Modding with KPR bulbs

Please help me with these KPR questions:

I am trying to mod my cheap crappy bicycle frontlamp into something better. It currently use 2C cell alkalines side by side, and its stock PR bulb is a kryton 2.5 volts 0.5 A. 2C cells overdrives it by 0.5 volts.

I can't find KPR112s or 118s in my area, but I did found some Rayovac KPR113s and bought them. On the other hand, Maglite's Kryton bulbs are easily available but I am not sure of their voltage, they are listed as for 4 C/D cells, 5 C/D cells, 6 C/D cells, etc. I guess one cell is 1.5 volts. <font color="red">Q1 Can anyone please confirm this?</font>

So I bought the Rayovac KPR113, its stated as 4.8V, 0.75 A, 3.6 Watts, but its also printed 6 Volts. <font color="red"> Q2 Does this means that this Krypton bulb is 4.8 volts but meant to be overdriven at 6 volts?</font>

Initally I was thinking of using 4AA alkalines(total 6volts) or 4AA NiMHs (1.2V X 4 =4.8 volts), but seems that 4AAs can't fit into the casing. So now I am thinking of using 2 CR123As with spacers (total 6volts). The issue now is Lithiums are expensive, even though I managed to get cheaper ones. <font color="red"> Q3 How long will 2 CR123As last on this KPR113 bulb? Whats the formula to calculate this?</font>

I have another 2C flashlight that I wanted to put in 3 CR123s and change to a KPR 112 or 118, but since its not available at my aread, what would be the Maglite's Krypton equivalent? <font color="red"> Q4 Should I get the Maglite 5 cell bulb or the 6 cell bulb? </font>

Thanx a million!!

my KPR112 is rated for 6V 650ma. When I get some cash, after I find a job, im going to Direct Drive it off 3 123 batteries in a 2C mag to make a nice throwing light for around camp at the desert. Not sure how much you can push into one of those but they get bright when you overdrive them. /ubbthreads/images/graemlins/grin.gif

3.6 watts is a tone, your going to kill batteries dead in no time if that is right.

Thanx, please help me with my questions.

Too difficult to calculate values, can't really help....I jsut want somethign bright. Bulbs are cheap. Your is probably 4.8 V I guess, go by what it says on the bulb.

doing the 112 mod tomorow went to get the bulb today but they didnt hAVE IT but got my maglight ready and the batts in it .lol even tryied the stock bulb instant blow out 9 volts is a tad high for a 3 volt bulb but i didnt need the bulb anyways

I come across a number of bulbs with the 4.8/6V rating. I believe these bulbs can tolerate the overdrive, anyway they're cheap so I'd just give it a shot. Patience, patience, there is plenty of info on CPF, just let it bubble to the top /ubbthreads/images/graemlins/smile.gif

Your stated current is 0.75A, or 750mA. Theoretically, a 9V bulb requiring 0.75A will require 3 lithiums, but the battery will last as long as a 6V light requiring 0.75A and running on two lithiums, because there are more cells and each cell always delivers the same current. As long as you have enough cells to make up the correct voltage you can just take the current as-is.

For drain, look at the battery manufacturers' datasheets. Check duracell.com for their 123s (under Technical Information), there is a graph that gives runtime vs constant current drain rates. Based on the graph for their 123s, you are probably going to get as little as just 80-90 minutes of light from two lithiums. Assuming all else stays constant, I would buy a Surefire E2e and strap it onto the front of the bike because that gives me around 75 min runtime and a heckofalotmore light than the little KPR bulbs. Less fun than modding but very practical.

Do you happen to do a lot of riding at night? Even for those with cheap lithiums it could punch a hole in your pocket pretty soon. You may want to consider a rechargeable system. Luxeon 3W on 3 or 4 AA NiMH would be a great idea. You could even use a simple resistor if you don't need max brightness all the time, after all you can top off the cells any time.

