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  1. #1
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    Marwi ViewPoint Mod

    I have this light kit that someone gave me. The light isn't very bright and the battery packs wont hold a charge. I would like to convert this to use a DX P7 LED drop in. I priced out the part and it seemed more expensive that to just buy a new MagisShine Kit. I know people convert these so there must be an economical way to do it and thought I would post here.

    I am pretty good at building stuff but I will admit that I am not an electronic guru. I was hoping someone could point me in the right direction as to what parts I can reuse and a parts list of what extra I will need.

    I want to build at lease one 4 cell battery pack and I have read that balanced charging and discharging can be a challenge. Any advice would be appreciated.

    Thanks,

    David
    Attached Thumbnails Attached Thumbnails Marwi ViewPoint Mod-light.jpg  

    Marwi ViewPoint Mod-pscloseup.jpg  

    Marwi ViewPoint Mod-components.jpg  

    Marwi ViewPoint Mod-pbcloseup.jpg  


  2. #2
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    Sounds like you want to speak to El34 :-)

    http://www.hoffmanamps.com/MyStore/p...age=BikeLights

  3. #3
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    A great place to learn the basics about batteries is http://batteryuniversity.com/.

    Others will correct me is I err. NiMH have a lifespan dictated by basic design, time, treatment, and termperature. This is the 'older' Marwi light body, I have no idea when the last of these was sold, and the prior owner may have replaced packs, but I'm guessing they are so old that is is not surprising they no longer hold a charge. Actually older NIMH cells lost charge in storage normally. It is a matter of how fast. What may be surprising is that they take a charge at all. They will in all likelihood, not be recoverable.

    So you will need new packs. NiMH were great compared to SLA (sealed lead acid), but the newer Li technologies hole more power in less weight at competitive cost. The charger needed is different. So you need battery pack(s) and charger(s),

    EL34 is a great guy and since you have one or more mounts, and a light head, your shopping list is smaller than some. The P7 in his setup is within 20% or so of a triple XP-G and with the reflector, better placed light so the result is a draw. Simple battery, holders, charger, and driver setup, too. No balancing needed you charge each pair of cells.

    The thread for EL34 light:
    http://www.candlepowerforums.com/vb/...d.php?t=220241

    My Bullet shaped (newer Marwi Thread (to show I relate to your situation):
    http://www.candlepowerforums.com/vb/...d.php?t=260534

    A thread converting your style light with a triple XP-G light engine (LED + driver):
    http://www.candlepowerforums.com/vb/...d.php?t=288706

    A thread of your style light with copper pipe cap heat sink:
    http://www.candlepowerforums.com/vb/...d.php?t=254367

    A quad conversion:
    http://www.candlepowerforums.com/vb/...90#post3073690

    A thread discussing the copper pipe cap heat sink approach:
    http://www.candlepowerforums.com/vb/...d.php?t=252568

    You can search this forum yourself. Have fun.

    EL34's heat sink is cheap relative to the time adapting a copper pipe cap. His reflector is proven. His P7 star looked to be a fair price, though you might find better elsewhere. The charger and batteries ditto , but shipping from one place has economy, too.

    You are unlikely to undercut the MJ-808 price by much, if at all since you need batteries, too. If you ordered from Geomangear.com, you would be well backed. However, you would not have the same sense of accomplishment that building/modding one yourself brings. With care, it should be a better light. You would also be versed enough to upgrade it again if you wish.

  4. #4
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    Thanks for the links gents.

    Regarding what is re-useable in that pile.

    The Black Marwi light shell with the slide on mount
    Possibly the switch.
    The wires if you want to continue to use the trailtech connectors

    Other than that, not much you can do with the rest of it.

    A new Magic shine will be cheaper to buy than to buy the parts to mod that light, buy batteris and a charger, plus all the labor
    And you must have the DIY skills to do all that.

    see this page for Marwi mod ideas.
    http://www.el34world.com/Misc/bike/BikesLights1.htm

  5. #5
    MHC
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    Pics show one of many Marwi nightpro conversions I've done, if using the batteries in your picture you'll need a boost driver like the Maxflex from www.taskled.com & the alloy heatsink is just a bit of ally bar turned down to be a nice tight fit in the housing.

    I think the cheapest/easiest way would be one of El34's kits from the link in the post above or you might get lucky finding a drop in module on the DX/KD websites DIY sections.





    Last edited by MHC; 10-23-2010 at 11:52 AM.

  6. #6
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    This is what I am thinking. I would love any feedback.


