Battery Relocation DIY

[tmontague]

I finally finished my battery relocation this weekend and have a bunch of pictures to post up for anyone interested in doing it down the road.

There were a few reasons I wanted to do this. For one, this removes 25-35 lbs off of the front left of the car in a very high position and bring it to the lowest height possible in the Yaris, between both axles and on the passenger side.This helps with weight distribution, lower center of gravity and better weight balance. Some people put them in the trunk but I did not want the battery outside of the axles as this increase the moment of inertia which is the opposite of what I want for a tight road course track car.

The other reason was to remove more stuff from my engine bay so I have easy access to power bleeding my brakes. I had to remove the battery every time I bled the brakes before track days last year. It became a pita over time. I also now have easy access to the top trans mount as well ass some space to put my coolant overflow bottle when I swap in my dual row Vibe/Matrix radiator.

Now that the battery is inside the cabin of the car I can leave a charger on it over night without having to worry about someone stealing it. I just run a cord into the cabin and leave the charger there with the car locked. Because the battery is in a sealed box accessing the terminal for a charge is more of a pita so I installed some battery relocation terminals if I ever needed to jump it or charge it easy. The charger can sit in my trunk and has easy access to the remote terminals without ever having to leave the battery box open. This keeps potential hydrogen vapors vented underneath the car and not in the cabin.

This isn't as inexpensive as you would think to do, but it is fairly straight forward and worth it if you are constantly bleeding your brakes, working in the engine bay or track your car and weight distribution matters. I still have to figure out what I am going to do with the connecton of the main power wires in the engine bay. I have the main power set up on a 100 amp ignition protected beaker but I still would like to keep the fusible links intact. I don't mind the set up now but I also have an insulated stud coming in the mail. I originally planned to mount that somewhere and then mount all the power wires to it, but the current set up is functional and works fine.

DIY Part:
The battery relocation is actually really simple in what you need to do to get it to work. You simply have to run a 12V wire from your new battery location all the way to the original factory location and attach them.

As long as the wire is the appropriate gauge then the car will have the power it needs to start. There are fancier and cleaner ways to do this, but this is a somewhat inexpensive and simple but effective way to do it. I would highly recommend running a main fuse or breaker right after the battery as well as keep your main fuses (fusible links) in the engine bay. They serve a protective purpose and limit damage to the ecu if you ever ground out your alternator. The breaker will protect you if you ever have a short in your main wire you are running.

I highly recommend you run your main power wire through your cabin and not outside underneath the car. You will have to drill a hole in the fire wall to run the wire into the engine bay but I have pictures showing you where to do this. Wrap the wire up in some sort of split loom, protective covering just in case. The wire can be run in a well protected area underneath the door sill, but protect it anyways.

I used a Moroso battery box from TDOT Performance, 10' of 4AWG welding cable from my local Princess Auto, a 100 amp Bussman (Eaton) breaker that is waterproof and ignition protected ( so the starter doesn't trip it), a Moroso remote battery terminal kit, pre made 2x12" and 2x48" 4awg cable with terminal ends from Canadian tire. I reused the factory yaris positive battery terminal and purchased an oe style terminal from CT for the negative side.

You need to connect the negative terminal to the chassis so that the whole chassis essentially becomes a ground. Therefore you do not need to run a ground cable all the way into your engine bay. First figure out where you want your battery to go. I chose in front of the rear passenger seat as it is the lowest point you can go between the axles and it is the furthest you go go to keeping it to the right of the car.

Once you mount the box - which is straightforward as it comes with instructions - you can then start running your ground cables. There is an empty threaded hole above the passenger seat belt near the floor that once you sand down to remove the paint, becomes a great ground point.

You then need to ground your engine/trans. Technically you only need one ground wire for this as the engine and trans are obviously touching, but I opted for two for some redundancy. I used the original ground point on the trans and then used one of the threaded holes originally for the stock airbox to connect the ground to the frame.

I then used a tap to chase threads into a blank hole found on the passenger strut tower and connected one of my braided flexible grounding straps to it. The other end connected to one of the bolts on the valve cover that is used to hold in the intake VVT solenoid. I used flexible grounding straps so that the movement of the engine doesn't snap them.

You now have a mounted battery box and all of the ground wires running to their proper place. The battery box comes with grommets so you can run the ground cable into the box. Drill the holes for the wires as high on the box as you can I drilled mine slightly too low for the current sized battery and it just makes things more difficult. It will fit well with the slightly smaller AGM battery I plan to buy in the future, but for now it's a bit of a pain.

You can also run your positive wire and terminal into the box. The non battery end should terminate at the breaker only 8" or so away. I used self tapping screws to mount the breaker to the side of the battery box. On the inside I stuck pieces of rubber on the sharp parts of the screws so I don't catch my hand on them.

I used pre made cable lengths found at my local CT for all the wires except the long main wire going to the engine bay. When I did a cost analyses and noticed how strong the terminals were that they came with, it was an easy decision for me.

Now all you have left to do is run your main cable. Lay out your cable in the cabin of the car and eyeball where you are going to run it. I ran mine under the passenger side plastic door sill/trim and ziptied it in place once it was covered with split plastic wire loom. The spot make it a direct shot through the fire wall.

To drill the hole in the firewall you need to peel back the passenger side carpet in the foot well as well as cut out sound insulation and remove a large piece of rigid foam. I was surprised how well the Yaris is insulated for an eco box. You will see a circular pop up on the fire wall metal, you want to drill an inch below that. This has the wire coming out an inch below the ecu and away from the exhaust header or anything else. It also allows you to use the ecu harness to ziptie your wire to.

There is also an open threaded hole right below this point which was perfect to use a bolt to secure the wire with an insulated clamp. 3/8" clamp worked perfectly for the 4awg cable. I used a grommet on the firewall, make sure you do this or you will cut the main wire and cause a short - bad news bears.

Once the wire is through the firewall, ziptie it to the engine harness until it sits in front of the the factory main power terminals. Then crimp a copper 4 gauge terminal to the end of the cable. If you don't want to spend $25 on a large terminal hammer type crimper, then use a vice grip and a punch to crimp it onto the wire. I bent the terminal in my bench vice 90 degrees so that there was less stress on the wire. I also covered it in heat shrink.

I originally had one of the self crimping/thread on terminals but it wasn't bendable and left all the stress on the copper wire which over time likely would have failed. I ended up swapping it with a proper crimped terminal that I could bend 90 degrees.

The factory positive terminal plastic guard will still fit over the connections which is a bonus. With this set up you can de power your whole car by just flipping off the breaker. I can also charge my battery easily using the remote terminals all while keeping the battery box sealed.

The battery box is also vented out the floor of the car, My local time attack series requires a plastic marine grade battery box which is why I went with plastic over metal.

I will clean up the pictures later so that they correspond with their respective paragraphs. For now you can likely figure out what goes with what, if you need any specifics answered or clarified just post on this thread. This is a straight forward DIY but until you have seen an actual set up in person or in detailed pictures, it's hard to wrap your head around the set up of it.