The runtime formulas change slightly for rechargeable cells - alkalines and to some extent lithiums perform differently at different drain levels, but rechargeable cells perform consistently until you get to EXTREME drain levels of 3-5C (then you have a slightly different problem.). For a rechargeable cell I'd feel reasonably safe taking total capacity in mAH divided by current, that will give you runtime in hours.

A Lux3W pulling 700mA and 4AA NiMH pack would deliver something in the order of 3 hours on 2100 mAH cells (assuming constant drain. Direct drive/resistored setups have a falloff curve which extends runtime at the expense of brightness). Plus, guilt free lumens. Lux3s are no small fry either, at 65 lumens (750mA) or 80 lumens (1000mA) they are pretty darn bright - brighter than the KPRs, definitely. See my TWOL vs Mag-Num Star Xenon beamshot. No contest.

(edited to fix some numbers)

Thanx Justintoxicated, Thanx Raggie, Thanx kelvin!!! You know what, on that day and time you posted the Rayova mod thread is that day and about the same time I bought an exact same Rayova Industrial 2D for my kitchen drawer, and I have the same GP rechargables too! Yes, I usually cycle in the early mornings, evenings, and night, cause Singapore got a nasty hot weather its not really enjoyable to cycle in the day. I was planning for 4 AA rechargables but they won't fit into the light...

I am not getting an E2E, coz I am looking for a cheap economical system, hence planned to mod. So 2 CR123As will last about 90 minutes on a 4.8 volt KPR bulb?

Thanx a million!

Today I went out and done what I planned, let me answer my own questions:

A1 Yes, Maglite refers their bulbs by the number of battery cells they are meant for, instead of volts. Hence one alkaline cell is 1.5 volts.

A2 Yes the bulb is 4.8 volts, its mean for 6 volt lights, so its mean to be overdriven.

A3 Perhaps I will do a run test once I finished the current set of batteries and pop in fresh ones.

A4 I gotten and used the 5 cell bulb, so that the Krypton would be overdriven, I think it will be brighter to overdrive a 5 cell bulb than use a 6 cell bulb. Kryptons are often overdriven right? Anyway I also saw Maglite's 6cell(9watt) Xenon bulbs, but did not buy it. They cost SGD$7.50/- per bulb, compared to SGD$3.60/- for two 5cell bulbs.

Very happy with the results, I used 2 CR123As for my bicycle headlamp, I used the PVC pipe with the screw and nut trick to turn the CR123As to C cell size. It's very bright, now my bicycle headlamp looks a motorcycle headlamp.

I used the Maglite 5 cell bulb on my 2C Maglite. 5X1.5=7.5 volts, popped in 3 CR123A (3X3volts=9volts), hence overdriving the light by 1.5volts, very bright!!! At last an amount of brightness befitting a flashlight of this size. Nearly as bright as my Streamlight TL3 Xenon, except the Mag's bigger and hevier, and the corona is smaller than the TL3 and not as smooth. The CR123As are housed by using a sleeve made from PVC pipes and I replaced the tailcap's 2cell spare bulb with a spare 5 cell bulb too. I am going to put this into my workbag. /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif /ubbthreads/images/graemlins/smile.gif

[ QUOTE ]
SJACKAL said:
Please help me with these KPR questions:

I am trying to mod my cheap crappy bicycle frontlamp into something better. It currently use 2C cell alkalines side by side, and its stock PR bulb is a kryton 2.5 volts 0.5 A. 2C cells overdrives it by 0.5 volts.

