Circuit breaker for trunk-mounted battery?

[jlwdvm]

I have my optima battery mounted in the trunk of my 69 Firebird LS3 track/street car with the battery cable running up the center of the inside of the car to a master on/off switch mounted in the dash, then to a firewall pass-through terminal, and then on to the starter. I have a on/off positive terminal end mounted to the battery. I just saw in another build thread that a guy used a 200amp manual breaker mounted about 18" from the battery. It seems like this would be a good way to protect against any shorts in my long battery cable. Thoughts from the electrical gurus?

[Richard454]

I've seen circuit breakers welded closed after a dead short....

I prefer these if you want to fuse the battery cable-

Link-http://www.autoelectricsupplies.co.uk/product/1024/category/192

[jlwdvm]

What amperage fuse should a guy get? I will have to look for an American source.

[72BBSwinger]

I use a 200 amp Marine circuit breaker between battery and alternator.

[Richard454]

What amperage fuse should a guy get? I will have to look for an American source.

I'd go with a 200A.
I've bought a bunch of stuff from them- really quality stuff. NOT made in China. Shipping isn't bad-not to mention the current conversion rate to the pound makes buying things from them a super deal. Plus I haven't found any that are made in the USA

[Kenova]

I have a 150 amp breaker between the alt. and trunk mounted battery. The starter cable is live only when I crank the engine over.

Ken

[Richard454]

I have a 150 amp breaker between the alt. and trunk mounted battery. The starter cable is live only when I crank the engine over.

Ken

You want the circuit breaker as close to the battery as possible. If the alternator shorts out you'll see a puff of smoke and it stops producing power. Now if the battery shorts out-you'll see smoke- then the wire will glow red and more than likely start a fire.

Think of the gas tank full of gas as a "battery"- and the carb as the "alternator." If you have a leak in the fuel line- where would you want your shut off- The Carb or the tank?

Richard

[Kenova]

You want the circuit breaker as close to the battery as possible.

Richard

Oh yeah, it's right there next to the battery.

Ken

[65 drop top]

I think it's best to use a solenoid next to the battery, if your concerned about a short. When wired correctly it's hot only during cranking. Then run a circuit breaker or fusible link on the alternater wire that goes to the battery. I can try to elaborate more if this is something you're interested in. Here is a diagram of the set up.

[jlwdvm]

I ended up ordering the fused clamp from the UK. My AAW wiring harness has fusible links between the starter and ignition & alternator already. Basically, the Ford solenoid acts as a circuit breaker in this instance?

[Richard454]

Well- not really.... Say the wire from the solenoid gets shorted-and you try and start the car -ALL 800+A from the battery go to the short when you turn the key...and hopefully when you let go of the key after seeing smoke- the remote solenoid doesn't weld closed- as you run to the back of your car to hit the kill switch or disconnect the battery or get a fire extinguisher...

I think a solenoid near the starter- away from heat-is a good idea...TO me- it just doesn't make sense to put it in the trunk- because you'll have the possibility of unprotected power running the length of the car anyway- unless you fuse the battery.

BTW- the company in the UK has some really neat stuff AND it's not made in China

Richard

My favorite is the combo fuse /relay holder- totally configurable- and modular

[65 drop top]

Basically what the solenoid does is allows the main battery cable to be completely disconnected, except during cranking. The alternator charge wire can then use a fuse or circuit breaker. It really isolates the battery and protects the car. Especially if you get in an accident, the battery would basically be "disconnected".

[65 drop top]

Here is a sticky thread on the topic

https://www.pro-touring.com/threads/...ery-Relocation

And another

https://www.pro-touring.com/threads/...ounted-battery

Or just do a a search on the topic. I'm sure there are a bunch of threads. It is pretty much accepted that it's the safest way to relocate a battery in the trunk. I am no electrical guru or engineer, but from my research it seems like the way to go.

[ilikeike]

Basically what the solenoid does is allows the main battery cable to be completely disconnected, except during cranking. The alternator charge wire can then use a fuse or circuit breaker. It really isolates the battery and protects the car. Especially if you get in an accident, the battery would basically be "disconnected".

That's how I wired mine also.
Similar to this,accept my alternator is wired a little diferent.

[Richard454]

Basically what the solenoid does is allows the main battery cable to be completely disconnected, except during cranking. The alternator charge wire can then use a fuse or circuit breaker. It really isolates the battery and protects the car. Especially if you get in an accident, the battery would basically be "disconnected".

