Cold Temp LiFePO4 Charging Test

[Will Prowse]

What do you guys think?

I am guessing that the pack needs heat to be pumped out of the cell while charging. Or the rate needs to be higher. Pretty interesting results.

I was pretty quick to start charging after I took the battery out of the freezer too. It was less than a minute.

How would you modify this test?

 

[SeptemberMorn]

Hi Will, cycle inside the freezer. Try various charge regimes to simulate a solar start morning.......

 

[Will Prowse]

Yes, doing that right now

 

[hankcurt]

I've been looking forward to this test with interest because I've been considering how to design a solar shed for Midwest winters. Lag in cooling of the thermal mass of the batteries along with the speed of heating during low temperature charging are important for determining how cold I can allow the shed to get overnight.

One suggestion I would have is to get an electronic temperature probe inserted inside the battery between the cells. You're kind of flying blind in these test as to how the cell temperatures are changing throughout the cooling and charging cycles. Since degradation at temperature is what you're testing for, this is worth throwing a few bucks at to be able to verify the internal test conditions. I had to buy a couple of temperature loggers for work, and they're pretty inexpensive (less than 12 grand anyway )

I appreciate the time and effort invested so far.

 

[Sillyputty]

Nice work, and surprising results. Finding the true internal temperature of dense objects like these larger cells is problematic, and that density may protect them from reaching ambient temp as soon as we think they would.

My layman's example is that when I "cold-crash" my fermented home-brew beer in my already below freezing garage (20 F) the 5 gallons of liquid drops from 65 F to 48 F in 24 hours. It takes another 24 hours to drop another ten degrees to ~38 F which coincides with what I've read about how liquids need low temperatures for a longer time to reach ambient the lower that ambient temp is. So perhaps removing the cells and freezing them separately for a longer period (a week?), then testing them would give results more like what we've read about.

Also, order the cycling machine, dammit! We need that data!

 

[Deleted member 9967]

On youtube and here it says the video is private.
Why can't we see it Will?

 

[Supervstech]

What do you guys think?

I am guessing that the pack needs heat to be pumped out of the cell while charging. Or the rate needs to be higher. Pretty interesting results.

I was pretty quick to start charging after I took the battery out of the freezer too. It was less than a minute.

How would you modify this test?

Video is pulled? Private linkey...

 

[Forbisher]

On youtube and here it says the video is private.
Why can't we see it Will?

Will's cat deleted the video!

 

[Will Prowse]

Yeah, I'm going to redo the video and destroy the pack. People were not satisfied

 

[Deleted member 9967]

Yeah, I'm going to redo the video and destroy the pack. People were not satisfied

Oh
Ok

 

[grizzzman]

What do you guys think?

I am guessing that the pack needs heat to be pumped out of the cell while charging. Or the rate needs to be higher. Pretty interesting results.

I was pretty quick to start charging after I took the battery out of the freezer too. It was less than a minute.

How would you modify this test?

Why won't the video load? Says its "private"

 

[grizzzman]

Oops nm

 

[Sillyputty]

Yeah, I'm going to redo the video and destroy the pack. People were not satisfied

Lol - I love this guy! (people = him) ;-)

 

[Supervstech]

Yeah, I'm going to redo the video and destroy the pack. People were not satisfied

Awww. Seeing the before and after videos sometimes is important.
Remember... negative comments help as much as positive ones sometimes.

 

[Will Prowse]

Cycling in a -20C freezer right now. Should be interesting

 

[Deleted member 9967]

Cycling in a -20C freezer right now. Should be interesting

I am curious if the amps or such go down when cold.
My mobility scooter goes a lot slower when it gets cold.
About 5 Celsius or lower it gets affected.
So I am very interested in the outcome here.

 

[curiouscarbon]

Cycling in a -20C freezer right now. Should be interesting

Thank you for directly challenging the recent LFP Safe Cell Operation Temperature Claims. Practical experiments are so valuable.

 

[upnorthandpersonal]

I ordered some extra cells (smaller ones, from gwl.eu) to do some tests here in real world environments. I have destroyed cells in the past testing this, but this time I might make it a video as well

 

[Will Prowse]

Previous capacity was 176-179Ah. I just got 155Ah from cycling at -20C in a freezer. I have a new temperature probe system and will cycle some new cells. Will also have a soc curve with new capacity tester.

 

[hankcurt]

So the question in my mind is how much of the loss from 176 Ah to 155 Ah is just the reduced capacity of using the batteries at a low temperature and how much is permanent degradation from the damaging effects of charging at low temperature.

This will be interesting.