Thread: trunk mounted battery short protection

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what do you guys with trunk mounted batteries use for short protection on the positive cable between battery and starter/fusebox? i cant find anyone who makes a heavy duty type fuse or breaker to mount at/near the battery. anyone with any info on this??

Originally posted by Albrainya
what do you guys with trunk mounted batteries use for short protection on the positive cable between battery and starter/fusebox? i cant find anyone who makes a heavy duty type fuse or breaker to mount at/near the battery. anyone with any info on this??

Far as I know Albrainya this is it. Put it in the neg. bat cable, use extra grommets where it might rub.

http://www.jegs.com/webapp/wcs/store...tegoryId=14471

I agree with Mike. I know of no circuit breaker/fuse that will handle the amps a starter draws, so usually the positive cable just goes to the battery straight.

Also depends on if car is street driven or raced at a strip. If raced, the NHRA or whomever, will dictate how you mount , vent, and switch your trunk battery(s). If street driven, you just want to use good common sense.

I use marine grade battery cable, because that is my industry, and the cable is high quality, and available at most marine centers. I use crimp on terminal ends, because that is what is specified in boats, and I am not great at soldering. I use shrink tubing on all connections, run the cable through grommets, or even slip a length of bigger hose over it and shrink wrap the hose in place where it goes through the trunk, etc. I secure the cable with clamps to the frame every foot or so, and use a large enough diameter cable to offset the long run.

I also try to terminate the negative cable on the bell housing, or a starter mounting bolt, so I get maximum kick at the starter. If you have to use a frame ground in the trunk, use a braided ground strap from the bellhousing or starter ground to the frame in that area.

Use a battery that is maybe a group 27 or 31, secure it in a bolted down box or tray, and if you can afford it, use an AGM battery as it is gasless. I forget what the A stands for, but the G means Glass and the M means Mat. I just got one for my Sons rod, as he is sharing space with the battery in the cockpit, and I didn't want him to get fumed.

With the long run, you take on some additional problems of current drop, but a strong battery with alot of cold crank amps, large cables, and tight clean connections and a good ground, will usually get the job done.

If you are going to go to the strip, get the rule book, and build your system as they outline.

Originally posted by Albrainya
what do you guys with trunk mounted batteries use for short protection on the positive cable between battery and starter/fusebox? i cant find anyone who makes a heavy duty type fuse or breaker to mount at/near the battery. anyone with any info on this??

You can use one of these....... You can get them at most stereo shops or electronic stores You can get the fuse in sizes from about 50 amps to 600 amps I used them on a batt cable that I ran inside a frame rail

MM64

It may be time to show this again.....

Battery Relocation:
First of all, why would you want to move the battery from its stock location? Well, in the case of a ricer, you may need the room for an aftermarket intake pipe or in the case of a rear-drive car, you may want to improve the front/rear weight distribution and put more weight on the rear tires. Now, a front motor, rear drive car twists the frame under acceleration in such a manner that the left front gets lighter, the right front gets heavier, the left rear gets heavier and the right rear gets lighter. That's why you see so many worn-out right rear tires on a car with a one-legger (open, non-posi) differential and the driver "peelin' rubber" at every opportunity. The left rear bites because it has more weight on it and the lightly-loaded right tire spins. Even if you have a posi or a spool, doesn't it make sense to try to equalize the weight on both rear tires so the system can work more efficiently? So if you're going to move the battery, it makes sense to mount it in the extreme right rear corner of the car, no matter if the diff is open, posi or spool.

