Using a T-fuse without the fuse block?

St8kout

I read that you should locate inverter fuses close to the battery.

For my small off grid system, (more like an emergency backup), I was looking at the T-fuse for the inverter and is there any reason I can't mount one end directly to the battery post of my Vmax SLA battery without using the fuse block? As big as the T-fuse is, it fits quite nicely using a few washers to lift it up a bit to clear the battery case. From there I just need a short cable run to my battery disconnect switch, then on to the inverter. (I could actually attach the other end of the T-fuse directly to the switch without a cable. I only need to widen the fuse hole a bit.)

So since it's not a flooded lead acid battery, what is the downside of doing this since there are no corrosive/explosive fumes to deal with? (Yeah, I know, SLA's are not fully sealed, but they will not be in an enclosed container.)

Marc Kurth

I am a fan of fuses at the battery/battery bank, sized based on the cable and cumulative peak loads size -  and of course a fused inverter.

With batteries commonly used in off grid systems, the energy levels are nothing short of fearsome. Heck the typical 2v, 1200ah that I deal with, can go to 9,000 amps on a dead short.  No, I'm not exaggerating! Watching the short circuit tests is pretty awesome actually.

Did I mention that I really like fuses?

Estragon

I did it something like that for a few years on my initial small temp system. Kinda mickey mouse but it worked. Obviously the batteries have to be somewhere out of the way to avoid accidents.

Horsefly

I'm going to be using one of these:

http//www.samlexamerica.com/products/ProductDetail.aspx?pid=8

mounts directly on the positive battery post, and the cable connects to the other post on the fuse holder.  Any reason not to do this? 

Steve

softdown

Horsefly said:

I'm going to be using one of these:

http://http//www.samlexamerica.com/products/ProductDetail.aspx?pid=8

mounts directly on the positive battery post, and the cable connects to the other post on the fuse holder.  Any reason not to do this? 

Steve

I think you need to discard the first http: as the link does not work.

Back to OP:
As for me....I bought a bunch of fuse blocks and a whole lot more fuses. Of course the fuse blocks are nice to have. Having fused power lines put one ahead of many, many solar installs....whether a fuse block is used or not.

This isn't a car that is going to vibrate over 100,000 miles of road. Whether one needs to take a number of large safety precautions may depend on whether children and guests have access to the battery bank.

Horsefly

Sorry. I fixed the link.

softdown

Horsefly said:

I'm going to be using one of these:

http//www.samlexamerica.com/products/ProductDetail.aspx?pid=8

mounts directly on the positive battery post, and the cable connects to the other post on the fuse holder.  Any reason not to do this? 

Steve

That fuse looks pretty ideal to me. Our host does not carry it. What kind of price tag is normal for such a fuse?

Horsefly

$34.56 on Amazon, and spare fuses are $13.71.

https://www.amazon.com/Samlex-Solar-DC-FA-300-Fuse-Assembly/dp/B005ELATP6

westbranch

Look at BlueSea terminal fuses Msrp $26.39 https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

Horsefly

westbranch said:

Look at BlueSea terminal fuses Msrp $26.39 https://www.bluesea.com/products/5191/MRBF_Terminal_Fuse_Block_-_30_to_300A

That one looks pretty much identical to the one I pointed to, except my link came with a 300A fuse. I think the fuse comes separate for the one you are linking to. Still, not much difference.

mike95490

I'd suggest not reaming out the hole of the fuse end, that may disturb the internal element. 
Unlikely disturbing would increase the rating, but rather decrease it.  Use copper washers (harbor freight has a good cheap kit of many sizes) and SS bolt with lube ( I like the McMaster Carr copper flake conductive lube ) should give you a good connection,  Steel or SS is not very conductive and will heat up under large loads.

St8kout

You know, I saw those terminal block fuses but since I kept seeing everyone using T-fuses for inverters I thought I should go with those.

What I didn't like is having to buy/use those T-fuse holder blocks which take up a lot of space and need an extra cable run.

Horsefly

St8kout said:

You know, I saw those terminal block fuses but since I kept seeing everyone using T-fuses for inverters I thought I should go with those.

What I didn't like is having to buy/use those T-fuse holder blocks which take up a lot of space and need an extra cable run.

Those two reasons (size and extra cable) are the reasons I decided to avoid the ones you are talking about and instead go with the terminal-mounted fuses.

WaterWheel

With the Blue Seafuse blocks you can find most amp sizes from 30A to 300A on Amazon.       A battery short seriously scares me.       Lots of heat in a short with that many amps.