Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
18650 in use 24/7 outside, how to prevent overheating?
#1
I'm building a solar panel (12 volts, 3 watts, 250 mA) + battery powered weather station type of thing + autonomous gardening with arduino and sensors at the heart of it. I need 12 volts for a couple of the components in this project as well as 5 volts for others, so I figured I'd throw 18650's in 3s1p or 3s2p to get 12 volts and run a small buck converter off that to get 5 volts. Most of the components, including the 18650's, will be housed inside a 16" cube box and will sit in direct sunlight most of the day. The box will be painted white and the top half of it will be all soffit vents (16" wide on each side) to help keep the heat down inside. Is this enough to keep the 18650 from overheating or is there something else I could do for prevention?


P.S. - I also thought about lining the inside walls and roof of the box with reflective foil insulation (used as insulation in roofs, walls, garage doors in homes and RVs to help keep them cooler in the summer), but wasn't sure if that's a good idea with all the electronics inside. Maybe make a double wall and put the insulation between the walls??

P.P.S. - Also, I thought about installing a Noctua 120mm fan (12 volts, 50 mA) and an outdoor dryer vent in the box to act as an exhaust system so the fan kicks off when the box reaches a certain temperature, but worry it'll draw too much current from the panel, charge controller or battery and hamper the circuit. Maybe add a second solar panel in parallel to help with the extra load and only run the fan during sunlight hours??
Reply
#2
How how in shadow during the day?

If its below 50c i dont see any major issue. Make sure the box is white and have a shaded thing on top so it doesnt sit in direct sunlight. Thats how many of my IOT devices are set up
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Reply
#3
(06-22-2019, 06:47 AM)daromer Wrote: How how in shadow during the day?

If its below 50c i dont see any major issue. Make sure the box is white and have a shaded thing on top so it doesnt sit in direct sunlight. Thats how many of my IOT devices are set up

So that's 50 C/122 F inside the box, correct? Also, what do you mean by "a shaded thing on top"? Can you provide a picture?
Reply
#4
I talk about outside temp. IF the device creates more heat incorporate heatsink so you can have same temp inside as outside.


Think of un umbrella on top. That Will make sure it never sees direct sunlight
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Reply
#5
If you plan on using a buck converter, might as well go 4s, you'll get longer life out of the cells (cycle life and run time)

Using a white box is probably sufficient. Put the cells at the bottom of the box, put a few vent holes on the bottom and a few on the top on the sides. This will create a positive air flow through the box. Use a small drill bit to minimize insects getting inside. Some professional boxes use around 1/16th if I remember correctly. It won't keep all out, but will significantly make it harder for the bigger ones to get in.

I don't think you'd need a shade over the box. I doubt it'd get that hot inside the box if it's white and with the holes. But you could just set the box with a thermometer in it for a day and check it at the end of the day just to verify. This is before putting any gear in it.
The other thing you could do is put the box under the solar panels (not sure how large they are). The panel would take the brunt of the sun and help shade the box. Just make sure there is a slight air gap between the panel and the box to allow air flow around the panel.
crashintoty likes this post
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#6
You give lots of irrelevant information and omit the most important thing .... LOCATION

Are you in Norway or Saudi Arabia where air temperature can reach over 50C ...

Temperature is not an issue unless you are somewhere very hot and drawing large currents.
Reply
#7
Dont put box under solar panels korishan. Its easy 100c under them....

Shade on top does ALOT. You can half the inside temp in the box. And you dont need to cut holes and expose the electeonics. Having Hole in the box only works of the electeonics are weather proofed or in dry area.

Having electronic Gear outside that should last years require some basic design thoughts. I have mounted many many esp8266 devices outside that Still are working 4 yearslater
crashintoty likes this post
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Reply
#8
(06-22-2019, 12:13 PM)daromer Wrote: Dont put box under solar panels korishan. Its easy 100c under them....

Considering he was talking about pulling 250mA, I was assuming he'd be using a small panel, around 150mm * 100mm or so. The heated generated under one of those would be very small.

