Circuit Breaker vs Maxi Fuse

-
my68barracuda

my68barracuda

Well-Known Member
Joined
Dec 6, 2009
Messages
2,629
Reaction score
2,627
Location
Indianapolis IN
I am wanting to add protection to the battery cables for the rear mounted battery and also to the alternator charge wire.

I think I understand the basic difference between a resettable circuit breaker and a maxi fuse in that on the CB, when tripped, one would simply re set a lever while on a maxi fuse one would change out the blow fuse for a good one.

Can some one that knows explain the more subtle differences. is one better that the other for battery cable or alternator cable protection?

for a circuit breaker I am looking at one like this
Del City Marine Rated Manual Reset, Surface Mount - 3/8" Stud

for maxi fuses
https://www.oreillyauto.com/detail/...littelfuse-200-amp-mega-fuse/meg200bp/5841888
 
Last edited:
I have the circuit breaker on my second battery, to protect the truck. I had something shift, and a short circuit on the rear battery occurred. Fire in the back of my truck, i got lucky and put it out.

What im getting at is, either will work, one is a buy once and done, other you can tailor fuse to your needs.

secure and protect the battery.which i have taken the time to do since the incident.
 
The trouble with breakers is they can take a long time to trip, and by then there might be a fire. EXAMPLE Our power wheelchairs (24V) use a pair of 70A breakers to feed the system. When I test new drive modules, I stop the chair against the building and firewall the joystick. I do this both front and rear for about 10-15 seconds. These are huge high capacity LiFePo batteries. THEY WILL DRAW over 200A during this time AND WILL NOT NORMALLY pop either breaker!!!!

The trouble with fuses is that sometimes they pop TOO fast. The bigger things get, the more difficult things get. The LAST thing you want is "that critical time" (driving at night, trying to start the car in a tense situation, whatever) and have a critical fuse/ breaker open.
 
Just do the @crackedback trunk mount battery wiring install. That'll solve the whole thing. I THINK this is it.

CRACKEDBACK TRUNK BATTERY DIAGRAM.jpg
 
I don't ever, as in NEVER, fuse the line going to the starter. No circuit breakers or fuses.

If you want to protect the car, put a maxi fuse in the line to your starter relay from battery. That's IF the black wire is removed from the alternator and rerouted to starter relay feeding it, like the MAD approach.

I don't know how you plan to wire the car, using the schematic RRR posted is a solid approach using a master cutoff.
 
Note that if you mount the Ford relay very close to the battery, the big high current wire traveling the length of the car to the starter is only energized when you are starting. This leaves a lot less wiring energized all the time, and thus reducing the fire hazard.
 
continuous duty
see here: questions about battery disconnect wiring

As far maxi fuses vs. links.
The main purpose was to prevent the battery from massively discharging when shorted to ground.
You know there's enough juice in there to arc weld!

Size protection for the weakest link downstream.
The fusible link can tolerate short periods of somewhat high current. This is a trade-off of providing protection against major overloads while limiting the chances of disabling the vehicle for minor overloads.
 
my68barracuda said:
I am wanting to add protection to the battery cables for the rear mounted battery and also to the alternator charge wire.

I think I understand the basic difference between a resettable circuit breaker and a maxi fuse in that on the CB, when tripped, one would simply re set a lever while on a maxi fuse one would change out the blow fuse for a good one.

Can some one that knows explain the more subtle differences. is one better that the other for battery cable or alternator cable protection?

for a circuit breaker I am looking at one like this
Del City Marine Rated Manual Reset, Surface Mount - 3/8" Stud

for maxi fuses
https://www.oreillyauto.com/detail/...littelfuse-200-amp-mega-fuse/meg200bp/5841888
Click to expand...

Old thread, I know. But I'm wondering what you ended up using for the charging circuit and main power feed - fuse, or breaker? How'd it end working out? I'm roughing out the electrical in my 66 Dart and am pondering the same question for my relocated battery.
 
I ended up putting a Maxi Fuse on the alternator output line and no fuse or circuit breaker on the battery end.
I have the main power feed cable from the battery running inside the car and added two layers of insulation, a corrugated cover and a woven cover over the main positive line.
I also have a battery disconnect switch accessible from outside of the car.
 
my68barracuda said:
I ended up putting a Maxi Fuse on the alternator output line and no fuse or circuit breaker on the battery end.
I have the main power feed cable from the battery running inside the car and added two layers of insulation, a corrugated cover and a woven cover over the main positive line.
I also have a battery disconnect switch accessible from outside of the car.
Click to expand...
Would love to see some pictures of what you did, John.
 
