was sitting for a few days at 4v and the delta is currently at 0.27… So after 2 days i switch bal. only when charging back to on?
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Charge the battery first, but yes
Is this normal after an overnight charge?
Wondering why the cells aren’t going all the way up to 4.2v… maybe a VESC setting?
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Vesc wouldn’t have any control over how high the cells charge. It’s got to be a BMS setting or your charger tops out at that voltage. The first thing I would check is the output voltage of the charger. If it’s not easily disassemblable that might just be what you’re stuck with if it’s the charger. If it is disassemblable there is probably a potentiometer inside you can use to adjust the max voltage.
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Also if it is the charger even if you can adjust it I’d probably not worry about it. you’re not losing much and if you adjust it wrong or adjust the wrong thing you could mess things up if you don’t know what you’re doing. You actually want the charge to be capped by the charger and not the BMS AFAIK. Otherwise, your BMS will keep cutting things off and on when you get to the top of the charge instead of the charger going in to CV mode and decreasing the current smoothly.
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Charger indicates 50.4v on the brick, so that shouldn’t be it. You’re probably right that it’s not worth messing with. A bit frustrating though, I need every mile of range I can get 
Indicates how? They’re adjusted at the factory, but they tend to rightfully err on the side of having the voltage a bit low AFAIK. Also, we’re talking about a 0.4% difference in voltage. Unless you’ve got some pretty precise equipment that isn’t a big error. One multimeter to another can pretty easily give a different measurement by that much unless they’re precision units.
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Those cell voltages are typical for a 4.20V charge at a high charge rate or if the charge was stopped before the cells were “topped off” by letting the cells continue to charge (after reaching 4.20V) until the charging current drops to a certain level, often 1/10th or 1/20th bulk charging rate.
After charging stops, the cells drop down a bit to their true “testing voltage”. Even a charger at 50.40V allowed to run until the 12S pack is topped off will leave the cells at under 4.20V after they’re allowed to settle.
I wouldn’t be concerned
There’s verrrrry run time difference between a cell with a 4.18V resting voltage and a cell with a resting voltage slightly above that (but under 4.20V).
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I’ve been thinking, that as the saying goes “force follows stiffness”. We glue our cells together for assembly, but hot glue or silicone placed along the centerline of the P group will provide orders of magnitude less bending stiffness than a nickel strip, particularly a strip that is folded over the top of the P group. Meaning, the structural integrity of the group is coming almost entirely from the welds (and possibly a bit from fiberglass tape if it is used afterwards), so the welds will be stressed out by anything that happens.
I’d like to try removing the shrink from my cells and just loading up the gaps between them with J-B Weld bonded directly to the casing, to get a thicker cross-section and actually make the group stiffer than the welds. Anybody see a problem with this, assuming they are covered in fish paper and tape as usual afterwards? Any magical abrasion resistance properties of the heat shrink that I will be missing out on?
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https://a.aliexpress.com/_EuQacqT
I ordered this on 10th December and it arrived last week. Did the scratch and salt water test and seems to be pure 
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Appreciate it.
I ordered some last week from 2 random Ali places …
Not this one unfortunately.
So wish me luck!
One possible issue is that if the cans of any two series-connected cells touch then one or more of the cells will short circuit. You’ll probably need spacers of some kind.
I was going to wrap them in fishpaper anyway, but extra plastic dividers are a good idea
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I recommend a lot of pack cycling at the highest and temps and power levels you’ll use it at too. The cells can expand a bit when warm and I’m wondering if that, over time, could potentially pop off the JB Weld?
hmm that’s a good point. My build right now won’t be pushing P42a nearly hard enough for that but it would be good to know. 5 minutes of half assed googling tells me that JB expands at about 9*10^-5/degC, do you know what the cylindrical cells do?
Welp, even if that happens I’ll just be back at square one with the welds and tape taking the loads. I’ll try it in the name of science and impatience
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This is more or less what some car makers, mainly Tesla comes to mind, are doing, isn’t it? They probably have some R&D into what epoxy works well and can handle thermal expansion and stuff, but at its core, their new structural packs are a bunch of cells epoxied together AFAIK.
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Sorry, I don’t.
Ive potted a couple batteries using 60D duro polyurethane and told that’s what pro places use and good for the cell expansion. Polyurethane not epoxy is good gets down to 60D. I use bjbenterprises stuff.
What you connect balance wires with? Soldering is so much heat n work. I just c-glued these thin wires on. I imagine not ideal. Is there a quick curing conductive glue
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