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How to: Relocate the battery to the rear storage box

33929 Views 50 Replies 29 Participants Last post by  Geezy1014
_____Relocating a 2nd Gen Battery_______

I wanted to move my battery to the trunk, but didn't want to sacrifice space I use all the time. The cargo container behind the passenger seat is a good place for the battery. It's a little closer to the engine bay, I rarely use it, it can be latched and locked, and best of all, its almost a perfect fit for an OEM sized battery. I've seen this done with smaller batteries, like a Harker Odyssey, which is pretty easy given their tiny size. I decided to use an Optima Yellow Top, #D51, which is the same size as the stock CRX battery. You can get these at auto parts stores or order them online. I picked mine up at the local Sears auto center for about $140. I don't know about the other places, but Sears won't give you a core back for the old battery.

What you need:

Optima D51 Yellow Top
2 or 4ga wire, about 2m for the longest piece, and 2m to cut up for the rest
Battery terminals if the cables don't have them already
ring terminals
heat shrink (don't use tape! do it right!)
distribution block (or alternative, see below)
phillips head screwdriver
10, 12, 14mm sockets
utility knife
multimeter (optional)
sandpaper/wire brush
dremel/air grinder

Removing the Old Battery

First off, you need to take out the old battery and tray, and remove some of the stock wiring. Begin by taking the leads off the battery. The negative goes right to the frame underneath the stock tray. The positive splits and goes to the underhood fuse box and the starter. Pull them all out, and If you can, try to save the boot that covers the starter lead. Now unbolt the battery itself, and take it out. It's going to be very dirty, I was surprised, mine looked clean but was sitting in a puddle of grime. Now take out that battery tray and get rid of it. At this point I cleaned that side of the bay, it was filthy. Also you can now remove the main ground for the battery.

Fitting the Battery

Unscrew your cargo container and pull it out. Lay the battery in it and cut out the bottom of the container all the way against the passenger side edge for it. You also need to cut out the bottom corners so it can sit flat, otherwise the bottom edges will sit in the round corners and the compartment won't close flush. Finally, cut the lip in the front of the compartment so your cables will fit. Now comes the painful part: you need to hammer a little bit of frame. I suppose you don't need to do this, but if you don't the compartment will close and latch, but it won't sit completely flat. You don't need to go crazy, just flatten down the front part of that depression so the battery won't sit with the front corner tilted up (you'll see what I mean when you fit it). Screw the container back in, but don't install the battery yet.

Running Power

For this part, run all the wires first without putting any terminals on them, just find the right length. It's a lot easier to use the heat gun/torch/whatever you use for heat shrink if it's not in the car. Don't use tape on the terminals, do it right and heat shrink them all, it won't come off and it's a lot cleaner. For this, I had a 2m piece of 2awg red wire a friend gave me, and then I got some more 4awg at an auto parts store. Both had battery post terminals on one end already. The positive post will be closer to the driver's side of the car, so start your red cable there, and go across the front to the passenger side, then back down the side and out the back/bottom of the compartment. Run the cable under it and out the front. Now pull the carpet up along the door all the way up to the front of the passenger footwell. There is a little grommet behind the glove box you should easily be able to pop out, take it out and save it. Honda conveniently left a bunch of wire clips along the bottom of the door, so clip the wire in there (2ga fits perfectly) and then send it out into the bay with about 30cm slack. This wire doesn't need a terminal, so you can strip the sheathing off the end and then tuck your carpet back in. Now you are going to need to make the two power wires, one to the starter and the other to the fuse box. For this I used 4ga wire. These won't be too long, you just need a couple of short pieces to go from where the power comes in from the back to the two components. They each need a bare/stripped end and a ring terminal. the terminals for this size wire won't fit in the fuse box without some modifications though. You need to grind/cut the sides of the ring slightly, and cut away some of the plastic fins that hold the stock wire in the fuse box. When it's done, installed and box closed, it will fit and look stock (except for the huge wire) so don't go crazy trimming it down. The starter wire just needs a ring terminal, and you can try to put that boot over it too if you like (mine was torn when I took it off).
Ok time to distribute power. If you want, you can get a distribution block at a stereo place for $20-25. OR, you can get a cheaper one at Home Depot that won't look as nice, but will work just as well. The Home Depot one is basically a bolt with a slot up the middle, and a nut that clamps down on the slot. You put the wires in, and tighten the nut, then seal it up with some big heat shrink and creative stretching. If you use this method, MAKE SURE IT"S SEALED. Since it's metal and not necessarily secured to anything, you need to make sure it's not going to contact the frame or body anywhere.

