The Jehu PCB v1.1 Testing and Review thread

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Card Edge Connector 2x15 Row 30 Pin 3.96mm Pitch

This is the connector they used on the other board, they are all over eBay.

I like the idea of the jehu board since I can add capacity 7 cells instead of a hole row of boards. Also means if there is an issue I can pull out that tray for service.
 
mike said:
Can you please start uploading the pictures to the forum, rather than imgur, so I don't have to keep rehosting them? Or is something not working properly with our image uploader?
Click to expand...

I was used to using Imgur because I use it on other forums that have space limitations for uploads.

Ill give what you said a try on my next post.
 
Crimp Daddy said:
mike said:
Can you please start uploading the pictures to the forum, rather than imgur, so I don't have to keep rehosting them? Or is something not working properly with our image uploader?
Click to expand...

I was used to using Imgur because I use it on other forums that have space limitations for uploads.

Ill give what you said a try on my next post.
Click to expand...

I was wondering why I couldn't click on the image to get a bigger view. Now it makes sense. Uploading the images to the forum allows for larger views if the image is high enough quality.
Don't worry about space. Mike is hosting the forums ;) or at least has connections :p
 
Korishan said:
CrimpDaddy said:
mike said:
Can you please start uploading the pictures to the forum, rather than imgur, so I don't have to keep rehosting them? Or is something not working properly with our image uploader?
Click to expand...

I was used to using Imgur because I use it on other forums that have space limitations for uploads.

Ill give what you said a try on my next post.
Click to expand...

I was wondering why I couldn't click on the image to get a bigger view. Now it makes sense. Uploading the images to the forum allows for larger views if the image is high enough quality.
Don't worry about space. Mike is hosting the forums ;) or at least has connections :p
Click to expand...

It's not a big deal, just was curious. There's no reason to create extra work.

I own the hardware, it's not leased or anything. If it fills up, I'll justadd more disks. There is still several terabytes free, so good luck filling it up. Imgur's terms of service disallow using it as a CDN to host content for other sites. Obviously a lot of places do it and they don't seem to care, but I have seen a couple get their domains blocked in the past. It sucks when you're browsing another forum and the images are dead from posts over a couple years old. Just trying to be proactive and make sure that doesn't happen here :)
 
Good point Mike. I actually started using Imgur because the other forum I go to has such limited space that I end up needing to delete my own photos to make room for new posts... which creates the exact problem you mentioned.

It is annoying but I was trying to combat that in my own way.
 
BTW, guys, you should try PostImages.org.

I personally donate to them since they have a very useful service, but it is free to use.

You can resize the images, put the pics in folders, and even put an expiration date on the pics to get them deleted in a determined amount of time.
 
Latest update from Justin:

 
I'm sorry if I'm a bit dumbfounded, but what did he mean at the beginning to not use PCB trace fuses at higher voltages?

What kind of reason is there for this?
 
High voltages would be connecting cells in series, then hooking them to this board. Or, using traces in general with higher voltages. In this video where he states that, that trace created plasma with just 20V. It could probably make plasma at a lower voltage, too, maybe around 14V(?) or so.

Some people might try to use the board, or other boards with thin traces, as fuses on a higher voltage setup. I recall someone on this forum made a board that was designed to handle series connections. I'm not sure if they uses trace fuses, or soldered fuses. I hope they used soldered fuses after seeing this. Especially if they are running 48V on them.

Since Justin is the maker/designer of the board, and he has the know-how and equipment to do testing, he's doing everything he can to show what the board can and cannot do.
 
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.
 
Someone can correct me if I am wrong, but here is how I understood it

I dont 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.
 
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.
 
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
 
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.
 
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!
 
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.
 
rev0 said:
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.
Click to expand...

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

Thanks!
 
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.

image_slcqvi.jpg


image_xkyxpq.jpg
 
are those made with M3 25mm standoffs? or M4 25mm ? or taller, like 30mm ?
 
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