Step 6: Add Battery and Switch

At the back of most helmets there is a space  were you can place the 9 volt battery. (picture 1)
I hollowed this space out with the pen knife.  The Dremel tool works, but it takes longer.  You also need to keep the new hole space snug to the battery.  This is because the battery is not held in with anything but the elasticity of foam, so don't go over board with the knife.

Then solder the + from the battery clip to one of the connections on the switch. Next solder a  wire to a different connection.  In other words, solder it so it works as a switch. 

You will want extensions on the wires so they reach all the way to the front LED assemblies.

Four LEDs at the front are ok but I'm sure you'd be just as visible with two at the front and then put two red LEDs at the back. I like the way the lights are integrated into the helmet, but I'm afraid with everyone else regarding the batteries and modifying the helmet structure.
Got to agree with the others here, <br /> <br /> Nice idea and explanation, but you shouldn't modify your helmet structurally like that. In fact that would be illegal here in Australia, I wouldn't be suprised if it was too in your area.<br /> <br /> The manufacturers don't put that foam in for no reason - they put the minimum in to provide the required amount of protection. If you take some away, there isn't the required level of protection anymore.<br /> <br /> Maybe a re-think and come up with another solution? You could use some self-adhesive velcro to &quot;stick&quot; the battery on the outside.<br />
Good idea. Pretty slick looking.&nbsp; But I'm a little leery of the way you've hollowed out a space for the battery--the foam that was there isn't protecting your noggin anymore.&nbsp; An impact on the back of your head might drive that battery into your skull.&nbsp; Maybe a flat cell-phone battery stuck to the outside of the helmet in back?<br />
&nbsp;Li-Po Batterys (lithium polymer) are thin, light, last longer than that 9V battery, and they're&nbsp;rechargeable.<br /> <br /> <br />

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