Niochrome wire is an idea I’ve never used for putting cells in parallel to balance. If a coin is lower conductivity (is it?) that sounds even better. I imagine the very small voltage difference will result in very small current
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I think it’s good, it’s a 16s5p of samsung 50s, the wire is 10awg so maybe too thick. The tin is 60%Sn 38%Pb 2%Cu
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you don’t get that your risk tolerance is higher than others.
that what is possible is not always advisable, unless you have an understanding and have weighed the risks yourself. Your advice rarely hints that there are risks the receiver of your advice might not be aware of.
you get attacked for it, then you stand your ground even firmer and it all just spirals into hyperbolic statements. and now there’s a history. so it starts off hyperbolic.
FWIW, I think you’re off on the thinking of the wall wart charging. you seem to have perceived that it’s a current limited device. It’s a max current rated device. In your experiments it’s likely only current limited by it’s degraded failure mode, and for some wall warts this might be fire. just not he ones you’ve used.
You did mention not letting the cell over charge supplying it 5v. and monitoring for heat. but not as many times as you stated “it just works”. I get nervous someone would screw both of those things up easy with this usb wall wart method.
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Just to clarify I’m not a moderator, I’ve muted him for myself so I don’t have to read his nonsense. He’s refused to listen any time he demands evidence over and over even when we’ve given it many times. At a certain point, he’s just trolling for attention, and shouldn’t be taken seriously
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It might be barely passable but it’s def not good. Several obviously cold joints and what definitely looks like solder wicking up the wire. Not to be a dick but this person, whoever they are, needs to practice their soldering. Ultimately, if u r the client and u r happy, it’s all good. Personally, I’d be immensely unhappy if I paid someone for this battery.
Cold joints everywhere like that will dramatically increase resistence in the pack and will likely also create hot spots. They may even unsolder themselves although that’s less likely, but it’s a definite possibility.
Solder wicking up wires is also a serious issue and will often cause failure in an esk8 battery over time.
Will this battery work? Probably… but for how long? Caveat emptor, bruh.
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With two cells with 15mOhm internal resistance you would get 0.2V / 0.03Ω = 6.7A max of current flowing for a bit then quickly dropping as they balanced. Those cells can handle that.
That could take forever but should work if the BMS is set up properly.
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Couple things here.
First, I do hope you’re fully aware of the increased hazard and risk of a split onewheel pack. I’m assuming, it’s the 18s2p rear with 2s2p in the front. No idea what BMS you’re using, but either way, you should be fully aware of what the risks are, and why they are that way, before actually finishing and implementing such a battery. If the fact that there are increased hazards is new information to you, then it may be a good idea to take a step back from that project and comb through things more thoroughly.
Especially since the hazards of a series-split pack are much more heavy than whether or not 8 welds is too many.
Edit: I didn’t see the fish paper bits between groups. My bad.
On the subject of insulation, I don’t know if you intended to, but there should be something like fish paper under those balance tabs when they get folded over onto the valley between the cells.
Regarding weld quality, how they look is only going to tell you so much. Really, you should be doing pull tests on either dummy cells or cells you don’t intend to use. The nickel should tear at the weld, leaving some of it behind. This can happen with welds that look cold but aren’t. And a joint that looks hot can be weak from the joint being brittle.
Testing is the real way to tell, especially if you’re not really familiar with the welder and it’s behavior.
Best of luck.
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Easiest and most consistent way I’ve come across so far:
https://amzn.to/3VpgCnC
As was said, if the cells are new and from the same cases or batch, they should be essentially the same.
If they’re mixed in terms of use, age, batch, etc., then the VC8 would charge them or drain them to the same voltage, but you should probably test them in other ways as well for the sake of pack evenness.
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I have one of those VC8’s and it worked well to get all cells to the same voltage before building. No conplaints.
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Thanks mario, i am definitely aware of the risks of a split pack currently going to be temporarily installing and wiring this for a zbms then will later swap it for an ennoid. I may wait for their 12s+ or whatever they call their new split pack specific model in development but i think(correct me if im wrong) while the v4 is still monolithic temprature monitoring and being able to view cells through vesc tool should be sufficiant to properly moniter the pack(s) without the need for the split pack specific design? Again correct me if im wrong but from what i gather from the limited info available from ennoid on it, it basicly just helps mitigate the connection/disconnection order issues of split pack and monolithic bms issues?
However im not the set it and forget it type, my boards are a constant “work in progress” they rarely see over even 100 miles without me opening things up to add something, change something or to just open up the rear box to check the integrity or test the cells with my meter.
My previous 20s2p build, following your guide mostly, only deviated from your build when it came to cell seperation, i designed a 3d printed tpu (open sided) pack frame.
It wrapped every cell and provided 0.3 to 0.4 air gap between each cell and was open on the top bottom and both sides. That pack has been out of the board and tested numerous times in the 500 miles ive put on it.
This pack yes fish paper isolaton between cells, i will also have fish paper and kapton under folded over balance tabs and i also shrink wrap the balance tabs as well.
I use shrink wrapped tinned copper braid for the pack half bridge connection and use tesa tape in the areas that could possibly be exposed to abrasion. I minimize if not eliminate any wiring over lap or interation with sharp edges and if unavoidable add fish paper or tesa tape sandwhich in those areas.
