Author Topic: Purpose of "sand" inside a solar charge controller  (Read 2612 times)

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Offline DTJTopic starter

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Purpose of "sand" inside a solar charge controller
« on: April 17, 2019, 01:01:16 am »
Have a look at this short video.

https://www.youtube.com/watch?v=QzyZCdmQqH0&feature=youtu.be

It shows "sand" inside a sealed solar charge controller. I've read a few different opinions on why it is there:

1) Heat transfer.
2) Its not sand, its a polymer that helps to protect the electronics. Its also how it gets its IP65 rating.


Is there any truth in 2) above.

Perhaps they just use it as a very cheap filler to save on the cost of the epoxy by only having to put a thin layer on top to seal the unit.
Perhaps they want to avoid rigid epoxy over the thermally stressed parts to prevent fracturing as they thermally cycle.


Anyone seen this before?
 

Offline floobydust

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Re: Purpose of "sand" inside a solar charge controller
« Reply #1 on: April 17, 2019, 01:10:16 am »
Sand is a cheap filler in order to use less potting compound. It also helps extinguish any flames or sparks inside. I think it's just a cheap way to seal something big, chinese do that kind of thing.
 

Online Nusa

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Re: Purpose of "sand" inside a solar charge controller
« Reply #2 on: April 17, 2019, 01:58:06 am »
Plus there's the whole "Feel how heavy it is...there must be some beefy components in there!" thing! Most people don't open the box.
 
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Offline DTJTopic starter

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Re: Purpose of "sand" inside a solar charge controller
« Reply #3 on: April 17, 2019, 05:28:43 am »
Sand is a cheap filler in order to use less potting compound. It also helps extinguish any flames or sparks inside. I think it's just a cheap way to seal something big, chinese do that kind of thing.


Yeah I think that as well.

Plus there's the whole "Feel how heavy it is...there must be some beefy components in there!" thing! Most people don't open the box.

I reckon that's a side benefit. I've also seen products before that have a short length of black finish steel flatbar inside just to add that heavy "quality" feel.
 

Offline TERRA Operative

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Re: Purpose of "sand" inside a solar charge controller
« Reply #4 on: April 17, 2019, 07:53:24 am »
I reckon that's a side benefit. I've also seen products before that have a short length of black finish steel flatbar inside just to add that heavy "quality" feel.

My Roku network video streaming thingo has a metal plate in it for this reason.
Without the plate, it's a single PCB in a plastic box a bit bigger than the palm of your hand and hence weighs almost nothing.

The plate adding weight does make it feel nicer, even though I know it is there exactly for that reason. :D
Where does all this test equipment keep coming from?!?

https://www.youtube.com/NearFarMedia/
 

Offline mikerj

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Re: Purpose of "sand" inside a solar charge controller
« Reply #5 on: April 17, 2019, 11:36:34 am »
I reckon that's a side benefit. I've also seen products before that have a short length of black finish steel flatbar inside just to add that heavy "quality" feel.

My Roku network video streaming thingo has a metal plate in it for this reason.
Without the plate, it's a single PCB in a plastic box a bit bigger than the palm of your hand and hence weighs almost nothing.

The plate adding weight does make it feel nicer, even though I know it is there exactly for that reason. :D

Weight is very useful for these small streaming boxes as HDMI cables are quite stiff so you'd never get the box to stay where you want it.
 

Offline sanman

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Re: Purpose of "sand" inside a solar charge controller
« Reply #6 on: April 17, 2019, 03:02:10 pm »
I remember a lot of CB microphones had pieces of lead, or even rocks, inside to give them some 'heft'   :-DD
 

Offline JimRemington

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Re: Purpose of "sand" inside a solar charge controller
« Reply #7 on: April 19, 2019, 02:25:16 am »
Adjust antenna for best reception.
 

Offline AlienRelics

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Re: Purpose of "sand" inside a solar charge controller
« Reply #8 on: April 19, 2019, 02:39:01 am »
Not only that, it costs more for the model with an "antenna" than without.
Steven J Greenfield AE7HD
 

Offline Gyro

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Re: Purpose of "sand" inside a solar charge controller
« Reply #9 on: April 19, 2019, 10:10:10 am »
Sand is a cheap filler in order to use less potting compound. It also helps extinguish any flames or sparks inside. I think it's just a cheap way to seal something big, chinese do that kind of thing.

If it's Silica sand then maybe it is there as a cheap flame suppressor - turning the whole thing in into a sand-filled fuse. It would hardly help with IP65 rating - if moisture got in, the sand would get damp. It possibly lets them get away with a plastic, rather than  metal, enclosure.
Best Regards, Chris
 

Offline coromonadalix

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Re: Purpose of "sand" inside a solar charge controller
« Reply #10 on: April 19, 2019, 10:21:06 am »
In marine / boat transformers they are filled with sand to provide  humidity and rust and salt water protection ??
 

Offline MaTkEOxjC

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Re: Purpose of "sand" inside a solar charge controller
« Reply #11 on: April 19, 2019, 11:26:13 am »
I found a couple (like 20) neon sign transformers in the dumpster in Europe. The body of them was a mixture of sand and some resin (the actual transformer was surrounded by the resin/sand mix, giving it a sturdy cover, making it semi-waterproof (the lid was injection molded plastic with mains disconnect contacts but had no seal).

Probably again to save resin with some nice side effects (more robust shell, less shrinkage when curing)

Looks pretty much like the lower one of these:
 

Offline tecman

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Re: Purpose of "sand" inside a solar charge controller
« Reply #12 on: April 19, 2019, 03:20:46 pm »
One note, sand is primarily a thermal insulator and not good for heat transfer.  Think of a foundry casting steel using sand.  Or at a beach under the sun, a few inches down is not hot.

paul
 


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