    Purcahase this from El34

    HeatSinkMarwi Machined heat sink with screws
    R1Machined 35mm Machined reflector
    Glass34.8mm 34.8mm Glass Lens


    Purchase this from DX

    20330 Regulated CV/CC LED Driver Circuit Board for Cree MC-E/SSC P7 Emitters (8.4V Max Input)
    5790 TrustFire Protected 18650 Lithium Battery (2500mAh 2-Pack Blue)
    12721 SSC P7 C-Bin LED Emitter with 21mm Heat Sink Base (3.6V~3.7V)


    Stuff I already have

    Dual battery charger that El34 uses.
    Housing
    Switch,
    Battery connectors
    Helmet Mount


    I would build battery pack using 4 TrustFire Protected 18650 connected in parallel and modify my charger to use trail tech connectors I already have.

    This all seems doable and for under 60 bucks. My question at this point is about the driver. It accepts 8.4V but I am assuming that my 3.4V pack will be fine too? It doesn't specifically state what the output voltage is but I assume it is 3.7 since thats what the SSC P7 needs.

    This driver seems to be a single mode driver which is what I want. I want high and off, that's it, simple. I am assuming that hooking this up is just a simple inline connection?

    As a side note, I was wondering, when you have a multi mode driver, do you need a multi-mode switch too?

    Thanks,

    David

  7. #7
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    I've used that driver in the past with the multmode slave board too, it is a buck driver so the input voltage will need to be higher than the output voltage, ideally you should power it with 7.4v

    On the back of the board, the inner contact is positive, the outer ring is negative.

    With regards to the modes, for the multimode version of this particular driver, the modes are changed via cycling the power, you can do this on either the latching switch, or via another momentary push-to-break (NC) switch inline.

    A lot of the higher end drivers (taskled) will use a momentary push-to-make (NO) to change the mode etc.

  8. #8
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    OK thanks for the info. I will wire my battery pack in series/parallel then.

    I found this 18650 Lithium Ion 4 cell battery holder at digikey for under $3. I have orders sensors from them before and they are easy to work with.

  9. #9
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    MHC,
    Cool idea on the slug.

    Looks like the slug is almost as wide as the flat area inside the shell.
    Does your optics stick out past the threaded area once the whole assembly is in place?

  10. #10
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    MHC,

    What LED is that? Can you post a link to where you got it?

    David

  11. #11
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    One more question. El34, if I wire my pack in series/parallel can I still charge the pack with a mod'd charger like the one you have on your website? I have that same charger from DX and was planning on mod'ing it the same way you have accept using the trail tech connectors.

    Thanks,

    David

  12. #12
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    No, the charger is designed to charge a 3.7v battery with a cut off voltage of 4.2v.

    You will need to either buy a charger designed for a 7.4v battery, or remove the cells for charging.

    http://www.batteryspace.com/smartcha...ackseries.aspx

  13. #13
    MHC
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    El34 - the slug is just long enough to allow the optic/LED board to fit in to the housing & screw the the front on, the rear of the slug is chamfered to sit in the angled part of the housing, I use Bflex drivers & have the temp monitor set to 50C, in doors at 20C they dim after about 6 minutes from cold but on the trail they rarely dim at all here in the UK.

    djonesax - its just the standard Cutter MR11 kit http://www.cutter.com.au/proddetail....=cut890&cat=41
    Last edited by MHC; 11-09-2010 at 12:14 AM.

  14. #14
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    What is the lumen rating on that? How does that compare to the p7?

    David

  15. #15
    MHC
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    Anywhere from 700 for triple XPE to 1300 for a quad XPG I'd say better than a P7 because of the lower drive current & cooler running.

  16. #16
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    I have been researching this a lot over the past couple weeks, I have spent a great deal of time on El34's website and the Cutter site. I have the same MTE SSC P7 flashlight that EI34 used on his first Marwi conversion. I was thinking about taking mine apart and doing the same thing but I got to wondering why that was not good enough and he build another which included a fairly elaborate driver set up. I am wondering what, pitfalls there are to be considered if I were to build a light like his fist build.

    Thanks,

    David

  17. #17
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    I built those flashlight conversions before I figured out that the Marwi Halogen lights could be converted to P7 lights.

    Lots of lathe work is involved in the flashlight conversions and you still have to make some sort of mount.

    All that goes away using the Marwi shells.

  18. #18
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    Thanks for the quick reply. I was actually talking about the fist Marwi conversion you have on your website using the guts of a MTE P7 LED flashlight.

    http://www.el34world.com/Misc/bike/BikesLights8.htm

    I was thinking about purchasing the heat sink from your website and then based on that link above, I have all the other parts.