67Dart273 said:
The trouble with breakers is they can take a long time to trip, and by then there might be a fire. EXAMPLE Our power wheelchairs (24V) use a pair of 70A breakers to feed the system. When I test new drive modules, I stop the chair against the building and firewall the joystick. I do this both front and rear for about 10-15 seconds. These are huge high capacity LiFePo batteries. THEY WILL DRAW over 200A during this time AND WILL NOT NORMALLY pop either breaker!!!!

The trouble with fuses is that sometimes they pop TOO fast. The bigger things get, the more difficult things get. The LAST thing you want is "that critical time" (driving at night, trying to start the car in a tense situation, whatever) and have a critical fuse/ breaker open.
Click to expand...
Agree, long time to pop, A 20amp breaker I had kept popping, it was very warm. After a couple times it was toast
 
Here is an updated schematic

1WzTrQO.jpg


Why the fuse/breaker in the charge line? If you are using the CD, what purpose does the charge line protection provide?

Master disconnect side, think along the lines of a river and smaller tributaries that drop off of it. The main line needs a large fuse feeding the system. Each smaller stream needs a smaller fuse to protect the equipment at the end of the line. You have to think about where you want pull power for big draw items like headlights, elec fans, heater blower motors, etc.
 
Last edited:
RustyRatRod said:
Would love to see some pictures of what you did, John.
Click to expand...

91BD1179-844E-4EA9-8BB3-FBA43C159B60.jpeg

This photo shows the rear mounted battery box with the lid off. I have a Taylor 4 post battery disconnect, set up to interrupt the positive cable side with the large disconnect posts and the small posts interrupt the ground for a relay that is in series with one of the alternator field lines. When the disconnect is pushed in it takes the positive battery side out of the circuit and the field relay looses ground so it drops out the alternator. The engine shuts down when the disconnect is pushed in.
51018033-6914-42D7-91AF-51D2827B78F8.jpeg

This photos shows the fuse inline with the alternator output cable. It is a 120 amp alternator and the fuse is a 90 amp IIRC. This protects against the alternator going wide open and overloading the cars wiring
15890E4F-ECCA-423F-85C3-4F9E92281158.jpeg

This photos shows the covering that was added over the battery cables. The main power cable from the positive battery to the starter terminal is IIRC 1 gauge welding cable. It has the woven nylon cover shown on the left over the entire length and on top of that the hard plastic cover shown on the right over the woven nylon where the cable runs hidden inside the car. The negative cable runs from the battery to the engine block bell housing. It is the same gauge welding cable and has the woven nylon cover over the existing insulation. I used the woven nylon cover over much the cars added or modified wiring. I sealed the ends of the added insulation with heat shrink tubing.
D7C32EEA-F581-4AC6-A82D-81DCAD0AD5AA.jpeg

close up view of the added wire covers
 
Last edited:
I'm not home right now to scan my revision drawing, but on my 85 d150 the wiring was a horrible mess when I got it/to the point of wondering how it hadn't burned to the ground before I "rescued" it from the PO. Bad enough, that it was not only easier, but much safer, to start with a new harness from a junkyard refugee /to repair the damage done by previous owner "interference". I mean c'mon man...
The big hot wire off of the alternator changed gauge and color 3x in the length of the/6 valve cover.just twisted and crudely taped splices 2-3 fusibles had fried and were " fixed" the same way.
One of the repairs was hanging less than 1/2" above the gas feed line to the carb with bare exposed strands. It's a wonder if didn't arc out and burn.

My solution included (dare I say it,) including a Ford part in my repairs.i wired in an under hood fuse box (had all Maxi fuses in it) and I wired every original circuit that originally was "protected"by a fusible link thru a Maxi fuse. I also added a 2nd 10 ga (same as oem on my truck) charge wire direct from the alternator "hot" terminal to the battery thru one of the 60a fuse positions, in that fuse box.
I forgot to say that the fuse box I used was from a 90-92 ish ranger.
I consulted the Littelfuse company while I was at it and they actually sent me a bulletin telling about the development of the Maxi fuse and how it was meant as a replacement for fusible links.its on an old phone, not this one /so no more fusible links for me.
Im camping right now, actually not that far from @my68barracuda for the next few days. If anyone is interested in doing as I did, once I'm home, I can dig it out and post.
 
You must log in or register to reply here.
-

Back
Top