I can't find KPR112s or 118s in my area, but I did found some Rayovac KPR113s and bought them. On the other hand, Maglite's Kryton bulbs are easily available but I am not sure of their voltage, they are listed as for 4 C/D cells, 5 C/D cells, 6 C/D cells, etc. I guess one cell is 1.5 volts. <font color="red">Q1 Can anyone please confirm this?</font>

So I bought the Rayovac KPR113, its stated as 4.8V, 0.75 A, 3.6 Watts, but its also printed 6 Volts. <font color="red"> Q2 Does this means that this Krypton bulb is 4.8 volts but meant to be overdriven at 6 volts?</font>

Initally I was thinking of using 4AA alkalines(total 6volts) or 4AA NiMHs (1.2V X 4 =4.8 volts), but seems that 4AAs can't fit into the casing. So now I am thinking of using 2 CR123As with spacers (total 6volts). The issue now is Lithiums are expensive, even though I managed to get cheaper ones. <font color="red"> Q3 How long will 2 CR123As last on this KPR113 bulb? Whats the formula to calculate this?</font>

I have another 2C flashlight that I wanted to put in 3 CR123s and change to a KPR 112 or 118, but since its not available at my aread, what would be the Maglite's Krypton equivalent? <font color="red"> Q4 Should I get the Maglite 5 cell bulb or the 6 cell bulb? </font>

Thanx a million!!

[/ QUOTE ]

Congratulations on your mods, now you've started on a path from which there is no return /ubbthreads/images/graemlins/smile.gif About the E2e, I agree with you about cost, and the other half is the fun. I am planning to buy a C2 sometime in the future, but it's not quite the same as breaking out the soldering iron.

I tend to like the D-cell lights because I can easily pop a 2AA adapter in. 3AA is possible but not as cheap as those I can pick up locally. C-cell lights pose a slightly different challenge but one I see you've solved very nicely. I used to cycle a lot, and when dark fell it I was usually left in the dark. What bike lights I had in those days were awful... I can only look back and wish I had then what I do now.

Good call on the Rayovac, even in stock form it is quite a good light. It has potential, though. Mags have even more thanks to the availability of heatsinks from some well known CPFers, making for a very simple conversion requiring minimal tooling (soldering iron, hacksaw, that's about it). If you like the 2C Mag, you can give the Space Needle style mod a try. SNs were manufactured by Mr Bulk, but I don't think they're available any longer. You can build your own though.

The cookbook recipe would probably be Mag2C, 3x123 sleeved with 1" PVC pipe, Hotlips C or O-Sink C (heatsink), Luxeon FIVE watt emitter and 3 ohm 2 watt resistor for ~90 minutes (700mA), or 4 ohm 2W resistor for ~150 minutes (525mA). The Luxeon 5Ws put out a frightening amount of light at 700mA (more than twice as bright as your bike light), and you can stretch that to 150 minutes for just a little less light.

Wow, I need to learn more about the sinks then, and luxeons are not readily available here...

What is hotlips C and O sinks? Where can I read more about them?

Thanx. /ubbthreads/images/graemlins/grin.gif

The W-bin 5 watt Luxeons are very hard to come by but put out something in the range of 130-190 lumens. V-bin 5Ws tend to give you something like a max of 120 lumens but can be readily had from the Sandwich Shoppe. As you can probably guess W-bin Lux5s are hot property. I have one, somewhere in my future.... /ubbthreads/images/graemlins/grin.gif

If you want something cheaper, you can opt for a 3W Luxeon (Lux3) at 65-80 lumens. This one drives well on 3 C/D cells (direct drive, recommended only if you know what you're doing) or 4 C/D cells with resistor (recommended if you want to play safe). My TWOL setup is a Lux3 with resistor and currently 4 cheap carbon-zinc batteries for a lot of light with very little feeding. I'm doing up a webpage that provides guidance step by step, coming soon.

The Hotlips is a heatsink that facilitates mounting of the Luxeon in the Mag, and transfer of heat away from the LED before it cooks. http://hotlips.hotbeam.com. If you have problems getting Luxeons, he can supply a Lux3 with the heatsink. C and D are for the various sizes of Mag.

The O-sink is made by another CPFer called Yaesumofo, and they are functionally identical, now available in C and D flavors.

when you find one try the 112 bulb in the 2C mag with 3x123, I got mine at radioshack I don't know if they have those over seas. I'm still dying to do this mod, but 2C mags are hard to find and Home depo wants like $16 for a 2C mag /ubbthreads/images/graemlins/rolleyes.gif

I use M*g 5cell Krypton bulbs with 3x123 with nice results.