    Thanks,

    David

  19. #19
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    Cool,
    Let the fun begin, eh?

  20. #20
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    El34,

    In the mod http://www.el34world.com/Misc/bike/BikesLights8.htm....

    Am I correct to assume that if I only want to run the light at high power that I do not need a driver as long as my pack is wired in parallel? Since my pack will output 3.7v and that is what the light wants, am I good with out a driver?

    David

  21. #21
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    I have run them without current limiters before.

    The current level can be quite high on a freshly charged pack, for maybe the first 30 minutes.
    I have seen 3+ amps without a current limiter.

    After that, the battery pack voltage drops down enough to lower the current.

    If you keep the light super cool with lots of air it may be ok, but I am guessing that the P7 may have a shorter life.

  22. #22
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    What about the flashlight itself, doesn't it have a driver that I can salvage? Currently I am using my MTE flashlight as a bike light which I have mounted to my helmet. Works great, but it's heavy.

  23. #23
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    Quote Originally Posted by El34
    I have run them without current limiters before.

    The current level can be quite high on a freshly charged pack, for maybe the first 30 minutes.
    I have seen 3+ amps without a current limiter.

    After that, the battery pack voltage drops down enough to lower the current.

    If you keep the light super cool with lots of air it may be ok, but I am guessing that the P7 may have a shorter life.
    This is interesting. I've not heard of someone doing this before. If you used an SST-50 instead of the P-7 you might get near 850lm for 20min or so before the voltage/current began to drop. I'm not sure however if this is good for your batteries. The SST-50 can easily handle the current though. Wither it can handle the entire voltage drop of battery remains to be seen. Still, I would love to see a "Ghetto" set-up like that in action.

  24. #24
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    What about the flashlight itself, doesn't it have a driver that I can salvage? Currently I am using my MTE flashlight as a bike light which I have mounted to my helmet. Works great, but it's heavy.
    None of the simple MTE flashlights I own have drivers in them.
    They run direct off the battery.

    The two way flashlights that I have owned have just a resistor for the low setting.

  25. #25
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    Quote Originally Posted by El34
    None of the simple MTE flashlights I own have drivers in them.
    They run direct off the battery.

    The two way flashlights that I have owned have just a resistor for the low setting.
    So here is my thinking, albeit ghetto... I am currently using the MTE flash light as a bike light and it works perfect for me with the exception that it is heavy. I rode an hour in the pitch black yesterday on a full battery and had plenty of battery and light to spare at the end of the ride. I am only night riding because of the time change and cold weather goes along with that around here so cooling wont be a huge issue for me. The flash light stays cool as it is now in this weather. My only complaint is the form factor of the flash light and the battery life. I have this Marwi housing which has a much better form factor. If the flashlight has no driver and it works well for me, then I think I'm going to just gut an MTE and put it into the Marwi housing. I hate to be ghetto but I am also looking for easy!

    I want to keep my packs in parallel and It seems that unless I build a driver like El34 I am stuck with driver that requires a higher voltage.

    David

  26. #26
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    The no driver method only works when the LED can run with the max current able to be delivered by the battery. That is why the single 18650 cell P-7 flashlights work. The discharge rate of the 18650 does not exceed the 2800mA that the P-7 is designed to run at.

    Be very careful about running multiple 18650s in parallel with no driver. When you parallel the cells you double the available current (not truly double, but close enough for this discussion). Your P-7 that ran so nice on a single cell will likely pop on a 2 cell parallel pack and certainly on a 3+ pack.

  27. #27
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    Quote Originally Posted by Vancbiker
    The no driver method only works when the LED can run with the max current able to be delivered by the battery. That is why the single 18650 cell P-7 flashlights work. The discharge rate of the 18650 does not exceed the 2800mA that the P-7 is designed to run at.

    Be very careful about running multiple 18650s in parallel with no driver. When you parallel the cells you double the available current (not truly double, but close enough for this discussion). Your P-7 that ran so nice on a single cell will likely pop on a 2 cell parallel pack and certainly on a 3+ pack.
    Thats good information! I originally was going to use this driver but was wanted my packs in parallel so I could continue to use my charger.

    http://www.dealextreme.com/details.dx/sku.20330

    Also from what I read parallel packs are safer than series packs.

    At this point I think what I will do is get that driver and use series packs made from holders so I can take the batteries out and charge them individually. Unless someone knows of a a driver that will do what I need.

