Grassroots Motorsports

Register Log in to GRM
- Community

Birthdays
Recently on the Classic Motorsports forums

Subscribe get a full year for only $23.95 Sample Free Test Drive—no strings attached

Login to post Forums » Grassroots Motorsports » Oh wise & experienced GRM comunity, please teach me about battery relocation

1 2

Nov. 28, 2011 3:28 p.m. HappyAndy HalfDork

See, I avoided "learn me".

I am planning to relocate my SAAB c900 turbos battery from the OEM location in the front RH corner of the engine compartment (right next to the turbo & downpipe), to the trunk. I've already obtained a gel cell battery and plenty of copper cable, what else do I need to make a clean installation? My plan is to make a shallow recess in the trunk floor and weld in some brackets to hold it in place with a bar and J hooks, the finished product should be concealed under the hatch of the spare tire compartment. I want to use this car as a general purpose motorsports beater (Auto-X Rally-X HPDE and hopefully even a $20XX challenge). I know different sanctioning organizations have varied rules about this sort of thing, so what I'd like to know is if this plan is likely to fly or fail if checked out by a tech inspector? I will be using a gel cell battery, so hyI shouldn't need a vent to atmosphere, and it will be
under the spare tire hatch cover so it will be enclosed and separated from the cabin of the car.
Nov. 28, 2011 4:59 p.m. iceracer SuperDork

What size copper cable.?
Nov. 28, 2011 7:02 p.m. irish44j Dork

here's a good write-up of a good system. Very similar to the way I did mine in my wrx (except I used a blade-fuse box in the back instead of a circuit breaker)

http://wgbuckley.com/projects/battery.html

Even with the gel cell, it's best to seal it in a box, in my opinion, and vent it anyhow. IIRC gel cells CAN vent, they just don't under normal circumastances (coudl be wrong about that). I'm pretty sure most tech inspectors for track events are going to be looking for that (not autocross), though again I could be wrong.

As the previous post inferred...cable size matters. In the WRX I used 4-gauge (with heavy marine sheathing), but I definitely get some voltage drop along the long run of wire with that gauge, and the car cranks much slower. I would go no smaller than 2-gauge so you're getting full voltage to the starter. Even the stock e30 trunk battery cable is 1-gauge I think. I got the 4ga for free (parents own a marina), so I used it. If I was buying for the application I'd go larger.

Also when you run the wire, make sure to secure it well and anyplace it goes near anything with an edge, wrap it with some plastic/rubber tubing so it doesn't chafe through to the copper.
Nov. 28, 2011 7:08 p.m. TRoglodyte HalfDork

iceracer wrote:

What size copper cable.?

QFT amp draw on a cold start could be an issue. Welding leads or romex?
Nov. 28, 2011 7:14 p.m. donalson SuperDork

I've read of a number of people pulling the battery cables from BMW's at the JY to get cable for cheap... thats my plans here soon for the s10
Nov. 28, 2011 7:31 p.m. corytate HalfDork

very well shielded heavy gauge copper cable for sure.
maybe a box for it even
run the cables so they aren't going to be pinched by anything (of course)
idk what else
Nov. 29, 2011 6:04 a.m. xFactor New Reader

I like to double up a pair of 200 amp ANL style fuses (in parallel) in case things go really bad.

later, matt
Nov. 29, 2011 7:01 a.m. Ranger50 Dork

When I did mine in my Ranger, I used 00 welding cable with marine grade hammer crimp lugs on the ends. I just copied the OEM battery cable attachment points and it fired right up. Don't forget about a kill switch too. I know not everyone says to use it, but it makes killing a hot vehicle easier.
Nov. 29, 2011 7:04 a.m. HappyAndy HalfDork

iceracer wrote:

What size copper cable.?

2/0 welding cable, and I have I have the equipment to make properly crimped cable ends.
Nov. 29, 2011 9:12 a.m. iceracer SuperDork

I asked because some have been done with sound system cables. With poor results.
Nov. 29, 2011 10:10 a.m. steronz New Reader

NHRA requires an external kill switch (battery and alternator) if the battery is not in the stock location. As far as I know, they have they most strict rules about battery relocation. I don't know if the $20xx challenge uses NHRA rules for the drag strip portion, but I would suspect that nobody would care. That's all I have to add to this discussion.

