So I posted a note on the board at work asking for old laptop batteries for cheap or free condition irrelevant. I got a lots of question why I wanted old batteries and even more strange looks from my co-workers when I told them I was making a custom flashlight. Fast Forward 4 laptop batteries (3 good 1 leaking) and I had a perfect configuration for 3s2p.
The Mag is a regular incan 3D in black.
Here is where thing start to get ambitious. Using a 3/4 dia. carbide reamer I scalloped out about .055” per side 8.3” in the 12 and 6’oclock position with the switch being 12 o’clock. There was a lot of deflection of the tool while only taking .010 at a time. This required about 20 spring cuts to get the width deep in the tube. This was all done on a CNC boring mill so although it took some run time it was so bad.
The salvaged battery with the voltage monitor hooked up. As mentioned earlier 3s2p configuration.
The monitor is a FrSky from hobbyking. It only cost like $12 and looks neater than all get out. It will be nestled against the batteries and visible from a window I plan to cut at the 9 o’clock position (looking at the front of the light). I’m left handed to the monitor should be where my fingers are not.
For actually lighting things up I plan to use 3 series wired XMLs with a the KD 3v-18v buck/boost 30watt driver. One of those 50mm triple optics will be used
an all will be done on some sort heatsink I will make later. I’m waiting on the driver now.
I’ll try to get some more updates as thing progress.
I’m a bit worried by the differences in voltage shown by that monitor - 4.02 to 3.89V is a fair sized jump. Did you fully charge each cell to 4.2V before assembly? Can you balance charge the pack? How did you test the salvaged cells? I’ve tested 60+ laptop cells and the variation in capacity/ quality is huge. I don’t mean to come across all aggro, but that’s a fair amount of energy you’ll be sticking into that Mag and it pays to be careful about it
if you’re going to be using 3 XM-L I’d wire the pack 2S3P and use a dedicated boost driver - it’ll be more efficient (I think, read that somewhere) than a buck/boost and possibly more reliable. I might be making up that last bit, though it makes more sense to me to use something dedicated for a purpose than a driver that’ll go from buck to direct drive (?) to boost as the voltage discharges, especially as you don’t have to.
Neat voltage monitor too, good for diagnostics of the battery pack as well I’d guess.
I think thats the same FrySky i have. My battery moniter will also balance each cell.
It looks like you need to balance charge your cells and match them.
I haven’t charged any of them yet that’s what they read when I got them. They were already assembled like this. I’m not actually sure If I should just balance charge now or discharge first then do a balance charge.
Did some testing today and was thoroughly disappointed. Wired everything together with the 3 XML’s on an old CPU sink and my meter on the negative side of the battery. With the temporary switch in place I it turned on catching me off gaurd with the brightness It worked pulling 3.3amps. I was happy. So I started switching through the modes and then got confused. Where did high go? So I shut it off and tried again. Well what sucks here is that after about 1 minute the driver starts to get hot. Once the driver hits around 125 deg. the current starts falling fast, until it stabilizes at like 1.2 amps and the driver temp. holds around the same 125 deg. I’m gonna try and heat sink the driver but I’m not very pleased at this point.
condition irrelevant. I got a lots of question why I wanted old batteries and even more strange looks from my co-workers when I told them I was making a custom flashlight. Fast Forward 4 laptop batteries (3 good 1 leaking) and I had a perfect configuration for 3s2p.