Now that the new position is nailed down, let's address some of the NHRA requirements to make it work by the rules. The main things we're concerned with in an incident is keeping battery acid off the driver and also making certain the battery stays secured in the car. Here, I'll quote the rule on batteries from Section 8:1 under General Regulations in the 2005 NHRA Rulebook:
8.1 BATTERIES
All batteries must be securely mounted. Batteries may not be relocated into the driver or passenger compartments. Rear firewall of 0.024" steel or 0.032" aluminum (including package tray) required when battery is relocated in trunk. In lieu of a rear firewall, battery may be located in a sealed 0.024" steel or 0.032" aluminum or NHRA-accepted poly box. If sealed box is used in lieu of rear firewall, box may not be used to secure battery and must be vented outside of body. Relocated battery(s) must be fastened to frame or frame structure with a minimum of two 3/8-inch diameter bolts. (J-hooks prohibited or must have open end welded shut.) Metal battery hold-down straps mandatory. Strapping tape prohibited. A maximum of two automobile batteries, or 150 pounds combined maximum weight (unless otherwise specified in Class Requirements), is permitted. Maximums may vary according to class requirements.

Let's examine the rule.
A. Batteries must be securely mounted. No question there.
B. No battery in driver's compartment. What about a hatchback car? Well, technically, the rear of the car on the inside is a package compartment, not a driver's compartment. We pass cars all the time with batteries in this location, but we're pretty darned picky about everything being properly engineered. You can construct a metal bulkhead in one of these cars if you're bull-headed, but it's a lot easier and cleaner to mount the battery in a sealed box in the right rear corner. The one exception to the battery in the driver's compartment is the early VW bug with the OEM battery under the rear bottom seat cushion. If it's a stock bug, I don't say anything about it other than to make sure it's secured, but if the seat cushions are removed and the battery is visibly open to the driver, we've got to start talking sealed box.
C. Rear firewall (car with a trunk). If you're going to start cutting up sheet metal for a firewall, the easiest way is to make a template from heavy construction paper, butcher's paper or light cardboard and transfer the pattern to your sheet metal to be cut. This firewall has to be water tight (package tray too). The material can be secured to the "X" braces with pop rivets or sheet metal screws. These firewalls are tested by one guy shining a flashlight from the trunk of the car and another guy looking into the interior of the car to determine if any light is coming through. The best thing to do is to go to church before you start this project. Again, the common sense thing to do is put the battery in a sealed box and be done with it.
D. Box may not be used to secure battery and must be vented to outside. You want to secure the battery to the car, then cover the battery with the box and secure the box to the car. Run a vent line (a small rubber hose will do) from inside the box to outside the car (through the floor) so there is no buildup of hydrogen gas in the box from the battery being charged.
E. Battery fastened to frame or frame structure. Now, this is ME talking and not the NHRA, but I don't enforce this rule until the car is quick enough to require a roll bar (11.49). Slower than that, it is my opinion that if the battery is properly secured to the floor with the procedure that I'll explain shortly, it's not goin' anywhere. Most of the kids who show up with these slower cars don't have the welding/fabricating skills or tools to do it themselves or the money to pay a pro shop to fabricate the pieces necessary to mount the battery to the frame or frame structure. On the other hand, if he has the wherewithall/expertise to install a roll bar, then he certainly has the means to mount the battery(s) according to the rules.
Here's my logic for fudgin' a little and givin' these youngsters a break...
1. When the battery was in the original position, it wasn't mounted to the frame, it was in a tray which was spot-welded to the firewall or fenderwell sheet metal.
2. NHRA allows a 5-point roll bar in a unibody car to be welded to 6" x 6" plates which are then either welded or bolted to the sheetmetal of the floor. 5 of these plates have a total surface area of 180 square inches. In a 3,000 lb. car, that's a load of about 17 lbs/sq in. if the car is on its lid. Using the same math, a 50 lb. battery would need slightly less than 3 sq in of support on the floor.
F. Minimum of two 3/8-inch diameter bolts. What I suggest using is 3/8" allthread. You can pick up a 2 or 3 ft. stick of it at the hardware for less than 5 bucks and cut it to the length you need. It's easier than trying to locate 3/8" bolts of the proper length. Don't even think about using J-hooks, they are the cheeziest of the cheezy. I do not agree with rule that allows J-hooks if the ends are welded shut. Even at that, the only thing holding the battery in the vehicle is two thin slivers of sheet metal on the tray where the J-hooks go through. Position your battery where you want it and drill a 3/8" hole through the floor on each side. CAUTION: THERE MIGHT BE A GAS TANK UNDER WHERE YOU'RE DRILLING . You'll need 2 locknuts and 2 nice big flat washers at least 1/8" thick under the floor (like fender washers except thicker, or use several fender washers and stack them so they're good and strong and won't "cup-up" and pull through the floor). Use 2 lock nuts with the same large diameter flat washers on top of the floor, tightened to "sandwich" the floor and keep the allthread in place. Using 2 washers of 2" O.D. will give over 6 sq. in. of anti-pull-through material holding the battery in place and will calculate to a load of just over 8 lbs/sq. in. with a 50 lb. battery, less than half the loading on the floor of the roll bar plates. Make a metal hold-down strap from a piece of 1/8" thick x 3/4" or 1" wide steel strap material. There's no spec on this piece, but you want it to be stout. Like the rule says, no strapping tape or other cheezy material like plumber's tape. Drill a 3/8" hole in each end of the strap and use 2 lock nuts and flat washers on the studs to snug the battery down and you're bulletproof.

