Tab cooling prismatics.

Batteries, Chargers, and Battery Management Systems.
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flippy   100 MW

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Re: Tab cooling prismatics.

Post by flippy » Jun 02 2021 10:08am

Ianhill wrote:
Jun 01 2021 11:24pm
Don't try and limit others by your own ability i was fair to you but you keep been condescending of my ability and knowledge so watch on as i put a test rig together and start getting some useful data from cool cells not your hot air.
as i said, making a setup like that that works on a workbench is 100% not a problem. i have already done so and tried it. making one that can survive the shocks and viberations of a go cart for the packs lifespan is something else entirely.

and yes, i am condecending because you need to check yourself before you end up sitting on a gokart at 50mph enveloped in a massive battery fire because the tabs internally ripped and shorted because you didnt mitigate (micro) viberations properly.

there is a REALLY good list of reasons why no commercial application uses tabbed cooling.

understand, this topic is a nice academic exersise in battery cooling/heating. but actually hacking something together that has a pretty good chance to end up with you going down a track in a ball of lithium fire because a tab internally ripped is something you need to be aware of before going up this hill. we got PLENTY of examples on this forum from people with burnt down bikes, sheds, garages, homes and vechicles.
The bitterness of low quality remains long after the sweetness of low price is forgotten

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spinningmagnets   100 GW

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Re: Tab cooling prismatics.

Post by spinningmagnets » Jun 02 2021 2:49pm

We can,all disagree with each other, and discuss the reasons, but...this is drifting towards personal attacks. I need to lock this temporarily until I get time to review it.

Everyone come back after a while.

Ianhill   100 MW

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Re: Tab cooling prismatics.

Post by Ianhill » Jun 03 2021 9:43am

Bit of academic source material.

This is not taken lightly the concerns raised are on my mind too and if the design dont meet criteria ill cut the plug i will not make anything wildly dangerous all points taken on board.

My idea is to use a prismatic cell with tabs either side like the lg 60ah nmc cell ive been contemplating the design layout but for cell safety they will be stacked as a pyle on the horizontal plane to keep tabs next to each other at 3.7v if i stacked in groups of 3 i would have the potential for 18.5v to flow between terminals in the event of a shorting incident so thats a no go si the packs CELL dimensions will be in the order of 100×300×300mm give or take as i dont have the items to hand measurements will be finalized.

There will be 20cells not 21 this way i keep the power leads on the same side of the pack for ease of wiring the 10 tabs either side will have a pcb that connects to the tabs and flows its heat to a small square below one tab then above the next and so on so theres space for the SMALL water block.

On each of these tabs i will place a small ram heatsink on a thermal pad so in total i will have 20 small ram heatsinks each one connects to 2 tab faces all be it the postive and negative that will be a single tab respectively then i will form a cooling loop and epoxy the tab area of the chamber shut once tested.

This is no rush game im brainstorming and hoping i can get a design together that i can then try and finalize and make it, this will be nothing but profesional and treated with the respect it deserves i got a holiday coming up and then i will get the kart in 2 weeks so theres lots of times yet to play this idea out.
Ive choose a sodi kart rs3 nice stiff chassis perfect for a first attempt i got the controller motor and active bms so give me time and this will get a good shot at success as any will give it and if it fails it wont be for the lack of trying with proper research i will not allow the 7 p's be a factor.

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DogDipstick   10 kW

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Re: Tab cooling prismatics.

Post by DogDipstick » Jul 15 2021 3:01am

I just pulled 23.8 horsepower out of some Chevy 25Ah cells. They did not blink. The motor was blazin and the controller was a lil hot. 17,800w plus. 90 lb bike give or take.

The pack was built with a fan in mind. 12v, 120mm, PWM outputs on a Nuclear in mind. I do not think I need it. The pack did not get one degree hotter. On any of the sensors on the system, and with the thermal data. This shows a 9.72C peak. CA3.14 shows 28-40mOh for the pack IR. Data I have read states that the cells will not show any increase over RT until continuous current draw of 4C... 100A. From the limited data I got.

QS205. I did take pictures of it. I'll update when I can. The pack gets hotter on charge, than at this level of discharge. Hmmmm.

For reference, here is a pic of a RC lipo.. so called "65C " contin.. and only managed to push about 30C peak. This bike only pulled 163A on the 72v, 5Ah, 2mOh/cell lipo. Hot Potato Lipos are..... hot. Direct product of an undersized pack, faltering.

It is a little bit of a surprising volume for a Chevy cell NMC-LMO pack. It still gives good range and incredible power for its small capacity ( 1.85kWh) on this bike ( that can fit 3-4kWh of 18650 in it).

Point is.. I dont think we need cooling so much anymore... the cells are getting better and better.
Ianhill wrote:
May 31 2021 4:58pm

Id thinking of using 21 lg 60ah li nmc cells that can deliever 240amp a cell but heating occurs nothing drastic but 20 mins of that build up would lead to a hot pack.

If the cells do not get hot, they do not get hot. Kinda what I am learning.

Can confirm they will zap 240A pretty easy. This log is made on a Kelly of 8kW rating. 72v system. KEB72801X. 240A peak up a hill @ 50mph.

flippy wrote:
Jun 01 2021 5:35am

also, adding more capacity and cells in this manner will give you a considerable less amount of voltage sag, heat production and capacity.

Yes kinda what I learned. I wonder about the threshold.. where is to small, and what is too hot.. I guess it is kinda self explanatory.. Either your cells can hack it.. or they cannot. Temperature yields the data of the application ( sized capacity)...

Still..... How do you ABSOLUTELY know if the cells will hack it or not? That is in the questions?

As for ones implementation and design skill, use of tooling and time, I will not say anything, for I have a disagreement there, Flippy. Regarding the merits of a 600 cell spot welded pack vs a 21 cell larger format pouch cell design, housing and whatnot included. Personally. Personally I have seen many spot welded packs fail for poor mechanical designs. Time is the essence of control and the amateur builder is not skimping on time where the investment of 600 cells is involved or else risk expense.

Some of us are faster than others. Some may build faster, some may build slower. Truth be told, not a level playing field. Not a good comparison. But Yeah.
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83.1v of Ironhorse XC.. :) :bolt: by Chevy :bolt: :D Ok So that was what you call a "glitch:" :twisted: (...No Mom. The formula is Kaw > 1(Hr) = Impounded. The math checks out. I'll be fine. ).. :? Broke20Horsies! 17,830w !! :x 1 (pound / second) Horse Power = 338.24 M^2 Kg^2 / Sec^4 ( :twisted: prove me wrong :twisted: ) :| (gottenymoem4115thangs?Yall?) :confused: Fabricator @ BSECo. Inc.

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