Hi guys, I got a question regarding the cell level fusing 10S5P 30Q battery I’m building:
Will a 1,7x7,5x0.4 mm (0.06x0.29x0.016") brass plate be enough in order to avoid unwanted heatings or do I have to use a bigger one? Any suggestions about the right dimensions if that’s not enough?
I have also wondered this about the brass busbar. I plan on buying a copper sheet such as
And using a dremel tool to cut out busbars on my most recent build. Would be interested to see what other have to say about all this.
Looks good to me. (The diagram) Don’t know about the coppersheet tho. I used 0.4mm brassheet about 10mm wide and a bit smaller than the lenght of 5 cells. No issues so far. (10s5p)
Well if brass the same size or smaller works then copper should be even better.
Yup. Bit confused when wrote in cm and then mm…
Engineers measure conductance in square millimeters. So one way to calculate how thick bus bar you need is to look at ga ratings from a solid/multistrand wire and calculate radius * radius * pi…
Or geez look up resistance for copper and brass, something like
https://www.radio-electronics.com/info/formulae/resistance/resistivity-table.php
and take a ratio?
to each with his own method 
or just take a look at a chart theres a chart for everything related to engineering
Wooh sry for charing . the fuck 
I’m all for cell level fusing, but it doesn’t mix well with any kind of BMS, even if it’s charge only.
If a fuse blows, then the others in that P group take extra load and likely blow as well during riding.
And if any series connection breaks within the pack while you’re riding, suddenly your VESC turns off and you’re now feeding your full pack voltage through the balance wires surrounding the series connection instead of the expected 4.2V max difference. This situation would very likely burn up your BMS and i’d even go as far to say it’s an unnecessary risk of fire.
Why is that ? Sorry, did not read the whole message.
Regarding the first point, if you design your fuse to blow with the continuous discharge rate of the remaining cells, then it’s true. But if you assume that a shorted cell can deliver much more current in a short that its max continous discharge, you could design the fuse to be large enough not to blow with the remaining cells, couln’t you ?
You could, but then you have the issue of uneven discharge because you wouldn’t necessarily know that you blew a fuse, it’s inside your enclosure. For a 2P pack that means you’ll deplete the p group twice as fast as the rest, and after that… cell’s dunzo. A BMS can’t correct for that kinda difference in capacity.
That has been my interrogation with cell fusing. How do you know that you’ve blown a cell ?
If you have the diebiebms you could check via metr.
Maybe an alart could be set up as well.
You cant technically distinguish missing cell in P group. The only thing that can change it will discharge faster as capacity is lower which would make P group voltage lover than others but balancing can hide it…
This is exactly what concerns me with cell level fusing.
But whats the problem ? If you have a BMS, it will stop when the group reach the low limit voltage, won’t it ? The fact that there is a missing battery in the p group will not disable this feature.
@Lumaci : How would the DisBieMS notice the missing cell ?
For one thats super worriee about p groups dying or cells or whatever I would reccomend them to get the bluetooth bms, you can see each p group voltage and turn on balancing or turn it off and edit so many settings it will get really confusing