As far as the battery box goes, you're free to make your own (sealed) box as outlined in the rule. Those cheezy plastic marine boxes won't make it here. Use rubber grommets in the side or end of the box to run your cables through and remember to run the cables through the grommets and slide your heat shrink tubing on the cable before you install your cable ends . What I'd do is run the cables through the side or end of the box and bend up a nice, bolt-down, removeable top for the box so I could check the water level in the battery. A seal to go between the lid and box can be cut from an old tire innertube. Drill a small hole in the box that'll fit your vent tube. There is only one commercially available plastic box that's NHRA certified, made by Moroso. Summit part # MOR-74050 for $96.95. Taylor makes a real nice aluminum box that's certified under Summit # TAY-48100 for $83.39. Seal the box to the floor and secure it with bolts or sheet metal screws and you're golden. Just a couple of additional side-notes here. Gel-cell or other semi-liquid or dry-cell batteries are NOT excluded from this rule. If you're going to relocate the battery, no matter what type of battery it is, you're going to have to meet the rule with a rear firewall or box. The other thing is, a pickup truck with the battery relocated to the bed does not require a box, only the 3/8" studs/bolts and a metal retainer strap. The rear of the cab serves as a rear firewall to keep acid off the driver.

continued.....

MASTER ELECTRICAL CUTOFF SWITCH:
I've saved all the wiring info to put under this section. If the battery is relocated, no matter WHERE in the car it's relocated, a master cutoff switch is required. Most everybody uses a switch distributed by Moroso and available from Summit under part # MOR-74102 for $59.88. I know that's a pretty hefty price to pay for a switch and you've probably seen switches such as this for much less money, but keep in mind that the Moroso unit is rated at 300 amps continuous duty and 2,000 amps intermittent duty. It's bulletproof.
Not only must the switch kill the battery power, but must also kill the motor. On most cars, even with the battery killed, the motor will continue to run because current being generated by the alternator can back-flow through the exciter wire back to the ignition switch and be picked up by the +coil wire. I'll quote the rule first:
8:4 MASTER CUTOFF:
"Mandatory when battery is relocated, or as outlined in Class Requirements. An electrical power cutoff switch (one only) must be installed on the rearmost part of each vehicle and be easily accessible from outside the car body. This cutoff switch must be connected to the POSITIVE side of the electrical system and must stop all electrical functions including magneto ignition. The off position must be clearly indicated with the word "OFF". If the switch is "push/pull" type, "push" must be the action for shutting off the electrical system, "pull" to turn it on. Any rods or cables used to activate the switch must be minimum 1/8-inch diameter. Plastic or keyed switches prohibited. Switches and/or controls must be located behind rear wheels on rear-engine dragsters."

