DIY remote battery relocation questions.

I got 15ft of 2awg, heat shrink, 1/4" ring terminals, and a 1/4" terminal post.

My idea is to mount the battery behind the passenger seat, crimp both ends of the new positive cable, connect it to the battery, then connect the other end of the positive cable to the new terminal post, then connect the rest of the connections that were normally on the positive lead in the engine bay also to the terminal post which will be located in the engine bay at the previous battery location. The old negative will be reused and attached to the body somewhere.

Do I need to fuse the cable from the battery post to the terminal post? Should I fill the crimps with solder? Is heat shrink needed? Anything I'm missing?

If you don't have the equipment to get the connector and cable thoroughly hot, you can't fill it with solder worth a darn. So for most people, the answer is no solder. OEM isn't solder filled either btw. At least not normally.

Insulation on the connectors. I've had cars with the battery in the back passenger area get shorted before and catch the car on fire. More than once as a matter of fact. So use a battery box and cover, and a terminal boot. IMO and experience, you can't get too carried away with preventing contact.

Beware of hydrogen gasses, especially with a typical battery. Yes, the chances of an explosion are slim. But, it does happen some times, and has happened to me. It makes for excitement when the battery blows up and sprays acid everywhere.

To the hydrogen aspect, when gm put the battery under the back seat they had a vent tube that went on the battery vents and stuck through the floor. You could consider grabbing one of those.

I had one blow up recently. Not fun. I'm lucky I still have a face.

They shouldn't be in the passenger compartment without a proper box and venting.

Additionally, if you are going to race this, you will need a remote cutoff switch. A relocated battery is always looked at by track officials.

I forget the details, but several years back I relocated a battery and I wanted it to be both NHRA and SCCA legal.

There was only 1 battery box (made by Moroso) which was acceptable to both sanctioning bodies.

So I have a box. But my battery is an optima red top. Bought this year. I read mixed things about boxing an optima. Does it need it? If the slightest answer is yes then I will. Probably will anyways, just because of what was previously mentioned about open terminals shorting on things.

I always use a pass through terminal when running battery cables through firewalls

Miata batteries come with vent tubes, are compact and easy to get. I have Tee'd the hoses together and run a hose out through a firewall grommet under the car.

I would recommend yes to all your questions. I have a Red Top behind my passenger seat in the racecar. A 200A fuse sits about 2 feet down line on the positive cable, pass-through terminal at the firewall, then to a cut-off switch under the hood. All terminals are crimped, soldered, and heat-shrinked. When adding that much length and that many connections it is worthwhile to have the best continuity at EVERY crimp. I also keep a 13mm combo wrench right next to the battery for last resort battery disconnection if needed.

I don't run a box since it's an AGM, but it's not a bad idea to have one.

Good info!

In reply to The Hoff:

Are you saying you keep a combo wrench handy instead of a cutoff switch?

Not the same.

never put a battery in the cabin,unless compleatly sealed. never put gasoline in the cabin unless compleatly sealed. metal container is what I use to cover/seal them from your Axx. around here you cannot do either, at all, Period, in sactioned events.

GTXVette wrote: never put a battery in the cabin,unless compleatly sealed. never put gasoline in the cabin unless compleatly sealed. metal container is what I use to cover/seal them from your Axx. around here you cannot do either, at all, Period, in sactioned events.

There are a lot of (modern!) OE cars that break both of those rules. Fuel running through the cabin, filler necks exposed to cabin, un-sealed batteries in the cabin...

I work as an EV technician professionally, forklifts and other industrial vehicles.

We never solder power cable terminals, and factories seldom do either. A proper crimping is more than enough.

Use a fuse mounted close to the battery. 200 amp sounds pretty high to me, a lot could get damaged before that pops. Without doing any math knowing the particulars of the car I would guess a 150a would be a better starting point. If my presumption isn't correct, please explain why it's wrong.

Knurled wrote:

GTXVette wrote: never put a battery in the cabin,unless compleatly sealed. never put gasoline in the cabin unless compleatly sealed. metal container is what I use to cover/seal them from your Axx. around here you cannot do either, at all, Period, in sactioned events.

There are a lot of (modern!) OE cars that break both of those rules. Fuel running through the cabin, filler necks exposed to cabin, un-sealed batteries in the cabin...

older cars too.. VW beetles just had the battery strapped down under the rear seat. A really heavy friend could get the seat coils to touch the terminals

2 main elements to make Fire,fuel and spark.C Y A or in this case your battery.

