New easy lithium battery boxing system, can build 1KW of 18650 in 20minutes

[BatGroupCraft]

Hi there! I'm hoping for high quality feedback for this topic, so if you don't know very much about contractor alloys and have never worked with pressure contact design, unless you can state some industry materials related to the project, then that's not the kind of intel. i'm interested in!


It's an incredibly technical project, focusing on a small number of pieces, to tweak them for absolute maximum performance and safety, robustness, easy of use, so a lot cool tweaks will happen prior to the final version.

I'm aiming for a box cost of $30/KWh of cells for home-made versions, to $70/KWh if you glue the factory kit yourself.

It can be completely air-tight, for humidity and splashes, using 50 PSI rubber seals and a 15 PSI pressure equalization valve and color changing silica gel, for those that live in jungles as dry as a shower cubicles.

It's going to be open-source. Everyone can 3D print boxes components of and every every size enclosure using the box STL generator...

Other companies can make make their versions, I'll try and subsidize solar for DIY'ers from the Phillipines, Cambodia, Bolivia, faraway places.

Maximum electrical output is 100A for the big box from the video, when it's configured to 12V, and only 50A @ 24V.

The springs are not electrical, the current goes through 8AWG Copper busbars and 20mm² Aluminium-Nickel contacts compressed by 2KG force springs.

[mariush]

My problems with it ... lack of spot welding / soldering. You're adding a lot of wire resistance with the springs, and you're adding contact resistance not to mention the issues of humidity getting in and potentially having corrosion on the contacts.
Then you're having those locking screws through the lid, so there's another potential for water / humidity to infiltrate along the shaft of those screws and get the battery wet inside. Have a look at how multimeters and other devices have a double wall or a depression in the width of the wall in which there's some rubber or something that expands and seals the interior when the two parts are tightened.
You could easily lock the box without resorting to screws that go through the case ... for example my mind goes to metallic zip ties or captive screws on the outside of the battery holding area.

I don't see where one could put some temperature sensors or a connector to export battery health data, I didn't see (maybe I missed it) how you'd do 3S, 4S, 5S batteries and how you'd do balancing when charging etc etc...

[BatGroupCraft]

Hi, Thanks for the comments. That's generally off topic and nothing to do with the design I presented:

>>adding a lot of wire resistance with the springs
The electricity does not in any way travel through the springs... It goes through copper!!! sorry that's a complete misinterpretation. copper has 22% the resistivity of nickel, so my battery can take 460% more current compared to the equivalent of nickel.
The springs are mechanical, not electrical, they let you build 1KW in 30 minutes compared to 9 hours of spot welding, plus better recycling and safety, lower cost in tools, and many other advantages.

The only current limitation is the batteries, not the box, unless you want to discharge batteries in 20 minutes at 32 Watts a piece.

>>corrosion on the contacts
Nickel is completely rust-immune, so that's not possible. It's completely air-tight if you want it to be.

>>humidity to infiltrate along the shaft of those screws
The steel rods have rubber disks / elastomer washers, and the lid has a rubber gasket, air exchange of the box can be very carefully managed.

>> 3s 4s 5s and BMS balancing.
When you spot weld a battery, there is no armature for knocks and bumps and to protect BMS wires, and these boxes provide protection. You could jab it with a fork 50 times and it would be fine.
For 3s 4s 5s, you type 4s/5s in the free STL generator and print it on a printer. If you have a big BMS you can add 1x extra spoace to the series i.e. 4S 11p+1, and your BMS and wires are then protected inside. There's 1.5mm in between the cells, you can run thermistor wires in it.

[PlainName]

This isn't something I would want (at least, not yet) but it seems well thought out to me 

[BatGroupCraft]

it seems well thought out to me 

Thanks a lot DunkmeHigh!!! I also designed some cell level fuses some time ago, except that they're not very necessary lol, seeing as lithium is hyper reliable these days lol

[wizard69]

Like others this is not something I need or frankly want at the moment.    In my case if I was looking for a lithium battery I'd want a solution that is ready to go.   That is a battery running at a standard nominal voltage, with full battery management and protection.   That battery management must be validated to be working correctly and likely compliant with applicable industry standards.   The last thing I would want to do is to place a battery into service that is not compliant.

As for the design I'm not a fan of springs.    I know you argued the point above but I'm not buying it.

As for the plastic case it is likely fine for dry indoor locations but right now the only app I can think of, that i'm interested in, involves mobile usage.   Mobile usage by definition requires a sealed container that is rugged.  So right now I'd have zero interest simply based on that need.   I'm not trying to dismiss the low cost indoor market just that doesn't have a huge, personal appeal right now.