ETA: I also had a drag strip tech bitch about my gel cell battery not being in a vented box once. I tried to explain that it was a gel cell and didn't vent anything, but he didn't seem to care. The rulebook doesn't make a distinction.
Nov. 29, 2011 11:51 a.m. porschenut New Reader

I was concerned about chafing so I sprayed the cable with silicone spray and slip it into a braided garden hose for additional protection.
Nov. 29, 2011 12:00 p.m. MadScientistMatt SuperDork

donalson wrote:

I've read of a number of people pulling the battery cables from BMW's at the JY to get cable for cheap... thats my plans here soon for the s10

Yep. Most BMWs had trunk mounted batteries and they've got battery cables that are great for battery relocation. Using one on my Dodge Dart.
Nov. 29, 2011 12:04 p.m. Sky_Render Reader

Make sure the ground connections are secure and clean. (Sand the paint off before bolting them.) You may wish to run a separate cable for ground.
Nov. 29, 2011 12:09 p.m. corytate HalfDork

saturn ion's also had trunk mounted batteries. idk if only limited number of years or all production, but I saw one yesterday here (we used to be a saturn dealer so we still get a lot of saturns in)
Nov. 29, 2011 1:48 p.m. mad_machine SuperDork

I have thought about doing this to my c900 turbo as well. I think in the end I am just going to go with the same small gelcell I put in my BMW. hopefully 625CCAs will be enough to crank over the lowcompression engine... seems to work well on the highcompression BMW engine
Nov. 29, 2011 4:10 p.m. Karl La Follette Dork

Boats have really long battery cables in them
Nov. 29, 2011 5:28 p.m. irish44j Dork

Karl La Follette wrote:

Boats have really long battery cables in them

Most marine battery cables are 4 gauge. Ask me how I know ;)
Nov. 29, 2011 6:57 p.m. HappyAndy HalfDork

xFactor wrote:

I like to double up a pair of 200 amp ANL style fuses (in parallel) in case things go really bad.

later, matt

How did you come to this arrangement? Why parallel 200s and not a single of a higher amperage, and how does one determan the best fuse amperage for a given application?

I definitely want a fuse mounted near the battery , my seat of the pants guess would be a 175 or 200 amp single, but if there is a formula I'd like to know it.
Nov. 29, 2011 7:03 p.m. HappyAndy HalfDork

mad_machine wrote:

I have thought about doing this to my c900 turbo as well. I think in the end I am just going to go with the same small gelcell I put in my BMW. hopefully 625CCAs will be enough to crank over the lowcompression engine... seems to work well on the highcompression BMW engine

Have you inspected your frame around the RH lower control arm mounts for battery acid induced rust yet?
Nov. 29, 2011 7:06 p.m. HappyAndy HalfDork

porschenut wrote:

I was concerned about chafing so I sprayed the cable with silicone spray and slip it into a braided garden hose for additional protection.

I was planning to do the same thing with scraps of hydraulic hose as conduits in areas where the cables could chafe.
Nov. 29, 2011 7:14 p.m. irish44j Dork

HappyAndy wrote:

xFactor wrote:

I like to double up a pair of 200 amp ANL style fuses (in parallel) in case things go really bad.

later, matt

How did you come to this arrangement? Why parallel 200s and not a single of a higher amperage, and how does one determan the best fuse amperage for a given application?

I definitely want a fuse mounted near the battery , my seat of the pants guess would be a 175 or 200 amp single, but if there is a formula I'd like to know it.

I'm using an ANL 200 in a box just outside my battery box. If you have a long-term short, that will blow. But it's a slow-blow fuse, so even during long cranking at high amps, it's still fine.
Nov. 29, 2011 7:17 p.m. HappyAndy HalfDork

As far as an external kill switch goes, if the car gets to the point that its spending more time at the track than the street I'll add one in then, this car also does duty as a dog and MTB hauler too.
Nov. 29, 2011 7:59 p.m. mad_machine SuperDork

HappyAndy wrote:

mad_machine wrote:

I have thought about doing this to my c900 turbo as well. I think in the end I am just going to go with the same small gelcell I put in my BMW. hopefully 625CCAs will be enough to crank over the lowcompression engine... seems to work well on the highcompression BMW engine

Have you inspected your frame around the RH lower control arm mounts for battery acid induced rust yet?

I have surface rust.. caught the car before it got expensive to repair. Once I get the engine out monday, I can start sanding and painting the engine bay
Nov. 29, 2011 10:25 p.m. xFactor New Reader

Just about every relocation I do is v8 stuff in the trunk for customers, and while I want them to be safe, I also don't need it to fail out in South Krackolaka. The biggest single ANL fuse easily found is 300amps and that would probably be fine in 95% of the time.

I tested/sacrificed a 200amp ANL on a pat musi 555 crate engine and it cranked over for a while as we set the timing, maybe 15 times or so before it failed. I double up the 200's for a total of 400amps for a lot of headroom, in case of low voltage situations, but low enough so if they get in a wreck it will pop.

later, matt

1 2

You'll need to log in to post.