Apologies in advance if this is a dumb question, but before I take a dremmel to the battery box under the driver seat, I had to ask.  I have a spare battery that's currently sitting in the storage compartment under the hood but want to relocate it under the seat.  The problem is that its about 1/8th of an inch to wide to fit.  The box has 4 plastic pieces that purtrude from the side.  Now I was going to take a dremmel to this thing to make it fit, but the box itself looks pretty thin.  Thin enough I may have to go back with some abs plastic to touch up some spots.  I thought maybe that bolt at the bottom was holding some type of insert that was for smaller batteries but after removing bolt, everything seems solid.  So, is there any harm with cutting down some of that plastic?  I really do not want to go buy another battery.

[2015 Z Force 800 53/Trail EPS]

I forget how it actually looks but I feel those are in for box support and probably could do with a little less. If you can leave at least a little on you should be fine.

Question for you....are you planning on running two batteries or just having a spare?  I have an extra one from a bike that I don't ride and wondered about doing this as well, but I wouldn't want it to just sit in there without some sort of tender on it or ran in series with the main battery. 

You guys need a battery isolator/separator.  I run one in my rhino.  When the bike is shut off the 2 batteries are separated when you turn the key to start they connect to give extra cranking power.  Anytime more then 12.3v is sensed they connect but if for some reason there is a massive draw on the AUX battery then they disconnect.  This way the machine will ALWAYS run and ALWAYS get you home

So how are the ran with this isolator?  Do you have a diagram, like are they ran in series with each other, or...?

[2015 Z Force 800 53/Trail EPS]

Series means it will increase the voltage..like from 12 to 24, + to - like a golf cart going from 6 to 36 volts. Parallel keeps it the same. +to+,-to-. The isolator just breaks the connection between the main battery and the axillary when a trigger for a relay had no power on it..like if the key is off on keyed power. Useful if you intent to run stuff like a stereo when its not running. Have it pull from the axillary battery only. That way the main battery won't be drained.   

I have the stock battery as it came.  It starts the bike and runs the winch.  I bought this 20ah sealed Battery off Amazon.  It powers my 2 amps for stereo currently. That way if the tunes go dead, the 800 wont be. This thing has been great. I listen to it while I'm working in the garage on the bike or other projects and get some a lot of hours.  Also just installed one in a speaker cooler a guy had me build for him.   When its in the garage, it is hooked to a battery tinder so its ready to go whenever I am.  I did not want to spend the money on an isolator because of some other mods I am saving for.  A friend of mine took a look at mine and did the same.  Only he is running a stereo, 22'' Led light bar, and 2 4'' spots on the back of his rzr.  He has been fine so far because we do not do a lot of night riding.  But when I add my led, I'll probably test my battery's life before I spend it on an isolator.

But I again, its 1/8'' too big for under the seat.  I want the storage up front back plus with it under the seat, I can get the roof to fit just a tad better with power wires running out the back instead of the front

The problem with not running an isolator is when one battery goes bad it will take the other one with it.  Not as in ruin it but it will drain it and leave you stuck (either in the garage or out on the trails).  I ALWAYS build my machines to ALWAYS get me home.  I never want to be walking out of the woods leaving my rig saying "I wish I had just done that one thing and it wouldnt have ruined this day".  This is just my thought though.  I know a lot of people that have a "good enough" thought pattern on this subject,  and those are the people who usually get towed out of the woods.

Totally understand and you make a great point for those who are looking to add a lot of accessories.  In my current setup, these two batteries are not tied together.  So if the radio drains the battery, I just won't have a radio, but will make it home with the stock battery.

Apologies in advance if this is a dumb question, but before I take a dremmel to the battery box under the driver seat, I had to ask.  I have a spare battery that's currently sitting in the storage compartment under the hood but want to relocate it under the seat.  The problem is that its about 1/8th of an inch to wide to fit.  The box has 4 plastic pieces that purtrude from the side.  Now I was going to take a dremmel to this thing to make it fit, but the box itself looks pretty thin.  Thin enough I may have to go back with some abs plastic to touch up some spots.  I thought maybe that bolt at the bottom was holding some type of insert that was for smaller batteries but after removing bolt, everything seems solid.  So, is there any harm with cutting down some of that plastic?  I really do not want to go buy another battery.

I'm running two batteries and ran into the same problem. That box gets narrower towards the bottom so my battery wouldn't slide all the way in. Honestly I just ended up cutting it out completely. I used stainless steal tie wiring to hold the battery in place and it works great. I'll eventually fab up some sort of box and reuse the existing screw at the bottom to help secure it. Hopefully you have better luck and can make it work.

I haven't looked at it real close, but what is the purpose of that single bolt at the bottom.  Because once its removed, nothing really comes loose that I felt.

[2015 Z Force 800 53/Trail EPS]

I haven't looked at it real close, but what is the purpose of that single bolt at the bottom.  Because once its removed, nothing really comes loose that I felt.

I think it just gives some support between the plastic and the steel cage below. When I fabbed-up my rock sliders/skid plates, I cut the end off so I could box-in nice and tight.