So from my perspective I'd rather see a finished product operating at a common nominal voltage.    A 12 VDC offering, with a battery management system that operates well with recharge from an alternator or a solar charge controller, would be very attractive.   It would have to be vehicle rugged and sealed far better than this battery.   A 24 VDC nominal battery wouldn't be a bad idea either.    In any event there are a lot of cheap options already out there none of which is an interest at the moment.

[PeteH]

The springs themselves do not appear to be conducting current, just used to apply preload between the box and the current collector strip.

Rigid coupling of the current collector may make "different cells" (mixing/matching) more difficult to integrate of the heights are not exactly equal...


Edit: forgot to say that this looks great, love to see people exploring ways to reuse cells, complete interesting projects to this kind of detail/level.

[BatGroupCraft]

Hi, Those comments are not related to the design in the video. The box is hermitically sealed through rubber on all the thumbscrews and the sides, and I will supply a 50psi valve and color-changing silica gel for those who want to have major damp-proofing... It's not designed for submarines either, or strapping under a car and driving through ponds, it's a blank barebones design that can be specialized as necessary for different uses.

[Alti]

Hi. Of course this is not a solution for everyone in all circumstances. There are many applications where resistance to shock, vibrations and moisture is not a problem. Especially for low power and high capacity storage applications where the contact resistance is a secondary concern.

What bothers me is the applicability of this idea to refurbished cells. Your design does not offer any kind of balancing or even monitoring of individual cells and relies on long strings of paralleled cells. When you have brand new cells, well matched and manufactured in tight tolerances then this might not be a problem. But I think you are targeting the low end of the market with random cells of much wider parameter spread.

So a storage application with brand new cells might live with monitoring lets say 50 cells in parallel to reach certain MTBF level. But as the mismatch and state of health degrades, design needs to monitor smaller and smaller clusters for safety, ease of servicing and preventive maintenance. Down to monitoring each cell individually, with lowest quality cells. Otherwise the maintenance is going to be a nightmare. YMMV.

[BatGroupCraft]

Hi Alti! I will add clear illustrations with the BMS routing soon. BMS have to accompany every lithium battery. The video is a work in progress,  Sorry for the ambiguity.
The box is designed for new, balanced, high quality, premium batteries, because they are so good.
I will provide special braided contacts for those who want to use salvaged lithium. The thermochromic inlay will let people see warm high resistance cells and swap and balance groups so that they are very precisely the same, which is not possible with welded lithium. I do provide individual monitoring of cells via thermochromic resistance indicators. Bosch, Tesla, BMW, Porsche, don't do individual cell monitoring, so I haven't heard of that previously, my box can do it though through thermochromic resistance measures.

[Alti]

The thermochromic inlay will let people see warm high resistance cells and swap and balance groups so that they are very precisely the same(..)

Consider that electrical energy storage for RC planes or mobility scooters has vastly different requirements than energy storage for salvaged cells used for off-grid backup. I think you have no chance of competing on a market of brand new, well matched, high capacity, insane currents, battery banks with this idea. The only chance here is to focus on salvaged cells market where primary goal is high capacity per dollar, where mass or size is irrelevant, currents are low-ish and maintenance-ability is the key advantage and requirement at the same time.

[BatGroupCraft]

Did you even notice that it can do 150 amps on a 100 cell 12v box? Why would it not have many applications if it exceeds 99 percent of typical battery requirements???

You've completely missed the point of the project!!! The box can empty 18650's cells in 20 minutes, i.e. it exceeds 99% of typical battery use... Do you want to empty an ebike in 20 minutes at 100mpg? Do you want to empty a motorbike in 20 minutes? Of course not...

 

[ANTALIFE]

Nifty wee box!

I am also a bit iffy about using so many "spring" contacts for such an application (especially on recycled cells). Have yous done any lifetime/lifecycle tests? Like charging/discharging the box during varying temperature & humidity

[BatGroupCraft]

Hey, I was sceptical about the concept of compression contacts on 18650's so i did thorough testing as a first step: I found that the performance was incredibly high, way in excess of the maximum output from the batteries, 10A is what i tested at, draining the lithium batteries in only 15 minutes, which is crazy high performance.
That is why i continued researching.

Anderson powerpoles rated at 40A are actually a smaller surface area than the 18650 contacts in this box. Zero motorcycles has also patented braid contacts which can work with recycled cells...

But did I say that this will be certified for use with damaged lithium? That's certainly not what the design is for at the moment, the box is re-usable. it's not made for damaged cells with roughened contacts!!! You can use braid contacts for that, because they are flexible and apply fine to a recycled cell, but that's not the scope of the project.