Question about cooling solar gear...

[ericfx1984]

I am planning to convert my shed to be a solar gear shed... I plan to cool it in the summer... its will be well insulated and the roof is covered in panels(lowering the heat load on the shed itself) there will be inverters, MPPT SCCs, Lifepo4 cells, BMSs, etc... what could be a good target room temperature?

Would I need to run an air conditioner or would a vent fan make more sense?

 

[timselectric]

Most equipment is happy in the same environment as humans. Between 60f and 80f is the sweet spot.

 

[Symbioquine]

Most equipment is happy in the same environment as humans. Between 60f and 80f is the sweet spot.

Maybe worth noting that heat dissipation into the air is a function of the temperature differential, airflow, humidity, and surface area. You probably won't be able to change the surface area. Also you want to keep the air as dry as possible to avoid condensation/corrosion. So the variables that leaves you with are; air temperature and airflow.

You ideally want to keep the space a little cooler than you want the equipment to be and move dry air over/through the equipment.

 

[scoharri]

With all of that said "above", this mini split would be a perfect choice....
EG4 Hybrid AC/DC Solar Mini Split

 

[Leeds]

I have the exact same scenario as you, a power panel in a shed with 6 inverters, three charge controllers and some other equipment.
The panel itself has a fan to exhaust heat into the shed. But I use one of these to exhaust heat out of the shed.

https://www.amazon.com/gp/product/B07Z1VNGS8

They make larger ones of course and you can use more than one. They only draw about 50w each once they're up and running.

 

[Randy540]

I have the exact same scenario as you, a power panel in a shed with 6 inverters, three charge controllers and some other equipment.
The panel itself has a fan to exhaust heat into the shed. But I use one of these to exhaust heat out of the shed.

https://www.amazon.com/gp/product/B07Z1VNGS8

They make larger ones of course and you can use more than one. They only draw about 50w each once they're up and running.

Can I ask what state you are in? What are your typical min/max temps you reach in the shed?

 

[Leeds]

Can I ask what state you are in? What are your typical min/max temps you reach in the shed?

Pa. It gets cold here, there are single digit lows here this time of year but it very, very rarely goes below 0f.

The smaller system has been set up for years, the new 24v one is in a new shed and this is the first winter in it so I don't yet know how cold it might get.

Ask me next year and I'll share trendlog data on all that.

 

[Hedges]

Lifepo4 cells need to be 32F or higher for charging.
Higher temperatures shorten life for both lithium and lead-acid. For lithium, high SoC, especially at high temperature, shortens life.

Look for electronics that tolerates the temperature range and humidity. Then you only need to condition the battery.
Some inverters tolerate higher temperatures, with reasonable derating. Others derate significantly. Not all have published specs.

Compare derating at 140F for 4548-US (page 227) and 6048-US (page 230)

https://files.sma.de/downloads/SI4548-6048-US-BE-en-21W.pdf

 

[brandnewb]

Lifepo4 cells need to be 32F or higher for charging.
Higher temperatures shorten life for both lithium and lead-acid. For lithium, high SoC, especially at high temperature, shortens life.

Look for electronics that tolerates the temperature range and humidity. Then you only need to condition the battery.
Some inverters tolerate higher temperatures, with reasonable derating. Others derate significantly. Not all have published specs.

Compare derating at 140F for 4548-US (page 227) and 6048-US (page 230)

https://files.sma.de/downloads/SI4548-6048-US-BE-en-21W.pdf

you know I love you brother. I just want to remind myself I still do not love this farhenheit.

Weirdly enough those scientific measurement units do keep riming a bell to most of us

respect.

 

[Hedges]

Lifepo4 cells need to be 0C or higher for charging.

Pa. It gets cold here, there are single digit lows here this time of year but it very, very rarely goes below 0f.

0F won't cut it, too cold to charge LiFePO4

 

[brandnewb]

brother, I meant how may fiurlongs in a cubit is there squared pinky toe

aii. love

 

[Leeds]

Lifepo4 cells need to be 0C or higher for charging.



0F won't cut it, too cold to charge LiFePO4

Yes, that is an accurate statement.

And coincidentally, that's why I have a battery heater and also a low temp cutoff for the charge controllers should that ever not keep up. And it's in an insulated compartment in a shed.

 

[Hedges]

What is your low-temperature cutoff?
What "C" rate does your charger deliver?

 

[Leeds]

What is your low-temperature cutoff?
What "C" rate does your charger deliver?

It feels like we've diverted a bit from the cooling topic of this thread.

The low temp cutoff for the charge controllers is set at 35° inside the battery's insulated compartment.
The 1.9kw array on that project delivers 75A [nominal, max] and on a 200ah battery that's .37c.

 

[ericfx1984]

Yes, that is an accurate statement.

And coincidentally, that's why I have a battery heater and also a low temp cutoff for the charge controllers should that ever not keep up. And it's in an insulated compartment in a shed.

Yeah but it's not necessarily the temperature inside the compartment It's the temperature of the cells themselves

 

[Leeds]

Yeah but it's not necessarily the temperature inside the compartment It's the temperature of the cells themselves

I completely agree. However, I cannot forsee a situation where the batteries drop in temperature faster than the air in that compartment. I can get them to generate heat but not to appreciably sink any.
The temp sensor is actually glued to the top of the battery case so it's probably closer to giving me the plastic's temp than the air's but the argument stands the same regardless.

 

[Hedges]

The low temp cutoff for the charge controllers is set at 35° inside the battery's insulated compartment.
The 1.9kw array on that project delivers 75A [nominal, max] and on a 200ah battery that's .37c.