Also shrink wrap and 1mm foam padding top bottom and anywhere else i can fit it.
This build i am follwing stanley or vow’s pack design, while using your guide alongside in regards to all the addidtional safety measures and shrink wrap, i dont understand why he doesnt shrink wrap his packs…
Im using a pub box for the front controller box that i added a couple revisions to, one to accommodate the cannon core motor plug and an added 20mm gor tex vent patch to vent what is now a battery box as well. Also using the pub box thicc lid with a thor to hopefully mitigate even more heat in the front box.
As for the welds i did do a pull test on an old cell and it was difficult to pull off and did leave bits behind, i couldnt recall if that was “too hot” or just right.
I am pretty used to this welder at this point but it is a cheapy amazon special as i travel all over the US for work and live in a 5th wheel trailer so this welder is small and compact but does well for what it is, i just doubt it will last for more than maybe 4 packs, so far though ive been pleasently surprised for 60$.
I apologize for what is probably a terribly punctuated word wall but writing was never my strong suit, i appreciate the feedback.
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Any reason why the overkill solar bms app could be acting up?
It only shows voltage for the first couple of cells. Interestingly it knows the full pack voltage though?
The xiaoxiang app however shows the voltage of all cells.
I tried restarting my phone and connected to the BMS multiple times from both apps. The xiaoxiang always works, the overkill solar always worked perfectly before, but today I connected to it like 5 times and it didn’t work even just once.
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Apparently not. Looks like a skill issue to me but could be shitty solder.
In any case, OP doesn’t seem too keen on listening to feedback fwiw so 
This is not true, @jack.luis , no one has said or “confirmed” that with you, and I’d like to ask you to stop describing the forum’s admin position based on your interpretation. This thread is subject to the same rules as all other threads on the forum, and we enforce those rules daily through mod action.
What I’m seeing in this thread: Hummie insists that a highly questionable (and IMO, woefully unsafe) cell-charging practice is his standard. He does it, despite all logic suggesting that it’s a terrible practice. Others are readily disabusing him of this idea and providing better guidance.
That is how discussion threads work. Opinions are presented. If incorrect, then correct information is presented and prevails. It is up to readers to discern whether the source is valid and trustworthy, and up to all of us as a community to provide the best and most accurate information that we can.
We’ll review this thread closely, but keep in mind; if we zap a questionable post, that also removes the context for the corrections that follow it, which makes the thread unreadable. We lose the good content provided by others.
@hummieee - perhaps it’s time to stop insisting that this practice is OK? It’s clearly below community standards for safety. That should be your queue to drop it.
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My point is that discussion threads should not be a source of information for building lithium-ion batteries. Bummie is just the person that made me realize it recently.
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To me it looks more like a combination of a skill issue and shitty solder. The shitty solder is very visible, but most if not all of the joints look like the person who made that pack needs to learn how to solder first.
Also, there’s zero reason for 2x10AWG wire if the nickel is a ladder strip, so the current is limited to about 2-3x 8mm of nikkel. It’s just such a bottleneck in the current flow. That pack is good for like 50-60A assuming the nickel is at least 0.2mm.
It also looks like there isn’t any fishpaper insulation between the P groups. If I am correct on this that’s quite a serious issue.
If I were to pay money for that pack I would be pissed.
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Sorry, I know you were not speaking about my pack, but do you think I should put insulation between P groups also with my design where the cells are already separated by plastic? (or more commonly by glue)
I agree, it’s known as peer review, and even crazy ideas can be deemed good or bad and we all learn in the process (if we are open to it).
Sharing experience, ideas and knowledge constitutes the core of any healthy online communities, and even animated discussion are part of it.
I would silence discussions that a brings no added value and looks like pure troll instead like this one
Speaking about sharing experience and dangers, I had small accident just by testing with the multimeter the FIRST cell. I did not put the insulation fish ring yet on the positive pole and somehow it arched with side causing small spark/fire on the sleeve!!
Peer review requires everyone involved be experts in a profession or academic discipline, that is categorically not what this is and acting like it is is dangerous.
Almost no one here is an expert, and we have to behave as such. That’s why consensus standards here are to err on the side of caution. Academic peer review doesn’t allow publication of spurious nonsense, because putting it in a journal at all gives it credibility. It doesn’t treat each idea as equally correct and a matter of opinion, that’s just a badly structured debate. It is a filter that necessarily rejects ideas to maintain a standard.
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I think you’d be surprised, I think a lot of the people here are actually experts (Or at least, in such a niche market, the people with the most knowledge on it). There are so few bespoke battery builders outside of China. In the UK, I only know of about 30-40 people who are able to do it to good standard in the entire country and I think most other places are similar. We’ve even got Mooch here, probably the foremost expert in cells when used in the application of custom PEVs (Who else would actually know more? Chinese batteries are NOT well made, mass manufactured batteries follow an almost entirely different set of skills)
Of course there are often people who have no clue what they’re talking about too. But it’s a much more niche topic than would be expected.
There are very skilled people here, but no one’s done thermal modelling or mechanical simulations on pack design.
We’re not experts. We don’t work for auto manufacturers or battery labs, there are no measurements beyond “do a pull test”, there’s no repeatability or evidence
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