All the electronics involved would be in the box on the back so no grime. Heat also shouldnt really be an issue as the box will be air conditioned. Vibration is an ever present issue but I have isolated the battery and all components so it should be minimal.My wager is the less electronics involved the better. Vibrations heat and grim will never do them any good.
LOL, yes "robust"Looks very robust.
Is that a shunt in the middle?
Usually hear of fuse on positive, shunt on negative.
I was concerned with the double fuses at first but couldnt find an 800A for a reasonable cost. I originally wanted to connect the BPs above the fuses so the path would be the same distance but packaging forced me here. Im not really worried about it but will post anything if I have issues.I’m no electrical engineer so feel free to disregard my thoughts as they’re not based on much real world experience.
Seeing the dual fuses looks like a reliability concern to me. If one of them has a resistance a few miliohms higher than the other, you could very unequal current between them causing one to blow prematurely which would then cascade to the remaining fuse.
As for the arcing potential during a shutdown, I turn to plumbing analogies with the large inductive load leading to the equivalent of water hammer destroying your valve (or FETs). For this case could you install a zener diode to arrest the water hammer by giving the inductive current somewhere else to go before the voltage gets high enough to burn up the FETs and start arcing.
I was concerned with the double fuses at first but couldnt find an 800A for a reasonable cost. I originally wanted to connect the BPs above the fuses so the path would be the same distance but packaging forced me here. Im not really worried about it but will post anything if I have issues.
Yup, a multiplus through the single fuse and the left disconnect and 2 winches through the right switch and parallel fuses.Do you have multiple loads?
I use two class T fuses, but not in parallel, just "Y", branching to two circuits. (each of those is two inverters, four total)
Yup, a multiplus through the single fuse and the left disconnect and 2 winches through the right switch and parallel fuses.
Do you need the current rating of two fuses in parallel for a single winch? Or only if both operated together?
Assuming one fuse is sufficient for one winch, two fuses drawing current from a shared wire through two fuses may drive sufficiently imbalanced current to blow first one fuse, then the other.
The bars are quite wide, but resistance will be slightly lower for current going through fuse closer to switch as compared to fuse further away.
More optimum balance would be with bar on left as shown, but bar on right rotated so end of bar goes to bottom fuse, middle of bar goes to top fuse, then the blue boxes are connected. It would be further balanced if both bars were identical width. Without calculating resistance of bar and comparing to resistance of fuse I don't know if that would make any noticeable change.
What would be better, if one fuse is sufficient for one winch, to wire each winch to its own dedicated fuse.
800A - what size cable(s) do you wire that with?
How long is is the circuit drawing current? How high is the current steady-state, after any starting surge?
Each winch draws just under 500A
Im hoping that 300A headroom will be sufficient
just under 500A is the rated operating current for each winch. Im going to run twin 4/0 cable to each winch. You usually only use a winch for 30 seconds and let it cool for 30. How long that goes on for depends on how stuck you, how far you have to go and how many other trucks you are pulling through.
Thank you so much for your insight! I had not considered running separate parallel strings right from the fuses. Im going to consider it and see if it works with the rest of the down stream considerations.400A fuse run at 80% to avoid nuisance blowing, 320A
500A - 320A = 180A minimum desired through second fuse.
So 2:1 dividing of current is OK.
Length of 4/0 cable will have some resistance, assist with balancing if each has a dedicated fuse.
Consider output of each fuse separate, goes to its own battery protect, its own 4/0 cable.
The two 4/0 cables come back together at winch. (suppose other winch at other end of ?boat?, so two pairs of 4/0 cables)
I had two 60' runs of 6 awg carrying parallel current through two Sunny Island, joined through two QO270 breakers. Current imbalance was 3:1.
Replaced those breakers with 63A DIN rail Schneider breakers and it was perfectly balanced. Seems the QO vary considerably in resistance.
I would expect two identical model fuses to be better matched than breaker contact resistance.
Class T has a trip curve, unfortunately a single line not a width between "shall blow" and "shall not blow"
Nominally, 400A fuse can carry 700A for 1000 seconds.
Heating goes as amperage squared. 50% on time followed by 50% off time is half the heating, similar to current/sqrt(2)
500A/sqrt(2) = 354A equivalent heating
30 seconds is way under 1000 seconds, and 500^2/700^2= 0.51x or 51% as much heating.
"square wave" of current should have time to average out.
I think even a 400A fuse would hold up pretty well. Two in parallel will be more reliable.
As shown you probably can't fit a clamp ammeter around busbar to measure current of one fuse.
If you route separate 4/0 cable that will balance current better and you can measure it.
Im no electrical engineer but had read through as much documentation I could find regarding paralleling fuses and was pretty comfortable it was completely acceptable. The note in you link about temperature coefficient helping with current sharing sharing in a connection that is not absolutely symmetrical along with the significantly larger than necessary bus bars was why I was comfortable with the arrangement I settled on.Check the manufacturer's recommendations, but good fuses can be used in parallel as long as you have the same connection to both to match the impedance of the current path through each. Tinned copper bars with the full contact surface of each fuse would be sufficient.
You should derate the fuses by 0.9 to allow for fuse variation, and be aware that by combining them in this manner you are doubling the error. If a fuse is, say, +/-10%, then the combination should be considered +/-20%.
Make sure that in the extremes the fuses will still perform to your needs and expectations.
Per this application note:
The advantages include not only increased current capacity, but also spreading the heat dissipation to a larger surface area.
Ampacity of copper is far higher than any ampacity tables for wire.
After current (and heat) fans out to full width of bar, the wider bar is beneficial.
Short busbar, total power dissipation and voltage drop probably doesn't matter much. But don't want temperature rise that affects attached fuses, breakers, or wire with particular temperature rating of insulation.