HappyAndy wrote: I work as an EV technician professionally, forklifts and other industrial vehicles. We never solder power cable terminals, and factories seldom do either. A proper crimping is more than enough. Use a fuse mounted close to the battery. 200 amp sounds pretty high to me, a lot could get damaged before that pops. Without doing any math knowing the particulars of the car I would guess a 150a would be a better starting point. If my presumption isn't correct, please explain why it's wrong.

Starters can draw well over 200 amps, especially if the battery is a little low on charge and voltage drops a bunch.

I've never fused a positive cable, OEMs don't do it either. The closest thing I've seen to a fuse on a positive cable is some BMWs have a pyrotechnic device on the positive terminal that will blow the cable if the airbags deploy.

As alluded to upthread, you're more likely to short the battery terminal to ground than you are to short the cable to ground. Cover the terminal or put the battery in a box, that's plenty of concern needed.

mad_machine wrote:

Knurled wrote:

GTXVette wrote: never put a battery in the cabin,unless compleatly sealed. never put gasoline in the cabin unless compleatly sealed. metal container is what I use to cover/seal them from your Axx. around here you cannot do either, at all, Period, in sactioned events.

There are a lot of (modern!) OE cars that break both of those rules. Fuel running through the cabin, filler necks exposed to cabin, un-sealed batteries in the cabin...

older cars too.. VW beetles just had the battery strapped down under the rear seat. A really heavy friend could get the seat coils to touch the terminals

During my Air Force days I was called to the flight line to find a early 60s Ford Econoline van under a C-141 with a smoldering drivers seat. Someone had installed a taller than stock battery (located under drivers seat) and tossed the cover.

Dobbins? Sounds familier.

McGuire, but I'm sure it happened quite often. We had an airman assigned permanent tool room duty because he was attempting to remove a tire without jacking up the vehicle.

In reply to outasite:

Good lord. And these ppl defend America?

In reply to mad_machine:

Beetles had a cover over the battery originally, they usually got thrown away.

In reply to SVreX:

He has a cut off switch and also keeps a properly-sized wrench by the battery as an additional precaution.

Knurled wrote:

GTXVette wrote: never put a battery in the cabin,unless compleatly sealed. never put gasoline in the cabin unless compleatly sealed. metal container is what I use to cover/seal them from your Axx. around here you cannot do either, at all, Period, in sactioned events.

There are a lot of (modern!) OE cars that break both of those rules. Fuel running through the cabin, filler necks exposed to cabin, un-sealed batteries in the cabin...

Track officials don't care if OEM breaks rules. They totally care if you do.

I believe every time I've been to the track with my Miata, I've been asked by tech officials if the trunk was the original location for the battery. When I say yes, they walk away. If I said no, they would want a box, venting, and a cutoff switch.

I'm not sure why track officials have to ask me about battery locations in Miatas...I'd have figured they would have seen one before.

Trackmouse wrote: In reply to outasite: Good lord. And these ppl defend America?

If you only knew……...

SVreX wrote:

Knurled wrote:

GTXVette wrote: never put a battery in the cabin,unless compleatly sealed. never put gasoline in the cabin unless compleatly sealed. metal container is what I use to cover/seal them from your Axx. around here you cannot do either, at all, Period, in sactioned events.

There are a lot of (modern!) OE cars that break both of those rules. Fuel running through the cabin, filler necks exposed to cabin, un-sealed batteries in the cabin...

Track officials don't care if OEM breaks rules. They totally care if you do. I believe every time I've been to the track with my Miata, I've been asked by tech officials if the trunk was the original location for the battery. When I say yes, they walk away. If I said no, they would want a box, venting, and a cutoff switch. I'm not sure why track officials have to ask me about battery locations in Miatas...I'd have figured they would have seen one before.

To be totally fair to the track officials, they figure that if the manufacturer did it, it's reasonably safe. If it's something thought up by some random yahoo, who KNOWS what kind of hackery they did?

What is funny is, I get the opposite of that. In RallyCross, one of the cardinal rules is the battery must be held down. In some regions, they are anal-retentive about ensureing the positive cable is covered, too. That is all well and good, and I approve. But when I bring the RX-7 around to non-local events, the battery question usually goes like this:

"Where's the battery?"
"Behind the passenger seat" (points to box)
"...Eh, it's good."

Granted, the positive cable is covered, and it's held in with 3/8" all-thread (NHRA-legal!), but beyond that, nobody seems to want to bother with checking once it turns out that it will take actual work

There's a video I made some years back of a particularly grippy winter rallycross. I took the RX-7 out for tire testing. There was a strange clunking I could hear in the video through a slalom. After investigating, I realized it was the battery sliding around in the battery box even though I thought it was secured well enough