(06-22-2019, 12:06 PM)ozz93666 Wrote: You give lots of irrelevant information and omit the most important thing .... LOCATION

I completely agree. We haven't discussed his location yet. In Florida, USA, we wouldn't need to add any extra cooling other than the seal box. If you want to reflect heat, either spray chrome paint on the outside, or wrap it in aluminum foil tape. That will reflect the heat better than putting anything on the inside. Or, put the electronics inside of a Stainless container of some sort.
Proceed with caution. Knowledge is Power! Literally! Cool 
Knowledge is Power; Absolute Knowledge is Absolutely Shocking!
Certified 18650 Cell Reclamation Technician

Please come join in general chit-chat and randomness at Discord Chat (channels: general, 3d-printing, linux&coding, 18650, humor, ...)
(this chat is not directly affiliated with SecondLifeStorage; VALID email req'd)
Reply
#9
(06-22-2019, 06:49 PM)Korishan Wrote: I completely agree. We haven't discussed his location yet. In Florida, USA, we wouldn't need to add any extra cooling other than the seal box. If you want to reflect heat, either spray chrome paint on the outside, or wrap it in aluminum foil tape. That will reflect the heat better than putting anything on the inside. Or, put the electronics inside of a Stainless container of some sort.

I would definitely not paint it chrome or use foil on the box surface - the physics of reflective surfaces means they actually get HOTTER (yeah go figure but that's how it works!).
Paint the box white or leave it gray.
Mount a sheet of also white painted metal about 2-3 cm or more away to shade it. (they do this for speed cameras around here + guys in the bush do this above car roofs)
Mount the solar panel ~5cm above that & everything will work nicely.
The batteries themselves won't (& shouldn't) generate any significant heat but will be happiest between approx 5 & 45 degC.
If the electronics tend to get too warm in the shaded box you could use a metal alloy box & bolt the electronics to this to help dissipate heat.
Don't have air holes = moisture/corrosion problems.
If you need a vent, maybe have 1x tiny 1mm weep hole at the bottom only or use a special vent plug like these:
https://au.element14.com/hylec/jdae12pa-...st=2308394
daromer likes this post
Running off solar, DIY & electronics fan :-)
Reply
#10
Korishan it doesnt matter how much you pull from a panel. It basically get equally hot under.
IF the panel is small it works and IF its on a pole or equal. Mounting under a panel on a roof is a big NO in hotter climates. No matter wattage pulled.
And yes i assumed roof panel of some reason :S

As redpacket Said. No other options or suggestions should be followed here. White or Grey box 100% sealed with something shading. IF needed transfer heat with element but Still water right. Its not Hard to do and Will last years
The Ultimate DIY Solar and build place
YouTube / Forum system setup / My webpage  Diy Tech & Repairs

Current: 10kW Mpp Hybrid | 4kW PIP4048 | 2x PCM60x | 83kWh LiFePo4 | 10kWh 14s 18650 |  66*260W Poly
Upcoming: 14S 18650~30kWh | Automatic trip breakers, and alot more
Reply


Who read this thread?
57 User(s) read this thread:
daromer, Sean, mike, Majorphill, Korishan, PAF, ozz93666, jdeadman, wim, watts-on, Hanssing, BlueSwordM, Geek, Oz18650, CarelHassink, djuro, sturgeo, drchips, gpn, Chablis_m, Redpacket, Ibiza, Bubba, CBlack, crashintoty, Riplash, 100fuegos, w0067814, michaell, chuckp, emuland-metroman, Shawndoe, Bastler_Ro, ibikunle, Generic, stevelectric, ajw22, RikH, TimBelgium, kevinjaye, Huutran, mart1nn, OffGridInTheCity, Richard, bertvaneyken, JBonesaw, juanjo57, aventeren, billvon, Emiel, Saiya, Buffalo Board, kimbo, krobertson, evans.brett87, cx530559, kpeters000

Forum Jump:


Users browsing this thread: 1 Guest(s)