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View Full Version : Getting that spark of learning from your efforts (Fuse that Project!)



EVcycle
25 September 2010, 0311
Getting that spark of learning from your efforts or Fuse your project!!

Every so often I get someone who would rather email info back and forth than post to a forum.

I have been working with one such person who is working on their first project.

He has been popping fuses right and left but learning the issues and getting them fixed and now the
bike moves. His newest issue is the DC to Dc converter.

Imagine if there we no fuses in the system. :eek:

Do NOT cheat yourself (The house, car, pets) or all of your efforts by not taking the time to add fuses, big and small.
Even the 12 system on you ride will help burn it to the ground if wires get crossed. If you think it can spark , Fuse it!!!!



EV Ed

markcycle
25 September 2010, 0441
Also just to add, it's important to put the fuse in the right physical location in a circuit. Put the fuse as close to the source (battery) as possible so if a wire coming from the battery should short to the frame in a grounded system it will blow the fuse. If the positive wire coming off the battery grounds before the fuse then fire could still happen.

Mark

EVcycle
25 September 2010, 0703
Great bonus info!.... Thanks! (see Ted for your bonus Beer) :)

GUFF
25 September 2010, 0744
I have been using a fuse on the both sides of the pack (pos and neg) to protect against a short to pack pos and a partial pack short (odds increase for this the more batteries are in the pack).

Tony Coiro
25 September 2010, 0809
I always assumed fuse location didn't matter, since the current has be the same entering a node as leaving (Kirchoff's current law) so I'd think a fuse would blow at the same time, regardless of it's position in the series?

GUFF
25 September 2010, 0824
Thats correct for series circuits but a partial pack short would create a parallel branch of current independent of the positive end of the pack.

Tony Coiro
25 September 2010, 0831
True but you could short between any of the batteries and considering pack shorting to be of equal probability anywhere, fusing in the middle of the pack makes the most sense.

teddillard
25 September 2010, 0836
... (Kirchoff's current law) ...

don't be quotin yer big college edumacated electrical laws HERE mr. smartypants.

GUFF
25 September 2010, 0836
What happens if you get a short below that middle pack fuse?

__Tango
25 September 2010, 0842
In the Kelly controller documentation i have (for the brushless controllers), the diagrams show a direct wire from the negative end of the pack to the B- terminal on the controller. Also, it says:

Please securely wire B- before any other wiring. Never put contactor or break on B-
I assumed this also meant don't put a fuse between the B- terminal on the controller and the pack.

Is this a kelly specific thing? Or is this something that you'd recommend overall?

Tony Coiro
25 September 2010, 0844
What happens if you get a short below that middle pack fuse?


Same thing that happens if you short a pair of batteries above the grounded fuse.

GUFF
25 September 2010, 0854
My only reason for adding the pack - fuse is it protects against one more fault. There is no way to protect against all fault conditions but I try to protect against as many as I can.

Tony Coiro
25 September 2010, 1053
http://www.elmoto.net/attachment.php?attachmentid=391&d=1285437087

Fusing in the middle should protect as many cells as possible.

(I know, I am pretty much a Paint Artist. ;) )

BaldBruce
25 September 2010, 1332
My only reason for adding the pack - fuse is it protects against one more fault. There is no way to protect against all fault conditions but I try to protect against as many as I can.

Except every fuse is more resistance. The fuse itself plus the two more connections limits your current. Series battery connection needs one fuse physically close to the pack. In an isolated pack, location makes no difference. Only reason to add more is if the pack has separate remote parts to it.

BaldBruce
25 September 2010, 1339
In the Kelly controller documentation i have (for the brushless controllers), the diagrams show a direct wire from the negative end of the pack to the B- terminal on the controller. Also, it says:

I assumed this also meant don't put a fuse between the B- terminal on the controller and the pack.

Is this a kelly specific thing? Or is this something that you'd recommend overall?

It is a grounded battery pack thing. With a ground referenced system, you never want to break the negative. This type of system is frowned on by most people in the EV community. The preference is to float the battery pack. Then if any part of the pack wiring shorts to chassis, no sparks and no danger. With an isolated system it takes two faults to make that plasma cutter!

GUFF
25 September 2010, 1349
Except every fuse is more resistance. The fuse itself plus the two more connections limits your current. Series battery connection needs one fuse physically close to the pack. In an isolated pack, location makes no difference. Only reason to add more is if the pack has separate remote parts to it.

AC plugged in my bike frame is earth grounded on my bike.