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Heating Batery to Charge Faster
#1
Just came across this article and I'd would like to share and start a discussion on Heating of EV batteries and what it would mean for the uses after it's done in the car for degradation

https://www.realclearscience.com/quick_a...nutes.html
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#2
I'd question the longevity of the cells that are constantly put through this abuse:

Quote:the battery is rapidly heated to around 60°C (140°F) and held at that temperature during charging

In general, we toss out anything that heats up to 50-55C, and some even toss them if they get up to only 45C. Going to 60C is very harsh on the cells. Not to mention the amount of energy "wasted" during heating process. How many kWh of energy is just burned up, not to mention the extra energy to cool the system back down.

I'm skeptical about this process.
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#3
But they also go on to say that after 2500 cycles capacity was still at 91.7% which in their math was 500,000 miles(800,000km) Or 200Miles(320km) per charge So it does not look that bad as the heating is only for a short time. The heaters we deal with is internally caused heating due to charging not external.
******Hi My name is Jason and I have SOCD (Solar Obsessive Compulsive Disorder)*******
Current Powerwall - 1400 Cells 7s200p (modular 40p packs) ~ 12kWh of storage     4x 315W Canadian Solar Panels

Working on the next 7s40p packs     ~2.5kWh

Waiting on 2000 Cells of unused Sony vt4 (2000mah 30A) ~ 15kWh      hehehehehe  More Power
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#4
Heating is heating, regardless if it's internal or external. If you look at the spec sheets of any cell, it will tell you the optimal temps and max temp they are safe at.
In the article it states "held at that temperature during charging (facilitating energy transfer)". Facilitating energy transfer would mean the entire cell is at that temperature, not just the outside shell. So the complete cell is at 60C during the charge time.

I'm hoping someone here who is good with thermal dynamics and energy transfers can give a good breakdown of how many watts it'll take to raise ambient 24C (75F) cells to 60C in about 10 minutes. This type of math is a little over my head. But I'm gonna guess that it's over 1kW of energy just to heat the cells up.
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#5
External heating is not the same as internal.
Its nothing strange that lithium cells perform the best at higher temperatures.
In RC we preheat cells to 40+c and in the end they are 60. At 10c they are useless so for ev this is normal.

Many batteries cant even be charged att that rare unless heated... Just Google it and you find out.

Once again dont mix Apples with pears
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#6
The key here is that the cells are heated to 60degC in 30 seconds (really?), and then the charging takes place in just 10 mins. Afterwards the battery is presumably actively cooled somehow. So total spent at 60degC is less than 20 minutes.

Compare that to some of the Nissan Leaf batteries that are degrading to near uselessness after 6+years(?) due to heat buildup during highway driving (1hr?), quickcharge (30min), and driving afterwards (1hr?). Total of 2.5hrs.

So they've found a new method that achieves high charging performance while not (much?) affecting longevity.
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#7
Heat to 140F prior to charging?  I bet everyone is wishing they never threw away that big box of Sanyos.  Big Grin
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#8
Very interesting. My 18650 Lithium-ion battery bank is under the house.. and in the winter (Dec/Jan) the temp hovers at 13C / 55F In the summer its 24C/75F.

I don't have anyway to track cell/pack performance of the live system day to day (unless Batrium status could tell me something) BUT I have noticed that the overall efficiency ( AIMS-Inverter-Out / MidniteClassic-PV-In) has dropped from 86.4% (summer - ~24C) to 84.7% (fall/winter-coming ~14C).

Do you think 24C down to 14C ambient temp of my battery bank could be a primary cause of a 1.7% efficiency drop? 14C is getting pretty low per the comments in this discussion. Maybe I should think about heating the battery bank... and never thought of 14C as 'that low' but maybe I should?.
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#9
That is something I wish we had more data on. Efficiency vs temperature. I would think that low current draws (per cell) would not have much losses at lower temps down close to 0 Degrees C But There might be something to that. Also I think that internal heating due to use Heats the battery way differently than external.

Average Joe did a test last winter with a pack outside and I cannot remember the final outcome but I don;t think he was looking at efficiency but capacity.

I have mine in a temperature controlled Space that stays around 18C But I am going to be installing them inside a sealed unit where I can control the temps and it would be interesting to see the difference hot to cold. Might have to relegate some other cells to that test though. Smile
******Hi My name is Jason and I have SOCD (Solar Obsessive Compulsive Disorder)*******
Current Powerwall - 1400 Cells 7s200p (modular 40p packs) ~ 12kWh of storage     4x 315W Canadian Solar Panels

Working on the next 7s40p packs     ~2.5kWh

Waiting on 2000 Cells of unused Sony vt4 (2000mah 30A) ~ 15kWh      hehehehehe  More Power
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#10
jdeadman, keep us posted, very interesting. Exclamation

For your socd there is a cure, i am not fully sure, but it is something it is called fusion?
Somehow i can not get the proper components Cool
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