Ultimate DIY Bike light

Hi Guys

I’m new to the forum and new to Lighting, im not sure if i have posted on the correct board but i have a few broad questions spanning a few topics:)

I’m currently trying to put together a cost effective bike lighting system, but wouldn’t mind some advice.

I currently have two ebay XML T6 LINK

The batteries are only 3.2 V (2 x 18650 in parallel)

I was thinking of changing the battery to an 8.4V 2S2P for each light (hopefully the driver in the Light will accept this)

Im assuming 8.4v is the preffered voltage to run at as most T6 bike lights have 8.4v packs ?

Batt option I’ve been looking at are

4GREER 3100mAh protected
AW 3100mAh Protected
EagleTac 3100mAh protected

A123 LiFePO4

Or a selection of lower mAh rated unprotected cells here..

and then I’m looking to mount the cells in a 2S2P holder either;

Protected (if im using unprotected cells)
Unprotected (if im using protected Cells)(i realise the link is 4P but you get the idea)

I already own a XTAR WP6 charger (should i get a better charger ?)
is there any benefit to charging individually ? or should i wrap the cells and do a make shift charging connector LINK

How would you do it ? is there a preferred setup ? am i on the right track ?

Cheers in advance

Welcome cat,

You can't assume the driver will take the voltage mate, you risk burning it out, tho it may.

Why do you want to do this anyway? Have you thought about using torches in a bike mount, this is prob the preffered setup of many cyclists here on BLF.

Hiya and welcome.

A few comments, hopefully helpful.

Don't assume that the ebay listing is accurate with respect to the batteries being parallel or series. Check them with a multimeter. (Reason I say is that most magicshine clones are running 2S or 8.4v nominal.)

If they turn out to be between 3.7 and 4.2 volt packs, don't double that voltage without expecting bad things.

You'll find lots of good batteries in the 2600-3100 mAh range. I don't know what battery is underneath the Greer, but the AW and I think the Eagletac are based on the well respected Panasonic 3100. You'll also find these in Callies Kustoms, Orbtronic and Keeppower as well as clear wrapped like here: http://hkequipment.net/index.php?sp=&p=6&cat2=163&cat1=1&cat0=2&id=1318&cat1=1&cat0=2&new=&more=&s=c4b15eab5589ee1b9c09fc113ab83445&lang=en

EDIT: cautionary note about the batteries linked above... very initial findings indicate that half of them have charged to 4.13v and the other half to 4.18v. This might be my charger setup, second grade batteries, or something else entirely. I don't know yet. Please don't buy them without doing a bit of research. Edit to my edit: turns out it was the charger being flakey. Ignore all this.

(apologies in advance if it sounds like I'm shilling for HKE... it's just that I got a battery order from them that took 7 days to arrive to the UK. Pure joy!)

You can find on ebay those protected holders wired 4P. Nice to have extra protection, but not essential, I'd say.

The unprotected holder you linked to might possibly be the same as the one DX sells, and if that's the case, it's kinda crappy. Flat top batteries like AW don't make contact on the positive side and the wire is flimsy.

Digikey has sturdy 18650 holders, but you'll pay the earth to get them shipped from America.

These: http://uk.mouser.com/ProductDetail/Keystone-Electronics/1048/?qs=%2f7TOpeL5Mz5jXkg8vI8Dyw%3d%3d exist at Mouser, but I don't know of anyone that's tried them. Worst case, I think you might need a strap, as they look shallow.

If you are using parallel packs, then you can jumper to the charger, but charging will take double the time for two batteries. (Or quadruple for four, etc.) If you are using series packs, the Xtar charger is out.

Only thing missing is some cabling: http://dx.com/p/5-4mm-male-to-female-extension-cable-for-sku-29489-30864-100cm-32751?item=11

You'll also find some y splitters if you want to run the two lights off one battery pack.

Hope that helps...

Hi Jeansy

I figured that if the Lights blew then i would just get some more as they only cost £10 each, im only assuming they would be rated to 8.4v as they appear identical to the the 8.4v version from the same seller but a little cheaper with the smaller battery pack.

Yes i did consider torches but thought the lamps and remote battery pack would give me more flexability in that i can move the battery weight off the bars and run a larger battery pack, i also plan to add a third light on a helmet mount so keeping the battery remote allows me to put it in my backback and save the weight on my head.especially as im continplating using a Fluxient 3x XML T6 which will require a hefty batt pack to run for 4hrs

That said im still open to options, i may go trawl ebay and see if i can find a 3x XML torch....

