Correct Size Circuit breaker for trunk mounted battery?

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  1. Mheiron

    Mheiron Well-Known Member

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    I've searched the forum and the internet but as usual its a "drink from a firehose".

    I'm rounding up parts for a trunk mounted battery and I can't resolve the logical circuit breaker size.

    The Hellcrate instructions call for a max 200-amp battery.

    Is 200-amp the suitable circuit breaker size?

    Seems to simple.

    Apologies if its a stupid question!

    Thanks in advance.
     
  2. oldbee

    oldbee FBBO Gold Member FBBO Gold Member

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    Not a real electriction, but I stayed at a Holiday Inn. 150A oughta do it. IMHO
     
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    • kiwigtx

      kiwigtx Henchman #4 Staff Member FBBO Gold Member

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      My inner KernDog is wavering here...... I am an electrician, and I have stayed at Motel 6 in the past. :D

      I'm thinking 200 Amp fuse might work.....remember the starter motor requires a lot more than 200 Amps....so it depends upon how long you intend cranking the engine.

      Just my opinion of coarse. :lol:
       
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      • dadsbee

        dadsbee FBBO Gold Member FBBO Gold Member

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        No fuse... unless you like to walk..
         
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        • oldbee

          oldbee FBBO Gold Member FBBO Gold Member

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          I could be wrong,too many beers! Loved the inner KernDog.
           
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          • bm02tj

            bm02tj Well-Known Member

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            You only fuse load for max charging load so match alternator out put for fuse size and make sure wire size match's or larger
            There is no fuse in cable to starter
             
          • Mike67

            Mike67 Well-Known Member

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            • Mike67

              Mike67 Well-Known Member

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              So I will ask a stupid question since Im not familiar with how the Hellcrates starters are wired, but is there a constant hot on the starter ( like our B bodies) and the start signal goes through a relay for the bendix or is it like a Ford where the solenoid makes and breaks the power feed to the starter?
               
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              • kiwigtx

                kiwigtx Henchman #4 Staff Member FBBO Gold Member

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                Not sure, but my friend has a late model Subaru, and it's the same deal as our B-Body starter wiring. :thumbsup:
                 
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                • Mheiron

                  Mheiron Well-Known Member

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                  There is a constant 1/0 gauge hot wire to the starter and a 14-gauge wire to the solenoid.
                  The starter wire and alternator supply wire are spliced together near the alternator then proceed to the nearby power distribution module where the battery supply joins the first two.
                  The battery supply cable apparently needs the big circuit breaker but I’ve never seen one wired in.
                  Hence my confusion and question.
                   
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                  • Mike67

                    Mike67 Well-Known Member

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                    So 200 amp is the max recommended for the entire motors electrical system ?... I always like to keep my starter feed separate anyways. Same with the alternator but I would imagine your ecu will want to monitor.
                    I find it hard to believe that you would need that much power especially with the direct feed to the starter but I would do as directed. Having a circuit that has an ampacity rating larger than what is required will not hurt, it just needs to have the properly sized fused to protect the load its is serving.
                    I hate paralleling dc circuits as it can make a headache if you need to troubleshoot. I like to be able to isolate the circuits and have dedicated grounds for the heavier loads as well.
                     
                  • 69Bee

                    69Bee FBBO Gold Member FBBO Gold Member

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                    I was going to recommend 500-750 Amp because I thought you wrote "Trunk Monkey", then I realized you said "trunk mounted"... :monkeyleft:
                     
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                    • Mheiron

                      Mheiron Well-Known Member

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                      This circuit breaker is not mentioned in the Hellcrate instructions at all. Of course the instructions don’t consider a trunk mounted battery.
                      The internet info on mounting the battery in the trunk was the start of this circuit breaker idea.
                       
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                      • aldal

                        aldal FBBO Gold Member FBBO Gold Member

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                        Resettable_Circuit_Breakers_Shown_in_Moroso_Battery_Box-480x360.jpg

                        This is what comes with the relocation kit from CE Auto Electric that I am using.
                         
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                        • bm02tj

                          bm02tj Well-Known Member

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                          So 400 amp if slow blow type should work???
                           
                        • RJRENTON

                          RJRENTON FBBO Gold Member FBBO Gold Member

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                          IMO....
                          it depends on what you are trying to protect. Are you talking about the battery feed to the starter solenoid or are you referring to the charging cable that recharges the battery?
                          If you are referring to the battery feed to the starter solenoid, this wire is NOT FUSED. The starter will drsw in excess of 450 amps, more if high compression pistons or heavy oil is used. Because the starter motor is series wound (armature and field coils are connected in series), at locked rotor conditions (innitial engagement b4 the engine starts to turn), the starter will draw VERY HIGH CURRENT and this in rush current will cause a fuse failure. If the charging wire is fused, a good rule of thumb is 135% - 150% of the total connected load in amps.
                          BOB RENTON
                           
                        • RemCharger

                          RemCharger Well-Known Member

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                          I know magnum srts etc have the battery in the trunk..........what do they do for wiring..
                           
                        • RJRENTON

                          RJRENTON FBBO Gold Member FBBO Gold Member

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                          See my prior suggestion. To be absolutely sure, both the positive cable to the starter's solenoid connection AND the battery's negative conbection to the engine ground (on the block) should be the same size conductor. It would be 1/0 AWG stranded copper wire, with THHN or TWN or RHW or XLP insulation, with crimped and soldered ends. If you could find welder's cable this would be acceptable. Anything smaller than 1/0 AWG, (Ie, # 1 or # 2, etc) will introduce additional resistance, resulting in an additional voltage drop during cranking. Just my opinion of course.
                          BOB RENTON
                           
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                          • RemCharger

                            RemCharger Well-Known Member

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                            Yes I agree.. do not need fuse in main hi current feed.
                            My suggestion was based on chrysler already engineering the electrical system , simply see what they've done and copy ideals of the design. I've met the head Electrical engineer of the SRT team, and do believe they are qualified to design said system.

                            This of course, is just one man's opinion.
                             
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                            • RJRENTON

                              RJRENTON FBBO Gold Member FBBO Gold Member

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                              What a coincidence.......I'm a degreed Electrical Engineer (BSEE), and hold a Professional Electrical Engineer credential as well and with over 45+ years experience and have designed, installed and commissioned several chemical plants and process installations worldwide. It never hurts to obtain several suggestions when seeking a solution to a problem. Good luck.....
                              BOB RENTON
                               
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