FORTIFIED: Bike Light Battery Replacement

FORTIFIED made some great bike lights. Then, they went out of business. Unfortunately, they used a proprietary battery case that is now impossible to get. Keep the lights on by printing this Battery case and filling it with a 18350 battery.

I started using the fortified bike lights a few years ago and loved the design. I commute by bike every day so having bright, reliable lights is a requirement. Prior to finding these lights, I had a few issues with removable bike lights falling off my bike while hopping curbs and dodging cars. I really needed a light that was semi-compact, stayed firmly attached to my bike and was easy to charge/change the battery without tools. The theft-proof design was an added bonus. Fortified lights checked all the boxes and worked great. I ended up purchasing a few sets of fortified lights for a few different bikes. 

“FORTIFIED: Bike Lights That Last Forever. We Promise.” The lights themselves have lived up to this promise. However, the Batteries have not.

When I found out last year that Fortified had gone out of business, I was lucky to be able to swoop up a few extra batteries from re-sellers on the internet. Today, replacements are impossible to find and my batteries are barely lasting a day on a single charge. Winter is coming, along with short days and dark nights. I need to these lights to work or invest some serious cash into new lights. Something needs to be done to keep my lights and the thousands of other lights out there from being trashed.

Opening up the old battery, the obvious fix is to simply purchase new battery and solder it onto the existing leads. Easy peasy, right? Wrong, Unfortunately, battery tabs can’t be soldered. In order to do this, you will need spot welder and some skill. I lack both of these requirements.

Disclaimer: I have no idea what I’m doing. I’m just a guy who wants to keep the lights on. My profession is in no way related to electronics or bike part design. Lithium ion batteries are dangerous and are a fire risk if improperly handled. Follow my instructions at your own risk. 

BOM

18350 battery & Battery Charger Make sure to get the flat terminal type, not type that resembles a standard AA battery. The original battery was 850 mAh. I got 900 mAh, you could probably go higher, but don’t go too crazy. 

4mm copper tape with adhesive backing

The spring and metal clip from 1 Zebra Z Grip pen (1 pen will make 2 batteries). You may be able improvise here. 

1 hole punched 1/16” packaging foam, UVA foam or corrugated cardboard

Hair ties (optional, but convenient)

3d printed Battery Case (.stl link below) or on Thingiverse

Tools

Diagonal cutters for cutting the pen clip

Needle nose pliers the smaller the better

Hole punch (you may be able to improvise here)

Ruler (only necessary if you are terrible at cutting things into even pieces freehand ‍♂️)

Pen for marking cuts

Something to poke with, (My workshop go-to pokey thing is Orange sticks for fingernails)

Super glue for the foam

A lighter (or other source of heat)

Eye protection for use with the diagonal cutters

1. Disassemble the pen and remove any plastic bits from you the clip
2. Cut the pen clip into 4 equal(ish) pieces. You only need 2 pieces per battery
3. Cut the Pen spring into 2 pieces (not pictured). You only need 1/2 spring per battery.
4. Cut you copper tape to about 60mm
5. Attach one end of the copper tape to your foam piece. Don't remove all the backing.

1. Use a drop of super glue to secure the copper tape-foam assembly to the bottom of the battery. There is a small indentation where the foam circle should sit. you are only glueing it to one side of the battery case.
2. Using your pokey stick, press the copper tape into the groove on the battery case. Slowly remove the tape backing as you work your way up.
3. Push the tape all the way into the deep groove at the top of the battery case.
4. Wrap the tape all the way around one piece of the metal clip.
5. Insert the metal clip into the slot at the top of the battery case. You need to make sure copper tape is visible through the negative terminal. Once the clip is fully inserted, it must be flush with the battery case.

1. Insert one of the metal clip pieces into the slot on the top of the positive side of the battery case. Push it in until it is flush
2. Heat the cut end of the spring briefly. Then jam the spring into the hole all the way, turning slightly. This will allow the spring to make contact with the metal clip and melt into the plastic slightly, keeping it from falling out.

The battery case will still work without the bands. When you place the battery case into your fortified light, the two halves will stay together. However the battery case will not stay together outside of the light. This step makes it easy to just throw the whole assembly into your bag for later.

1. Insert the hair tie/rubber band into the groove and push it down with your poking stick.
2. Insert a piece of 1.75mm filament into the hole to retain the band.
3. Clip the filament flush with the battery
4. Repeat for the other end.

1. Insert the battery into the negative side of the battery case first. Make sure the negative terminal is making contact with the foam/copper tape.
2. On the positive side of the case. Push back the spring and slide the case over the battery. Make sure the spring makes contact with the positive terminal of the battery.
3. Slide the bands around to hold everything together

If all went to plan, you should be able to slide your battery case into a fortified light and turn it on! WooHoo!

Go for a ride! You earned it!

Troubleshooting:

-Make sure your battery is charged! My 18350 batteries did not arrive charged

-Make sure you did not rip your copper tape during installation, it is fragile.

-Make sure the copper tape wraps all the way around the negative metal clip. (step 2)

-Make sure the battery is making contact with both leads inside the case.

-Make sure the battery case is making contact with the LED lights: Inside the FORTIFIED lights are two springs that need to make contact with the terminals at the top of the battery case. On my older FORTIFIED lights, the springs were slightly worn out and did not press firmly against the tabs. I was able to use my needle nose pliers to (gently!) pull on the springs, stretching them out slightly. This allowed them to make reliable contact with the battery case. If you don't have needle nose pliers or don't want to tug on them, try adding a couple of layers of masking tape to the back of the battery case.

Ride on!

Hey! If you made it this far, you’re probably interesting in repairing your own gear. I support all right to repair legislation think you should too. Please consider donating to the Electronic Frontier Foundation to defend your right to fix your your own stuff.