battery pack idea

Batteries, Chargers, and Battery Management Systems.
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whatever   100 kW

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battery pack idea

Post by whatever » Feb 08 2019 10:07am

there are patents and research docs on rejuvenation lithium batteries by flushing the electrolyte then replacing the electrolyte.
Some large companies holding patents including general motors. So I'm assuming the process gives good results, its based on simply flushing with ec:dc or similar electrolytes without touching the copper/aluminium in the cells at all, it removes the old sei layer,
then new electrolyte with lithium is added, new sei formed and cell is rejuvenated.
This leads to my idea for large packs:
use the electrolyte as the cooling system. Instead of using an external cooling system for the pack, make the pack in such a way that
the internal electrolyte is flowing through the cells for cooling. This would make it easy to rejuvenate the cells and extend battery life.

Philaphlous   1 kW

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Re: battery pack idea

Post by Philaphlous » Feb 08 2019 1:01pm

Nah brah...that ain't gonna work. Trust me im sure it's been thought of before.

Plus the electrolyte is highly corrosive/toxic. I dunno what the heck is in that stuff but I've had one leak out when disassembling a pack and it'll melt plastic on contact...

Plus it's more about the cathode creating dendrites when charging/discharging at high rates.

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Matador   10 kW

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Re: battery pack idea

Post by Matador » Feb 10 2019 11:22pm

Electrolyte, I've heard is Lithium hexafluorophosphate (Li+ PF6-). When reacting with water (H2O), that stuff releases hydogen fluoride (HF). HF in it's pure form wich reacts with anything that contains calcium... Like bones. It is readily absorbed through skin. I don't know if it's that reactive in solution though... Probably not.

Good thing is Li-Ion cell don't need much quantity of electrolyte...
But google hydrogen fluoride, scary stuff.

whatever   100 kW

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Re: battery pack idea

Post by whatever » Feb 11 2019 8:30am

to philaphlous: plenty of plastics are used with lithium battery pouches, I dont think a big issue. Aluminium also no problem with ec:dec etc.
to matador: yes lipf6 does produce hydrogen and hf as you mentioned, but no water involved its a closed system.
How to get the electolyte to circulate around the foils to take away or add heat would require some thinking. I think the idea has some merit its certainly worth considering, the original idea is rejuvenation of cells, anyone interested would have to search lithium battery rejuvenation in the patents or research literature ( I've posted the links in the past).
The electrolyte wouldn't flow freely through the plastic separator between cell, its a slow diffusion process. But would allow for flushing of the sei layer ( perhaps even keeping the sei layer in working efficiently), the rejuvenation process involves flush the cells first with the base electrolytes ( ec/dec and other carbonates), the later add lipf6, which adds the depleted lithium.
I think its worth considering, no doubt it has been thought about before by others, but i've never seen any discussion on using the electrolyte as a heat transfer medium.

whatever   100 kW

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Re: battery pack idea

Post by whatever » Feb 11 2019 8:50am

did quick search found one research paper on using electrolyte for internal cooling of cell ( so its definitely been thought of before!)
https://www.sciencedirect.com/science/a ... 5315009362

whatever   100 kW

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Re: battery pack idea

Post by whatever » Feb 11 2019 9:03am

seems they call it "internal cooling" and another paper they used microchanels on the foils to allow electrolyte to circulate and cool the cells ( looks like theoretical paper only)
Quite a nice way to circulate the electrolyte, the results they calculated showed more efficient method than external cooling, but you would loose some active surface area in the foils ( given up for the mircochannels), but the microchannels would be very easy to create in the foils during manufacture of cells.
http://mtt.missouri.edu/Pubs/225_Mohamm ... r_2015.pdf

billvon   1 GW

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Re: battery pack idea

Post by billvon » Feb 11 2019 1:58pm

whatever wrote:
Feb 08 2019 10:07am
use the electrolyte as the cooling system. Instead of using an external cooling system for the pack, make the pack in such a way that the internal electrolyte is flowing through the cells for cooling. This would make it easy to rejuvenate the cells and extend battery life.
That could work, but you'd need a separate cooling loop for each cell. You can't mix the electrolyte of two cells (for obvious reasons.)
Also keep in mind that electrolyte weight is a very small fraction of the weight of each cell (2% or so.) So to have enough to cool with you are looking at a very large increase in weight.
--bill von

whatever   100 kW

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Re: battery pack idea

Post by whatever » Feb 17 2019 11:46am

why couldn't you mix the electrolyte from different cells?

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