  28. #28
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    Be very careful about running multiple 18650s in parallel with no driver. When you parallel the cells you double the available current (not truly double, but close enough for this discussion). Your P-7 that ran so nice on a single cell will likely pop on a 2 cell parallel pack and certainly on a 3+ pack.
    yes, in theory

    In real life I have run 4x18650 battery packs direct drive
    Like I said above, I have seen the P7 run 3+ amps and you may be shortening the life of the P7.

    Another way to look at it is that it is the brightest P7 I have ever run which was really bright and really nice. Also P7's are down to $13 at Dx, so take your chances and if the P7 last 30 hours, throw in a new one.

    A really simple current limiter is two or three resistors in parallel to bring down the current.
    Maybe .1 ohms (point 1 ohms) or less is all you need.

  29. #29
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    Quote Originally Posted by El34
    yes, in theory

    In real life I have run 4x18650 battery packs direct drive
    Like I said above, I have seen the P7 run 3+ amps and you may be shortening the life of the P7.
    A really simple current limiter is two or three resistors in parallel to bring down the current.
    Maybe .1 ohms (point 1 ohms) or less is all you need.
    Yes, my response is partially in theory. The reality is that it can work depending on circumstances. The selection of wire gage and length in a low voltage, high current application like this can be enough resistance that determines whether the LED lives or dies.

    My first LED experiment was to take a 3W 3 AAA direct drive LED module and put it in a 3D Mag light. I didn't understand the current issue at that time. 4.5V is 4.5V right??? Quick little flash and that was that.

  30. #30
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    yeah, for sure.
    The wire gauge, the wire length, every solder joint and every connector can add up to a resistance that will act as a current limiter.

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    Quote Originally Posted by Vancbiker
    Your P-7 that ran so nice on a single cell will likely pop on a 2 cell parallel pack and certainly on a 3+ pack.
    I've got faulty P7
    It didn't pop when ran direct-driven from 4 parallel 18650. Seriously, everything was ok (except heat).

  32. #32
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    El34
    Can you make a light to sell with just resistors as current limiters. (and on/off switch)
    I assume it would be much cheaper. You could put them in the newer Marwi bodies.
    _______________
    1x10 IS SO FINE on my 21.9 lbs IBIS SL-R
    11-36 XTR in the rear, 36T wide-narrow upfront

  33. #33
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    Quote Originally Posted by El34
    yes, in theory

    A really simple current limiter is two or three resistors in parallel to bring down the current.
    Maybe .1 ohms (point 1 ohms) or less is all you need.

    Why run them in parallel when I can purchase a single .1 ohm resister? Is it for longevity?

  34. #34
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    Quote Originally Posted by djonesax
    Why run them in parallel when I can purchase a single .1 ohm resister? Is it for longevity?
    Resistors in parallel decrease resistance but increase watt capacity. ie. two 1ohm by 1watt resistors in parallel result in .5ohms by 2 watts.

  35. #35
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    Quote Originally Posted by Vancbiker
    Resistors in parallel decrease resistance but increase watt capacity. ie. two 1ohm by 1watt resistors in parallel result in .5ohms by 2 watts.
    Thanks, believe it or not I'm learning a ton here!

    Next question... I was looking at the wattage of the p7 and under Power Dissipation I see 11.8 watts is that correct? I can get a .1 ohm 10W resistor at digikey for 2 bucks. I am not sure though if that means it will add 10W of resistance or if that means it will allow 10W though the resistor.

    Also, I found this cool resistance calculator but I don't know the voltage drop after the p7 LED. But using .1 ohm as the resistance value I can figure out that it might be 3.32 volts. Does any one know the voltage drop after the p7 LED so I can properly calculate the amount of resistance I need?

    Thanks,

    David

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    W is for Watt, not for resistance. Resistance is measured in Ohm. The voltage drop is about 3.4V for the p7 emitter.

    You use Ohm's rule to calculate resistance. U=R*I where U equals voltage (i.e. battery voltage - voltage drop), R is resistance and I is current.

    You calculate the wattage using the formula W=U*I (or W=U^2/R, or W=I^2*R)

    So at 2.8A and Vf=3.4V W=9.5W in the led.

    The resistance you should use depends on battery voltage.

    Example:
    3.7V battery

    Vr=3.7V-3.4V=0.3V
    Ir=2.8A
    Wr=2.8A*0.3V=0.83W => 1W resistor

    R=U/I=0.3V/2.8A=0.1Ohm

  37. #37
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    Quote Originally Posted by xyz-saft
    W is for Watt, not for resistance. Resistance is measured in Ohm. The voltage drop is about 3.4V for the p7 emitter.

    You use Ohm's rule to calculate resistance. U=R*I where U equals voltage (i.e. battery voltage - voltage drop), R is resistance and I is current.