O.K., let's examine the rule:
A. ....rearmost part of the car....
This does not mean on the side of the car toward the rear or on the trunk lid near the rear of the car, it means the REARMOST part of the car. Think about it this way. If you backed the car up against a wall, the switch handle or activation rod should be the first part of the car that touches the wall. When a crew member or track safety official approaches the car to kill the electrical functions in an emergency situation, they shouldn't have to look all over the car for the switch. You guys with dragsters sometimes mount the switch at the top of the differential in front of or beside the 'chute pack. You need to consider the worst possible scenario and that is the car off the end of the track in the dirt, upside down and on fire. If the switch is mounted toward the topside of the car and in front of or beside the chute pack, then when the car is upside down, the switch will be buried in the dirt and the safety crew can't get to it. One more time.....REARMOST PART OF THE CAR....
B. ...switch connected to the positive side of the battery...
I've had racers try to argue with me that the switch should be connected to the negative. Well, if you're an electrical engineer, you may know more than the tech guys at NHRA who write these rules, but the fact remains that the book says POSITIVE side, so that's the rule I'm going to enforce.
C. ...."push/pull"....
Rather than mounting the switch/handle to the outside of the car through a rather large hole, some guys prefer to mount the switch further into the interior of the car (like the trunk floor) and extend a rod with handle through a small hole in the sheet metal or a taillight lens at the back of the car. You can drill a hole in the switch handle and use jam nuts on the threaded end of the rod to sandwich the switch handle, thereby changing the operation of the switch from rotary to push/pull. I believe Painless Wiring (Painless Performance Products) has a new push-button switch, but I haven't seen it. You street guys who have a restored classic and don't want holes in the back of the car can build a mount for the switch off a bumper bracket or other suitable component at the rear, running the + cable through a hole/grommet in the trunk floor and again, remembering to run the bare cable end through the grommet and sliding your shrink tubing onto the cable before attaching the cable end/lug . If you were creative, you might even use a gate hinge from the hardware store to hinge the switch up and out of sight for the street. Spring-loading it would make it rattle-proof and some clevis pin or other arrangement could lock it in the down position for racing.

O.K., we have the switch mounted. Now, let's wire the whole mess.
First off, trying to save money on the cable and wiring by using offshore junk is not the hot tip. Use components from a reliable source such as Painless Wiring instead of that cheap stuff from your local auto parts house or use welding cable from your local welding supply or an online welding supply source. Welding cable is far superior to other types of high-amp cabling you'll find. The finer strands have a greater current-carrying capacity, the covers are made to withstand harsh abuse and it is more flexible than standard automotive cable. Jack Brewer, electronics tech at Painless, recommends #1 AWG cable, whether using their cable or welding cable. Their #1 AWG is a 133-strand cable, so it's good stuff. You can buy their battery relocation kit which has one 3 ft. length of #1 AWG black cable with terminals for the ground cable and one 15 ft. length of #1 AWG red cable with terminals for the hot line through summit under part # PRF-40100 for $69.95. Cut a piece off the red cable to run from the + side of the battery to the "battery" side of the master cutoff switch and use the rest of the red cable to connect to the "load" side of the master cutoff switch and to run to the front of the car. The switch is just a SPST switch, so it doesn't care which side is used for which. Remember to "clock" or properly orient the cable end that bolts to the switch before soldering the mounting lug to the cable so you won't have to twist the cable to make it lay on the mounting stud of the switch . Here are solder lugs from Welding Depot:
http://store.weldingdepot.com/cgi/weldingdepot/RLx.html . I've found that NAPA also has a good selection of terminals and lugs.
Also remember to slide the heat shrink tubing onto the cable before soldering the lug on . Make certain that you remove all paint or other contaminants from the spot where you attach your ground cable. You'll probably be grounding the cable to the body, so you'll have to remember to run a piece of #1 AWG cable from the engine block to the body and also from the frame to the body up front. Installing the negative battery cable to ground in the trunk, I like to use a bolt/lock nut, installing it where I can get to both the bolt head and the other end where the nut is so I can cover both of them thoroughly with RTV silicone to prevent air and/or water from oxidizing the connection. In my opinion, you can never have too many good grounds on the car. Now, drill a hole in the trunk floor, install a grommet and run your long length of red #1 AWG cable through it (you didn't put an end on the cable yet did you? ) to go to the starter or solenoid at the front of the car. You'll want to support the cable along its length with insulated Adel clamps (also called loom clamps) about every 12 inches which can be nailed to the under-car sheet metal with sheet metal screws. Here are the loom clamps that Jack at Painless recommended. There are 5 pages of them, from 1/4" to 3", so there's a size for every application.
http://www.delcity.net/delcity/servl...tid=285&page=1
There are at least 2 ways to kill the motor with the switch. If you have a multi-wire alternator with connections on the back side, you can either interrupt the exciter wire (usually labeled #1 on a Delco alternator, you'll have to consult a wiring diagram on other units) and run it through a solenoid or you can interrupt the alternator current output with a Painless shutdown relay kit #50105. There may be another option, if you're electrically savvy and that is to install a diode in the exciter wire so that the current can only go from the ignition switch to the alternator, not feed back the other way to energize the + side of the coil. I have no idea about the spec on the diode or whether or not it would work, it's just another idea. If interrupting the exciter wire and running it through a solenoid (relay), don't use one of those cheezy Ford units. They are not rated for continuous duty and will probably lay down on you at the worst possible place and time. Use the relay from Painless, kit # 50105, available at Summit under part # PRF-50105 for $69.88. It's rated at 250 amps continuous duty and includes some 8 gauge wire which is probably overkill for this application, but they don't sell their relay by itself. I'd mount the relay close to the alternator, cut the exciter wire, attach an end to each of the feed/output lugs ( the big studs) of the relay, one on each side, ground one side of the activation/energizer circuit (small studs) and run the other side back to the cutoff switch "load" terminal. In doing some research on this, I found another relay that might work. It grounds through the mounting tabs so it just has one small stud where you mount the hot 12v line to energize it and is rated at 85 amps continuous. http://www.delcity.net/delcity/servl...=743393&page=1 .
Now, if you're using a one-wire alternator or just want a bulletproof way to shut the motor without fooling with the exciter wire on your multi-wire alternator, use the Painless 50105 kit. Here are the installation instructions which Jack Brewer provided:

