With bespoke 1 off packs, thermal modelling/mechanical simulations probably aren’t possible, each pack would be so expensive after paying for the time to do it nobody would buy them.
Plus, a lot of the people here have seen the long term effects of certain methods, with packs made 5+ years ago still going. I may be wrong but I don’t think any other group has more knowledge on specifically PEV Custom packs
I understand where you’re coming from with this, but it’s like saying 1700s alchemists are experts in chemistry because it was a niche and they knew the most. Some here may have more experience putting together packs for PEVs, but no one is an expert in the actual risks or knows a huge amount of the broad areas science involved
I’m not even fully disagreeing with you here. I’m saying that this still means we aren’t experts, even if doing all the testing and work needed to become one is basically impossible on our small scales. Saying that a good builder here has done “as much work as is practical” is not the same as saying they’re an expert. They’re just the best hobbyist.
I’m not saying that packs that have worked well are useless, that’d be way too far. But the things that even the most experienced builder here has seen are still anecdotal, and don’t represent good evidence. The sample size needs to be so much bigger, the controls so much more strict. We’ve got information that’s absolutely better than nothing, but it’s flawed and unproven
They’re just the best hobbyist.
Yea I guess this is what I mean. If people here come to the consensus something is best practise, it’s probably the best advice available to anyone who reads it and wants to build their own pack too (i.e peer review here I think is the best possible)
Peer review is supposed to be a lot more objective. It’s usually anonymous and with specific review criteria, it has oversight and editorial requirements, with an authority that makes a final call. This is not that, even if we were all experts.
At the end of the day this is an unstructured public debate, with no requirements for informed opinion. It’s not useless, but it’s not a rigorous system of review, and a false sense of grandeur can only hurt the situation
I think you’re assuming the “peer review” term in a purely academic sense. Public forums are not that of course. But in many places, people do “peer reviews” which are just best effort reviews by people who are peers. I would argue that this more general use of the term is what was intended and is accurate here.
I am leaning far more on academic than professional, because I think that’s what most people associate the term with
But again, professional peer reviews have standards and require expertise. If an engineer asks the person in the cubicle next door to give a once over to a drawing before submission, they’d be called pretty pretentious if they then bragged about having “peer reviewed work”.
We’re getting pretty far away from battery building, but your reference is for peer reviews of NASA technical documentation. If you take something like a NASA standard for electrical harness production in spacecraft say, that is certainly peer reviewed as part of the process of publication. As I said before, forums are not that kind of peer review. However what that standard is comprised of is the result of hundreds of thousands of best practices gleaned from successes, failures, and yes, lower level technical reviews of designs by, yes, “peers”. Here, we’re at the lower end of the peer review spectrum. Still a peer review though, just not the one you’re talking about. In fact, NASA still calls these peer reviews and they are not confused with tech pubs peer reviews.
Look, saying that because we are in some way peers means that it’s technically a peer review is not a good idea. Even if it was technically true, it’s inflated and inaccurate language that doesn’t reflect the common usage of the term.
But it’s not even technically true. Who are the referees and how are they decided? What are the review criteria? Where’s the editorial or managerial oversight? Where’s the evidence of follow-up, what’s the retraction mechanism for mistakes, what’s the trust model? I can give you specifics examples of how review processes work and cite professional standards but at the end of the day the key words there are processes and standards. We don’t have those. We have received wisdom, anecdotal experience, and a willingness to help each other, but pretending that’s the same as organised rigour is ludicrous
Hee. I’m pretty sure nobody reading this forum is at all deluded that our use of the peer review term means what is contained here is all well vetted best practices that result in an industry standard highest probability of success.
Your design makes sure that the cells cannot touch each other by the plastic 3D printed spacers. That does the same thing in the end as fishpaper would on a glued pack. The purpose of fishpaper is that if the cells touch each other and there is vibration, the PVC heatshrink on the cell can get worn down easily. Fishpaper is abrasion resistant, therefore if you put that between the cells, you can have the cells basically touching (with fishpaper in between).
Both are fine to use and they both have their advantages. With the fishpaper / hotglue design you can pack cells into slightly tighter spaces, whether the space saving is needed or not depends on what the pack gets installed into. The spacer design allows a more professional looking construction with the same safety, however a bit larger size.
Make sure to put the fishpaper insulation rings on the positive terminals though, that’s always needed.
For sourcing wide nikkel I recommend nkon. Their prices are decent. More expensive then direct from china of course but it’s really not bad.
They ship from the Netherlands and it probably arrives to you within 3 business days.
Stacked nickel is not recommended, it’s harder to get it consistent and solid, not to mention it’s going to introduce more resistance than simply using a single layer of wide 0.2 nickel would.
Get the nickel I linked, use that for all interconnects on each of the 3 separate packs, and connect the 3 separate packs with wire. There I would rather use 2x 12awg (equivalent to 1x9awg) than 1x8 awg. Both work, but the 8awg is very overkill and it takes more time to solder it onto nickel which puts more heat into the cells.
2 x 12 awg is way overkill for a 3p battery. A single 12 is more than sufficient. I would even do 2 x 14awg if you have it @eliSk8. Easier to solder and less bulk.
Depends how hard you plan to use it and what failures you account for. But yeah for most people 2x12 is still very overkill for actual usage.
