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I have trunk mounted battery in aluminum battery box. 1/0 ga weld cable goes to mini starter. Thinking of using a 300 amp AMG fuse to protect system. Has anyone fused the negative side of battery? Thank you, Lenny
 

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I have trunk mounted battery in aluminum battery box. 1/0 ga weld cable goes to mini starter. Thinking of using a 300 amp AMG fuse to protect system. Has anyone fused the negative side of battery? Thank you, Lenny
Roadkill Garage used hi amp relays and fuses for both starter and main power Positives from trunk batt. Episode showed diagrams and installation. Genius idea. No power in main cables til keyed on.
 

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Roadkill Garage used hi amp relays and fuses for both starter and main power Positives from trunk batt. Episode showed diagrams and installation. Genius idea. No power in main cables til keyed on.
Do you know what episode it was. I would like to see it.

Jim
 

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I have trunk mounted battery in aluminum battery box. 1/0 ga weld cable goes to mini starter. Thinking of using a 300 amp AMG fuse to protect system. Has anyone fused the negative side of battery? Thank you, Lenny
Electrically, it makes no difference on which side of the battery you put the fuse.
 

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Electrically, it makes no difference on which side of the battery you put the fuse.
don't tell the high school teachers that

when you have a fuse bank it is more convenient to put it on pos side as there can be one pos line to it and ground (common) can be all over the place
if cars were developed with + being ground (common), then it would be more convenient to have fuse bank in - side
but in main line right off battery it doesn't matter
could even put a fuse on both + and -, that would add a bit more protection as which one blew would depend on which one, a short was closer to

almost ready to start the slow process of getting my car back together
my frame connectors, 4 link and now minitubs are done and all underneath primed

electrically I will probably put a fuse at battery on both sides and have alot more ground straps
edit...and too add I'll use lots of relays
 

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Relays don't protect against overloads and shorts. Neither do cut off switches.

For battery fuses, I like the post type fuses mounted directly to the battery terminal. For a recent resto-mod where we had the battery in the trunk, we used https://www.amazon.com/dp/B09NZYBQQJ/ for the battery fuse, and a positive terminal with a 3/8" post to mount that directly to the positive terminal. The terminal we used came from the boat/marine aisle at the local Walmart. It was about the same as the positive terminal in this set: https://www.amazon.com/dp/B0060YHLJS/

And I just used a crimped on 5/16 lug on the 1/0 cable we used for the battery cable.

could even put a fuse on both + and -, that would add a bit more protection
No added protection. The current out of the positive terminal of the battery is the same as the current into the negative terminal of the battery. All a second fuse does is add more resistance to every circuit at the battery connections (not good), and it means when you do blow a battery fuse, you'll have to inspect both of them to figure out which one blew out first.
 

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Relays don't protect against overloads and shorts. Neither do cut off switches.
don't know that anyone said they did
relays mean you don't need high current/big wires going to switches

All a second fuse does is add more resistance to every circuit at the battery connections (not good)
fuses shouldn't be adding resistance

No added protection. The current out of the positive terminal of the battery is the same as the current into the negative terminal of the battery
technically yes, especially if considering just steady state with battery and resistance, but strange things can happen with circuits with capacitance and inductance and cars are filled with both especially with modern electronics, unpredictable instantaneous currents and voltages can happen with shorts in complex electronic
I'm putting fuses on both sides and lots of relays
 

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fuses shouldn't be adding resistance
It's not a lot, but we are talking about a fuse on the battery cable here. For starter current, our 300A ZCase fuse shows about a 55mV initial spike and settles in around 30mV as long as the starter is running. I wouldn't want to double that with a second fuse. The resistance of our 300A slow-blow Z-case fuse is about 0.13mΩ.

strange things can happen with circuits with capacitance and inductance and cars are filled with both especially with modern electronics
Fuses are to protect wires, not to protect what's at the other end. Wires don't have significant capacitance or inductance in a DC power circuit, so the rest of your reasoning is based on a flawed assumption IMO.
 

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fuses are to protect everything in the circuit from over current and thus heat and yes burning wires and insulators is a part of what fuses protect

I did not say wires have capacitance and inductance, but the overall car circuit has many components with capacitance and inductance
 

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I researched mounting a battery in my trunk and found what I think is a better way to wire it. I used a Ford starter solenoid in the trunk at the battery, ran my positive cable from the Ford solenoid to the starter solenoid at the starter post and a purple wire from the ignition switch start circuit to the Ford starter solenoid "S" terminal. I believe I had to install a jumper wire from the starter battery terminal to the starter motor so the motor will spin as well as the bendix engaging. With it wired this way, the only time the positive cable is powered is when the ignition switch is turned to the start position, seemed to be safer that way. I also ran a fused 8 GA wire from the battery to the horn relay terminal, I believe, to power the rest of the accessories. The negative cable I ran from the battery to the engine block. I'm sure there was other wiring needed but that's the short version of the story.
 

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i did my other car the same way as scott. The rest of the car is protected with a big fuse but not the heavy cable going to the starter, like he said its only hot when cranking. It would take a really really big fuse to protect the one going to the starter
 

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I researched mounting a battery in my trunk and found what I think is a better way to wire it. I used a Ford starter solenoid in the trunk at the battery, ran my positive cable from the Ford solenoid to the starter solenoid at the starter post and a purple wire from the ignition switch start circuit to the Ford starter solenoid "S" terminal. I believe I had to install a jumper wire from the starter battery terminal to the starter motor so the motor will spin as well as the bendix engaging. With it wired this way, the only time the positive cable is powered is when the ignition switch is turned to the start position, seemed to be safer that way. I also ran a fused 8 GA wire from the battery to the horn relay terminal, I believe, to power the rest of the accessories. The negative cable I ran from the battery to the engine block. I'm sure there was other wiring needed but that's the short version of the story.
You should be careful about installing a jumper on the starter as this may cause run-on if you are using a PM starter.
If you look at any OEM rear-mounted battery installation, like BMW, Volvo, Jaguar, Saturn, etc., they don't use a secondary relay in the circuit. What they do is properly mount and shield the battery wire.
 

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Discussion Starter · #18 ·
Thank you for all the replies. Yes my concern is protecting weld cable to starter in case it ever grounded.

I have negative battery cable going from battery box to trunk opening body gusset on right side of latch. I’m planing to use a AMG 300 amp fuse bolted to gusset and negative cable bolted to fuse link. If this has draw backs I’ll post it. Regards, Lenny
 

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When I ran my 1/0 welding cable from my trunk to the starter I encased it in 3/4" heater hose. It would have to short through the heater hose and through the cable insulation. And I run a 300 amp fuse at the battery. I feel pretty safe.
 
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