continued......

1. Mount relay (solenoid) assembly in desired location using mounting tabs with sheet metal screws or bolts/nuts. Attach the black ground wire with one of the mounting screws/bolts to ground at the relay mounting tab, connecting the other end of this wire to one of the energizer posts (small stud) on the Painless relay. The relay doesn't care which small stud you use first. IMPORTANT; THE BLACK GROUND WIRE MUST MAKE A GOOD GROUND OR THE SHUTDOWN RELAY WILL NOT OPERATE PROPERLY. NOTE; LOCATING THE RELAY FORWARD OF, OR NEAR THE FRONT OF THE ENGINE WILL HELP REDUCE VIBRATION TO THE RELAY.
2. Remove and discard existing output wire from alternator to battery.
3. Run and attach (cutting off any excess wire) one of the large red 8 gauge wires supplied in the kit to the "battery" side of the master cutoff switch using the ring terminal provided in the kit, connecting the other end of this wire to either one of the output/feed lugs (large stud) on the Painless relay. The relay doesn't care which large stud you use first.
4. Run and attach (cutting off any excess wire) the other large red 8 gauge wire to the output post on the back of the alternator (may be marked "Batt") using the terminal provided in the kit, connecting the other end of this wire to the other output/feed lug (large stud) on the Painless relay.
5. Run and attach (cutting off any excess wire) the small red/white 18 gauge wire to the "load" side of the master cutoff switch, connecting the other end of this wire to the remaining energizer lug (small stud) on the Painless relay.

All that's left to do is label your "OFF" position if you're using the master cutoff switch in a rotary on-off application or label your push/pull rod with "PUSH OFF".

O.K., she's done. Turn the master cutoff switch on and fire the motor. Now turn the switch off. All electrical functions should stop and the motor should die. If not, go back over your wiring and correct your error.

