Looks a bit cold if you ask me. Its probably fine though. This is a non-flex pack right?
1 Like
it’s Flux at2, very little flex.
If you must use braid, it’s likely better to use it in a configuration like this…
It keeps the braid longer so that there is less chance of the solder wicking all the way through the braid. @TheRef has some good examples of this.
Personally I’d recommend silicone wire like this
Give it as much length/curve as you can to mitigate solder wicking.
8 Likes
Thanks.
Do these look alright?
.2mm, p42a, kweld on 5500mah 3s lipos in parallel
That’s 40j on the positive, 35 on the negative
ok, my first post.
I’m building my first ESK8 battery, 12S4P out of Molicel P42 (21700).
I’ll be running 2x 6376 160kv Trampa motors, open belt drive with 14T/76T gearing, 8inch offroad wheels.
reading the forum I’m still not 100% certain what specs nickel strips I need to use to join the 4P groups and to make fold-over tabs and then to join all 12 groups in series.
I note some people double up (double stack) nickel strips, is this necessary ?
Can I use just single nickel strip 0.2mm thick for the job ?
atm. I have at home 5m of 0.2mm x 8mm nickel strip, 2m of 0.2mm x 18mm nickel strip, AWG14 and AWG12 wires ( I’m unable to get a different nickel strips for another 2-3 weeks so I don’t want to wait unless absolutely necessary).
My plan is to run single 0.2mm x 8mm nickel strip across 4 cells in each parallel group and then create 2 tabs out of 0.2mm x 18mm nickel strip (one between cells 1 & 2, second between cells 3 & 4) and fold them over on top of the 4P group (both for + and -) and finally use 2x AWG14 to join all 12 groups in series (where the tabs were created).
would this satisfy the current flow requirements when I’m planning to limit my VESC to 60A per motor ?
Motor current has basically nothing to do with battery current. If you mean you plan to limit yourself to 60 battery amps per side, then no, two 0.2x18mm strips is not sufficient for that.
two 0.2x18mm strips would be good for ~100A at most, and I probably wouldn’t push them past 70 or so myself.
It would be significantly less hassle to just get some 0.15 or 0.2x30mm strip and do it all in one go rather than having to weld three strips for each end of each group.
Not with proper pack design.
Yes, if it’s wide enough. It’s all about cross sectional area. Doesn’t matter if it’s 1mm thick and 10mm wide, or 0.1mm thick and 100mm wide, either will have the same cross sectional area. If you’ve got the width for it (and you do, with 4 cells side by side you have over 80mm of width to work on) I might even suggest going down to 0.15mm thick strip because it’s easier to bend and weld.
2 Likes
That doesn’t look so good at all to me. What iron are you using? Wattage tends to matter much less than most folks think it does.
I’m also new here, but this plan sounds poor to me. 21700s on the positive side you have about a 9mm diameter positive terminal surrounded by a ~6 mm ring you don’t want to weld to. That means you’ll have 12 mm of your 18 mm strip over an area where you don’t want to weld and on 3 mm on each side to weld to if I’m understanding your plan correctly and you’re planning to have the 18mm strips run perpendicular to the 8 mm one creating the p group. If it’s the other way then you won’t really have much of a tab.
2 Likes
thanks
my bad, sorry. on my existing eBoard with 12S3P battery made out of same cells I limit battery max current to 37.5A per side so with same spec battery (except 4P) I should be limiting it to 50A
yes I have some 0.2x25mm on order from Fogstar in UK but they don’t ship to Australia so I had it shipped to a friend in Europe and once he gets it he’ll ship it to me, we just don’t live in an ideal World and I have to work with what I have at home. it’s 2-3 weeks wait but ordering from China is currently even slower.
I’ve seen that conductor rating table in this thread above but the numbers were significantly lower,
I would post it here but for some reason this forum doesn’t allow me to post images.
It’s because you’re new here. The forum limits your permissions as a new user with less than X amount of time spent reading. It’s a spam-prevention measure, with the added benefit of encouraging n00bs to read first and ask questions after.
I know your pain, and it’s hard to wait, but I would counsel patience. The battery is one of the most critical and important parts of a PEV build, and rushing it with suboptimal supplies and components just to have it done a little faster is not a good idea.
1 Like
not sure if I understood you, I’m not welding the 18mm wide strip to the battery terminals, I’m welding it to the other 8mm wide strip and there is a fish paper ring around the positive terminal if that was a concern
Still not a great design, and welding on top of anything but metal cell-ends definitely sketches me out significantly.
1 Like
I would recommend tinned copper braid… it doesn’t soak up as much solder. If you are in the states I can sell you a bit of good stuff. And I’m gonna say no on your joints being okay. They definitely need some love.
here is the other post with conductor rating table, different figures in that one (again, I cannot post the links either) :
forum.esk8.news/t/the-battery-builders-club/720/2660
Nickel to nickel welds are generally pretty useless unless you’re hitting the battery terminal underneath as well.
Welding ANYWHERE OR ANYHOW over the negative shoulder on the positive end of the can is an absolutely terrible idea.
2 Likes
well, I’m glad I asked.
sounds like it may be better to completely ignore the 18mm strip and instead create 4 tabs (directly out of each terminal) with the 8mm strip instead
That’s a link to a post that linked to the exact same thing I linked you to, except out of date. (The newer one has more sizes.)
Sounds even better to wait a couple more weeks and do it right with a single piece, eh?
1 Like
Or do an 18mm tab off each cell. You still need to join them in parallel tho
2 Likes
oh I get it, so the picture within that post was an auto screen grab from original post and when the post got updated the screenshot in this thread did not get updated. ok doesn’t matter, I got the correct table now.
probably, let me get this right so that I don’t misunderstand the “cross-section” concept, if I made 4 cross tabs 0.2x8mm, that’s a total of 0.2x32mm and according to that table 0.2x30mm is good for 56.67A, lets call it 60A (because I’m at 32mm rather than 30mm), that’s 60A for “Optimal”, that would limit me to about 30A per side ?
if I got this right then yes, it’s better to wait.
(having said that, reading this thread from the beginning for some 4 hours last night, I’ve seen worse setups than this, but I guess the information has changed/improved over the last 2 years)
1 Like
If you need bigger nickel let me know. I can sell you a bit of what I have if you are in the states.