How to Triple the Battery Life of AAA Flashlights




About: Autistic person who's interests include utility cycling, recreational cycling, cycling safety, electronics, gardening, Arduino, and LEDs.

When using 3 watt LED flashlights powered by AAA batteries, they last for about 30 minutes. There is a way to triple the run time by using AA batteries. In this Instructable, I will show you how to hook up a AA battery holder to a flashlight.

Step 1: Things Needed

Heat shrink tubing
Inexpensive flashlight to modify (eg. Techlite Lumen Master)
3AA battery holder with cover
3 AA NiMH batteries
Wire cutters
Sand paper

Step 2: Extended Battery Pack

To connect wires to the flashlight, drill a small hole onto the body and sand the edges. Cut the wires slightly longer than you need and solder them to the flashlight's battery holder and the AA battery holder. For my flashlight, the wires were long enough to reach my pockets. Heat shrink tubing can be used to cover the solder joints. To make it water resistant, add hot glue to the drilled hole.

If it doesn't come with a battery holder, you can make an adapter instead to hold the wires. This one fits AA battery holders so you may want wider dowels. To make the extended battery pack detachable, you may use 9V battery clips or DC power connectors.

Note that in the photos, I sawed the aluminum body.

Step 3: Helmet Mount

To mount the flashlight to a helmet, elastic bands or bungee cords may be used. Now your flashlight will run for a long time!



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    2 Discussions


    6 years ago on Introduction

    Nice idea - execution could be tidier. There are a stack of torch holders on which would be perfect for holding the torch down better.

    Personally I have a couple of old nokia phones and almost a dozen lithium batteries. I plan on gutting a phone and using the battery contacts and retaining clips, then permanently wiring it to LEDs on the bike.

    Recharging batteries will use a desktop recharger I have spare.... Instructable to come one of these days.

    1 reply

    Reply 6 years ago on Introduction

    Thanks for the suggestions. I just ordered a couple of bike mounts. Laptop batteries use 18650s which usually works well.