Yeah 0.05” (1.27mm) should be way better, 0.031” (0.8mm) is hard to work with when you need a lot of solder quickly. I use 0.063” (1.6mm) solder for battery building. As long as the solder you have is leaded 0.05” should work well.
I agree with Al, the more heat in the tip the better for fat joints. I only mentioned flux because not all flux core solder has great flux. But with quality solder I generally don’t add extra flux ever.
That makes me feel a lot better, appreciate the reassurance.
The flux I’m using is in a syringe, so the amounts are pretty controlled. I tend to use it sparingly already, so I’ll probably just bump it up slightly this time rather than flooding the area. Between that and the thicker solder, I’m feeling a lot better already. 
I would still love to see some layout pics if anyone has them as well.
Scratching surfaces you want to solder helps the solder stick better.
Oooo, that is a great idea! Definitely going to have to try this.
Yep, i always rub up the nickel with stone wheel on the dremel, it’s much easier to get the solder on
I use a qtip saturated with preferably 91% alcohol, then lightly brush on some liquid flux, the crosshatch the area with a sharp razor knife through the flux.
Seems like when I go to tin this prepped area, the solder nearly instantly spreads.
When i don’t it just beads and resists and takes longer, sometimes alarmingly so.
I stone wheel the nickel then tin it but don’t find the need to put flux on it, i only use flux to tin the wires
Been a while since I soldered to nickel.
Crosshatching cleaned copper with a razorknife through liquid flux before series connections are added is certainly unneeded overkill, but the solder seems to flow instantly and makes me feel good.
Is it weird I never had an issue at all? I just put my iron on the nickel and apply solder.
Same, just a little flux to make life easy. I find the flux in the 1.1mm solder i use gets very hard to clean up and doesn’t clean the surface as well so i put a little dab of no clean liquid flux on everything and the mix of that and the core flux wipes off much easier. Wets and flows well and where I want so i don’t do any more surface prep
Excellent.
I am always thinking ‘what if the worst happens?’
‘How can mitigate/ minimize the possibility of that occurrence?’
Say a silicone wire series connection fails because too much solder wicked up the stranding under insulation making it excessively crunchy, or:
What if what appears to be a beautiful solder joint actually pops off cleanly , and that end wiggles its way to an eventual dead short?
When researching how to build esk8 batteries, I saw a @ShutterShock video where he razor knifed scratches into his Nickel shoulder tabs on P groups, and it triggered my need for maximum mechanical tooth when adhering epoxy, polyester, or Vinylester resin saturated fiberglass or carbon fiber, onto many many different highly stressed substrates over the last 35 years.
I thought it was a very great idea and asked myself how much extra time does doing this require?
And decided it didn’t matter and I was doing it anyway, and more time was wasted thinking about it opposed to just actually doing it.
In another YTvideo I saw some guy soldering wire to an aluminum soda can successfully, using some high flashpoint mineral oil as an oxygen depriving agent around his solder tip.
So I have this high quality liquid flux, and thought if I am going to flux the tab anyway, and I am going to razor knife cross hatches, anyway, why don’t I clean the Copper as best I can, add some flux, and crosshatch the area with a razor knife through the flux which is preventing oxygen from touching the super brite freshly revealed copper from the razor knife, for the best possible result with lowest resistance, and the least likelihood of failure.
When I went to tin the copper tab, The solder flowed nearly instantly and I was like:
“Damn!, I was not ready for that!”, and did not feed in more solder quickly enough to make the pleasing mound in as short a time as possible.
But since I now expect this near instant flow I can do it quickly and efficiently and thus transfer less heat to the cell(s) itself / themselves.
Which makes me feel I am doing all I can to build the best possible battery for myself, using some of the best available cells at the time of the build, with the best known practices at the time.
Attempting to replicate the exacting precision and attention to detail that I have been truly impressed with since I joined this forum not too long ago.
Some of these above and beyond measures, that some might find completely and overwhelmingly unnecessary, they are certainly welcome to skip.
I am not saying they are totally necessary, or even highly recommended.
Someone else trying to learn might want to see what above and beyond might entail, and choose for themselves where their personal line lay.
I am personally going to keep using at least 0.2mm copper, under 0.1mm stainless, and use flux, even on non esk8 batteries that will never be asked pass more than 5 amps.
I am also going to take measures to prevent extra heat, whether from spot welding itself, or when soldering series connections, from entering the cell.
