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The Jehu PCB v1.1 Testing and Review thread
#31
Ah I hadn't made the link to why he would be concerned with it.

Now I get it, thanks. Why would you rely on trace fuses though? That would be extremely dangerous on non parallel connections. If the PCB was made to work in 1S 7P, then it would be fine.

As seen in the video, carbon still conducts electricity, which allowed the plasma to flow and you want a fuse to blow completely to instantly blow when extreme overcurrent is applied.
The power of lithium ion is in our hands!
We'll show them what we're made of!
#32
Someone can correct me if I am wrong, but here is how I understood it…

I don’t think those comments apply to this board design, but it was more of a general statement. In this board design the fused traces are for the balance leads carrying no more than 4.2 volts. While they appears to be suitable for this application, trace fuses are not suitable for all, namely in higher voltages.
#33
Yes that is it.

The main problem with trace fuses that are very short and thin, are high temperature and low voltage breakdown because of that first component.

Under very high temperature conditions, like when there's a short, the trace f sublimates, creating a low breakdown voltage for the air to turn conductive at high(4S+ voltages), and then still lets current through.

That problem could be avoided with 2 reasons:

1. Making the fuse trace thicker and longer. By doing this, you do up the fusing current, but make it so there is a much lower chance of rapid heat sublimation, and a bigger distance to prevent low voltage breakdown.

2. Bypass the fuse trace with a normal fuse/thin copper wire.

Edit: It's something we were taught about in physics class. If a metal vaporizes into the air, the air's breakdown voltage goes down, giving a higher chance of it being conductive, and creating plasma.
voxelman likes this post
The power of lithium ion is in our hands!
We'll show them what we're made of!
#34
Wow very cool. I'm gonna send this off to China to have some made! Can't wait to put one together.
I'm sure people have seen what Stuart Pittaway put together, but I was wondering if these two design s could be merged somehow (so the bms is on the pack pcb...).
...if a backplane solution is implemented then I'd be super happy.

Check it out if you haven't already; my pcbs & parts arrive this week!
https://github.com/stuartpittaway/diyBMS
#35
rev0/jkenny has made some more changes to the board. Maybe wanna check to see what he has available now.

Not sure if he's made the latest mods available yet, tho.
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#36
1st of all thank you for all your wonderful hard work, this is really neat, and great of you to make available to all!

rev0/jkenny Where can I find the latest files?
The only place I am able to find the files were on Jehu's page: https://mailchi.mp/jag35/pcbv1

Is there a "central" location were I can check periodically to see where things are & ensure I have the latest revision? I'm super juiced about this and don't want to miss any updates or planned updates.

Thanks in advance!
#37
There's no hard deadline for the new version. Jehu and another member of his facebook group have provided some feedback that the current balance connectors are very poor for reliability/current carrying, so we're looking for a viable alternative. Until this is found no new version will be made. The next version could be assembled in a "hanging" fashion from a pair of bus bars using M4 screws, which would be better for high current in large parallel packs.
voxelman, Korishan, Crimp Daddy like this post
#38
(09-20-2018, 02:48 AM)rev0 Wrote: There's no hard deadline for the new version. Jehu and another member of his facebook group have provided some feedback that the current balance connectors are very poor for reliability/current carrying, so we're looking for a viable alternative. Until this is found no new version will be made. The next version could be assembled in a "hanging" fashion from a pair of bus bars using M4 screws, which would be better for high current in large parallel packs.

OK cool, thanks for the update!
I look forward to see what's next.

Thanks!
#39
The brass standoffs are actually not that bad...  at 400 watts of load, we are seeing about a 5mV delta from the top to the bottom.  

R=5.4mV/15.38A=0.35mOhm

Pretty confident that the standoffs are not the limiting factor here... the cell holders are.  



Korishan, Shadeyman, voxelman And 2 others like this post
#40
are those made with M3 25mm standoffs? or M4 25mm ? or taller, like 30mm ?


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