here is how you relocate your battery to your air box in a 400ex (might work in other models)
1. you want to remove your air box from your atv

2. remove your air filter

3. draw a line like in picture 1,2,3 and 4

4.then use a dremel or cut off wheel to cut out the plastic peace

5. use dremel or file to smooth edges


6. place original battery box in place to check cut then remove when happy with your cut

7. take a peace of plastic or sheet metal and place it like in picture 1 and 2

8. then cut air box in 2 places like in picture 2 make shoure you don't cut the slits to long or wide or it wont hold as well

9. then place the battery box in place then place a small peace of wood under the left front edge of the battery box then remove battery box and drill 2 holls in wood and air box and bolt the peace of wood in place (you could use somthing else other than a peace of wood if you wanted to but that is what i had at hand)

10. place battery box in place (for the last time) drill some holes in air box and battery box and make shoure that thay line up

11. bolt or rivet battery box in to air box

12. drill hole in battery box were it will make contact with the peace of wood (from the inside)screw the battery box to the peace of wood

13.then drill a hole in the bottom of the battery box in the rear left corner and drill a hole in the peace of plastic or sheet metal and bolt or rivet the peace of plastic or sheet metal to the battery
box

14.your almost done seal the cracks around the battery box with red silicone cawk or rvt i think thats what it's called you can get it at napa or any auto parts store and let dry over night

15. then the next day paint over the cawk if you want to

16. place battery in the battery box and use the original battery strap to secure the battery by drilling a hole in the rear air box saport and bolt it in and srew the bottom of the strap to the peace of wood and your done


(warning) you may have to make your battery cables longer and it is also harder to remove and install the air filter with the battery box installed i used a K&N air filter witch might be shorter the the original so the original air filter might not work

pictures coming soon