Hi,

I'm going to use a 1050Ah 48V battery bank. Does anyone know where to get 1000A DC fuses and isolators in Gauteng?

Rubicon

A fuse with a limit of 48kw? I can't be certain, but I'm pretty sure by the time that fuse go, your battery would have said goodbye long ago. That fuse is capable to supply 60amp full load 3 phase. If you are going to get anywhere even remotely close to that load, that battery is way too small and the voltage is too low.

 

Maximum recommended draw for that battery is 130amps constant load, but best is to calculate the fuse for the inverter you pair with it. A 5000w single phase inverter would need no more than a 150amp fuse and 5000w three phase about 400amp. Anything larger than that on that battery bank and you risk damaging the bank.

http://powerforum.co.za/topic/284-dc-fuses/

Jip, 1000A sounds a bit high.

For that amp rating you will need 500mm2 single core cable

Well, you could use 500mm2 single core cable and just put a short piece of 4mm in the middle. It should have about a 1000A rating 

Rubicon has these Mersen fuses and holders. Only thing to bear in mind is that the 250A fuses are larger than the 160A ones and takes a different holder (that is also a bit more expensive). I believe between one of those you'll find what you need.

http://powerforum.co.za/topic/284-dc-fuses/

The 800A isolator/fuses are over 300mm H & W, poles also need to be connected in series for DC.

 

2 x 150mm2 can handle 1000A @ 2 x 1.5M

Ok, so I approached this from the wrong angle. The inverter won't draw 1050Ah, but rather upto 210A (10Kw inverter) so I only realistically need a 250A isolator.

Yup, that sounds about correct.

Instead of using isolators, what about these fuses with extraction handle ?.

 

Instead of using isolators, what about these fuses with extraction handle ?.

 

Won't they cause a big arc as well, when "mounting" the fuse?

You don't mount the fuse while the system is under load (though you often get a few large sparks as the capacitors inverter side charges), so the arcing should be minimal. The real arc comes if you need to pull them under load during an emergency... though of course if that emergency is more than 250A in magnitude there should be no arcing (because the fuse will blow).

You don't mount the fuse while the system is under load (though you often get a few large sparks as the capacitors inverter side charges), so the arcing should be minimal. The real arc comes if you need to pull them under load during an emergency... though of course if that emergency is more than 250A in magnitude there should be no arcing (because the fuse will blow).

I've seen quite a few ^shocking^ images and videos of battery arc's causing havoc on cables and other equipment. From what I understand, an Isolator prevents arching whereas there fuse holders can cause quite a bit of damage. Even if the inverter is switched off, i.e. there's no load. The problem lies with the fact that the internal CAPS need to be recharged.

Instead of using isolators, what about these fuses with extraction handle ?.

 

This looks like the internal working of a Mersen battery isolator where the casing of the unit contains the sparks.

I've seen quite a few ^shocking^ images and videos of battery arc's causing havoc on cables and other equipment. From what I understand, an Isolator prevents arching whereas there fuse holders can cause quite a bit of damage. Even if the inverter is switched off, i.e. there's no load. The problem lies with the fact that the internal CAPS need to be recharged.

Well, I figure inserting the fuse is still not a problem. Just turn the inverter off. Sure, the cap will cause a bit of a spark, and I suppose you could charge it slowly via some kind of resistor (old incandescent bulb), but I don't think this is a big problem. Tap tap.. spark spark. Done. Don't do it where there's lots of hydrogen sulphide :-)

 

Of course the other side is a problem. If you disconnect it under load, there will be an arc, and the arc will disappear as soon as the gap is wide enough, although (as a certain video recently showed), that might be enough time to seriously burn some stuff.

 

So I think you're right, perhaps the fuse is not the best breaker in the world. But I kinda think the breaker has the same problem on the inside. For that first split second until it can widen the gap enough, it's going to arc. So it's really about having something that can withstand the arc long enough and widen the gap quick enough to safely disconnect you. For my 24V system, these Mersen fuses will do fine.

Hi Silver

Attached picture of 250amp DC Braker I have used for my installation. I feel we need to have a braker as well as fuses for a large installation.

I have been in a situation where things went wrong, flames and smoke, and at that time I was so glad that I installed a dc disconnect. It saved me !!

Cheers

I use a 55DC4014 available from ACDC DYNAMICS. It has 4 poles and can break up to 250A 48V on a single pole, or if you use all of them in series it can break 250A 800V. Made for solar DC installations. I use two poles for my two inverters 5kw each with a 100A fuse each and got two poles spare for future expansion.

Edited December 17, 20186 yr by MalanT