    You calculate the wattage using the formula W=U*I (or W=U^2/R, or W=I^2*R)

    So at 2.8A and Vf=3.4V W=9.5W in the led.

    The resistance you should use depends on battery voltage.

    Example:
    3.7V battery

    Vr=3.7V-3.4V=0.3V
    Ir=2.8A
    Wr=2.8A*0.3V=0.83W => 1W resistor

    R=U/I=0.3V/2.8A=0.1Ohm

    OK great, more good info!

    It took me a while but I think I understand. My question now is about the the wattage to the LED. If I need to run multiple resisters in parallel to achieve greater wattage, what wattage am I trying to achieve? Each resistor I place in parallel reduces the resistance and increases the wattage. So will I actually need multiple higher ohm resisters?

    How do I get a 3.7v 9600mah battery pack to output 3.7v limited to 2800mah at around 10w? Is that even possible or do I need to jump up to 7.4v and use a 1.5ohm resister?

    Does the P7 LED acually need 10w as I have read in other articles?

    Whew....

  38. #38
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    The wattage is really only a product that depends on the current you want to feed the led with and the voltage over the component. As long as you have enough cooling at the led you don't need to thing about the wattage in it. But the resistors have to stand the wattage in them.

    In a serial circuit the current is constant.

    You want to limit the current to 2800mA, not mAh. mAh (or really Ah) tells you the total "amount" of current there is in the battery. A 9600mAh battery can theoretically provide 2800mA for 9600/2800=3.4h.

    If you are going to use the 3.7V battery with the P7 emitter you want to burn that extra voltage in the resistor, since the voltage drop (Vf above) in the led is 3.4V. Therefore the voltage over the resistor is (battery voltage - Vf)=3.7V-3.4V=0.3V

    Your wanted current is 2800mA (=2.8A).

    Ohm's law tell us that resistance=voltage/current.

    => R=0.3V/2.8A= 0.1Ohm

    The resistance needs to be 0.1Ohm to make the current 2.8A

    The wattage in the resistor is calculated: Wattage=Voltage*Current

    Therefore: W=0.3V*2.8A=0.84W

    The resistor has to stand at least 0.84W, but we want to go up a bit so a resistor that stands 1W seems good.

  39. #39
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    Resistors in parallel decrease resistance but increase watt capacity. ie. two 1ohm by 1watt resistors in parallel result in .5ohms by 2 watts
    Exactly.
    And with space being at a premium inside, small 1/2watt resistors is parallel seem to work out the best.

    Also, it's difficult to find exact values when you get down into the 10ths of an ohm region, so doing the parallel thing lets you come up with customs values.

  40. #40
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    Alright, I think I finally understand this enough to make it happen. I have learned a lot from this thread, thanks.

    I was talking to a guy the other day and he suggested instead or resistors, that I could use a voltage regulator like the 7805 if I could find one around 3.6V. Would are everyones opinions on that?

  41. #41
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    Quote Originally Posted by djonesax
    Alright, I think I finally understand this enough to make it happen. I have learned a lot from this thread, thanks.

    I was talking to a guy the other day and he suggested instead or resistors, that I could use a voltage regulator like the 7805 if I could find one around 3.6V. Would are everyones opinions on that?

    You can get a constant current driver for <$5 shipped. So either go with 20 cent resistor solution or get a proper driver. The voltage regulator isn't what you want anyway, it's regulated constant current (i.e. driver).
    Long Live Long Rides

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    I don't think I can use that driver because I am planning to build my packs in parallel which means my input voltage wont be high enough.

    David

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    Hi MHC,
    Would you happen to have the dimensions of the alloy slug you made for your Marwi conversion? I have a similar conversion I'm tackling but it sounds like you've done the work with a mirometer already!
    ta,
    Savvas

  44. #44
    MHC
    MHC is offline
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    32.54mm is the ID of the housing but I just turned the alloy bar down on a lathe until the Marwi was a nice tight fit, then parted off & added the chamfer.

  45. #45
    Carbon8er
    Reputation: El34's Avatar
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    Jan 2009
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    1,329
    I read 32.59mm on my digital calipers.

    That's the difference in calipers (mine are cheap chinese) or the difference in the housings.

    So, what you really have to do is cut an over sized slug and then turn it down on the lathe until you get to a diameter that you can press into the housing nice and tight.

    That's why I cut the rough slug on my CNC and then trimmed it down on a lathe.

    It gets down to removing 1/1000" (inches) at a time when testing the slug fitting to the housing.

    Loop: Test slug fit in housing -> too large -> remove another 1/1000 -> repeat loop

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