As title.
I have a solar watering system running in a box, this box:
Sun will hit the box without any shelter, in it there is this circuit with a 18650 battery:
is it dangerous?
will high temp can damage or make the battery explode even if it's inside a box?
Possibly, if it gets overheated.
So, put it in the shade, problem solved.
Your box.
Monitor the temperature inside and check the data sheet of the battery you are using for its safe operating limits.
Simple.
That is going to get seriously hot in the sun, you could probably cook inside there on a hot day. It needs a sun shield.
I don't know if the battery will explode, please do let us know if it does....
PerryBebbington:
That is going to get seriously hot in the sun, you could probably cook inside there on a hot day. It needs a sun shield.I don't know if the battery will explode, please do let us know if it does....
this is a sun powered project, a sun shield is not the best bet for me, or I should put the solar panel far from the battery but I would like to have a self contained project.
sblantipodi:
this is a sun powered project, a sun shield is not the best bet for me, or I should put the solar panel far from the battery but I would like to have a self contained project.
Can you put the box under the solar panel with just a small gap to allow air flow around the panel & box.
If the box then goes into the sunlight your not positioning the panel properly of you could also drop a small skirt from the panel to allow more shading.
This is a sun powered project, a sun shield is not the best bet for me
Is the solar panel inside the box? It's not clear to me from the photos.
What Riva said.
Put a temperature sensor inside the box. Read the data sheet for the battery.
PerryBebbington:
Is the solar panel inside the box? It's not clear to me from the photos.
A closer look at the images seem to point to a solar panel being inside the box so my idea will be no good. I had wrongly assumed from the second image that it was the solar panel.
Can you put the elects another enclosure with a solid cover to reduce solar heat gain? You can use another piece of liquid tight to connect the two.
sblantipodi:
this is a sun powered project, a sun shield is not the best bet for me, or I should put the solar panel far from the battery but I would like to have a self contained project.
So measure the temperature in the box !!!!!!!!!!!!!!!
How can the forum possibly know how hot it will get ?
You have not said where in the World you are, and its just a suspicion mind, but I suspect the box temeprature will be higher in a sunny location where the air temperature is +45c versus a location where the air temperature is 0c.
PerryBebbington:
Is the solar panel inside the box? It's not clear to me from the photos.What Riva said.
Put a temperature sensor inside the box. Read the data sheet for the battery.
yes it is
srnet:
So measure the temperature in the box !!!!!!!!!!!!!!!How can the forum possibly know how hot it will get ?
You have not said where in the World you are, and its just a suspicion mind, but I suspect the box temeprature will be higher in a sunny location where the air temperature is +45c versus a location where the air temperature is 0c.
I live in Italy and in my are temp goes up to 30-33°C in summer in hot days but if the Sun hit the box,
I suppose that the temp goes a lot higher.
I live in Italy and in my are temp goes up to 30-33°C in summer in hot days but if the Sun hit the box,
I suppose that the temp goes a lot higher.
OK, so, Italy is maybe 10 degrees or so warmer than the UK (you lucky people! (love your food by the way 
)). In the UK dogs quickly die when idiots leave them in glass boxes, also known as cars, in the sun. UK sunshine is enough to make the inside of a glass box very hot, very quickly. Must be even more so in Italy.
Put the battery - which is really not very big - in a second box! 
PerryBebbington:
OK, so, Italy is maybe 10 degrees or so warmer than the UK (you lucky people! (love your food by the way
Ok, the there is a glass and the sun can enter the box, ok, but in my case the sun can't enter the box.
What is the temp of the inside of the box in full sun? More or less, considering a 33°C day?
Are we taling about 50°C? 80°C? how much?
I know that a sensor could do the job better but I want to have an indication.
Sony VCT6 can work up to 80°C as far as I know.
What is the temp of the inside of the box in full sun? More or less, considering a 33°C day?
Only you can find out, you have the box...
The solar panel will absorb light from the sun, AND heat from the sun. That heat will add to the heat generated by the electronics and make the box temperature rise more than it would without the heat from the panel. The actual temperature rise is difficult to estimate, but I imagine that you could achieve 80C just by placing a black painted sheet of steel inside the box facing the sun.
Have you considered mounting the solar panel on the lid of the box, spaced out by about 50mm? In this way the solar panel would be exposed to more solar light (the polycarbonate lid may attenuate the solar radiation), and the panel itself would shield the electronics box from direct solar radiation to some extent. Additional shielding for the box could be cheaply added with aluminium foil on its exposed surfaces.
Putting the lithium battery in a metal (fire-resistant) enclosure is a good move, as previously advised.
Why not put the box in the shade of the solar panel?
I think the upper limit on lithium batteries is 60C/140F. Above that, or perhaps, close to it, it will start venting to relieve internal pressure. Venting also causes some loss of battery capacity. Any possibility to vent your case?
MK1888:
I think the upper limit on lithium batteries is 60C/140F. Above that, or perhaps, close to it, it will start venting to relieve internal pressure. Venting also causes some loss of battery capacity. Any possibility to vent your case?
I would like to have a waterproof project for both summer and winter...
am I the only one who made a box with a solar panel and a lithium battery? 