fuse confusion

[garyc]

I need to fuse my inverter, what would be wrong with using the ANL type fuses instead of the T type fuses? would it be ok to just connect the T type fuse directly to the inverter terminal and the battery cable to the other end of the fuse with a through bolt, instead of using another short cable and fuse holder ect....

[electronbaby]

not sure what the difference is between the fuses you named. It should be a DC rated fuse or disconnect (breaker) and it should be located at the batteries preferably. If this is not an option, mount as close to the batteries as possible. Most inverter manufacturers sell a DC disconnect box that houses the breakers neatly. I still believe in a fast acting fuse at the battery terminal as well.

If you are using the inverter to charge as well and you have multiple battery strings, make sure you have equal lengths of battery cable for + and -. You also could charge from 180 degrees apart on the battery bank. This will help to better distribute the charge current equally across the bank. This will allow your bank to last longer.

Im sure others will offer more info.

[maker of toys]

so long as the cable connections out to the battery bank CANNOT transfer force or vibration to the fuse, physically, there will be no problem.  If force or vibration is applied to the fuse, it will change its rating and/or shorten its working life.

BUT!

I don't think I'd like to have to manipulate cables with batteries connected to the other end and no fuses, though.  I've . . .heat-treated. . . a couple of wrenches that way. (they're never quite the same, somehow) So, caution is the watchword.  Disconnect at least one battery terminal before working on the fuses.  

Too, a blown fuse may not have the strength to keep the cable attached to the inverter, and I can forsee a situation where your battery could end up shorted because a cable touched something it should not have. . . . and with no fuse in the line, this is a VERY BAD THING waiting to happen.

the fuse is supposed to protect your batteries, structure and cable runs from a short anywhere after the fuses. . . . like a blown inverter, or two cables touching when they shouldn't.  the closer they are to your batteries, the better able they are to do that job.

fuses are not especially good at protecting semiconductors. . . so connecting them right to the inverter is going to defeat most of their usefulness.

Cable is  (relatively) cheap, terminations are easy.(once you''re set up for it and in practice.) Do it right and you'll be happier in the end.

Dan

[DanG]

The type ANL is an instant action fuse - current rise bangs it open by melting the element atomizing the filament into an arc 'flash' that will continue conducting until it dissipates, with some serious higher current if the system is having a catastrophic failure event like a direct short of heavy cable.

The T type fuses are current-limiting usually by having the filament surrounded by sand having some heat absorbing anti-flash properties, plus by design the filament sags and separates at multiple points so any continued conduction is difficult to sustain.

If you are fusing high amperage and have heavied up your entire harness - lugs and are satisfied in your safety procedures you can get away with non-UL listed ANL fuse IF you use mechanically solid fuse holders that are well isolated electrically; the way they are constructed there are chances the halves will separate leaving a loose cable.

The fiberglass tube 'T' type will likely retain mechanical rigidity after a catastrophic event so is the best choice for inline fusing - but keep cable supported anyhow...

I found a bunch of these fuse blocks cheap a while back - pictured is a 300A ANL fuse.

$9 or so is the cheapest I've found the ANL's online - the T-type are more spendy.

Remember you also should have a disconnect switch between batteries and inverter, that would be a good place to clamp a fuse in, to have the switch fused too...

[mckayped]

IMHO the inverter supply fuses are not the place to save money.  Your safety and the safety of your equipment are worth the price of the proper and recommended protection.

In this application UL rated fuses are especially important because very high fault currents are available (instantly) from batteries.

Here is a handy link to a Bussman fuse catalog - Class T fuses properties are discussed toward the end of the section.

http://www.bussmann.com/library/docs/Edp-3.pdf

Take care

Pete

[DanG]

Whoops - I couched my earlier response to cover not using a fuse-holder with a particular style fuse and wrote some fiction. My apologies..

A Class-T fuse helps best with zero-crossing currents as the entire system can be tuned to keep the number of AC cycles into a fault low while allowing normal overloads like multiple circuits randomly starting up at once from opening circuit.

All fuses consume some power and Class-T are built heavier among other reasons to better sink their internally generated heat during surges; remember they are designed for process work where buss-bars, cabling and fuses as well as primary devices may demand forced air cooling.

As long as an instant action fuse can survive inrush currents in a non-resistance DC circuit the ANL are preferable to better protect solid-state electronics; not necessarily individual FET, IGBT and transistor devices but the whole assembly by keeping misfires from melting silicon and charring the entire PCB, harnesses, case, etc. while non-instant fuse reaction time elapses.

The ANL fuse will do fine in a holder - but not to use them on battery or inverter terminals to act as fusible links since its not meant to wholly contain the arc and is not that mechanically strong. I intend to do an "equal length cable to buss bars" battery installation and have the fuse well outside of the immediate battery area, a solid application for the ANL type fuse and holder shown in previous post.