beam is very good. However My issue is with the poor 18650 cell. The cell is pretty rubbish when calling for anything more than a C rate of 1/10th. It only offers the full high beam for about 10mins before it drops off and its like the torch is in low mode.

Its enough to be seen on my commute but its not lighting up like it is off a full charge.
So I was thinknig of running a couple of thin cables from the plus and negative torch points and using a DC to DC convertor to step the voltage down to 5v.

Something like this

HRD Series Converter DC 12v 24v 36v 48v step down to 5v or 9v or 12v max. 3A | eBay

Can any of you foresee any issues with this?

 

[wurly]

That is a lots of volts to drop. I'm just wondering about the rating on that device. My p7 torch draws 2A at 3.7V. I expect your torch maybe higher?
I doubt it will supply that current after dropping the volts down to 5Volts, but i stand to be corrected, and i see a big heatsink, so maybe i am wrong. I was looking at buying one (or more) to run my lights.

Ah! i've just re read the ad, and it says a switching regulator, so i think it should supply a low volt torch ok. the output may have a bit of ripple on it, but for a torch it should be fine if your torch draws less than the rated current.

 

[BrianSmithers]

Hi Scotty, if you have to find somewhere to tuck the assembled DC-DC convertor in some kind of case, then you have the same problem if you used an external battery holder like this from Maplin AAA Size Battery Holders : Battery Boxes : Maplin Electronics - but with less complexity and cheap rechargable batteries that will last quite a while. Four 1.2v rechargables makes 4.8v which is near enough.

- Brian

 

[Scottyf]

Well i could just buy some better 18650 cells.
But I have more than enough battery power already and it would save me botherring to charge up the lone 18650 cell. It would also mean I have loads light time and not have to worry about it.

Thanks for the idea's.

I would imagine the torch will drain 3.7v @ 2 amp. Maybe a bit more but that switch can handle 3 apparently.
If anyone else has better links I'd be happy to review it.

 

[NRG]

I had the same worries as wurly, reading the cree TM-L spec they list max of 2000mA for long life so if thats the draw then for a fully charged battery say 42v you need to drop 38.3 volts at 2amp or 77watts will still need to be dissipated with a linear regulator but the switching regulator should be unaffected....think I may get a couple to try....

 

[wurly]

Is your torch 900 lumins Scotty? if it is, mine also is rated at that, so i reckon the power consumption will be roughly the same. The best way is to hook it up to an ammeter and see what current it draws.
I use Trustfire 18650 2500ma protected cells. Although i only use the torch for 7-10mins each morning, it does last a whole week. I tend to click from high power to low depending on what roads or paths i'm travelling on though.
When i tested mine i found it would start dropping power around the 25minute mark and gave out completely at 45mins. That was the protection in the cells cutting out power around 2.7Volts.
I going to buy a couple of those dc-dc converters anyway...they are cheap enough. I seem to have endless amounts of battereries to charge up this time of year......

 

[Scottyf]

My point exactly.
The torch uses a 18560 Cell of 4.2v protected. (Saves the charger being complex for a single cell) I've spoke to the ebay seller who is sending me another cell in the mean time just in case it is completly shot.
Its a 1000 lumens and is really more than a need for my commute but its nice to have that beam.

However the ultrafire 3000mah are really poor on test. An to be honest its the same in practice. The torch clearly wants quite a large draw from the little battery that its just not up to.

A better cell like a trustfire that you listed would perform much better. But still not last long enough at full draw. Despite the claims of the manufacturer.

To be honest I didn't expect much else but it would be nice to know that I could get a cheap DC to DC step down and have full beam without worrying about if it was going to collapse and turn off. I could also design a flash button too.

 

[Deleted member 4366]

If you send me your address by PM, I've got a few used 18650 cells that you can have. They're from laptop batteries, but I'll test them before I send them so they should have probably about 1.5aH each . You can put a few in parallel and then they'll last as long as you want.

My Cree T6 has a 4 pack of 18650s 2s2p and lasts at least 2 hours on full beam.

 

[Scottyf]

My Cree T6 has a 4 pack of 18650s 2s2p and lasts at least 2 hours on full beam.

I think this would have been better becasue the T6 clearly is a hungry little light. It will last for hours at the lower level but its just asking alot from the current cell.

Looking at the spec sheet for it...
CREE XM-L T6 Emitter by LED-TECH.de

Its min is about 280 lumens which is what I think the poor cell is cranking itself down to save itself from dieing. The only time I get full light is when its fully charges and can deliver the required Amperage.

As you say I could use a couple additional 18650 cells and make a pack for it which would probably be easier and safer than hardwiring it.

I could always put a couple balance leads and a JST lead for balancing the cells if they have no protection.

 

[Deleted member 4366]

I womder how mine works at 8.4v?

If you want to make a pack of 18650s, you just wire them all in parallel, so you don't need a balance lead. You'll still be able to use your existing charger, but it'll take a lot longer. You can also use your lipo charger set to 1S, which will probably be a bit quicker. Do you want me to send you some?

 

[Haku]

However the ultrafire 3000mah are really poor on test.

