Here’s a shot of the rear of the battery. I had to use braided copper because silicone cable wouldn’t fit because the enclosure was modified by eBoosted before being shipped to me (heatsink was removed, and it was reglassed, and gel coated) in such a way that I lost several mm’s of critical headroom. I should have put the batteries in the other end of the enclosure but I wanted a nice flat surface so that I could make the most of the potential to sink heat through thermal pads into the enclosure with regard to contact area.
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yep same issue on 1 group, was able to manually change it in that screen
Looks nice and tidy bro 
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Thanks, I definitely put a lot effort into that aspect.
It’s nice to be able to adjust it so easily.
Two interesting things here
@Battery_Mooch do you think either of these things (mostly the current path lengths thing) are worth keeping in mind for our packs?
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It is definitely a measurable effect that does happen in real-world applications. It’s usually pretty small, but with a poorly optimized pack, with lots of cells in parallel and high-resistance bus bars, it can become more noticeable. Minimizing it where possible (within reason) is a good idea.
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I don’t know specifically which other things you’re referring to but minimizing and equalizing current paths through a pack will always lead to better performance and longer pack life.
Whether it’s a tiny, unnoticeable amount or a huge fundamental difference in how the pack performs and ages depends on how the pack is assembled (or could have been) and how it will be used.
Keeping all the cells at about the same temp is really important for equalizing the aging of the cells too. Though that’s about impossible with the sealed packs typical of esk8.
IMO most esk8 pack builders will prioritize convenience and pack assembly speed over pack performance as the paths are already fairly well equalized for most decently made packs and the ROI for beefing things up and adding cooling just isn’t very high.
Most builders are willing to sacrifice a bit of performance to keep the pack easier to build and to not have to add cooling (which is often impossible for the desired pack voltage/Wh).
Bottom line…it’s always good to keep the various best practices, like low interconnect resistance and good cooling, in mind but each builder needs to decide how far they will go for the resulting performance and cell life increases.
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I finished my battery builds and even though they work perfectly I cannot get them to charge through the BMS all the way to 4.2V per cell. I changed the setting in the android LLT app that considers “full” to be 4.15V, but still it stops the charge at approx 4.16-4.17V
This happens to the 4 batteries I’ve built (12S4P Samsung 40T brick packs), but I’ve only tested one charger. The charger is a YZPower 50.4V 8A BUT I’ve only seen up to 6.3A in the BMS app. Any ideas?
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Post all of your parameters settings.
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Here they are:
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I changed a parameter to 4.2 and it seemed to do the trick. I think what this does is as soon as any P group reaches 4.2v it stops charging them all to prevent overcharge. If I’m not mistaken
The setting I changed was “Overvoltage release”
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I changed it to 4.2 but it did nothing. Also the packs are very new and almost perfectly balanced, I have not seen any of the groups reach 4.2 while charging (I’ve been closely monitoring the first charge)
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Weird. My pack was stopping at 4.15v and changing that parameter did the trick… sorry dude.
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I’ll keep at it, maybe I need to discharge it a bit to force a new “cycle”…also settings seem to sometimes not stick using the android app 
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Yeah, I had to write the new config a couple times for it to stick iirc. Good luck!
If it’s any consolation, last time I brought this up around here people told me that 4.15->4.2 is basically a negligible difference… but I want all the range!
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The amount of energy added to the pack between 4.15 and 4.2 is negligible imho but keep an eye on if you are looking at the actual cut off point (when the bms is stopping a charge cycle) vs the voltage of the cells after charging has stopped and the voltage has settled. It is totally normal for a cell to get charged to 4.2 then after a few minutes to an hour the voltage settles to 4.15 to 4.17. This is the resting voltage of the fully charged cell and any attempt to cram more watts into it not only won’t add actual capacity but can be hard on the cell causing unnecessary wear
Tldr: 4.15-4.17 is fully charged, charging just stops at 4.2
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First time building a battery pack (or at least first time doing it properly or for such a large pack), and looking for some confirmation that I’m doing things right.
First, the layout. I’ve got the MBoards XL enclosure, so that’s what determined the overall space for the pack. Trying to fit a 12s5p pack of P42A cells means I had to get a little funky with the shape, arranging each 5-cell p pack in a semi-stacked pattern, with two p packs side by side in alternating orientation.
With six of these end to end I can get the full 12s5p, with just enough room for connecting wires and a thin foam wrap around the whole pack. With some room at the front for BMS and (hopefully) VESC.
Second, the nickel strips. I found some 0.2mm x 50mm strip on aliexpress that at least claims to be pure nickel (will do the brine test when it gets here). So I’m thinking about cutting some custom shapes like this:
The slots are there if I can find a good tool to cut them, otherwise I’ll just leave them out.
Last, I’m looking for either a thumbs up or some criticism on my construction method.
3D printed jig for glueing the weird orientation:
Some 3D printed spacer things to give the pack some rigidity (ABS of course):
Then a wrap of fish paper and fiber tape:
The nickel strip won’t be here for a couple weeks, but that gives me some time to practice my welding.
Any pointers or things you’d do differently?
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I use similar 3dp spacers all the time. big thumbs up from me. my only criticism would be that you should have also made them to be used in betweeen the groups so that each row gets fully stuck/glued/taped together
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In between the groups as in between the two alternating p packs so that each set of p packs is effectively one larger unit?
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