I suggest checking if 0.37C charge rate is OK at 35F temperature. Adjust if not.

Why you cannot charge LiFePO4 below 0 degrees Celsius

...I glazed over...Soooo far past me...... but, does this mean that the claims of the -20F chargeable LiFePO4 cells could be true? Based on what i’ve read in this forum, not for any practical use. I’m no expert on the matter, though.

diysolarforum.com

Why you cannot charge LiFePO4 below 0 degrees Celsius

I am not an expert either but my understanding is: The simple answer is just don't charge under 32*F The complicated answer is... its complicated, but still no.. ;) There are a number of variables to consider with low temperature charging (1) temperature (2) C-rate (3) SOC (4) degree of...

diysolarforum.com

Yeah but it's not necessarily the temperature inside the compartment It's the temperature of the cells themselves

My thought too. But uninsulated cells, inside insulated box, temperature sensor inside box will follow cells. That's Leed's setup.

 

[brandnewb]

ok admins. do we need an auto convert option here to convert obtuse units uttered by the most briliant amongst us, to globally understood units read by the rest of us ;(

I know, I am old and lame..

 

[timselectric]

It would be helpful. I don't use the metric system for anything. So when I see it, I have to get Google to convert it. So that I know approximately what is being discussed.

 

[Symbioquine]

It would be helpful. I don't use the metric system for anything. So when I see it, I have to get Google to convert it. So that I know approximately what is being discussed.

If you'll excuse me being pedantic, arguably "seconds", "watts", etc are metric system units. ?

 

[OffGridForGood]

Knowing both can be handy,
A few knowns allow quick (close) approximations:
Freezing point water: 0C 32F
Boiling point of water 100C 212 F
HWT temp 60C 140F
Normal Body Temp 37C 98F
-40 is the exact same in C or F (aka damn cold)
1 degree C is 1.8 of a degree F

So if you see "-5C"
you know this is 5 degrees C lower than the freezing point, 5x1.8 = 9 degreesF lower than 32 F so 23F

If you see "-20F" you know this is 20F higher than -40 (where C and F are the same temp) 20F /"1.8 is about" 10C degrees warmer so -30C (close enough).

I grew up with both metric and SAE, have used both most of my life. Working on a car - metric, working on a house addition -imperial. (feet inches)
Need to size wire AWG, ask me how far to Vancouver I will tell you in Hours LOL.

 

[timselectric]

If you'll excuse me being pedantic, arguably "seconds", "watts", etc are metric system units. ?

They were all around before metric.
And seconds aren't base 10.

 

[timselectric]

I will admit that metric (base 10) is a better system.
But I will always use what I know, and is common place in my location.

 

[Danke]

Knowing both can be handy,
A few knowns allow quick (close) approximations:
Freezing point water: 0C 32F
Boiling point of water 100C 212 F
HWT temp 60C 140F
Normal Body Temp 37C 98F
-40 is the exact same in C or F (aka damn cold)
1 degree C is 1.8 of a degree F

So if you see "-5C"
you know this is 5 degrees C lower than the freezing point, 5x1.8 = 9 degreesF lower than 32 F so 23F

If you see "-20F" you know this is 20F higher than -40 (where C and F are the same temp) 20F /"1.8 is about" 10C degrees warmer so -30C (close enough).

I grew up with both metric and SAE, have used both most of my life. Working on a car - metric, working on a house addition -imperial. (feet inches)
Need to size wire AWG, ask me how far to Vancouver I will tell you in Hours LOL.

How I do it in my head when I hear Celsius to get Fahrenheit: Double Celsius take 10% off of that and add 32.
(C x 2 - 10%) + 32 = F

Simple ones to remember:
0C=32F
10C=50F
16C=61F
28C=82F
100C=212F
-40C=-40F

 

[v_green57]

I live in the Phoenix Metro area, where summers are long and hot. My shed is fully insulated with 1" foam board, and is shaded by a mesquite tree, but some active cooling was needed.

I use one of these mounted to the inside of the shed door:

Hessaire Reconditioned 1300 CFM 2-Speed Portable Evaporative Cooler (Swamp Cooler) for 500 sq. ft. in Green MC18V-RFB - The Home Depot

This Reconditioned Hessaire 1,300 CFM Evaporative Cooler is compact in size, pleasing in aesthetics and the performance exceeds coolers of a much larger size. This performance is achieved through expanding

www.homedepot.com

and a Dial evap cooler thermostat:

DIAL Evaporative Cooler Digital Controller 7617 - The Home Depot

The Evaporative Cooler Digital Controller automatically turns an evaporative cooler on/off at your pre-programmed temperature setting. Room temperature is constantly displayed on the LCD screen. To ensure

www.homedepot.com

to keep things around 85F.

Had I known about it, I would have used one of the $10 12V thermostats from Amazon. They are actually easier to set up and a WHOLE lot cheaper.

Before implementing this, I would regularly see 110+ ambient temps in the shed and occasional battery temps approaching 100.

Ouch. Bad juju.

The Hessaire only needs 65W on low speed. I re-engineered it to have a better (brass) float valve than the crappy plastic one it came with, a manually operated drain so I can change the water every week, and a bleed-off kit to keep turning the water over so that mineral buildup on the pad is minimized.

Been using it for a couple years and I am happy with it. Of course it needs water to operate. Because it's so dry here, the added humidity resulting from its use isn't really an issue. I haven't seen any corrosion issues with terminals and wiring.

Bonus effect - I use far less battery water in my L-16's due to the combined effect of lower temps and higher humidity. The attached image is showing the GC-2's I had when first putting things together. And it is less messy in there now that the configuration has "settled" two years later.