Marine Rated Battery Fuse Trip
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- Опубликовано: 8 фев 2025
- I purposely wired this 300A fuse to 15' of 8GA wire and a 400Ah LiFePO4 lithium battery bank for illustrative purposes only.
I am a HUGE proponent of over current protection for battery banks and seen too many examples of boats burned due to lack of over current protection.. The ABYC allows for an "exemption" of fusing on "starting circuits" but there is lots of gray area and still you have the potential for dead short circuits.
Most small engine starting circuits, diesel or gas, can easily be fused to protect the wire and prevent "nuisance trips"...
This illustration is NOT to suggest you fuse 8GA wire with a 300A fuse then connect it to your boat but to show that dead short circuits, what we are trying to protect the WIRE from, will still instantly blow the fuse even when the wire is multiple sizes too small.
PLEASE DO NOT TRY THIS AT HOME OR ON YOUR BOAT.
I have a 50 year old Egg Harbor 37 unfused on the starter bank that has never had a short on the main wiring. I just added a 2 gauge 15 foot round trip to the generator for starting it from the main engine starter battery and decided to use a 300 amp ANL Blue sea fuse and holder before seeing this video. plan to run a short wire from starter bank positive to fuse holder, then from fuse holder to starter bank selector switch. That will fuse protect all the wires for all starters. And your video is exactly what I thought, the fuse will blow and the wire will be safe. This is an old MCCK 6500 watt and it cranks fine on the 2 gauge wire. That 2 gauge wire I saved from my other mid 60's Glastron which I cut up and the wire is still in good shape over 50 years old. None of the wires in my Eggharbor or very few, are tinned like new marine wires, but they are still ok. Egg used 2/0 wires for the engine starting circuit. Engines are 392 IH and always crank well. One thing that has helped the wires survive so long, they never get wet as the boat is a wooden cabin cruiser, no exterior wire exposure. To secure the starter wire run to gen, I used some plastic Carlon 1/2" conduit clamps screwed to the side of the wood stringers. Near the gen, I am going to use a 2 foot section of foam pipe insulation over the wires for some protection to their insulation as the wires are bent over the wood edge support on top of the water tank.
Just for the benefit of any viewers who may not fully understand. Because you are protecting the wire, you have to use a fuse smaller than the ampacity of the wire. This is not for preventing the wire from overheating in a short circuit. That is easy because the fuse blows right away. The problem is that you don't know what kind of load malfunction you may have. If the load is faulty and causes a slight overload current, the fuse must be sized to blow before the wire insulation melts or thermally degrades in some other way. With starters, though, the wire is probably a bit undersized because the starter doesn't run continuously. If there is a fuse you can use on the starter that will let you start the motor but doesn't blow when you need it, that is great. Even if the starter fuse is higher ampacity than the wire would normally be rated for. But I agree with everything in the video as it pertains to starters. Great video and thanks for actually showing the fuse blow!
Excellent demonstration, even 300 amp fuse protects down to 8 gauge wire from shorts. I think the idea of smaller fuses downstream of a larger fuse on branch circuits is so they blow separate circuits and not have the entire circuit losing power (within reason regarding wire sizes, dont expect a 300 amp fuse to blow protecting a 12 gauge wire). But you know for fusing the entire starting bank of wires which may even have some 2 or 4 gauge wiring running every which way, 300 amps will protect all of those wires from catching fire. Glad you posted this common sense video.
As a telco technician I have always fused the battery bank(s) as the instant current capacity (short circuit current) can be several thousands of amps, I have seen examples of where a tech has dropped a spanner accross busbars and we can ask what spanner (only a tiny bit was left).
wow what a great test. yes its all about safety. Loved the test. thank you for taking time to do this. And if you don't use a fuse or circuit breakers and you House or car or boat burns down. then your insurance should just not pay out.
'Shmemmied'??? Glad to have a new technical term in my lexicon.
