|Batteries DIY||Back to the HahnTronix Web Page|
This page was last updated on: 11/7/10.
A lot of folks have asked me why I don't sell Lithium Ion batteries with my lights.
The biggest reason is I don't want a garage full of things that are very, very hard to extinguish if they catch fire.
Then I'd also have to worry about my liability if your garage should burn down.
Finally, the Post Office and other carriers are starting to get finicky about moving them on aircraft.
Evidently aircraft fire suppression systems don't do a good job of extinguishing burning Lithium Ion batteries.
Oh great, something else to worry about when flying.
So I decided I'd just sell NiMh batteries. They are a bit heavier, but not that much. They have many less safety issues.
But if you are the sort of person who likes to tinker and are handy with a soldering iron, you are welcome to build your own LiIon battery packs.
Below are directions for building an 11.1 volt 2.2 Ah battery using protected 18650 LiIon cells I bought from China for very little. 4 cells and a charger cost me around $24. I'll post links to them on my Backup Lights page.
These directions assume you know how to solder.
I left them a bit vague on purpose.
DO NOT ATTEMPT TO BUILD ONE OF THESE PACKS IF YOU DON'T UNDERSTAND WHAT YOU ARE DOING!
You might burn your garage down :-).
There are some nice 18650 Lithium Ion battery cell holders made by MPD and available from
Search for "18650 holder" on their site to see which ones they carry.
My lights run on anything from 9.6 to 25 volts. I came up with a way to use one of the new standard MPD holders and a camera bag to make a reasonably rugged battery pack based on cheap protected cells from Deal Extreme in China. Here's a halfway decent cheap charger for the above cells.
Some disadvantages to dealing with Deal Extreme (DX) are the quality of their products is very uneven, shipping can take anywhere from 1 week to several months, and your ability to return defective products is anybody's guess. That said, I've bought a lot of LED flashlights and batteries from them and had only a few failures, but I have had to fuss with several of the flashlights to get tehm to work reliably.
If you would like some better quality protected 18650 cells and charger from a US based source, you might want to check out all-battery.com.
I have not used the batteries and charger from all-battery, but have generally been impressed with their customer service and the quality of NiMh battery packs I've purchased from them.
Here's a shot of the completed pack, note the odd orientation of the batteries.
Here's a shot of how I wired it up. We are looking at the back of the battery holder in the shot below. Note the + and - markings were photoshopped in. One of these days I'll probably print up some stickers to put inside the holder indicating the right polarity for each cell. Hopefully that will prevent me from inserting fresh cells in the wrong direction some night when I'm way far from the trailhead. I think the protected cells won't blow up if you put one in backwards, but I'd rather not find out. I did the odd arrangement I used here so the positive and negative leads for the power cord would both wind up on the same end of the holder.
Here's the pack with some sticky back foam stuck on the back to keep solder points from shorting against anything, some foam on the front to hold everything tight, and a zippy-tie used as a strain relief for the power cord (pointed at by blue arrow). The red arrow points at one of the corners I notched to make inserting the whole thing in my camera bag easier. The plastic seems to handle high temperatures pretty well. I just soldered wires to the pins coming out the back of the holder and didn't seem to melt any of the plastic. It trims pretty well with a pair of diagonal cutters. It does seem a bit brittle, so be careful when cutting it. I think I'll file off some more of the sharp edged on the next one I build. The edges catch on the fabric of the camera bag and make getting the completed holder in and out of the bag a bit bothersome. Perhaps for my next pack, I'll just wrap the whole holder in some 1/4 inch thick foam to cover the sharp edges.
I'm sure somebody can come up with something more elegant than sticky back foam on the back of the holder to insulate solder points, but it seems to work and takes no time to do (if you happen to have the foam lying around).
I ran this pack with one of my 20 watt dual MCE lights (BFL-2010) just to test it out and it ran for 1.25 hours, about what I'd expect from cheap DX batteries. This will make a great spare pack to take along on longer or cold weather rides. It isn't terribly waterproof, but I guess I could just shove the holder in a plastic bag before putting it in the camera bag.
Here's the battery holder stuffed into an attractive camera bag I picked up at DX for $3. The camera bag has a belt loop that makes a handy place to slip a velcro stap through so that you can chinch the whole mess to your handlebar stem.
More to come!