I want the battery to run as cool as possible, as I am in Florida, so will choose cool running cells and will choose connections with the least resistance to reduce heat added into the enclosure and the cells themselves and to reduce sag as I am running a light rig with a 2P battery that has in the past exceeded its maximum temperature, in my usage.
“Good Enough” is subjective.
Opinion.
I am absolutely sure 0.2mm nickel and p45b’ s are more than good enough.
I wanna build a new pack with Tenpower 50XG’s, or Ampace JP50, or Reliance RS50, or EVE 50PL and 0.3mm copper, because I can.
I am super excited for the newest cells Molicel and Tenpower and others are teasing us with.
But I don’t need a new battery now as my current pack is performing well beyond expectation, and it has only 0.1mm copper, under 0.1 nickel plated steel, as that was all my previous 23$ PCB welder could weld at the time.
That is no longer the case, and 0.35 copper is within the range of the equipment on my desk, and the skills and techniques that I have learned on this forum.
I am appreciative of all I have learned here , and want to give back and help innovate going forward, not backwards, in any way I can.
Crosshatching shoulder tabs through flux on copper just makes sense to me, even though I am sure it is an unnecessary extra step, or 3, and one I have skipped on the non esk8 batteries.
Hey guys,
Has anyone here used these small JBD Smart BMS units in their battery builds? I found them on AliExpress for under $10 each, which seems kind of wild.
From what I can tell, these are:
JBD / Jiabaida Smart BMS
12S, 20A
For 3.7V Li-ion
Common port (charge & discharge same)
With balance leads (up to B15 visible)
UART / Bluetooth capable (label shows UART + MAC address, so smart features should be there)
I really like the idea of a compact smart BMS for a 12s2p pack I’m putting together. Size-wise they’re way smaller than the usual JBD bricks, which makes layout a lot cleaner.
Before I commit:
Any long-term reliability feedback?
Balance current any good, or super slow?
Any gotchas with these smaller JBD boards (heat, current limits, app quirks)?
Curious if anyone’s actually run one in an esk8 setup rather than just bench testing. Appreciate any real-world input. 
I’m not very good example. But here it is nonetheless @fearlesstvn
Thanks, Rafael!
I couldn’t find any photos that clearly showed the BMS — was it one of the smaller JBD-style boards? Also, do you happen to remember which cells you used?
I’m also stoked to see you running a single 12-gauge lead between groups. I’m planning on a single 10-gauge, but all of my previous builds have used dual leads, so I’ve been a little cautious about it.
These have been pretty much the standard for the last couple of years for 14s and lower..
@Tony_Stark has employed these in all of the 2024 mach ones, I don’t know if there’s any real gotchas, I haven’t paid close enough attention to mine to notice any significant idle drain..
I think @Pecos warned against using them at their upper charge limits due to heat, if you plan on much more than 10a charge it might be better to get a higher specced one. I think they come in 20, 30 or 50a
This is exactly what I was hoping to hear, thank you!!! 
Good to know about the charge limit, though. I will plan on keeping to my dinky 5a charger for this one.
Take a look here.
I have not used these bms myself. I have 2 of them here for future packs…
edit, I think balance current is around 50ma.
I have 10 of the SP14, and a couple of the SP17 models
They seem to have a fairly low standby current, and seem to evenly drain from all cells as opposed to just the first few.
I do disconnect the BMS if the pack is going to be unused for more than a month or so.
Last year I experimented with ldle drain current, I don’t have exact numbers, but it took roughly 6 months to drain a 13s ~300wh battery from 3.8 volts per cell to 3.0vpc.
Note that an active BT connection will pull more current, you can tell if BT is active when the blue LED is flashing on the BMS.
You can use the OverkillSolar app to get access to all the settings on the BMS.
JBD’s app after about version 3.1 is neutered to only allow access to the most basic settings.
JBD’s communication protocol is very well known and documented online.
I have a project that implements an ESP32 as a bluetooth esp-now bridge to get battery telemetry into any VESC based controller with a VESC-express.
This is exactly the kind of info I was hoping for, thank you!! 
Stoked to hear this model is so commonly used, think I am going to have to pick up a few more.
As for the idle numbers, that does sound reassuring. I can’t imagine a board of ours going more than a month without use.
Shame to hear about the JBD app, especially because mine is past 3.1…. but damn you go all out on the battery details, huh!! I have a ton to catch up on, but did you get the bridge working?!?! That is some next level stuff, for sure!