Hi Ruffles

Thanks for the responce and links looks like i will be safe with the panasonic based cells then, i will take a closer look at the holders but it certainly looks like i will need to mess about with them to get protected cells to fit and to waterproof (but thats just fine tuning once i can get the correct set up)

Interesting to here you say i can only use the Xtar charger for parallel, what would you use for serial ? the cheap Chinese lights come with a Serial batt packs and just a cheap wall charger which i would have thought would be worse than my Xtar charger ?

The difference is those cheap wall charger are set up to charge more than 1 battery in serial. As in the put out 8.4v to charge you 2s2p pack. If you want a triple xm-l a member here is going to be sellling a triple xml board with optics.

Cat, I bought dedicated lights first of all, I spent a bit of time on bikeradar and didn't heed DIYs suggestions of using torches instead but for my use, I soon gave up on the dedicated lights, they just don't do what I wanted at a reasonable cost.

My DX XML magicshine clones are too spotty and can't match what you get from a torch. For example the Roche F12 sits on my bars, small and unnoticeable, it has a great flood beam and renders trail colours much better. The light will run on high for about an hour and then I just swap the cell for one in the camelback. The Roche is so small and light you can easily helmet mount two of the and have two on the bars. If you want a little more range I also use a solarforce with intl-outdoor drop-in, which while a little larger, really is no issue on the bars.

I see the appeal with dedicated lights but they just didn't work for me. The best one I had used a MCE LED rather than XML which gave a nicer beam.

As Scaru mentions, PilotPPK is making up some awesome kit which if done properly will make a great light. If you do go DIY deffo look into these.

Thanks guys your input is greatly appreciated,

Iv just had a trawl through a few threads on here and the overwelming opinion is that torches will yeild a better light for my £/$

looks like it may be back to the drawing board

I suppose i dont have a problem changing cells every hour (after all i stop every 20mins for a rest these days)

ill have a search for PilotPPK system in short while.

A quick look on ebay has just brought these up

Torch 3 x T6, 4 x 18650 1.5Hrs run time 14.8V!

Torch 5x T6 compact

Torch 7 x T6 3.7V

Torch 3 x t6 14.4V

Torch 4 x T6 14.4V

As i already have access to cells and a charger its only the best mountable (handle bar and head) torch's that i need then really ohhh and a mount (are mounts available for the Fat torches ?)

I know im probably getting on dangerous ground of asking the same old questions 'whats the best touch ect' .. so ill go get myself acquainted with the search function for a while.

Jeansy - i forgot to say before... Nice Gixxer , i have a K8 750 :)

Cheers mate, its on Ebay this week, it has to go to fund a house move :( The 750s are awesome, i had an old one before the 1000, i may go back to one when funds allow.

As for torches, id stick with small single emitters and have several, heres a pick of my Reign ready to illuminate the forest...

The last pic looks useless but its on the 'standardish' BLF settings of iso400 F5.6 1\2sec. Pretty bright!

Yup, the normal magicshines do come with a regular wallwart, but I think (/hope?) that they've got balance charging smarts in the battery pack to permit that.

Talking about PilotPTK's emitter/driver, I think zemike over on the http://forums.mtbr.com/lights-diy-do-yourself/ forum was talking about making a 35mm housing... not sure where that is, production-wise. If you're handy with a soldering iron, you could also check out that forum for integrated driver/emitters by lux-rc.com (Quazzle) in a smaller zemike housing. The only curse is waiting for parts to arrive from all around the world.

Jeansy - I did not think it posibble, but i think i have Light envy !

Why do you say single emitters ? is it just a cost thing ? i would have thought several multilple emitters is best ?

Whats your prefered torch on your set up ?

Ruffles - Cheers for the link, a lot of useful info on that forum

i also just had a look at my xtar charger reviews and they seem pretty good even though it cant do serial, which is not to much of a problem now as it looks like i have been persuaded that torches are the future so no need for a batt pack now.

