Minor new year emergency. Help please.

[smac999]

Originally Posted by cyan

+1 on the recommendation for Type-T fuse instead of ANL. An ANL fuse is designed to operate for a period of time in an OVER current state, usually to allow motors to start up with current spikes. If your washing machine demands this, so be it. I just wouldn't sleep well if it was under my own bunk.

Also, the fuse holder in question has a MAX current rating of 750A. The 750A ANL fuse in question will allow MORE than 750 amps for a period of time. This doesn't feel kosher.

try and find a class t 750a fuse. over 400 they get hard to find. ANL is fine for inverters. class T is better. running 2 class t's in parallel could be an option maybe.

the 750a fuse in the 750a fuse holder made by the same company would be just fine.... both would be continuous ratings. both would have higher short term ratings.

[smac999]

Originally Posted by Montanan

In this vessel's configuration, won't the fifth jumper cable at the end of the chain be carrying approximately five times the current compared to the first jumper cable in this end tapped parallel battery circuit? The fifth jumper cable link carrying about 5/6th of the full current flowing through the much larger single/unparalleled cable leading to the to the battery switch and much smaller than the paralleled cables leading from the battery switch to the fuse block that connects to the inverter..

yes, the jumpers need to be able to carry 700+ amps as well. and should be as big as the feeders leaving.

if I have a 4/0 cable leaving a bank all the jumpers will be 4/0 as well.

[CatNewBee]

That is true, the jumpers need to be the same size, simply because they may exceed the 700A of the inverter. The Quattro 5kVA inverter takes up to 400A permanently under full load and for some seconds up to 700A before shutting down. On the other line of the house there are power winches, windlass or the watermaker running on 12V that can add another 100..200A short term. I assume, there is a 200...300A fuse on the second line.

It is true, that the wire size is calculated by crosssection and length to mitigate a significant voltage drop, but you need also cabling that does not get hot. Even unlikely, the maximum load in a worst case without burning a fuse could be near 1000A on the jumpers.

[Montanan]

Originally Posted by smac999

yes, the jumpers need to be able to carry 700+ amps as well. and should be as big as the feeders leaving.

if I have a 4/0 cable leaving a bank all the jumpers will be 4/0 as well.

And the entire parallel configuration should be changed from its truly mucked up lay out to a much more balanced current circuitry, which balanced circuitry would avoid incrementally adding amperage by linking the jumpers in series to an end tap chain of batteries. This vessel's configuration is the worst possible. It is like example 1 of the article referenced below and preferrably would be configured ike example 3, but example 2 or 4 would be enhancements over the present amateurish circuitry that is similar to example 1. Example 3 provides for only the amperage draw from one battery to be feed through the conductor to the common tap hence each of those single battery connection cables can be sized to 1/6th of the full maximum load instead of the much higher current carried by the end tap daisy chained set up which inappropriate arrangement also drastically imbalances the draw [and the charging] between the different batteries that form the parallel bank.

http://http://www.smartgauge.co.uk/batt_con.html

I would also recommend placing the battery switch so as to be fuse protected by reconfiguring the arrangement so as to position the fuse between the enhanced reconfiguration of tap from the battery bank and the switch, instead of having the switch between the battery bank [source] and the over current protection device [i.e. ANL 750A fuse]. I hope the battery switch is of adequate current rating to sustain such high amperage draw. And a faster acting fuse would be beneficial, something downstream could become smoking hot before that ANL will blow open.

Wow, I sure hope this battery bank is not an original install from the production manufacturer as it would mean that the vessel manufacturer has dubious engineering. From briefly watching the Daley Adventure videos on Youtube of which I believe the OP produces the vessel appears to be a Lagoon cat. Perhaps others can identify the make and model of this craft and advise if the depicted battery bank is OEM or a post production conversion. There are a lot of Lagoons in the water, hope not many are configured in a similar manner.

Happy Sailing and Happy New Year.

[Montanan]

Time to call in the marine electrical system experts. Real experts.

[Pascals Wager]

Lagoon configure the FLA bank with positive and negative draw from opposite ends of the bank as is best practice. Any change here is after market. Whilst a T type fuse is the better choice on an inverter feed I haven't found one over 400amps as previously stated. The configuration of fuse and cable size on Dave's boat is as per Victrons recommendation. Lower fuse rating may offer a greater level of protection but in this case the fuse was not at fault. It didnt blow as its rating was not exceeded. The washer in the current line created resistance which created heat which created more resistance, so the connection was unable to handle the load. A load less than the fuse rating. Replace fuse and holder, redo crimps and lower loads. And big thanks to Dave as I now have a new way of lifting the bed base and mattress...