Grounding Out

Ok, finally, the last wire. You can ground to almost any bolt in the frame,a lot of people like the spare tire bolt hole. I chose not to do that because I have a spare in there and I have to remove it for autocross and stuff, so I didn't want to have it in the way. If you pull out the rear interior, you can see that there are quite a few places you can use. I chose one of the mount screws for the "wall" that separates the trunk from the compartment. You will notice that it is in fact a plastic anchor, not a screw into the body. I only used it because it's close and when I cut my last wire I didn't realize it was plastic. It's been working fine, here's how I did it:
Pull the screw and the anchor out of the car. Now take your sandpaper and get all the paint off it and make it smooth. To make sure it won't oxidize, put some Vaseline on there, then set the ring around the hole, and finally push the anchor through it. You will probably need the hammer to get it all the way down. Some Vaseline should come out the sides, that means you're forcing it out and making a metal-metal contact that isn't exposed to air (especially the very moist air that is usually found in the CRX trunk). You can use the meter here to test the ground if you like. Now you can put eveything back together.

Battery ground location

Finishing Up

Drop the battery in and start the car. You might want to check the battery with your multimeter, I got mine in and THEN realized it was just a little too low to start the car. The other thing that you can do is make some new grounds with the scrap wire. If your car is like mine was, the stock grounds are old and frayed 10ga wire, they could be replaced.

Optima D51 Yellow Top installed

Engine grounds to replace
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Great write-up. My setup is very similar.

I have my battery relocated in mine as well. I went with the Hawker battery which is currenly installed in the storage compartment with my amp. I have it wired with two distribution blocks, one under the hood to the fuse box and starter, and the other in the storage compartment running to the amp. I also have an ANL 100 Amp fuse within six inches of the positive battery terminal for fire safety. I purchased an amp wiring kit from Circuit City that included all the terminals, 4 gauge wires, and 100 amp fuse.
I work at a battery place and made my own kit with 4ga welding cable. Did it pretty much the same way you did, just not in the carg container. Sounds great though.

BTW, That Optima 51 might be a little trouble getting ahold of. JCI ( owner of optima) hasnt produced any 51 or 51r's since around November. They may be dropping it from the line as well. Sucks because I wanted one :cry:
I got mine at Sears, in the fall. I've been back a couple of times and they still had a few in stock. Anyway, if I were more patient, I would have ordered an Odyssey. has the Odyssey probly cheaper than anyone else around, don't forget the brass terminals along with - the mounting bracket is worth a few extra $ too. Had mine mounted right up to the frame under where the factory one sat, perfect fit - if you can get your mounting bolts to go past that fan w/out too much cussin'.
Good write up Tom (ive read it before :p) You should add this to the "HOW TO" section.

I just bought a new Odyssey PC545 on ebay for $68.75 SHIPPED. Its going in the back of my 91 DX hatch.
I can't post in the How-To, it has to be put there by a mod. Anyway, I was wondering if anyone has done this and strapped it down. Mine is just held in by the box, and it doesn't go anywhere since it's so damn heavy. I always pass tech at autocross fine too. I'm a little afraid to screw into the frame there because the fuel tank is just below it, and I've heard self-tapping screws come loose pretty easily in a collision. Also, I have to have the battery in a sealed container for some of the track events (even though the battery is sealed, I don't know why), so I was thinking about making the container so it seals when it's closed. I'll have to get another container or make a bottom for the one I have, but I was going to put some kind of gasket around the edge so it will press into it when closed. Any ideas?
Nice write-up Tom.
Don't mean to thread jack but did you say battery in the back???? How about 2 group 31 yellows??