The small single emitters are much sturdier in the mounts and you can mix and match to get exactly what you want. I love the Roche F12 but running on high, temperature is an issue. I would recommend without doubt a Solarforce host with the intl-outdoor drop in, you can mix OP and smooth reflectors and the NW tint looks great. They are still small enough that good fixing works, try DH with a triple emitter torch and I doubt it will be with you at the bottom lol. Helmet mounted torches are also advised if the terrain gets bumpy

I had a look at a few torches last night, assuming that i should be able to find somthing that fits the bill easily. but its not working out that way !

I did have a look at the Roche F12 as its a good size for the bars (i could even fit 6 on) and has a good light but im concerned that a lot of cells dont fit and overheating may be an issue it seems.

my new set of requirments are:

  • 4 x torches to the bars (2 top 2 bottom) or 6 small torches (4 top 2 bottom)
  • Good sturdy construction as i ride spiritedly off road (lost batt connections seems common on those with end to end cells or their any multi cell torches that are side by side like the skyray king style?)
  • 2 x small tourch helmet mounted
  • Must accept protected cells 3100
  • Must be cablable of running for 1Hr minimum on max (i ride for around 3hrs)
  • Hand held temp is not a major issue as i will use gloves but must not overheat when used for prolonged periods

once i have the right torch i will try to source a sturdy handlebar mount to suit or i may even machine my own so im not worried about mount compatability at this stage.

i shall keep looking but if anyone has any recommendations that would be great :)

These seems to be a favorite on the Bike forums....

UltraFire WF-501B XM-LT6


So i can use these as a benchmark for single emitter single Cell

Cat I know it depends on your budget but the solarforce L2 or variation is really the equivilant of the Ultrafire 501b but much better quality. You can buy the entire torch from solarforce or as I suggest, just the host (body) and buy the drop-in (LED and driver) from intl-outdoor. Have a look around the forum for threads like must own lights and almost always a L2 type of solarforce is suggested more than any other light. They really are an upgrade over the UF. In the picture above the front facing torches, the left ones are a 502b top and L2 below. They are both p60 so drop-ins are interchangable. Search solarforce on facebook.

Same reason for single cell as single emitter, size and sturdiness suit a single cell light. Connections can also be a problem as you mentioned, springs at both ends help and tight fitting cells, so ones like the Xtar 18700s may work better.

I did have a look at the solarforce but i must admit i got a little lost at first with all the different options (L2, L2P, L2T, L2M then different bulb modules) and gave up but after some perseverence it seems i want a L2 or L2P , cost is not a huge factor (£25 L2P is ok),

Now the next question is what drop in ?in guessing a LC-XML and i guess i just need single mode ? but what volt ?

Iv had a look on intl-outdoor and only found this XML-U2 drop in.

Cheers for the help, im sure im asking a lot of newb questions

L2P with T6 on ebay ?

And these L2P kits

Well all was looking good on the SF L2P front until i read this - LINK

It seems the L2P may not take my protected 18650 3100

For the L2P body its narrow, as we got report, the CR123A are moving 
around problem, before, so verions 2011, we make it narrower

Reportedly SF L2P 2011 is available in 2 different inner diameters.

My L2P fits my protected Panasonic 3100 (clear wrapped from DX), it's snug but not gonna damage it, just keep it rattle free, perfect really. My L2P is fairly recent but not sure exactly when I bought it.

The drop in you link is the one, the U2 emitter is slightly better than the T6 for brightness but it is a cool tint. I personally went for the neutral T6 at 2.5a

So I'd suggest that drop-in with this body, cheap but great and I think it works better than the L2T for grip in the mount


Multi modes may be an idea as they greatly extend run time and a lot of the time medium is enough, especially when your riding up. But they do require more fiddling.

Thanks Jeansy, i think I'm going to go ahead and get the L2P (I'll just get two at first)

Im still thinking of a T6 the they seem to be prefered by many (I may get a 3mode)

Do you know the difference that the volt makes ?

A single 18650 is 3.2v so I guess the 3.7 - 8.4v is for a serial configuration ?


The T6 will only be preffered if its a tint the U2 is not avalible in or budget. The U2 is a better emitter.

Yes the voltage allows for multicell use on the 8.4v driver. A single cell will be between 3-4.2v ideally, they say 3.7 as thats nominal voltage.

Perfect, looks like I'm all set then ..

2x L2P host

2x U2 3mode 3.7v drop in

All I need now is a mount.

I'll hopefully get everything ordered tomorrow (before I go to the isle of man )