Trunk mounted battery fusable link size (Page 1/3)
gatorfrey JAN 15, 03:22 PM
I mounted another V8 Archie battery tray in the front of my second GT Fiero.
Last time, I ran two #2 welding cables all the way to the back. Never had an issue. But, in the back of my mind, I could see a short going badly wrong if the cables were compromised.
So, this time, I would like to do a fusible link at the battery. But I am not sure what size link to use.
Anyone out there know?
Thanks

Wayne
Raydar JAN 15, 04:53 PM
Good question. And I don't know the answer. (Do they make fuses that are large enough to handle cranking current, and still be practical?)
Keep in mind that the factory cables are not fused.

I just installed a knife switch in my ground wire. Right at the battery.

Sorry. Pic is kind of dark.

[This message has been edited by Raydar (edited 01-15-2022).]

gatorfrey JAN 15, 06:26 PM
Raydar,
Thanks for answering.

Yes, they make some mo-honking heavy fuses with holders, that can do it.
Factory wiring does not expose you to the length of possibilities that can happen with full battery amp and volts traveling the nearly full length of the car.
So, maybe someone knows the safe,practical size and will chime in.
Amazon carries several at around 15-20 bucks. I would do that this time when I wire it all up.

BTW, what size ends for the engine side of this install ? It's been about 20 years since I did the first one. When I lift it to wire it, I don't want to be down long. I remember I tied in where the factory battery cables bolted to the car.
It's my daily driver.

Throwing in pics of the V8 Archie battery tray,my second one. I really like how it fits.
[img]https://images.fiero.nl/us erimages/gatorfrey/20211215_155258.jpg[/img]

[This message has been edited by gatorfrey (edited 01-15-2022).]

Dennis LaGrua JAN 15, 06:33 PM
I installed a Moroso battery kill switch that I turn off when the car is not in use. I put a 20 amp fuse across the switch terminals so that that the PCM doesn't lose memory adjustment and we also have short circuit protection. With the PCM and clock still energized and drawing a small bit of current a battery maintainer is used all winter long.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

cvxjet JAN 15, 06:35 PM
I did not like the large welding cable that runs along the gas tank being energized at all times, so I used a ford-style separate starter solenoid mounted up front that energizes the cable only when starting. I then used AWG-8 wire to run the car- I ran that in the schdule-40 tube that holds the ground cable, and installed a 40 amp fuse on it; If I get high-centered, and the AWG-8 wire gets compromised, it will (Hopefully) short to the ground cable and blow the fuse, thereby shutting power off. (Note; I have not tested this via high-centering the car)

Here is a diagram of what I did;

[This message has been edited by cvxjet (edited 01-15-2022).]

gatorfrey JAN 15, 06:43 PM
I saw that somewhere here.
Interesting. And I like the idea of running it through a pvc tube.
Still, though, would like to do the fusable link and call it good.
Hoping a reasonable fuse rating will get chimed in to help me, and anyone doing a search later for something like this.
I saw something on a web search about 10% over alternator output. But do not take that as gospel. I am still unsure.

[This message has been edited by gatorfrey (edited 01-15-2022).]

theogre JAN 16, 02:50 AM
Starter draw 120-150 amps if have 12.6v to = 1.5 to 1.7 kw (Stock type rated 1.5kw. some upgrades 1.7kw.)
If battery is low volt or have cable problems then will try to draw More amps.
See my Cave, Electric Motors

And that's main run power. Starter when first started the Inrush Current can be much higher for fractions of a second to 1 second.

So Fuse/breaker of any type have to handle 200 to 300a minimum or expect a lot of Nuisance Trips often at the worse times.

Even if you install any fuse or use starter solenoid like above to prevent cable to the back shorting...
Front mount battery can still short out during or after a crash.
Metal battery box,
Spare tire rim,
Rad Fan motor,
Even the radiator itself,
can short out the battery terminals and/or cables near them.

Even if not a front end wreck...
~ 35lb for Group 75 battery can move or act as a hammer when the car hits whatever or gets hit by other things.

"But OE mount can have same problems..."
Very unlikely even when clamp fails because how where and what can short out.
IOW near impossible to short battery + and cable to anything in a wreck that people can survive.

OE mount limits battery moving a little or a lot even w/o clamp depending on direction.
Nothing close to + side on top of that if battery moves back or strut tower pushes forward.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

eti engineer JAN 16, 09:38 AM
[QUOTE]Originally posted by gatorfrey:

I mounted another V8 Archie battery tray in the front of my second GT Fiero.
Last time, I ran two #2 welding cables all the way to the back. Never had an issue. But, in the back of my mind, I could see a short going badly wrong if the cables were compromised.
So, this time, I would like to do a fusible link at the battery. But I am not sure what size link to use.
Anyone out there know?
Thanks

In electrical work, fusing is usually sized to protect the conductor so that it doesn't become the fuse. For example, in your home (and yeah, I know this is AC and not DC, but I am just using this as an example) 14 AWG wire is protected by a 15-amp breaker. 12 AWG is protected by a 20-amp breaker. The smaller the AWG number, the larger the conductor is. This is all selected by what the wire itself will handle. 2 AWG wire is designed to handle continuous 100 amps. 8 AWG is designed to handle 40 amps continuously. Fuses should be selected to handle 125% of continuous load rating to allow for intermittent in-rush loading (like when you first turn on the AC or heater motor, etc. and in the case of starting, should be a slo-blo style fuse. I guess the question is, how did you select the 2 AWG size wires? They sound plenty healthy to me but was just wondering. If you have a DC clamp-on meter (you can buy one cheaply at most any automotive store) I would measure the cranking current on the starter just for your comfort to ensure you are not drawing more than 100 amps when cranking. If you are, and since you already have the wiring installed, I would size the fuse accordingly at 125% of what you measure. Since starting is a short intermittent load, you should still be ok, but if a short occurred, because the current would be much higher than cranking current, there could be heating of the conductor until your fuse blew, so I certainly would not go much over what the conductor is rated at.

This is just my opinion based on what I know about electricity and Fieros. For what it is worth...

I just did some checking and it appears that 2 AWG will handle 115 amps DC safely at a temp of 75 degrees Celsius, so you are good to go on wire size. But to boil it down, you can safely fuse a 12VDC circuit using #2 wire at 150 amps. One consideration is that with DC, there is can be a bit of a voltage drop in even a 10-foot length of #2. This will cause the starter to draw more current. But based on what I have read, you will be fine using #2 and 150 amp fuse. If you don't need that large of a fuse, I would go with something slightly smaller, just to be safe. You have to forgive me. I worked in Prime Power for over 40 years, but everything I did was with three-phase AC voltages, 230,000 volts on down. It's a whole different world with three phases....

[This message has been edited by eti engineer (edited 01-16-2022).]

gatorfrey JAN 16, 09:26 PM
I think I will try 150 amp for now, on the link.And keep spare 200 amp, if I upgrade the alternator,
Anybody remember what size terminal rings go on the cable at the back of the car ?
I see 3/8, 5/16, and 1/2 inch. I would like to attach at the same point the old cable went to.

[This message has been edited by gatorfrey (edited 01-16-2022).]

eti engineer JAN 18, 09:05 AM

quote
Originally posted by gatorfrey:

I think I will try 150 amp for now, on the link.And keep spare 200 amp, if I upgrade the alternator,
Anybody remember what size terminal rings go on the cable at the back of the car ?
I see 3/8, 5/16, and 1/2 inch. I would like to attach at the same point the old cable went to.




Which connection point do you mean? Just asking for clarification.