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Flashlight Enthusiast
Bill gave me permission to reveal the details of my contribution to the USL: battery pack construction and design.
For now, there are no pictures, but I will be taking some over the next few days and will add them to this thread.
OK. So, to start with, for those not familiar with light design in this power range I wanted to mention that building an Aurora class light involves problems not normally at issue in a SuperBulb incan mod. You can get a much more comprehensive understanding of these things by reading Ginseng's Aurora thread and the threads of the people whom he credits in that thread and also the link which can be found in his sig line. But for an overview, here are a few of the more prominent issues:
1. Heat. No plastics need apply. No solder joints too close to the lamp will stay solid. No hot glue will keep its grip on the battery pack. In so many ways, on so many levels, heat considerations dictate the design.
2. Current. 8+ amps is a whopping rush of electrons, and few switches are up to the task, but more importantly, thin resistance welded bands of metal are no longer able to adequately electrically join batteries together. They WILL work, but will also add a non-trivial amount of resistance.
3. Batteries. This sort of goes with no. 2 above. Very few cells that are relatively small in size will deliver 8 or 9 amps and hold a decent voltage. Cells this potent are rare and must be specifically and specially manufactured.
4. Space. This ties in with all of the above. Trying to find batteries that will handle 8 amps and then joining them together all while observing proper safe distance from the heat source is difficult. Many, many factors must be balanced against each other.
5. Cost. Sure, you can have a custom body machined around everything else, but it will drive your costs through the roof unless you are doing a run of hundreds. Plus, chances are the first proto-type will have problems and won't work, which will mean another, and the proto-types are the expensive elements.
And then, of course, there are all the usual issues that go with incan light design, such as matching the battery pack to the lamp, and finding a way to hold the lamp in position, and so on.
To get a feel for the USL pack, and the key idea behind it, grab a Mag D sized light, if you have one, and then remove the switch core and head. Now take four AA alkaline batteries and push them into the back of the light. You will see that they just fit in a square or diamond shape formation. In fact, orient them so that the points of the square are top and bottom and left and right. Now remove the top battery and let the other three slide all the way to the snap ring, directly underneath the round switch opening. If you look in from the front of the light, you will see that there is a good bit of room from the round switch opening to the top of the bottom most battery. Room for a switch of the right design.
This is the essential feature of the USL battery pack design. It is simply four stacks of three AA's with one missing AA in the top stack. That is the positive battery pack terminal. Then at the back of the light there is a jumper to the leftmost stack (looking in from the back of the light). Then there is a jumper from the front end of that stack to the bottom stack, and then a jumper from the back end of the bottom stack to the rightmost stack, and thus the negative pack terminal is at the front of the rightmost stack.
SOME CONSTRUCTION DETAILS
The USL pack is made from 11 www.cheapbatterypacks.com 1650 mAh AA NiMH batteries. In my initial testing these cells held better than 1.1 volts/cell at 8.3 to 8.5 amps, or 12.1 to 12.3 volts or better for the pack. These are the best high-current AA cells available: as good as KAN 1800 4/5A's but with a bit less capacity. These cells are the main reason that the USL is a reality and not just an idea, although the KAN 1300 AA's would have been able to handle this current as well.
Now, unfortunately, the CBP 1650's are just a bit larger than, say, a Duracell or a Ray-O-Vac, and thus the Mag body needs to be bored out a small amount. Not enough to touch the threads, however, and not enough to impair the structural integrity of the light. OK, since that is not my problem, I will move on.
So, since the batteries cannot be resistance welded together for an 8 amp draw, they must be end-to-end soldered. This is a tricky operation and involves a lot of work to prepare the surfaces of the + and - contacts, then tin them, then heat up both solder puddles at once and push them together before they cool, joining them over the entire surface of the smallest contact in a minimally thick layer of solder.
I have covered the details of this operation in my TigerLight Custom Batterypack construction details thread. Anyone who is determined enough can master it, but it is a skill which takes time and practice to develope. And in the case of the USL, it is a skill which is actually necessary for the best battery pack performance. I am not the only person on CPF who can end-to-end solder batteries. Ginseng and Tweek can also do this, and there are probably others. Also, scads of people on www.rcgroups.com end-to-end solder their battery packs because they are asking them to deliver 20 or 30 amps.
After end-to-end soldering and taping and/or wrapping, the stacks are glued together using GE RTV 108 silicone adhesive and sealant. Why this and not something else? Why this, which I heard someone laughingly refer to as bathroom caulk? Simple: it is flexible and resilient and very very tenacious and strong, while at the same time being capable of withstanding very high temperatures.
Next the electrical connections are made bewteen stacks with 25 amp tinned copper braid, soldered directly to the battery contacts.
And finally, two high strand count silicone jacketed 20 gauge wires are threaded through the center of the pack and soldered to the + and - contacts at one end of the wires. At the other, a Molex micro-fit connector is attached for the charging connection, and the connector at the end of the pack resides in the space of the tail cap and the end of the mag body, since no mag spring is needed to carry current to a ground return path through the body of the light.
A 16 gauge wire is soldered to the + contact and then to one of the switch leads. Then one of the socket wires is soldered to the other switch lead, while the other socket wire is soldered directly to the - battery contact.
So as you can see, there are negligibly small amounts of resistance in the batteries and wiring and switch, which is important in a high current, high powered light. Thus, almost every bit of juice that the batteries have gets to the lamp. And what a lamp it is--but I'll leave that for someone else to tell.
I hope you guys like your USL's. Thanks, Bill, for taking on this MONUMENTAL task. I have it easy. All I have to do is build (gulp) 60 plus battery packs. hehe.
