100a PSI fuse

oatnet

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I bought a bunch of PSI blocks and cells from the Cycle 9 clearance. The block kits came with two types of connecting bars, one that was simply a metal strip with two holes in it, and one that was necked down in the middle and marked "100A".

I didn't need the fuses on the PSI pack, but they are coming in really handy on an 8kw pack I am building. Unfortunately, I need about a dozen more to complete the pack.

I've been to AndyH's site http://www.rechargeablelithiumpower.com but I didn't see any fuses listed, and I don't know if they are even a PSI product. Does anyone know where I can source these 100a connecting-bar/fuses?

-JD

PS: This is what the regular connecting bars look like - I need fuses that look roughly the same...

strap45_1_320.jpg
 
Hmmm... If this is a high voltage pack I sure as heck wouldn't want to use the cell interconnects as fuses!

This is for the vectrix pack right? How's that going? I'm still saving for mine, in the meantime I'm making a VX2 (lead acid - yuk!)
 
heathyoung said:
Hmmm... If this is a high voltage pack I sure as heck wouldn't want to use the cell interconnects as fuses!

Never heard that one before, can you educate me as to the risk? I thought it was standard practice to fuse between the layers of battery in a high voltage pack, and one fuse in the middle of a low voltage pack. When this pack was in the VW Bus, I had a 400a fuse between each of the (3) layers.

In this configuration, the pack will have (9) layers stacked on top of each other. Each layer will be 5s5p - 5 headway 'supercells' connected end-to-end with set screws. Each 'supercell' is (5) headway paralleled with copper strap on each end.

The 5s5p layers are connected by (5) straps that connect each of the 5p cells to its mate in the next row. I planned on using fuses for all the 5-serial-row joiners, now I am considering just fusing the ends I can get to without disassembling the pack, on the controller side. (5) 100a parallel fuses would service a 500a load, so I'd expect the 200a main fuse to blow long before them...

-JD
 
If you have a few of them in parallel it won't be an issue, the worry is when you have one open fuse like this being the sole element - when it opens, it has the full pack voltage between both ends, and will arc and cause all sorts of nasty stuff. I thought you were planning to use the interconnects as the main fuse.

The 400A fuse would have been rated for the correct voltage - and so wouldn't be an issue. These are usually sand filled to suppress the arc. I've cracked one, but never blown one apart (yet).
 
oatnet said:
Each 'supercell' is (5) headway paralleled with copper strap on each end.

So one question keeps nagging me: how do you protect against one of the cells in such a 'supercell' shorting out internally? Or does that never happen?
 
Malcolm said:
oatnet said:
Each 'supercell' is (5) headway paralleled with copper strap on each end.
So one question keeps nagging me: how do you protect against one of the cells in such a 'supercell' shorting out internally? Or does that never happen?

There is no way to protect against a cell shorting out internally from a manufacturing defect, one can only protect on the consequences. With LiPo, a defect/short would likely result in thermal runaway, fire, etc. I use LiFePO4 instead, so the subcell would simply go flat, and the supercell would be degraded to 4p/40ah; with sufficient DOD I might catch the voltage drop or I might over-discharge the supercell, and make it go flat.

An individual LiFePO4 cell is already a 'supercell', a paralleled collection of LiFePO4 cells packaged together, so if I used a single 50ah cell, the risk would be identical. Maybe worse, if the defect took out the whole cell.

There is a good body of experience with paralleling LiFePO4, we have seen a lot of emoto and ebike builds using paralleled Headways\BMI\PSI etc. Heck, these cells were configured as 8p in my VW Bus using the same harness for several years, I'm just cutting it down to 5p.

-JD
 
BMI said:
I have 100A and 150A fuseable cell links if these are what you are looking for. PM me if you need some.

Yep, those are just what mine look like, thanks for the picture! I really appreciate the offer, but I decided to put only put fuses on the front of the pack where I can get to them, and I'll put copper bars on the back instead since I'd have to take the pack apart to get to them.

-JD

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