In trying to find a good source of 18650 cells (to re-cell my ebike battery pack) I've been doing a lot of websearching & reading of forums for other people's real world experiences of the various 18650 cells out there, candlepowerforums.com has perhaps the most user generated info on 18650 cells and the biggest thing I've learnt from reading & reading & reading is that the best 18650 cells are the Japanese made (Sony, Sanyo, Panasonic etc.) and the Chinese made ones don't compare.

Indeed, I'm near completion of making a 18650 charger which can charge/discharge/tell the capacity of 4 individual cells at the same time, so I bought 4 cheap "3000mAh" cells from China for testing purposes and 2 hold less than 1000mAh and the other two were dead, so I took the wrappers off the dead ones only to discover they're used Panasonic 17670 sized cells with plastic tubing and welded end caps to make them 18650 'sized'.
The 3 Panasonic 18650 cells salvaged from an old laptop battery which had been left discharged for a couple of years fair better at tested capacities of 1500mAh to 1800mAh.

 

[banbury frank]

Hi

I would strap one off these battery's on a rear rack problem solved

HAZE HZB-EV12-200EV 220AH CYCLIC AGM MOBILITY BATTERY | eBay

Frank

 

[Willin']

With reference to the performance of ultrafire batteries on test I looked at this link below. The results are very .....errr, illuminating.

Torchy the Battery Boy: 18650 Batteries / Chargers

 

[Deleted member 4366]

I bought a job lot of used laptop batteries. I opened them up and got 100s of cells for about £50. All the ones I've tested have been close to the specified aH on the datasheet. I've found no duff ones so far (after testing about 150). I don't know why the batteries were taken out of the laptops, but it can't be because the cells were worn out. I've converted all my big lead-acid battery searchlights and dry-cell torches to lithium - loads better.

 

[jerrysimon]

My Cree Q5 led focus just turned up

I must say I am blown away with the beam of this thing. I got one with a zoom so I can run it on a wide beam as I don't need a spot commuting across the city. Will be running it tomorrow for the first time on my dark commute home.

Mine can run on 3 * AAAs or a single 18650 cell if you use an extension ring. I have a few Konion 18650V cells left over from a failed o) project that came out of a 36v Makita drill pack. These are 3.7v nominal with a 1.5-1.6 Ah capacity. They can be discharged at 10C (15-16 amps) with very little drop in voltage.

I am panning to run this torch mainly on the lower setting (even that is about 10 times brighter than my Cateye) and will be testing how long I get on AAAs or the Konion cell. My current three led Cateye takes three AAAs and last about 60hrs but I am hoping with the Cree on the lower setting I get 4+ hrs with the 1Ah, AAAs or a minimum of 2.5hrs which is a weeks dark commute for me. If not I will pop a Konion cell in.

These things are dirt cheap (direct from China) at about £5.50 including a bracket but no cells. I am glad I went for this instead of a nine led upgrade to my Cateye which costs £20+.

Although I purchased this one for more in the UK I like them so much that I have ordered a few standard ones (without the luminated color ring on the bike ones) direct from China for my wife and daughters for the winter nights. They also do a much smaller one that uses a single AA cell or the 3.7v 14500 Li-ion cell.

Regards

Jerry

 

[Scottyf]

I also read that test on the ultrafire cells. Not good at all.

Tonight it has been alot better staying at max alot longer with no drop.
D8veh I will take you up on the couple of cells. I would imagine you can run the light at the higher voltage but I would imagine the heatsink for the led would need to be larger to allow the heat to release.

The torch as I said is good and lights up loads but it's being let down by a ropey cell. Which is a shame really because if I knew nothing about lithium cells I would have returned it back to the uk supplier.

I don't think I'd ever re cell with 18560 cells for an ebike battery. It just looks like to much effort. As you could just use rc lipo and re cell with that as they already have the balance leads you could parallel up.

But I guess getting the 18650'cells are quite cheap as well as being more robust if not heavier.

I'll let you know how I get on and how I parallel up the additional cells.

 

[NRG]

All the Cree lights I bought came with the 2s2p battery config but all have shown to have some imbalance, the worst set almost dumping me into a hedge one night when the light cut out after 20mins with me going at a fair old lick down hill! I've since fitted them all with balance leads, well worth doing...

 

[Scottyf]

Nicely done nrg!
Glad I'm not alone in getting something that works correctly and using a chemistry we use in our bikes already.

I'm now wondering if I can run mine at a higher voltage to squeeze more light out of it.
I should stop monkeying about with things.

 

[Deleted member 4366]

All the Cree lights I bought came with the 2s2p battery config but all have shown to have some imbalance, the worst set almost dumping me into a hedge one night when the light cut out after 20mins with me going at a fair old lick down hill! I've since fitted them all with balance leads, well worth doing...
[/IMG]

Thanks for that. Very interesting. I wondered how they dealt with balancing. That PCB under the end cap then is just LVC then?

 

[NRG]

Both I believe LVC and over charge protection. The S823x chip is one of a series of battery protection chips, the other two chips are dual N_channel MOSFETs used I presume to disconnect the battery when LVC of overcharge is reached....doesn't stop them going out of balance though!