Cable sizing for battery switch, bus bars etc

[jonase]

Will also try to anser some of your comments/questions

Originally Posted by Frankly

Might want to reconsider that 500 amp class T. You will need a class T to safely interrupt the huge possible fault current from the Li batteries but I start and have started my 3GM for years on a 250 amp class T.

Done, the 500 amp class T was mainly to just protect the battery from a major short circuit. With realistic loads I can easily downsize that fuse to 350 amps (or even less).

Originally Posted by aa1bflyboy

Another idea would be to consider relocating the bussbar. Possibly double checking your diagram dimensions as well as I don’t understand why you have a 2m cable from start motor to the motor...

Sorry My bad. The length of that cable is is 0.2 m, copy and paste error. The negative bus bar is unfortunately located at the best place right now. The other option would be to add another negative bus bar for the bow windlass, MPPT and the consumer circuit breaker in the middle of the boat.

Originally Posted by Checkswrecks

4. The cable lengths indicate fuses and breakers will be in different places. Try to group them physically.

5. The "Always On Bus Bar" needs to be just that, meant for absolutely essential loads and downstream of its' own fuse/breaker. This essential loads bus would not be be downstream of two switches and two fuses, as shown. You have it just going to the stereo (is it that essential? ). The stereo normally is downstream of the C/B panel.

7. The fridge, heater, etc, would be downstream from the switched side of the C/B panel, not parallel to it as shown.

8. The wind generator is 6V @ 420W according to the C/B?

9. The alternator fuse is a bit small and likely to trip at full load. For example, right after running on battery power for a while and then starting the engine.

Sorry for not commenting all your topics

4, The fuses and bus bars on the positive side are grouped together as much as I can. I just have to fit them when I mount them. The circuit breakers are as close as possible to the bus bars that can be easily accessed.

5. This always-on stud is not really used as an always on stud. The stereo is connected to the C/B panel with the ”ignition” cable as well. This part needs to rewiring in the future. Right now what is needed as always-on it is connected to the switch on the same side as the cable running to the batteries/fuses. But this is a later project.

7. These are kind of ”always-on” since switching them off with the switch going to the C/B panel will break them if they are running at the time.

8. No its not 6V @ 420W ;-) . The circuit breaker is according the size the manufacturer of the wind generator recommends (double the needed size).

9. Thanks, there will be a MC-614 regulator controlling the Balmar alternator. What fuse size would your recommend?

Originally Posted by smac999

the wire between the battery and upper "link bar" is a cranking circuit, and is also less then 72". so you don't need that fuse to meet ABYC if the wire is protected. therefor the wire size does not need to be required to conduct 500a.

I would do that in 2/0 or 4/0. it's cheap that short.


and as mentinoed above. the alternator and charger fuses should be 150%. you can't put a 100a fuse on a 100a alternator.

Thanks