For now, there are no pictures, but I will be taking some over the next few days and will add them to this thread.
OK. So, to start with, for those not familiar with light design in this power range I wanted to mention that building an Aurora class light involves problems not normally at issue in a SuperBulb incan mod. You can get a much more comprehensive understanding of these things by reading Ginseng's Aurora thread and the threads of the people whom he credits in that thread and also the link which can be found in his sig line. But for an overview, here are a few of the more prominent issues:
1. Heat. No plastics need apply. No solder joints too close to the lamp will stay solid. No hot glue will keep its grip on the battery pack. In so many ways, on so many levels, heat considerations dictate the design.
2. Current. 8+ amps is a whopping rush of electrons, and few switches are up to the task, but more importantly, thin resistance welded bands of metal are no longer able to adequately electrically join batteries together. They WILL work, but will also add a non-trivial amount of resistance.
3. Batteries. This sort of goes with no. 2 above. Very few cells that are relatively small in size will deliver 8 or 9 amps and hold a decent voltage. Cells this potent are rare and must be specifically and specially manufactured.
4. Space. This ties in with all of the above. Trying to find batteries that will handle 8 amps and then joining them together all while observing proper safe distance from the heat source is difficult. Many, many factors must be balanced against each other.
5. Cost. Sure, you can have a custom body machined around everything else, but it will drive your costs through the roof unless you are doing a run of hundreds. Plus, chances are the first proto-type will have problems and won't work, which will mean another, and the proto-types are the expensive elements.
And then, of course, there are all the usual issues that go with incan light design, such as matching the battery pack to the lamp, and finding a way to hold the lamp in position, and so on.
To get a feel for the USL pack, and the key idea behind it, grab a Mag D sized light, if you have one, and then remove the switch core and head. Now take four AA alkaline batteries and push them into the back of the light. You will see that they just fit in a square or diamond shape formation. In fact, orient them so that the points of the square are top and bottom and left and right. Now remove the top battery and let the other three slide all the way to the snap ring, directly underneath the round switch opening. If you look in from the front of the light, you will see that there is a good bit of room from the round switch opening to the top of the bottom most battery. Room for a switch of the right design.
This is the essential feature of the USL battery pack design. It is simply four stacks of three AA's with one missing AA in the top stack. That is the positive battery pack terminal. Then at the back of the light there is a jumper to the leftmost stack (looking in from the back of the light). Then there is a jumper from the front end of that stack to the bottom stack, and then a jumper from the back end of the bottom stack to the rightmost stack, and thus the negative pack terminal is at the front of the rightmost stack.
SOME CONSTRUCTION DETAILS
The USL pack is made from 11 www.cheapbatterypacks.com 1650 mAh AA NiMH batteries. In my initial testing these cells held better than 1.1 volts/cell at 8.3 to 8.5 amps, or 12.1 to 12.3 volts or better for the pack. These are the best high-current AA cells available: as good as KAN 1800 4/5A's but with a bit less capacity. These cells are the main reason that the USL is a reality and not just an idea, although the KAN 1300 AA's would have been able to handle this current as well.
Now, unfortunately, the CBP 1650's are just a bit larger than, say, a Duracell or a Ray-O-Vac, and thus the Mag body needs to be bored out a small amount. Not enough to touch the threads, however, and not enough to impair the structural integrity of the light. OK, since that is not my problem, I will move on.
So, since the batteries cannot be resistance welded together for an 8 amp draw, they must be end-to-end soldered. This is a tricky operation and involves a lot of work to prepare the surfaces of the + and - contacts, then tin them, then heat up both solder puddles at once and push them together before they cool, joining them over the entire surface of the smallest contact in a minimally thick layer of solder.
I have covered the details of this operation in my TigerLight Custom Batterypack construction details thread. Anyone who is determined enough can master it, but it is a skill which takes time and practice to develope. And in the case of the USL, it is a skill which is actually necessary for the best battery pack performance. I am not the only person on CPF who can end-to-end solder batteries. Ginseng and Tweek can also do this, and there are probably others. Also, scads of people on www.rcgroups.com end-to-end solder their battery packs because they are asking them to deliver 20 or 30 amps.
After end-to-end soldering and taping and/or wrapping, the stacks are glued together using GE RTV 108 silicone adhesive and sealant. Why this and not something else? Why this, which I heard someone laughingly refer to as bathroom caulk? Simple: it is flexible and resilient and very very tenacious and strong, while at the same time being capable of withstanding very high temperatures.
Next the electrical connections are made bewteen stacks with 25 amp tinned copper braid, soldered directly to the battery contacts.
And finally, two high strand count silicone jacketed 20 gauge wires are threaded through the center of the pack and soldered to the + and - contacts at one end of the wires. At the other, a Molex micro-fit connector is attached for the charging connection, and the connector at the end of the pack resides in the space of the tail cap and the end of the mag body, since no mag spring is needed to carry current to a ground return path through the body of the light.
A 16 gauge wire is soldered to the + contact and then to one of the switch leads. Then one of the socket wires is soldered to the other switch lead, while the other socket wire is soldered directly to the - battery contact.
So as you can see, there are negligibly small amounts of resistance in the batteries and wiring and switch, which is important in a high current, high powered light. Thus, almost every bit of juice that the batteries have gets to the lamp. And what a lamp it is--but I'll leave that for someone else to tell.
I hope you guys like your USL's. Thanks, Bill, for taking on this MONUMENTAL task. I have it easy. All I have to do is build (gulp) 60 plus battery packs. hehe.
