Introduction: How to Make an Armband Battery Holder to Charge Your Running Watch During an Ultramarathon
If you're a trail runner, you know how it is. If it's not on Strava, it didn't happen.
What if you're in the middle of a 15-24 hour race and you run out of juice in your watch? Will anybody believe you completed the race? Of course, there's always the race results, but that doesn't show your route or your pacing or your heart rate. How do we know you didn't just bribe the RD?
The only way to get that Strava cred is to bring a battery and plug-in your watch to charge on the go.
That's what I did for my 100-mile attempt last September and I caught the whole 62 miles of torture (well, only the last 10 were actually torture due to a quad blow-out, but that's not popular to say. ;)
During that race, my hand began to cramp as I held my perfectly sized lipstick case battery. I stuffed the battery in my vest, but the thing would bounce so much it came unplugged.
I recently came up with a solution and before my 100k in September, I'm going to try and complete this project. It's an armband battery holder for a portable battery. Let's get crafting.
Step 1: Gather Supplies
What You'll Need:
- Neoprene material
- Measuring Tape
- Lithium battery
- Velcro (grip and backing)
- Fitness Watch w/ GPS and ability to charge on the go. If it plugs perpendicular to the back, it won't work. Clamp style or micro-usb into the side are the only way you'll accomplish charging on the go with these watches. I use a Suunto because their lower model features this ability.
- Charging cable for your watch
- Sewing machine (not pictured)
Step 2: Create the Template: Measure Your Arm, Trace the Battery, Trace the Band
You'll want to measure your arm first. If the band is too big, it will just be this annoying hung sliding into the crook of your arm.
You want your measurement to be tight against your arm as neoprene will stretch.
My arms are skinny runner's arms, so they were about the circumference of a length of printer paper. You might need a roll of paper to accomplish this step if your arms are bigger.
Use the circumference to measure the length of the band template on a piece of paper.
Trace the lithium battery at the center of the length. Depending on the height of the battery, you may have to make this a little bigger than the battery itself. You want it to be snug enough that it won't go bouncing out and that it will catch on the lip of the neoprene and stay inside its pocket. Be sure to get enough neoprene to experiment. You might get it right the first time, you might have to make a few to get it right.
Had a neoprene strap from another thing ready to trace. You'll probably want to just measure a template instead of wasting more material. But trace a two-three-inch strap centered on the traced battery.
Mark about an inch above and below the battery. I made an octagonal shape. You can make it square or rectangular if you like. But trace from the top and bottom marks back to the strap.
As you can see in the last image, part of the middle will wrap around your arm as well.
Step 3: Create Backing Template: Cut Out Base Template, Fold and Trace Backing Template
You're going to need a backing to keep the battery in. So, cut out the base template, fold in the arms and trace the backing.
I traced the battery again so I know where it will go and how to sew it later.
Cut out backing along the inside of the lines so it will be slightly smaller than the original template.
Now you have a backing template. Hooray!
Step 4: Make Sure Your Neoprene Material Will Work/Test Width of Pocket
As I said, this will be an experimental thing. But if you have enough material, you can cut a strap the length of the device to see if your lines will work.
Place the strap over your template and press with your fingers where you traced the battery. If the material is really stretchy it will already accommodate the battery. If not, you might have to widen your stitch pattern.
I didn't have a sewing machine. I'll have to borrow one before I complete this.
But the last steps would be to trace and cut your band and your backing.
Cut a slit in the band where the battery will insert and make it the width of your battery stitch pattern.
Sew the backing onto the band and then sew the stitch pattern for the battery pocket.
Measure it around your arm and test the battery pocket before sewing on the velcro pads.
Remeber, measure twice, cut once. This will help you save on material.
Happy trails ya'll! (I'll amend this once I actually finish this project. But just wanted to get it up to see if anyone had suggestions.)