Battery heat capacity

Batteries, Chargers, and Battery Management Systems.
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alihanif   1 µW

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Battery heat capacity

Post by alihanif » May 15 2018 4:07am

Hi all,

First of all, apologies if this post is not suitable for this forum. I'm currently in the process of modelling lithium-ion batteries for my thesis. My objective is to compare NMC and LFP pouch batteries for a specific application. I have found a perfect LFP pouch battery, which is A123 AMP20 (20Ah). The A123 really put detailed specifications of the battery (discharge curves at various C-rates and temperatures, resistance, cycle life, etc.).

Firstly, do you guys know any battery companies which produced NMC pouch battery cells that give a detailed specification like A123? Preferably European companies since I'm planning to buy several of them to be tested. I've searched and contacted a lot of companies and none of them replied.

Secondly, I'm missing a heat capacity value for my battery. Is there any simple experiment to measure/estimate the heat capacity of the battery (preferably without using calorimeter)?

Thanks a lot!

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eee291   10 kW

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Re: Battery heat capacity

Post by eee291 » May 15 2018 2:06pm

Yeah about that, A123 is an exception. Other big companies like LG Chem, Tesla and Samsung SDI don't release specs of their Automotive grade Cells.

You can always buy some cells and test them yourself. But you'll probably only find them used, unless you like buying from China.

999zip999   100 GW

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Re: Battery heat capacity

Post by 999zip999 » May 15 2018 2:58pm

Weststart had a NMC 3.7v normal I gave them the money after one week their whole stock was bought by a company and it won't be selling any to outside customer. Then they sent my money back really weird. They contact me again for a 25 ah cell at 8 C it had a tab on each end and I like both tabs on one end. Plus the past trouble with them I didn't think it would be wise. At least it's something for you to read about. Yes A123 20 amp hour pouches our great-great cell high discharge High charge rate long battery life they are heavy.. I have a 24s pack about 5 years old almost 1,200 Cycles on it at 90 AMP draw.
Sony VTC6 30a 18650 NMC cell.

alihanif   1 µW

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Re: Battery heat capacity

Post by alihanif » May 17 2018 8:15am

999zip999 wrote:
May 15 2018 2:58pm
Weststart had a NMC 3.7v normal I gave them the money after one week their whole stock was bought by a company and it won't be selling any to outside customer. Then they sent my money back really weird. They contact me again for a 25 ah cell at 8 C it had a tab on each end and I like both tabs on one end. Plus the past trouble with them I didn't think it would be wise. At least it's something for you to read about. Yes A123 20 amp hour pouches our great-great cell high discharge High charge rate long battery life they are heavy.. I have a 24s pack about 5 years old almost 1,200 Cycles on it at 90 AMP draw.
Sony VTC6 30a 18650 NMC cell.
Hey 999zip999, thanks for the answer! The company actually replied back and they said they have a Europe distributor, so it's really easy for me to get them. Thanks, you really saved my thesis (and my life)!!! :) :) :)

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eee291   10 kW

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Re: Battery heat capacity

Post by eee291 » May 17 2018 8:57am

That's great to hear.

It would be great if you could inform us afterwards, about what cells you got for what price etc.

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jonescg   1 GW

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Re: Battery heat capacity

Post by jonescg » May 17 2018 9:05am

I have some data on the specific heat capacity of a Li-ion cell in my literature collection. I'll dig up the relevant papers, but from memory it was a range between 1100 and 1700 J/kg.

miro13car   1 MW

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Re: Battery heat capacity

Post by miro13car » May 17 2018 4:17pm

WestStart company?
Google doesnt show that company

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amberwolf   100 GW

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Re: Battery heat capacity

Post by amberwolf » May 17 2018 6:56pm


alihanif   1 µW

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Re: Battery heat capacity

Post by alihanif » May 23 2018 7:16am

It's Westart: http://www.szwestart.com/

Their NCM 30Ah cell is US$32.4/pc.
jonescg wrote:
May 17 2018 9:05am
I have some data on the specific heat capacity of a Li-ion cell in my literature collection. I'll dig up the relevant papers, but from memory it was a range between 1100 and 1700 J/kg.
Thanks for this, however, I'm afraid using these numbers is not good enough for me since the heat capacity varies with each battery. If anyone has a way to measure the heat capacity, I would really appreciate it :D

Thanks guys!

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spinningmagnets   100 GW

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Re: Battery heat capacity

Post by spinningmagnets » May 23 2018 8:03am

I haven't found any prototyping research data that has been published yet, but...the EV battery packs with the longest warranties have been using active cooling.

On another related note, many square flat foil packs have been using compression cases to reduce any developing puffiness from creating low-conductivity spots inside the cells (usually referred to as localized higher resistance). Since those "compression plates" are already there, many designs made them from thermally-conductive materials to draw heat away from the centers of the stacked cells to the edges, where coolant running through tubes could carry the heat away from the pack.

A recent publication showed better results when constructing the cell with the largest-area tabs possible, and then cooling the tabs. This didn't make sense to me at first. If you imagine that the cell is a hundred very thin stacked sheets with separator/anode/electrolyte/cathode layers, then...cooling the flat sides may sound good, but...only for the outermost layers. The electrical insulating separator-sheets are not only an electrical insulator, they slow heat migration from the central layers to the outer sides.

The anode and cathode collector foils are copper and aluminum, both excellent conductors of HEAT. This revelation was the result of someone asking why a certain new cell had the positive tabs on one side, and the negative tabs on the complete other side (normally they might both be on the same end to make all the connections on that facet of the pack, with the other five sides being uncluttered). Doing this was because they wanted to make the tabs as large as possible, so each tab encompassed the entire edge on that side.

Here's a pic of a common-construction cell. Imagine the tabs are the entire width of the cell (three times longer than shown?), with positive on one end, and negative on the other.

Image

Image

999zip999   100 GW

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Re: Battery heat capacity

Post by 999zip999 » May 23 2018 8:50am

Westart is funny as I don't see 25ah 8c cell now. I tried to order the 20ah 10c cell and they pulled it . They have offered two high discharge cell then pull it off the market ???
Found the 25ah 8c cell. Sorry It's still a bad fit for my bike.

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eee291   10 kW

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Re: Battery heat capacity

Post by eee291 » May 23 2018 9:08am

Thought this might interest you guys


this guy gets his hands on some interesting stuff. He even sells a bunch of different batteries on his website from time to time.

Punx0r   10 GW

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Re: Battery heat capacity

Post by Punx0r » May 24 2018 11:04am

alihanif wrote:
May 23 2018 7:16am
Thanks for this, however, I'm afraid using these numbers is not good enough for me since the heat capacity varies with each battery. If anyone has a way to measure the heat capacity, I would really appreciate it :D
I'm sure you can find a way to measure it. Maybe even put a (discharged for safety) cell in a well insulated box along with a small resistive heating element and log temperature of the cell/box over time compared to the watts pumped in to the heater. You should be able to get a ~50°C temperature increase without risking damage to the cell if starting at room temperature.

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