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downest said:
I can't post in the How-To, it has to be put there by a mod.
I kinda figured that... At first I wrote "talk to crxfisher about adding this to the how-to section" Then I went to the how-to section and there were no "rules / directions for submission", so I changed my post.
Please tell me that you have an inline fuse in that positive cable running to your starter.
If not you could be looking at a car-b-que.
Yes I do, it came with the wiring. My friend gave me the positive wire that runs from the battery after replacing his with quick-release ends, it has a fuse, though it's not in the best spot. It's under the carpet, about 2' down from the battery.
As good as the cargo area is, the best spot for anything heavy is as low and as centered in the car as possible. That is why I put a sealed gel cell battery (generic brand lawn mower battery) on the floor right behind the passenger's seat.

I just read this, and it's something that I'll want to do in the future. It would be helpful if you could post images of the storage area after it's been dremmel'ed so I can better understand what is going to be done. It's going to be a few months though ;).

Visual cues help and make everything alot easier to get done.
Here's a pic I took while I was doing it:

I don't have any pictures of just the container, but I can take some when I get some free time. I'll try to get ahold of a digi cam tomorrow, I'll be in the shop supervising my roommate's brake swap and cleaning the inside of my car, so I'll try and take some pictures. It's pretty simple, put the battery in the tray (out of the car) and trace it, then cut. You also need to bang down the frame a little underneath the tray if you use the Optima.

Ollie: Someone told me the fuse is too far away, that it should be within 12" of the positive terminal. Is that true? I don't see how it would make a difference. On the other hand, mine is kind of a pain to replace if it were to blow. I was thinking about putting in a cut-off switch anyway, so I would probably rewire it a little and relocate the fuse if that's true.
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I reread your post and noticed that I totally missed that you wrote you located your fuse 2' away from your battery! :shock:

Also it DOES matter where your fuse is mounted.
Lets put it this way.If your positive cable were to chaff or otherwise short out somewhere between your battery and BEFORE your fuse theres no fuse to protect the circuit.That = car-b-que....
Current will ALWAYS take the shortest path to ground!
On my trunk mounted battery I ran the fuse directly on top of the battery box.(3" from the positive cable end)

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That makes sense, can't see your pic though. I guess I'll move it. So is the only worry the chance that the cable will rub and short out? I'm pretty confident that won't happen the way I have it, but I will plan on changing the setup soon.
Fixed the pic so you could see it.
But yeah if the circuit isnt fused close to the battery any thing that closes the circuit could lead to a really big fire.
I've heard of it happening its not pretty.
Good luck and I hope you get a nice clean result.
I would worry about the battery coming loose in a big accident - kind of like being in a stuck in a dryer with a bowling ball... this sucks...OUCH...this sucks...OUCH...

Might want to use pop rivets and epoxy to hold a metal strap over that.
xxpaulcpxx said:
I would worry about the battery coming loose in a big accident - kind of like being in a stuck in a dryer with a bowling ball... this sucks...OUCH...this sucks...OUCH...

Might want to use pop rivets and epoxy to hold a metal strap over that.
If that one was directed at my setup.I put bolts and washers through the body so the box wont move in a collision.
But Yeah I get your idea. :lol:
ouch.....what the....ouch... :lol:
Ive come very close to having broken many bones or being killed by batteries coming foward in my work van.

So I'm out delivering batteries one day, had alot to do. Just got loaded up, 2 pallets, one in the side one in the back. I'm doing 45mph when someone pulls out in front of me. I slam on the brakes, the batteries in the back come up, hit the batteries behind me. Next thing I know I have 5 group 31 optimas between the seats and one hit my leg. The other dislodged the center console. If the console had moved my foot would have been toast, not to mention if a battery hit the gas peda :shock: . I work with batteries every day and they still scare the hell outta me.
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