Fusing a control component

[garetwo]

Shouldn’t any control component with dinky little wires, attached to a battery, be fused?

We have all 16 LifePO4 batteries (4S4P) now connected to balancers, and it has made a huge difference. So, the Band-Aid for a poor way to do things seems to be helping immensely. We are going to install the shunts on each group of four in series and notice the control cables on the shunts have inline fuses, but the balancers have no fuse, just ring terminals designed to connect right to the batteries.

Of course, there is no website for the manufacturer of the balancer, but the two specs available state:
Compensation current: 0-10A
Rated Voltage: 4S (7-18v)

It seems the control wires should be protected. If this is true:

What voltage rating?
What ampere rating?
Slow-blow or immediate?

I found an Eaton/Bussman Ceramic Body, G 15 amp - Fuse, 15 A, 250 VAC, 125 VDC

Thanks!!

 

[OzSolar]

Yes, every wire in your system needs to be protected from being damaged.

I am electrician, not an EE, but that fuse you've mentioned does seem to be in the realm of reasonable. Certainly better than nothing.

 

[hwy17]

It's common for people not to fuse balancing leads. The logic, if there is any, is that the wires are thin enough that they will self fuse in a short.

 

[garetwo]

It's common for people not to fuse balancing leads. The logic, if there is any, is that the wires are thin enough that they will self fuse in a short.

Very interesting...Thank you for taking the time to reply. Do you think/feel/know, that if the balancers can "shift" up to ten amps, an eleven-amp fuse may be ok?

 

[garetwo]

Yes, every wire in your system needs to be protected from being damaged.

I am electrician, not an EE, but that fuse you've mentioned does seem to be in the realm of reasonable. Certainly better than nothing.

This is my thought as well. Especially with the control wire on the victron shunt coming with an inline fuse

 

[garetwo]

I found an Eaton/Bussman Ceramic Body, G 15 amp - Fuse, 15 A, 250 VAC, 125 VDC

Thanks!!

I found 10 x 38 mm fuses at 11 amps for DVMs. Buss and various Chinese manufacturers sell them. I cannot find a DC rated fuseholder. If a fuse just has 1000V rating, is it implied AC/DC? If the fuse holder is only stamped with 600V AC 30A 50kA, why will they not support a DC circuit of substantially less voltage and 1/3 the amps?

 

[Partimewages]

They probably would but have not been tested for it.

 

[garetwo]

The logic, if there is any,

i just let that register

 

[Partimewages]

If for the sake of conversation apply some NEC.
T taps are allowed for short distance without a fuse or breaker.
Low voltage class 2 is allowed to run free air if under 100 VA.
If a single wire is enclosed in a case then I don't see any issue. Example Andy's Garage BMSs on his shelf.
If exposed like some installs it would be an issue for me.
This is just my opinion. I'm trying to apply NEC intent not the buy the book.
An example of this is in the county I live in. The inspector wants residential basement switches and receptacles in protection run down the walls pvc or emt but just before the box he was requiring to put a connector with a bushing at the end of the pipe then another connector in the box. This was to accommodate the code for not running romex inside the pipe. I understand the code but to leave a gap between the pipe and box with back to back connectors is beyond logical. The pipe is to provide protection for the romex.
Sometimes things are not logical by the book but the book is the only thing lawyers will look at if there's a failure. Make it safe I don't care what the book says. An old electrician when I started years ago told me. The NEC is the minimum standard. If you meet that you're only doing the minimum. Nothing but money keeps you from doing better!

 

[garetwo]

T taps are allowed for short distance without a fuse or breaker.

I will have to look that up, that would mean no code violation then.

Low voltage class 2 is allowed to run free air if under 100 VA.

These "manipulate" up to ten amps, so they are a little over 100 VA - means they should be in a raceway?

If exposed like some installs it would be an issue for me.

For sure exposed

Make it safe I don't care what the book says

Yes

I understand the code but to leave a gap between the pipe and box with back to back connectors is beyond logical. The pipe is to provide protection for the romex

It would seem reason would dictate the intent is merely to protect.

 

[Hedges]

Consider silicone insulated wire. If the wire burns up, insulation will contain it so doesn't bridge to anything else.

Fast blow is better. Never any need to handle > 10A for a period of time, not starting a motor or warming up an incandescent lamp.

A design could maybe have PTC fuses. But they aren't rated for the potential fault currents.

Normally thermal fuses would be 1.25x continuous current. DMM fuses are fast, high voltage, 11A for 10A application, but that isn't expected to operate for hours.

I don't think fuse holder matters AC vs. DC. Just switches, relays fuses, which interrupt current.

 

[rhino]

I used https://www.digikey.com/en/products/detail/mpd-memory-protection-devices/BF303/2330519
and
https://www.digikey.com/en/products/detail/optifuse/FCD-3-15A/12090372 (note they are ceramic)

for the leads on a JK BMS.