Safe Ambient Temperature Range for 18650 Powerwall

Dr. Dickie

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Sep 23, 2020
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Okay, I started a month ago with putting my Powerwall inside my house.
HB recent vid and thread changed my mind on that.
I then figured a way to get a steel cabinet into garage (advantage: Powerwall would be right next to service panel which it would be hooked into. Disadvantage: Would be about a 100' run from solar panels to powerwall.
I have dismissed the idea of a shed, as I have a plastic shed (8' x12.5').
If I am putting it into a cabinet, then I could use the shed (advantage: Solar panel run is only a few feet; long run would be 120V; and this would be about 25' away from my house).
Disadvantage, I am in Florida, and this shed has a little shade, but I still bet it get 100+oF during the summer.
Is that temperature too high to have the battery in? It would seem that starting off with the cells at 100oF without internal heating might not be a good idea.
Thanks for any opinions--I will at least slow down with the questions soon.

I saw this thread:

And it makes me think I could have problems.
Ground water for cooling is actually trivial to get--5 feet down around here you strike water, I have put in a handful of shallow water wells, and have one close by that is currently on a solar pump.
But, that would create a whole new can of worms. I am trying to learn everything I need to know about these powerwalls right now.
 
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LithiumSolar

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The battery definitely needs to be outside. You don't want to risk it catching fire in your home and burning everything.

I do think 100F is too high for normal operating temperature. My idea would be to get a small shed for the battery/equipment and run the AC line back to the house. You could use 2" foam board insulation to insulate it and maybe a small/cheap window AC for cooling. You could shade it with a small ground-mount solar array - which would both provide power AND take a tremendous cooling load off the AC.

As for the question "safe temperature range", the datasheets for the cells will indicate this, but anywhere from 50-90F is optimal in my personal opinion.

Just my thoughts.
 
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Dr. Dickie

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The battery definitely needs to be outside. You don't want to risk it catching fire in your home and burning everything.

I do thing 100F is too high for normal operating temperature. My idea would be to get a small shed for the battery/equipment and run the AC line back to the house. You could use 2" foam board insulation to insulate it and maybe a small/cheap window AC for cooling. You could shade it which a small ground-mount solar array - which would both provide power AND take a tremendous cooling load off the AC.

As for the question "safe temperature range", the datasheets for the cells will indicate this, but anywhere from 50-90F is optimal in my personal opinion.

Just my thoughts.
I am thinking more like you, perhaps I could fit a very small shed, which could be placed in the shade. With cooling fans, I think it could be kept to 95oF max, as we get bit of cooling breeze in the afternoon. So you think as long as it is 90oF max, it should me okay.
I will work toward that.
Thanks LithiumSolar
 

daromer

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Agree with LithiumSolar regarding the range. Its basically what the papers says. Papers even approve up to 40+C ie 100F
 

Dr. Dickie

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I'm an idiot.
I have the spec sheet and did not even think to look:
2.10 Operating Temperature
Charge 0 ~ 45℃
Discharge -20 ~ 60℃


So max out at 45oC, or 113oF--as it would be charging during the day.
I should be able to keep it a lot closer to 90oF with a bit of fangeling.
Thanks
 

Redpacket

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You might also want to ramp down the charge current if the temp is heading for the upper spec sheet limits....
 

hbpowerwall

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Max ive seen my powershed is 42, and battery shed is 45 mid summer in Australia
 

intra

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In Western Australia the weather can be quite variable, but this summer the enclosure that houses both the inverter and batteries can get a little toasty. I've added a 120x120mm fan to the enclosure to help move some air around and keep it cooler and lowered the charge current to take up more the day so that the inverter isn't heating up and also to move some air for the batteries (Tesla Model S modules).

Will be an interesting week as its supposed to be quite warm.
 

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ajw22

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Note that Lithium cells will degrade quicker at higher temperatures. So while 45℃/60℃ might be safe, but you're definitely eating into longevity.

TL;DR: after 250 cycles at 25℃(55℃) capacity dropped by 4%(13%), IR up by 34%(93%).
Here's a very interesting paper on this. I think main interest for us is Figure 5 & 8.
 

Dr. Dickie

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Going to play it by ear. I have not tested the actual temp inside the shed during the summer, as I had not considered it a possibility for having a battery inside. However, now that I am going to be putting the powerwall inside a steel cabinet, I feel I can use it.
The average temp here in July and August is probably 32 oC, with of course days of 35 oC or so. I though the shed was more in sunlight during the afternoon hours, and so the temperature would climb quite a bit higher than that; however, my neighbor recently planted a bunch of bamboo just West of the shed, and when I checked yesterday it was almost in complete shade by 1:30 PM thanks to that high grown bamboo--very unexpected. That is winter, but given its location I do no expect a lot more sunlight in summer, so I think with good fans and careful monitoring, it can work.
I might want to move my oxygen / acetylene tanks out of there, even with a steel cabinet :cool:

Thanks, learning, learning, learning, thanks to this place!
 
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Bubba

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Going to play it by ear. I have not tested the actual temp inside the shed during the summer, as I had not considered it a possibility for having a battery inside. However, now that I am going to be putting the powerwall inside a steel cabinet, I feel I can use it.
The average temp here in July and August is probably 32 oC, with of course days of 35 oC or so.
in Windows you can use Alt+0176 (most setups) to make the degrees °C
 
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