Introduction: Mega Torch - the Ultimate Guide
Mega Torch Build!
Welcome! This instructable has been 'written' mainly as a set of detailed videos (10 in total including the 'fake' advert above). As such, you will find the text is sparse but, this is more than made up for during the in depth descriptions in the vlogs.
I hope you enjoy this build and hope you can find the time to subscribe to my YouTube channel.
In this series, each video is between 5 and 15 minutes long and so its time to get a nice cuppa, sit down and lets get started!
Step 1: Safety
This is a low voltage project and so you'd be hard pressed to get electrocuted. On the other hand working with any batteries can present a danger as they can provide a lot of current in a short period of time. So if you accidentally short out some part of the circuit there is a likelihood that parts will get hot/melt very quickly so....
Please be careful!
In addition, when the project is finished please ensure you charge the lithium battery with one specifically designed to do the job. I recommend a GENUINE imax B6. These can be bought online but beware most on ebay/aliexpress are fakes. Buy from a reputable source if you are unsure. Here is the manufacturers link:
Step 2: Parts List
The parts used in the project are varied and it might take a while to collect them together from the various sources but hopefully they are all easily obtainable in your local hardware shop or via eBay. I've submitted a pdf and an excel spreadsheet with direct links for all the purchased parts.
A few of the main parts are salvaged from old PC's and laptop batteries. There are a couple of videos in the steps which go into all the necessary details on how to salvage used 18650's from old laptop batteries. Not all will be good enough (capacity wise), so you may need to source more than the 18 pieces you need before you have ones which will be acceptable to build in a pack.
Step 3: 100W LED's - the Good the Bad and the Ugly!
This is the first video and it looks at a small selection of 100W available on the web. Some are OK and some are not! 100W LED's from a tier 1 manufacturer would be too expensive for a home build (typically $80 @ 2017 prices) and so, at best, the ones I tested here are seconds. What does this mean in practice? Well the LED's may have broken/shorted LED's in the matrix or possibly there are other manufacturing defects which will shorten the life. It's a bit of a lottery really you have been warned! However, perhaps I was lucky as 3 out of the 4 I purchased were 'good' so I'm not complaining!
This seems a good source: (well the 2 I got from them worked ok)!
Step 4: Recovering Laptop Batteries
In this part I take a quick look at most of the parts that will be used in the build then get stuck in pulling the old laptop batteries apart and testing the 18650 cells. This can also be a bit of a lottery but if you have obtained these from a free source then what can you loose?!
If you are in the market for new cells then I'd suggest these 2 websites (I have no affiliation to either). I think the LG Chem MJ1 3500mAh cell is the best price/performance/capacity at the moment (Feb 2017)
NB: I do not recommend ebay as a good source for batteries (period). waaaaaay too many fakes!
Step 5: Building the Battery Pack
In this 3rd video the 18650 cells are reassembled into a 6s3p battery pack. I complete a series of calculations to ensure the battery pack will be up to the task of delivering the required voltage and current and also run time duration.
Step 6: Powering the LED
In this video I set-up the DC-DC converter to power the LED and do some thermal testing to ensure the LED remains cool enough to ensure a long life.
EDITED: I can not recommend using Constant Voltage CV as a method to power the LED - they really should be driven by a Constant Current (CC) power supply. I've had a lot of warning messages posted to this instructable with dire warnings of disaster hence this edit.
As an alternative you can use this power supply (link below). If you want it should do the job and you can still implement the potentiometer to vary the current to alter the LED brightness as shown in a future step.
As for me I'm sticking with what I have at the moment I may do a follow up video showing the set-up for the above CC source.
Step 7: A Method to Vary the LED Brightness
In this step I show how to vary the brightness of the LED by using a resistor divider and a 10k pot. You will need 2 1/4watt resistors, one at 10k Ohm and the other at 12k Ohm. A bit of soldering required here but I'd class this as 'easy'.
Step 8: Finishing Off the Battery Pack
This is just a short video showing how I wrapped the battery pack with blue heat shrink tubing.
Step 9: Cooling Fan Control
The battery pack is 24v and the fan is 12v so I just used a DC-DC buck converter to reduce the voltage. This video shows me setting the voltage up and wiring the fan in.
Step 10: Low Voltage Tester
18650 batteries need careful looking after. They don't like to be under/over charged. The addition of a low voltage test module will keep a check on each of the sets of parallel cells and will set off an alarm if the voltage goes below a set level. This video shows me checking these out and finding some surprising and disappointing performance of the modules I bought. Buyer beware!
Step 11: Final Assembly and Testing
Finally, all the parts can come together and we can test the performance of the Mega Torch.
Step 12: Comments & Suggestions?
Please feel free to comment and suggest any improvements.
Have you made an even bigger torch? I have seen some insane water cooled ones on YouTube (see link below) but they are not really as portable as my design is!