Weatherproof enclosure for 14.3kWh DIY LiFePO4 battery?

[fafrd]

Moving my 14.3kW LiFePO4 battery out of my basement and onto an outside wall is very appealing.

Has anyone done that?

I’ve seen these waterproof enclosure that seem big enough to hold 16 280Ah cells with a shelf: https://www.amazon.com/gp/aw/d/B0CYC955J7/ref=ox_sc_act_image_1?smid=AHPHU8PR0H6L2&psc=1

Thoughts?

 

[Hedges]

I'm considering using a refrigerator or chest freezer, with suitably high thermostat.
They aren't good at keeping rain out, need a lid over the top that comes down to drip edges.
For my mild San Jose climate, this should keep them comfortably cool.

My particular battery assembly has heating pads, otherwise would repurpose defroster as heater.

What you're looking at seems like it would work.
I think the door seal has a lip on the box, doesn't rely entirely on gasket.
I'd make drain holes at the bottom.

 

[AntronX]

If you run the freezer to keep batteries at 10 - 15°C they would last a LiFetime.

 

[fafrd]

I'm considering using a refrigerator or chest freezer, with suitably high thermostat.
They aren't good at keeping rain out, need a lid over the top that comes down to drip edges.
For my mild San Jose climate, this should keep them comfortably cool.

My particular battery assembly has heating pads, otherwise would repurpose defroster as heater.

What you're looking at seems like it would work.
I think the door seal has a lip on the box, doesn't rely entirely on gasket.

I'd make drain holes at the bottom.

Good idea .

I’m not too far from you but was not planning to worry about temps. I suppose I might be able to add a temperature sensor controlling a couple DC fans…

My charge/discharge rates are modest (0.1C / 0.02C) so I believe high ambient temps are the only thing I need to worry about…

Need as shallow as I can get-away with (PoweeWall-like) - no room for a chest freezer.

 

[Hedges]

Dorm fridge?

If you're near SF, may not get as hot as me.
As Antron said (puns not withstanding), cooler would likely extend life.
If not active cooling, I might rely on earth sheltering of the retaining wall they will be mounted on, and wrap on 5 sides with insulation.

Maybe just their thermal mass averaging day/night will be all you need. After you make sure no direct sun or radiant heat sources.

 

[fafrd]

Dorm fridge?

If you're near SF, may not get as hot as me.

Yeah, my weather’s much closer to SF than SJ. We’ll get a few days in the 90s every year, maybe 10 that get into the 80s. 60s to 70s all summer long…

Lot’s folks have Tesla Powerwalls near me - do they have any active cooling?

This is on the side of the house with a walkway along the property line, so even losing 8” is pushing it…

So no, no room for a dorm fridge.

As Antron said (puns not withstanding), cooler would likely extend life.
If not active cooling, I might rely on earth sheltering of the retaining wall they will be mounted on, and wrap on 5 sides with insulation.

Are there any rules of thumb for cycle life versus temperature?

The EVE cells are rated for 25C = 77F which, as I said, we only exceed ~10 days a year…

Maybe just their thermal mass averaging day/night will be all you need. After you make sure no direct sun or radiant heat sources.

Direct sunlight is probably my biggest concern. A couple fans against the vents could probably keep the interior close to ambient.

Then, since our nights are cooler, I’d probably get through most of the day before the cells get past 25C / 77F…

I can insulate the top of the box easily enough and also the front if push comes to shove…

Very curious to know what the Tesla PowerWall does about this…

 

[BarracudaBob]

I like the fridge idea. Bitcoin Miners do it. Do something about the condensation like desiccant or something with a weep hole.

 

[Bananaman321]

Moving my 14.3kW LiFePO4 battery out of my basement and onto an outside wall is very appealing.

Has anyone done that?

I’ve seen these waterproof enclosure that seem big enough to hold 16 280Ah cells with a shelf: https://www.amazon.com/gp/aw/d/B0CYC955J7/ref=ox_sc_act_image_1?smid=AHPHU8PR0H6L2&psc=1

Thoughts?

For peak efficiency and minimal degradation are 15 to 25 degrees C as you get below this efficiency tappers off but we do not experience degradation until we try to charge near and below zero degrees.

From 25 to 45 degrees c the LFP batteries will operate at maximum efficiency however the difference in the two temperatures have a great difference in degradation like a ratio of 8 to 3 at least by the EVE cell data for LF280k v3

This is part of the data specs and test procedures from the cells that I ordered I believe this would correlate to most LFP batteries check out the temperature vs cycle life at the bottom of this page.
Keep in mind this is with compression.
And cell temperatures tend to run about 5 degrees C higher when charging and discharging.

This could be the latter.