Here are some of the main links I've referenced and others of interest:
www.summitracing.com
http://www.painlessperformance.com/index.htm
www.delcity.net
www.moroso.com
http://www.aeroelectric.com/articles/big_term.pdf
http://www.timskelton.com/lightning/...y_relocate.htm
http://home.indy.rr.com/tlorek/buick_1993_buildup.html

Now, if you don't feel the need to comply with NHRA standards or, are relocating the battery solely for personal desire, you can easily use a fuse and holder intended for CA use.
http://cgi.ebay.com/Lightning-Audio-...QQcmdZViewItem

200A is just an example, I'm sure no starter will draw this much amperage. CA fuses come wth cases. Locate the fuse near the battery to minimize melted wire incase of a short. Will you have only one PWR coming from the battery or multiple? If you have multiple, you need to fuse them all.

CA is something I am deeply enveloped in, and wiring and fusing is a large portion of it.

I try not to think about it too much.

Thank you, very informative. I'm getting ready to install my battery in the trunk of my '67 chevelle. I've bought the moroso box and switch. I was going to drill through the trunk sheetmetal to the frame rail to bolt the 3/8 all thread directly to the frame, Is that legal?

Originally posted by 427chev67
Thank you, very informative. I'm getting ready to install my battery in the trunk of my '67 chevelle. I've bought the moroso box and switch. I was going to drill through the trunk sheetmetal to the frame rail to bolt the 3/8 all thread directly to the frame, Is that legal?

yep

Well I saved this thread while I figure out my electrical setup. I ordered a 20 circuit wiring harness from TPI for much less than a Painless 12 circuit harness so I hope it is not a bear to install. The first order of business is the battery setup. Today I decided not to wait for my backorder from Summit and so I bought 11 feet of 1/0 (red) and 3 feet of 2/0 (black) welding cable from Arcet along with some terminal connectors. I want the cutoff somewhat hidden for theft protection since the on-column Camaro ignition switch is probably easy to hot wire? Any further suggestions on a street setup? I have a 100 amp single-wire alternator.

Don Shillady
Retired Scientist/teen rodder

Here's an excerpt from the long-winded explanation above.....

If you were creative, you might even use a gate hinge from the hardware store to hinge the switch up and out of sight for the street. Spring-loading it would make it rattle-proof and some clevis pin or other arrangement could lock it in the down position for racing.

That's an idea Tech1, I need to think this over pretty well. The Moroso 74102 ($59.88) is available from Summit although it is not in their catalog. They also have a 250 amp cutoff for $49.95 and a push/pull with provision for the alternator cutoff for $78.88 but only rated at 150 amps continuous with 2000 amps surge. The 300 amp cutoff looks good, but I am scratching my head over where to put an external switch in the rear if I put a resto-rod luggage rack on the back of the roadster, although I suppose there are ways to put it back there and still be hidden. Overall I think this is forcing me to just get something safe for the street and not worry about the 1/4 mile at my age. I'm still studying the Sweeden book and probably will follow his street circuit. Just facing up to my age and trying to get the car on the road for touring while I can enjoy it. Thinking it over in edit mode I suppose it would be possinle to have a setup where the luggage rack could be unbolted easily.

Don Shillady
Retired Scientist/teen rodder

Sorry to ask more dumb questions, but if the cutoff switch is in the rear of the car accessible, but hidden maybe with a screen door spring-loaded flap, with a cutoff on the alternator as well as the battery that means the single wire from the alternator has to go all the way back to the cutoff switch? And of course there has to be enough slack in the wires to the cutoff switch that the flap can move up and down. I have sweated out circuits a lot before and burned up quite a few with micro-amp applications but here we are talking hundreds of amps so I need to get it right the first time! The TPI guy boasted that their harness has an 8-gauge alternator wire compared to a 10 in the Painless kit, but I will have to unravel the harness to figure out if the alternator wire is long enough to go to the back of the car. If not I guess I can use No. 8 welding cable; my local supplier had quite a range of sizes and the welding cable is really flexible.

Don Shillady
Retired Scientist/teen rodder