Yeah I’m with John on this one. Having soldered in a similar fashion before I can confirm that when done properly, they do not get that hot.
I think this method is perfectly fine as long as it’s done correctly. Of course we cannot know the temperature the inside of the cell might reach, but it is not such a good conductor of heat that it heats up instantly
Food for thought, but probably fine. ESPECIALLY since he’s been riding one for so long and it’s cool
Again, Mario, you know how many TERRIBLE packs are out there not catching on fire. It’s very nitpicky at this point
Unfortunately, that’s not something I personally feel is currently worth testing. Between sinking hundreds of dollars into explosive testing, and eating the cost of packs that I don’t think are good enough to hand to a customer, I just don’t have the bandwidth to test the temperature differences of where you’re soldering compared to where I’m usually soldering.
I of course, made no mention of soldering directly on the cell. That’s not the comparison I’m making.
The comparison I’m making is to soldering off of the cell, which I have tested and measured, to send somewhere about half to a third of the heat from the iron beyond the fold, depending on the thickness and width of the nickel.
If you insist on relying on the stock PVC wrap of a cell to serve as a heat brake and adequate insulation within an eskate, then I’m not really sure I can convince you away from whatever you’re likely to do. And that’s perfectly fine, as that’s purely a series of judgments that you make based on what info you prioritize.
As I said above, many packs are out there that are built 'good enough", and I’m sure yours work just fine. And for companies like ChiBattery, much success can be found in ‘good enough’.
But that’s not enough for me, so I lean towards being more critical of things that can be done better.
I acknowledged that above, but I don’t think it’s a good idea to respond to requests for critique with “sure that’s good enough”, especially when it’s the work that a company is producing for customers.
In those cases, it seems prudent to genuinely attempt a steady path of betterment, and not a series of excuses for how something is good enough.
I’m with Mario, soldering your series connections that way is not good. I agree with pretty much everything he has said.
Additionally, I find your pack construction method seriously lacking, and not fit for sale to anyone. I wont go through the whole list of things I disagree with, but one thing that no one has mentioned is the lack of any sort of solid connection between the cells of each p-group.
I see that you siliconed everything to the enclosure after spot welding and soldering, but that’s not (in my opinion) an adequate substitute for gluing your p-groups together before welding.
My view is that your nickel strips are being forced to function as the sole mechanical connection between the cells. This means that when your battery experiences the micro-flexing and vibrations that all esk8 components are subjected to, all that stress will be applied directly to the welds.
I strongly urge you to reconsider your battery building methods, especially if you plan to sell packs to customers. You are doing so many other things about these builds really well, you should have a battery that matches the level of care and effort you’re putting into every other aspect of these boards. Especially since the battery is the one part of the board which will gladly burn a customer’s house to the ground.
@BenjaminF & @TheBoardGarage
Thanks for you valuable opinions it is exactly what im after! I dont agree with all of it but I will definetly go back to the drawing board and change a couple of things based of it.
The first board that got sent out to the local customer will be taken back and be updated with the changes as well.
PVC terminal rings vs fish paper? Is there a big difference? Its a lot easier for me to find the plastic ones for 21700 cell size and I was wondering if there is reason to choose one over the other
Depending on the type of PVC it can melt at a relatively low temp, possibly allowing a short-circuit to occur in a pack that’s already in some type of trouble (melting the ring). Fishpaper rings won’t melt and will only char unless there is a cell in runaway…in which case nothing will help and you should just run away.
Is this a common thing to happen? No.
But as part of considering which “best practices” we’re willing to use it’s something to consider. Weigh the pros and cons based on your priorities and preferences and choose the rings that fit what you need.
A side note…fishpaper might not be a good choice if the pack gets wet but that should never happen with esk8 packs. It’s more of a vaping thing where eliquid often leaks everywhere.
Voltage in the equation refers to the average (nominal) voltafe of the system throughout the charge cycle. in tbis case, 3.6-3.7V per cell. no one calculates pack Wh based on 4.2 V per cell; the cells don’t sustain 4.2V all the way.
however you can calculate W at any given moment at whatever the voltage is at that point in time
Not sure I understand your question…
Thermal transfer, or lack thereof, wasn’t a part of my conversation. Just melting points. How well a plastic conducts heat isn’t really related to its melting point.
A plastic with a higher melting point will indeed protect the cell a bit better from possible problems but the question was about PVC rings and there are some very low melting point types of PVC that would be a poor choice IMO compared to fishpaper.
I do not know the type of plastic or melting point of the rings used by the big manufacturers.
You’re very much on the right track, & unlike others, it does seem like you want to do well & are willing to make changes.
Your stuff will definitely work as is, hard to tell for how long, & definitely can’t say it doesn’t have a much higher chance of causing a catastrophe (for somebody else, too) than more refined packs.
I would try to implement the advice you’ve been given by the others. Not much to change & you’ll have incredibly high quality packs, unlike… many others, who have much to change, & still likely wouldn’t have very high quality packs in the end…
Thank you I appreciate that!
Yeah I’m always happy to listen to feedback. The criticism is the best as that is where attention probably should be spent on improving things. Or at the very least seriously reconsider the options & possibilities.