J

Thread '3 years later...batteries swelling'

Jun 18, 2024

About three years ago I built a 24vt battery from 8 280ah cells from shazen. everything seemed to work fine up to about a month ago when a couple of the cells register 0v. Taking things apart I find that they are pretty swollen. I assume the cells are no longer safe to use? How might I dispose of them? Should the BMS be suspect as well?

• johnontheweb
• Replies: 18
• Forum: General Battery Discussion

• 

 

[fafrd]

For peak efficiency and minimal degradation are 15 to 25 degrees C as you get below this efficiency tappers off but we do not experience degradation until we try to charge near and below zero degrees.

From 25 to 45 degrees c the LFP batteries will operate at maximum efficiency however the difference in the two temperatures have a great difference in degradation like a ratio of 8 to 3 at least by the EVE cell data for LF280k v3

This is part of the data specs and test procedures from the cells that I ordered I believe this would correlate to most LFP batteries check out the temperature vs cycle life at the bottom of this page.
Keep in mind this is with compression.
And cell temperatures tend to run about 5 degrees C higher when charging and discharging.
View attachment 243668
This could be the latter.

J

Thread '3 years later...batteries swelling'

Jun 18, 2024

About three years ago I built a 24vt battery from 8 280ah cells from shazen. everything seemed to work fine up to about a month ago when a couple of the cells register 0v. Taking things apart I find that they are pretty swollen. I assume the cells are no longer safe to use? How might I dispose of them? Should the BMS be suspect as well?

• johnontheweb
• Replies: 18
• Forum: General Battery Discussion

• 

45C = 113F

I have <1% of days at 90F = 33C,
<3% of days at 80F = 30C,
>95% of days <= 25C.

No way my cells are heating up by +5C when being charged at under 0.1C, so my cells will be operating below 30C.

Even if I assume linear degradation with operating temperature, that’s at least 7000 cycles (with compression).

My 14.3kWh battery is under compression now, so I probably have more to gain by figuring out how to include a compression fixture inside a cabinet than screwing around with temperature control…

Again, would be very interested to know what the Tesla Powerwall does regarding temperature management…

 

[Bananaman321]

45C = 113F

I have <1% of days at 90F = 33C,
<3% of days at 80F = 30C,
>95% of days <= 25C.

No way my cells are heating up by +5C when being charged at under 0.1C, so my cells will be operating below 30C.

Even if I assume linear degradation with operating temperature, that’s at least 7000 cycles (with compression).

My 14.3kWh battery is under compression now, so I probably have more to gain by figuring out how to include a compression fixture inside a cabinet than screwing around with temperature control…

Again, would be very interested to know what the Tesla Powerwall does regarding temperature management…

Absolutely understood I keep my batteries in a climate controlled space usually between 72 and 76 degrees F i've seen cell temperatures as high as 88 degrees F. On Power Pro wall mount batts.

 

[fafrd]

Absolutely understood I keep my batteries in a climate controlled space usually between 72 and 76 degrees F i've seen cell temperatures as high as 88 degrees F. On Power Pro wall mount batts.

So the PowerPro outside wallmount batteries do nothing for heat mitigation?

Even if those cells you saw were at 88F / 31C all the time (which they are not) that should only reduce cycle life from 8000 cycles to more than 6500 cycles / 17.8 years…

If the PowerPro and Tesla PowerWall don’t do anything about active cooling, I think I’ll be OK doing the same.

 

[Bananaman321]

So the PowerPro outside wallmount batteries do nothing for heat mitigation?

Even if those cells you saw were at 88F / 31C all the time (which they are not) that should only reduce cycle life from 8000 cycles to more than 6500 cycles / 17.8 years…

If the PowerPro and Tesla PowerWall don’t do anything about active cooling, I think I’ll be OK doing the same.

These are just the things they don't share as you can absolutely operate your batteries in these higher temperatures and they will perform at their peak efficiency however they will experience early degradation due to these factors.

 

[fafrd]

These are just the things they don't share as you can absolutely operate your batteries in these higher temperatures and they will perform at their peak efficiency however they will experience early degradation due to these factors.

‘Early’ is all relative to your expectations, isn’t it…

My first DIY LiFePO4 battery was from the ore-pressure fixture days and we were aiming for 3500 cycles / ~10 years of daily cycles back then.

The EG4 PowerPro battery has a 5-year warranty which is less than 2000 daily cycles.

There is a point that the added cost of trying to absolutely maximize cycle life is a game of diminishing returns…

 

[glandpuck]

If the battery is DIY, why isn't the enclosure?

Just frame it out with 2x4's, OSB boards, Tyvek wrap, some hardy board, and a top with some roofing paper and shingles. Or get one of those plastic Lifetime sheds from Costco or Walmart.