Where do you keep the Poowerwalls?

cmg_george

cmg_george

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Joined
Oct 24, 2017
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84
Hi all.
I saw a lot of locations for keeping the powerwall (rack, basement, etc).
My plan is to have it in house next to the heater, close to the power distribution. However i'm concern about having those DIY cell in house.
From those holder the powerwall in a shed...what are you doing in the winter (in that parts of the globe were you have it)? I my region i get in the winter -20C and in the summer +30C...so i don't think that putting them outside is an option.
So, where do you keep the powerwall and how do you handle the weather problem?
 
In my workshop. 75meters from the house. Its on 1st and 2nd floor. The house is temperature controlled.

My end goal is a bunker under ground... Thats my fantasy to dig up this crazy tunnel system with rooms :D
 
I won't be using mine without supervision and it is very small so it will find its place in the livingroom. If I'm not at home the main switch will be turned off. If I had a house and a bigger system I would put it in the basement or outside in a shed.
 
Underground bunker would be super cool!!
 
DarkRaven said:
I won't be using mine without supervision and it is very small so it will find its place in the livingroom. If I'm not at home the main switch will be turned off. If I had a house and a bigger system I would put it in the basement or outside in a shed.
Click to expand...

Well... i don't have a basement :( and outside... what about very low temperatures?
 
cmg_george said:
DarkRaven said:
I won't be using mine without supervision and it is very small so it will find its place in the livingroom. If I'm not at home the main switch will be turned off. If I had a house and a bigger system I would put it in the basement or outside in a shed.
Click to expand...

Well... i don't have a basement :( and outside... what about very low temperatures?
Click to expand...

How low is very low?

At lower temperatures, the internal resistance increases. This means that you get a capacity drop and you have to reduce the charge and discharge rates to reduce cell aging/damaging.

I've read that you should try to avoid charging below 0 deg C if at all possible, and significantly reduce the discharge rate below zero C

Maybe in a a small enclosure that is really well insulated with a gentle heat source could keep the cells above zero C?

There's probably members who are in a colder climate than mine who can offer better advice.

I just checked the Tesla powerwall 2 operating temperature and they specify -20C to 50C, which is lower than I was expecting. Given that they offer a 10 year warranty, my guess is that their management systems dramatically reduce charge and discharge currents at -20c. I don't know that for sure though.

More info here:

http://batteryuniversity.com/learn/article/charging_at_high_and_low_temperatures

They say charge lithium over 0c and discharge over -20c
 
Yes, 0C and -20C are the usual thresholds. Discharge down to -20C with reduced capacity, charge down to 0C. On the other end, environmental temperatures of around 50C are the limit.
 
Well low during the winter means daily under 0C ( 1-2 months). I some cases -25C (we had 2 years ago when temperature didn't raised above -25C for 3-4 days)... so it will be hard to keep the temp positive all year. Thank you for advice, i think i will start by keeping them in house and when the wall will grow analyze the option to move it outside.

Nobody keeping the powerwall in cold regions?
 
cmg_george said:
Well low during the winter means daily under 0C ( 1-2 months). I some cases -25C (we had 2 years ago when temperature didn't raised above -25C for 3-4 days)... so it will be hard to keep the temp positive all year. Thank you for advice, i think i will start by keeping them in house and when the wall will grow analyze the option to move it outside.

Nobody keeping the powerwall in cold regions?
Click to expand...

The coldest it gets here is around -15C, and generally only a few times per year. Typical temperature in the winter is -5C to -8C. Last year I left my batteries outside like this and didn't have any issues even though I understand this is not good for them. I used foam insulation but they still got pretty cold.
 
Insulation is only useful if there is a source of heat inside. Since the cells generate heat they could potentially keep themselves (relatively) warm but for that they have to be under constant load so they get warm and stay warm. That's a contradiction, this is almost the exact opposite of how most powerwalls are usually operated as most of us design them so they don't get warm.
Maybe an external heater of some kind might be useful under more extreme conditions. Not for 24/7, but for times when it gets really cold.
 
Now outside are 4C so... i'm afraid that keeping cells work will cost significant from the economy i make with them :D
An other problem i have with and enclosure is condense, It it gets cold (<0)C and heat, cold and heat condense will form inside i think.
But there us also a good think with the enclosure... i can mix in also some fire resistance material (i know one holding 1000C).
 
DarkRaven said:
Insulation is only useful if there is a source of heat inside. Since the cells generate heat they could potentially keep themselves (relatively) warm but for that they have to be under constant load so they get warm and stay warm. That's a contradiction, this is almost the exact opposite of how most powerwalls are usually operated as most of us design them so they don't get warm.
Maybe an external heater of some kind might be useful under more extreme conditions. Not for 24/7, but for times when it gets really cold.
Click to expand...

I had several layers of the foam board insulation from Lowe's around mine, except the bottom which was 1/2" plywood. During the day, the termometer inside the cell "package" was generally 15F above the ambient air temp. Even at low temps of 20F, it still maintained 8-10F above the ambient air temperature. This is with a small constant load of about 100w. Honestly I'm not overly concerned with the temp in the battery area dropping to 20F overnight and going back above freezing in the morning. It needs to go to 20F and stay there for the batteries to freeze. That being said, I am still working on insulation my shed so it won't do this because it's obviously still going to decrease lifespan.
 
Probably because we all live in areas where this doesn't happen :) I just had a look at the archives, the highest temperature ever recorded for my area here was 38.5C. The average maximum is 24.0C.
Personally I'm not bothered with low nor high temperatures. The average minimum is about 1C here and the average temperature during winter (Dez/Jan/Feb) is about 3C.

But you are right, if someone happens to live at such a place some extra cooling for the batteries might be a thing!
 
The solution for hot area is the same: good isolation ... and add a cooling system :D
 
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