The reason I build overkill is to avoid any potential issues. My raceboard battery survived an ESC short where a cm of 10AWG literally disappeared from the ESC side of the cable… That’s thanks to the weakest link in the chain being the 10AWG soldered to the ESC and not something battery side. The weakest link on the battery side of things was the 8AWG terminal cable on my 21S4P pack. Internal 3x12AWG and 0.2x75mm
That’s an incredibly rare failure mode though. But I like to have the weakest link outside of the battery pack just in case that happens…
2x14awg is good from usage standpoint. Equals to 1x11awg roughly. Wouldn’t heat up from hard usage and wouldn’t have much voltage drop.
I prefer to spec for the worst case though, which is an external short circuit, especially after my blown up raceboard ESC.
If the battery in cable on the ESC is 10awg I would go 2x12awg (equals 9awg), if it’s 12awg I would go 2x14AWG (equals 11awg).
This would ensure the whatever blows up, if the cells can handle it the rest can too.
Hello guys, I live in europe, and im building 14s4p, what copper braid should i use for p packs and where would i get it in europe? Thanks
If something like an esc “blows up” and is shorting…why not just add a fuse instead of hoping ur wiring melts before the battery burns?
I’d like to think an esc shorting wouldn’t last long and the circuit would be cut but seems not the case
I don’t think an esc shorting is that rare
Using a 5v supply could blow up the supply. Hasn’t happened to me but don’t doubt it. Do I think that’s a big deal, not really and I’ll be doing it again in a moment actually. Do I think others should try it? If they’re aware of the risks. As I understand it the risk is solely that u burn up the little power supply. Some think that’s a big deal and too dangerous. I think it’s for them to decide what they do. I’m not here writing a tomb for posterity just passing on methods I’ve used related to this
I do believe other things I’ve written on here such as possibly charging cells even if they get to 1v or 2v can be supported by the manufacturer’s data sheets. They should be used as a guide. Anyone who thinks I’m too dangerous in my advising people follow what the manufacturer states is possible… that’s obviously silly. Similarly if people don’t understand that cc/cv isn’t necessary and all that’s necessary in that regard is the cells don’t get charged with a current that’s too high thats their misunderstanding and not my being dangerous.
Similarly if people advise others to throw out batteries that MAYBE got wet instead of actually removing the battery shrink wrap to look for water marks or check voltages… different strokes for different folks but my advice in that regard isn’t dangerous. Opening a battery shrink wrap n using a multimeter isn’t dangerous
What they shouldn’t be doing is cursing and insulting which happened a lot.
People up above the thread said that they were testing fuses and the fuses were too slow to blow during most ESC shorts, the connection got broken elsewhere first.
Although I guess in the case that the wiring blows a properly specced fuse could be better. But it’s not easy to spec the fuse properly… You most likely won’t get it just right without actual testing. And who wants to test something that can potentially ignite a battery pack?
An ESC short itself is not rare, but one where the shorted ESC doesn’t disconnect the connection before the wiring blows is very rare. I only saw two in total on this forum. One of those were mine…
I’ve had it happen. My esc was smoking and pulled out my melted qs8 loopkey quickly before the wiring melted. The key was melted. This was with 87v and 3p of super powerful a123 cells and still the esc never broke circuit.
Putting a fuse on, despite the complexity of finding the right size, is for sure safer than hoping ur 10awg or whatever burns up.
@mr.shiteside you would be surprised how poor the review process for many academic papers is nowadays (I know first hand), especially because there is little incentive to make a deep analysis given you are not payed or credited for the review process, and who does it, is for pure love of science and personal interest in the subject.
I was referring broadly as peer reviews as a process were domain experts overlooks the works of other less experts, advising for best practices
This thread here and endless sphere are the only source of people with hands on experience for batteries in the planet and access to real human expertise is something that is becoming incredibly scarce on this planet!
So let’s keep up the good mood, and thanks again for all the nice advice that you all gave me!
Agreed but it’s really hard to find the right one with a datasheet that has time to blow vs current on it, is high enough voltage, isn’t huge, and then I need to spec it properly regarding the current, which is just as hard. And then find a store that stocks the version with the correct current rating, as you need to nail that very accurately.
For example I think I read it multiple times on the forum that your discharge fuse should be rated for 2x what you draw. That couldn’t be wronger after actually looking at a datasheet. During my last short circuit a fuse rated 2x what I draw would have taken the full short current for half a minute before blowing.
To have a fuse that still may or may not be quick enough to actually blow during a short circuit, at least from the model I am looking at, and calculating with my battery pack, I already need to go for a current rating that’s below what I regularly draw as peak values.
Depends on what you’re trying to protect.
The electronics can’t be reliably protected with a fuse but it can help put out the fire once it blows so well just say that a fuse selected for another purpose can help with an ESC fire too.
The pack can survive huge pulses of current before going into runaway so that’s not hard to protect.
The wiring can be protected with a bit of thought about response times, what happens to the soldered-on wires if the solder melts, etc.
Fuse selection for esk8 is indeed a total PITA due to the high voltages but it can be done for packs and wiring IMHO.
I’ve gone over this; if you want to redefine peer review to exclude any of the structure from it, and redefine expert to include “someone who’s tried it before and not died”, then I can’t stop you. But it’s irresponsible, and framing the posts here as “peer reviewed” is laughably arrogant.
There’s some useful information here, but it needs to be taken with less confidence in its accuracy, not more.