That is true...but it's sort of redundant w/ a solenoid AND fuse/circuit breaker.

You just run one LARGE wire to the starter- then use that (starter terminal) as your junction block to the alt and other power hungry accessories. Or a marine terminal block works well-see below..

If you're in an accident w/ a fuse at the battery- it is STILL protected weather or not the wire is "hot" all the time.

Look at your house--make sense to turn OFF the circuit breaker- for a light switch and a light? Yes -the light switch is "hot" all the time but it's still protected by the breakerpanel...




Here's my set -up

twin 6v batteries to save space -

DSCN4917 by Richard Hayes, on Flickr

1/0 gauge running to the starter-

DSCN5052 by Richard Hayes, on Flickr

DSCN5081 by Richard Hayes, on Flickr

Power post to run all the stuff up front- fans/horns/headlights/electric headlights-

DSCN5170 by Richard Hayes, on Flickr

The fuse/relays to protect the devises-

DSCN5160 by Richard Hayes, on Flickr

headlights & headlight motor protection

DSCN5113 by Richard Hayes, on Flickr

fuse panel for ECU/Starter/injectors/coils etc.

DSCN5030 by Richard Hayes, on Flickr

alternator-

[jlwdvm]

My car is already wired with a AAW Power Plus 20 kit (at the time they didn't make a specific kit for 69 Firebirds). I would have to rewire/run new wires to use a trunk-mounted solenoid, so I went with the battery post fuse. I have a master kill switch mounted in the center of the dash, and the ignition and alternator wires came with fusible links already installed by AAW.

[TheJDMan]

I'm running a pair of 200 amp circuit breakers in parallel mounted in the trunk about 12" from my battery. You can buy a complete circuit breaker kit like this.

https://www.ceautoelectricsupply.com...tbreakers.html



Or you can buy the individual circuit breakers here.

https://www.amazon.com/Rockford-200-...ircuit+breaker

[j.d.roost]

I know this is an older thread but it looked to be the latest on the topic.
I have currently been going back and forth on trunk mounted routing this week enough to make my head spin.
I have a Falcon (64) with a 5.0 efi and spliced in harness from a fox body. Running the 0 gauge was difficult enough (still not happy with how I have it). Running the solenoid in the trunk with the extra wires needed was not only going to be a task....but because of the stock pickup points of the fox harness..it would be a mess under the hood.
Other concerns are if a 8 gauge wire would be enough to run all lights,wipers,fans ect.
Obviously I am concerned with a fire from the constant hot 0 gauge inside the car and had not thought of a breaker.

Any issues with running a single 200 amp unit?
Also can I run a 300 amp anl fuse in line with a breaker for added protection?

Thanks for any advice and the info provided.

[blitzer454]

I really don't see the benefit of mounting a large circuit breaker in the trunk. The circuit breaker needs to pass a high enough current so that the starter can function, and a starter can draw as much as 800A initially. I copied this from one of the web pages linked above:

Need a Circuit Breaker designed to protect a super high current accessory? Or maybe, you’d like to protect a length of cable that runs through your vehicle. Either way, these breakers fit the bill! These breakers will pass 200% of their rating for 5 seconds, 150% of their rating for 10 seconds, and 100% of their rating for over 30 seconds. They include a valet type push-button that allows you to manually open them for safety or security.

The kit they are advertising uses 2 circuit breakers in parallel, effectively doubling the current that can run in the starter wire cable. So for 5 seconds the current allowed can be as high as 800A and for 30 seconds or more the current can be as high as 400A before the breaker will open. Just think how much damage 400A can do in 10 seconds much less 30 seconds or more.

I understand that having to re-route the starter wire from the engine bay to the trunk can be messy but if your doing this for safety I would still deal with the mess and mount the starter solenoid in the trunk.

As far as running the lights and other accessories you need to remember that after the engine starts the main source of power comes from the alternator, not the battery. The 8 gauge cable is mainly for charging the battery and not running the accessories.

[j.d.roost]

Ok.
I appreciate the advice.
Funny..I have been beating myself up
over this for a few weeks now...
Somthing that seems so simple after I have gotten so many difficult roadblocks with the project handled has not only brought me to a halt..it has me questioning other things on the car.
Drilled a large hole in the firewall tonight for a bulkhead pass through for the + that is not going to work (and now I will need to weld it back shut)
I have hit the "I don't think it will ever be done" zone...