You win!
So that’s all it was. Some bad connection somewhere. I just swapped the BMSs and it turns out they were both good. So glad because I was planning a Alibaba order of a bunch more JBD BMSs.
You win!
So that’s all it was. Some bad connection somewhere. I just swapped the BMSs and it turns out they were both good. So glad because I was planning a Alibaba order of a bunch more JBD BMSs.
Now to find the dodgy connection
so. I accidentally sliced a lipo cell with a razor knife. how to dispose of it?
it had no tab left exposed, but I wanted to discharge it for recycling. so I was cutting away some of the wrapper to expose some tab.
just when i was almost done, I slipped and sliced a tiny slice in the pouch. got my first sweet smell of success. (electrolyte)
I decided to FAF, and i setup a firesafe area, and went ahead and discharge/destroy the cell. it didn’t catch on fire. and it’s dead dead now. smells sweet still tho.
what can i do with it now? can I take it to the recycler? maybe I could super glue the hole… tape it… and… then take it to the recycler?
Forbidden cell nectar
I wouldn’t recommend superglue. You never know what kind of chemical reactions could occur between the glue and the electrolyte. Personally, i would tape it up, double bag it, and recycle it. If you fully discharged it then there should be zero potential to start a fire. So the bags are just to keep the highly toxic cell guts from getting out.
Let me introduce me here. I am Nelvick Berrios. DIY500AMP.COM I am new here on the site but not to the topic.
I can tell JP40 cells are amazing cells and there is so much drama around the cell. The true is the cell is an amazing performer and is sad that Ampace it self can not sell the cell directly, (at least not yet).
I have been testing this cell, You can see in my youtube channel. This cells all came in different voltage from “factory” and after 2 or 3 hard cycles they all stabilize to the same voltage. Is interesting all the findings and how perform the cell.
I see in this group people with amazing knowledge at Mooch level and this make me stay here.
I hope I can join the group.
Ok… I got a malectrics spot welder w/ a gtech 5300 lipo 11.1v 100C lipo. I’ve been test welding on some .15mm nickel. Just stacking 2 strips and welding together. To get what looks like a good weld I have to set the “weld pulse duration” to 50ms. This seems very high from other posts I’ve seen here and elsewhere. A lot of them reference times of 4ms and 6ms. This is the last weld I did and ripped apart.
1: Is the “weld pulse duration” being set to 50ms way higher than it should be? Maybe I should get a car battery or bigger lipo?
2: Does nickel to nickel require more power to successfully weld together, as opposed to nickel to cell terminals on 18650, 21700, etc. cells?
I’m running the same welder but on a 12v car battery. I run 23ms. If I’m going nickle to nickle I’ll weld it 2x in the same spot.
Probably, yeah.
You’re correct that your battery plays a big role in your weld power/quality. Try benchmarking a weld and see what your measured weld voltage/amperage is. To benchmark, activate a weld pulse and continue to hold the trigger for a few seconds after the weld pulse.
Yes it does. This alone could explain your high weld pulse length. Try doing test welds to a steel razor blade or something. Though nothing is going to be a perfect representation of the cells you plan to use. Aside from, you know, the cells you plan to use.
If you haven’t read this, it’s pretty much all my thoughts/experiences about welding.
thanks brother… i’ll try a few other materials and the benchmarking thing.
Hi!
I’ve never built a li-ion cell battery before, but always wanted to. Plus, my experience is outdated by couple of years. Currently I plan a new dual 6374 85A motor/ two 75100 vesc build.
So can someone give me an advice on the following?
Thanks in advance!
Most builders these days are using 21700 cells unless there is a space constraint. The energy density and discharge performance available with 21700 cells is pretty good.
A consideration for determining voltage would be how it impacts your desired speed. Another would be the potential impact to your VESC selection. Anything greater than 12s typically requires a different tier of VESC.
Thank you for your reply!
Got you, 21700.
Is there any rule of thumb, how to choose cell model? It is pretty clear for me how to combine cells into pack with desired specs, but cell market is an overcomplicated puzzle for me.
I’m sorry for being so vague, last time i did that in 2018, and that was lipos.
Speaking of VESC tier, as I mentioned, it is
To be exact, it is flipsky 75100 v2. Seems like it is build around HW 6. And yes, I’m aware of this vendor QC, but it is an honour for me to play Russian Roulette, considering Russians are almost glued to aliexpress nowadays. That’s why I’m searching for aliexpress suppliers.
There are a ton of factors, but Molicel P45Bs are usually the go-to unless you’re going to do a massive battery where you don’t require much current per cell. There are some newer cells that are better, but as far as I’ve seen, those aren’t worth the price they’re selling for yet unless you’re willing to burn a lot of money to get the absolute best. If you’re doing a massive battery where energy is more important than power, there are also probably better options.
My opinion on cells currently: previous replies are on the money. 21700 cells unless space is a constraint.
My picks: molicel p42a - cheap and good for lower p counts
Molicel p45b - better by about %20 in every way and the price is very close to the p42a. Easy upgrade imho and my current cell of choice.
The p50b have another 10-20% performance boost but the cost is nearly double and the maths don’t work for me.
Samsung 50s is more capacity but way lower amps and higher draw sagging. Good if you are in the higher p group counts, i wouldn’t use it under 7p as more amps per cell will just lose you any capacity gains over the p45b
There are some tabless cells coming to market and a front runner ampace tabless cell seems really promising and lower cost but i dont trust it yet. Needs to be vetted by the community with some actual use before ill commit and none of my regular stateside wholesalers stock it currently making my choice easier.
Not saying I recommend this, but on Nothing Fancy I’m currently running 20s on my 12s rated apex motors
Thank you for your reply!
Considering I’m aiming to build 14s4p, I think I will use p45b then.
Which size (i.e. width/thickness) of a nickel plated strip I should use to spot weld to this powerful cell?
Absolute maximum battery output I can imagine will be 170a (42.5 amps/cell), but, in reality, during a hill climb, continuous current shouldn’t exceed 15-20 amps/cell. Anything more than that can occur only during acceleration.
.2 in 30mm pure nickel is what i use for 99% of what i do. See the link below for some good eskate use case ratings. 30mm is the width i use to bridge but the dimension that carries the current is the length that spans the cells so if flat p groups it will be something near 50-60mm of .2 nickel putting you calmly in the 90a green column or 180a ish for maximum which seems about right in my opinion to keep your pack running cool.
Wire and nickel current ratings
I get my nickel from amazon and have had good luck but remember to rust test every order - i had the same seller i used a few times before send me nickel plated steel. They fixed it but it was a pain to wait for the second shipment.
I have already seen this table, but what I forgot to mention is that pack I want to build should be flat&semi-flexible, so the way i see it is each p-group will be connected the following way on each pole:
This way p groups could be connected by flat copper stranded wire.
As shown on the drawing, strip A physically connects cells, strip C ampacity can be easily increased by soldering stranded copper (and it will be during series connection)
Then it comes to strips B, and that’s where all my confusion happens, because they physically can’t be wider than 21 mm, can they?
And also, i don’t think each B strip should have ampacity of more than 20-30 amps if 4p pack is 80A continuous. That’s why I thought about 0.2 10mm or 0.2 12mm. Am I wrong?
The preferred way to make batteries like this is to have a single folded piece of nickel. If you use a 30mm strip as suggested, you can have ~15 mm on the top/bottom of the cell to weld where you have A, and ~15 mm where you have C to do your series connections. This means for a 4p battery, the total width of the nickel in the direction of current flow is nearly 80 mm, replacing what you have as B.
There are many examples of packs built like this if you look through this thread.