Many people mistakenly believe that the size of the fuse is selected to protect the load...the radio, autopilot, heater, whatever is ultimately using the power. It's a common misperception. The reality is that the fuse is selected to protect *the wire*, not the load. To state it in a more meaningful way, the fuse amperage is selected to *protect the boat*.
Thanks for the demo.
Overcurrent protection as referenced by NEC and ABYC includes overload, short circuit and ground fault. ABYC does not fully define overcurrent in general terms like NEC. ABYC prefers to address the term in the context of DC and AC power circuits. For purely a DC device most of the time ground fault and short circuit are the same. As shown, DC short circuit is easily addressed with a fuse. Overload, however is much more of a challenge.
I am adding a 300 amp ANL fuse off the positive starter battery lug which will protect all the starting related wires below it. Consider that a starter wire carries lots of current for a few seconds of engine cranking, not designed to carry continuous high current flows. Then what your really desiring is to protect starter bank wires from a dead short. I recently ran a 2 gauge wire to start my gen 15 feet away and thought about adding a fuse to the whole starter system at the battery. Logically, for a starter, all I care about is the dead short seeing it is not a continuous load system. That long 2 gauge wire is made by Standard Motor Products, blue rubber jacket, not tinned, and is from the mid 60's. And it cranks up the old Onan MCCK 6500 watt gen fine. The wire when I compare to a modern 1 gauge wire looks identical in cross section to me., but there may be small changes I dont notice. That wire was originally used in a mid 60's glastron for starting a Chevy 350 engine.
Thanks for your testing and info. You seem to like the Idea of fusing a cranking battery circuit so I would suggest you measure voltage drop across the fuse in that application while cranking to get an idea of what the engine is really "seeing" for cranking voltage.
Thanks for your helpful suggestions, please add the Battery rack installation guide
Can you run your test with a 2/0 cable instead of 8 away. I would like to see if the MRBF will hold up to AIC
Saikil kitne .h
Can you run fuses of the same type and size to increase IAC? Trying to learn more about fusing battery banks. I am looking at upgrading my battery bank. Most likely going to be around 20k WH at 24 volts. So I'm guessing a Class T fuse but even than I'm not sure. I might end up going with LTO cells and I've seen 45 AH LTO cells with a short circuit current around 4000 amps so a larger LTO battery bank could hit some serious numbers.
Great video, thanks.
Nice videos. I appreciate you putting them out Very informative.
Question: What kind of life have you experienced with these cells under heavy use? 50% - 80% daily discharge
Reason for asking is I am in the process of replacing an aged set of AGM batteries in my solar power system and am considering the Iron Edison Nickel Iron as well some LiFePO4s.
have you tested volt drop and thermal rise at 3/4 rated cap of fuse?
Amazing demo
Thanks 🙏
I have this same batteries, but 60ah ones. I'm connected two groups 180ah to make two separate batteries with two separate BMS then connecting them to make 360ah. The highest terminal block they make is 300a, would this be alright for 360ah?
top video mate :) loved it
Nice informative video! I installed these fuses (3) one ea for windlass, starter, main panel after watching your video. I currently have an old 750Ah AGM bank wanting to convert to LIFePO4 but having a difficult time locating larger LFP batteries in stock other than ordering from China, any suggestions would be most appreciated. These (4) 100Ah Winstons or 4 banks of (4)130Ah CALB would fit my desired space nicely - Thanks...
I was wondering what is the brand of the 400 Ah lithium ion battery bank.
I know this is a old comment but I'll add that it is a Thundersky Winston lifepo4 cells I think
these kind shop.gwl.eu/Winston-40Ah-200Ah/WB-LYP400AHA-LiFeYPO4-3-2V-400Ah.html?listtype=search&searchparam=400Ah
You have a huge resistor in the circuit with all of that small wire. This test is meaningless.
I think you missed the point of the video.
Thanks for your helpful suggestions, please add the Battery rack installation guide