Need help with a new mod

[3D black mag]

Hi Im relatively new to modding Ive only made a few direct drive lights and Ive decided to make a p7 maglite but I need a little advice. My host is a 3D black maglite I am using a C bin p7 led from 4sevens.com and a p7 heatsink from 4sevens.com. For the batteries for now I am going to be using two NiMh 12,000 mah CTA D cell batteries and one NiMh 4,500 mah radioshack battery all are rechargable. I know its probably not good to mix two kinds of rechargable batteries but for now due to a small budget it will have to due. And I am using a glass lens from DX.I already have all the listed parts.

It is going to be a direct drive light I think. But here are some of my problems and questions.first and most important is the anodizing on the heatsink is thin and has spots of metal which will short out the p7 because the heatsink contacts the inner wall of the maglite which is negative and the positive slug on the bottom of the p7. I need a heatsink compound that is non electrically conductive that will conduct heat and hold the LED in place on the heatsink. I was thinking maybe something from Dow Corning but im not sure. I only need a small amount and it can't be over ten dollars.

I was also thinking of maybe putting a circuit board in it nothing fancy no more than five modes if any. It also has to be less than ten dollars . And as small as possible no more than 10mm tall and under 18mm wide any suggestions. And one last thing can someone explain to me about mah and amps I have been told two different explainations are they the capacity of the battery and can two many mah or amps hurt a bulb lets say 28.5 to 36 amps to a p7 if I cant find a circuit. Can someone please help?

 

[DM51]

Welcome to CPF, 3D.

We have a sub-forum which deals with Homemade & Modified lights, so I'm moving your thread there - I think you'll get a good response.

 

[Benson]

Hi Im relatively new to modding Ive only made a few direct drive lights and Ive decided to make a p7 maglite but I need a little advice. My host is a 3D black maglite I am using a C bin p7 led from 4sevens.com and a p7 heatsink from 4sevens.com. For the batteries for now I am going to be using two NiMh 12,000 mah CTA D cell batteries and one NiMh 4,500 mah radioshack battery all are rechargable. I know its probably not good to mix two kinds of rechargable batteries but for now due to a small budget it will have to due. And I am using a glass lens from DX.I already have all the listed parts.

It's not the specific type of battery so much -- LuxLuthor (a respected battery-pack maker), for one, has built many packs mixing AA cells with a subC in the tailcap -- but the capacity really should be matched. Since one of your cells is less than half the capacity of the others, you'll have to stop using it and recharge all the cells when that one is empty. Even in a DD, it may be hard to notice this in time to prevent damage to the weak cell, and you don't gain anything from the higher capacity of the other two. If at all possible, I'd recommend buying two more of the low-capacity cells, and using them -- you'll get essentially the same run-time, with greatly reduced chance of hurting one of your cells.Or better still get another of the 12Ah cells for 2-3x the runtime.

It is going to be a direct drive light I think. But here are some of my problems and questions.first and most important is the anodizing on the heatsink is thin and has spots of metal which will short out the p7 because the heatsink contacts the inner wall of the maglite which is negative and the positive slug on the bottom of the p7. I need a heatsink compound that is non electrically conductive that will conduct heat and hold the LED in place on the heatsink. I was thinking maybe something from Dow Corning but im not sure. I only need a small amount and it can't be over ten dollars.

The standard recommendation is arctic alumina -- either plain arctic alumina (a grease-like thermal compound), with 5-minute epoxy around the emitter to hold it mechanically, or arctic alumina adhesive (a two-part epoxy) for thermal and mechanical. But you can also insert the batteries backwards (requiring small modifications to the tailcap spring and switch), and wire it for reverse polarity -- then you can solder the LED to the heatsink for the very best thermal path.

And one last thing can someone explain to me about mah and amps I have been told two different explainations are they the capacity of the battery and can two many mah or amps hurt a bulb lets say 28.5 to 36 amps to a p7 if I cant find a circuit. Can someone please help?

A = amps -- current draw -- in an incan, this varies smoothly with the voltage. For an LED, the current varies quite sharply with voltage over the operating range, so DD do not provide real good control of actual current; it depends greatly on the internal resistance of the batteries used.

mAh = mA * h -- battery capacity; the current multiplied by the time the battery lasts under that current. Usually tested at 0.2C/h (or 0.2C for short). So if a battery lasts 5 hours under a 2.4A load, it's a 12000 mAh battery.

Since you're combining the cells in series, they each see the full current draw, but share the voltage. So if your P7 runs at 2.8A and 3.6V, each cell will be running 2.8A, and the total will be 3.6V (maybe the large cells would be 1.23V each and the small cell would be 1.14V). Likewise, since they each see the same current draw in a runtime test, the whole pack has a current capacity equal to the weakest cell --- 4.5Ah, not 28.5Ah. But since that's capacity, it says nothing about the current they'll deliver in DD.

 

[3D black mag]

Thanks for the help benson. Can someone suggest a reflector for the p7 that will drop into my 3D maglite in case the stock reflector is too ringy. I'd like it to have a good throw with some spill and not too many rings under ten dollars maybe something from DX please help