As to the beam shape problem, search about Writeright and Acrylite on this site. I have a couple Acrylite lenses on my best M*g mods. I have Writeright on many other lights. Both ways are NICE!!!!

I find the beam quality acceptable, perhaps will try Writeright if I can find the monochrome ones, I am also using the 5 cell krypton bulbs with 3XCR123A getting good results. Its brighter than a King Pelican 8D searchlight, thought I am using new batts and not sure if the King Pelican is running low on batteries.

I paid about SGD$39/- for a 2C here in Singapore, which is about USD$22/-. Right they are hard to find so I got no choice, 2Ds are more common. Can anyone knows of any article or tutorial to diy a D to 4AA converter?

If you're asking about a 1 D cell to 4AA converter, that's going to be difficult. I've heard many a source say that it's not possible without boring out the inside of the Mag.

If all you need is a total of 4 AA cells, thought you saw that one already :


Buy two cheap AA battery holders, they are an almost perfect match for the height of D batteries and they are the correct size. You can either place them on a plastic backing like I did, or just drop them in. Ensure they do not short each other (hence the foam padding). Mine are hardwired in series as you can see from the soldering work, but you can simply add metal spacers at the top and bottom and solder the respective red/black leads to them to make direct drop-in D cell replacements that will work with any D cell light.

Wait a minute Kelvin, what about glueing those two AA battery holders back to back, will they be bigger than a D cell in this way? If so, how about 4AAAs? Maybe get two double AAA battery holders and glue them back to back? Then we will have a 4AAA to D cell conversion, hence 2D cell light becomes 8AAA = 12 volts!

I tried holding the two of them together back to back, and indeed they won't fit. Your idea for 4AAAs is a good one, in fact, it gives me an idea that you might be able to use - why not try fitting a 2AAA adapter inside your bike light C cell housings? That's what I do with 2AAs and D cell housings.

Elektrolumens.com has a 3AA to D adapter that fits D cell lights. 9V in a 2D platform.. very nice. Actually, wherever I can use AA cells, I find myself using NiMH rechargeables so that I can enjoy the light more and worry less about how much it costs to run, so that would give me around 7.2V, realistically closer to 7.5. Then we do things like put 5W Luxeons on their heatsinks (5Ws require something like 6.9V minimum, 7.5 is a comfortable fit) and get an unbelievable amount of light in a tiny, rechargeable package with 3-hour or longer runtimes.

My main objection to AAA cells is their miserable capacity. Most common rechargeable AAAs come in either 700 or 800mAH capacities. Driving a Lux3 off 4 of them with a 700mA current drain will result in 700/700 = 1, that's just 1 hour of runtime before you have to throw the cells back in the charger. A good AA on the other hand will give you as much as three times the capacity (2100mAH).

Still, if I didn't have a choice, I'd use them. Give the 2AAA-inside-a-C-housing idea a shot. It might save you a lot of lithium batteries.

http://www.candlepowerforums.com/ubbthreads/showflat.php?Cat=&Number=607438&page=9&view=collapsed&sb=5&o=&fpart=1&vc=1
/ubbthreads/images/graemlins/thumbsup.gif

Thanx Kelvin, you got a good idea!

Yeah, AAA have low capacity, but if you buy the AAAs by the boxes from clearance sale, they are not exactly that expensive compared to CR123s.

Whats the difference between running 4AA in series and 4AA in parallel?

The Rayovac 2D Industrial you are modding now, I find that I can drop in 4AAs side by side just by themselves without adaptors, they fit into the flashlights D size tube rather nicely. So if I first drop in a flat metal disc (D cell diameter), put in the first 4AAs, then drop in another metal disc, then another 4AAs, then another metal disc again and screw in the tailcap. Will this work? Whats the different between running in series and parallel? If I did not put in the center metal piece, then it becomes 2 AA in series and with 4 parallels of them.