[lelolay]

Ohh MY! My house uses a 200 amps box. An I have never had a boat with a main bigger than 60a. An had more toys than you have in yours. Even on shore power.. oh My oh MY....

[Montanan]

Originally Posted by lelolay

Ohh MY! My house uses a 200 amps box. An I have never had a boat with a main bigger than 60a. An had more toys than you have in yours. Even on shore power.. oh My oh MY....

Just be glad your home is not restricted to receiving 12 V DC power like is being provided by the six paralleled battery bank. Low voltage dictates excessively large amperage and amperage causes exponential heat losses and the need for comparatively oversized, heavy and expensive conductors. Heck, the long distribution lines running to service your home are sized about the same size as the 12V DC cables to the vessel's inverter.

When we design motors and controls for automotive applications our engineers loath having to operate from legacy 12 volt DC power to operate the permanent magnet 3 phase variable frequency drive inverter motors. The voltage drop and the bEMF on such archaically low voltage systems is incredibly inefficient compared to operating at higher voltages. I recall evaluating the final electric power conversion efficiency of of motorized accessories for internal combustion engine powered automobiles to be just 14% of the energy derived from the gasoline - 86% wasted as useless heat.
Standard vehicle alternators are incredibly dismal but then you get what you pay for as they are dirt cheap but fuel isn't.

Whereas, our engineers love designing and operating from the 450 to 650 volt DC battery packs for developing the propulsion systems for eBuses and Heavy Goods Vehicles, albeit with much greater caution due to the high voltage dangers. Our earliest motors used aboard US Navy vessels benefited greatly from their ships much higher operating voltage, which standards I believe are 155V, 375V and 650V DC power interfaces.

If I was designing boat systems, at a minimum I would desire to reconfigure to a vessel to a 48 volt battery bank. It is efficient to have Vin be nearer to Vout for power conversion.

[KP44]

Originally Posted by lelolay

Ohh MY! My house uses a 200 amps box. An I have never had a boat with a main bigger than 60a. An had more toys than you have in yours. Even on shore power.. oh My oh MY....

Funny. ….
And 200 amps at 230 volts AC is about 46,000 watts; about 10 times as much power as the OP's boat was using.

[cyan]

Originally Posted by smac999

the 750a fuse in the 750a fuse holder made by the same company would be just fine.... both would be continuous ratings. both would have higher short term ratings.

I'm sure you are correct.
However, the 750A ANL fuse can withstand more than 1500 amps for several minutes.
Short term ratings scale up to dangerous levels when you are already at the max rating of the fuse block. It's a non-linear problem yet devices have linear ratings for over-current numbers. In other words, doubling up big current more than doubles up the danger. Been there.

[CatNewBee]

Just do it right. Even a 10 Amp load on a poor corroded wiring can start a fire. So check your systems frequently and do it the right way, than even 1000A loads can be operated safely.

Keep moisture away from the contacts, secure screws from loosening, check crimping, prevent vibrations and have the tools and spares to fix issues...

[NorthCoastJoe]

Nobody mentioned the distance between batteries and the load. There are tables that state the wire size based upon the distance and load. If the wire insulation melted and the fuse did not blow I would be scared. 12 volts at 5000 watts is 416 amps. I would never do that, too worried about fires.

[davedindubai]

Thanks for the concern and advice. I’ve cleaned the fuse, moved the washer to between the nut and fuse as it should be and checked the whole system under a large load.

See pic: I put 550a thru the system for half hour and the wires became ‘warm’ to touch but nothing I’m worried about. I’m not using the inverter for anything other than float charging the batteries until the replacement fuse and holder arrives on Tuesday anyway.

Also, here’s another nice way to access the battery compartment in a hurry... lift the mattress, pull out the wooden cover and slot it into the gap aft of the battery compartment. It wedges and holds back the mattress. [emoji6]

[CatNewBee]

I guess, you are ok, if the connection does not get warm, well done as quick fix, replace the melted thing soon. You can continue to use your inverter.

I still would insert 2 fuse holder with smaller fuses instead the one ( half the amps, one per wire ) to distribute the current to a larger surface and add some redundancy. The fuse holder are usually stackable next to each other.