spray on PC board protectant

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spray on PC board protectant

Electric Vehicle Discussion List mailing list
I'm in the process of testing a bunch of very grungy looking miniBMS
cell modules.  The good ones, I'd like to spray with something to make
them more weather resistant.  Looking for suggestions.
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Re: spray on PC board protectant

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Hello Willie,


I pick up these products from my local motor shop.  These come in a spray can.  There is a cleaner, dielectrics, and electric motor enamels.


Roland


________________________________
From: EV <[hidden email]> on behalf of Willie via EV <[hidden email]>
Sent: Monday, May 8, 2017 7:14 AM
To: Electric Vehicle Discussion List
Subject: [EVDL] spray on PC board protectant

I'm in the process of testing a bunch of very grungy looking miniBMS
cell modules.  The good ones, I'd like to spray with something to make
them more weather resistant.  Looking for suggestions.
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Re: spray on PC board protectant

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In reply to this post by Electric Vehicle Discussion List mailing list
Willie via EV wrote:
> I'm in the process of testing a bunch of very grungy looking miniBMS cell
> modules. The good ones, I'd like to spray with something to make them more
> weather resistant. Looking for suggestions.

Hi Willie,

Most of the sprays provide pretty weak protection. In an outdoor environment
where rain, fog, and condensation are very likely, I'd suggest a conformal
coating. If nothing on the board is getting hot (no heatsinks)...

I use Dow Corning 1-2577. This is a thick silicone-based conformal coating that
is totally resistant to water and most solvents, and works over a very large
temperature range. You paint or dip the boards in it. It's clear, so you inspect
parts through it. It's soft and rubbery, and can be easily removed if you need
to make repairs.

If you want something cheap, you can also used paraffin. Melt the wax, and paint
or dip the boards in it. It too is clear, and easy to remove if necessary. The
main drawback is that it melts if anything on the board gets hot.
--
Obsolete (Ob-so-LETE). Adjective. 1. Something that is simple,
reliable, straightforward, readily available, easy to use, and
affordable. 2. Not what the salesman wants you to buy.
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: spray on PC board protectant

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Lee, you are correct about the Dow 1-2577 coating (I like it); however, it is a pain to remove and makes troubleshooting difficult.  I have never seen a conformal coating that is not a pain to remove.  The best conformal coating is applied in a vacuum chamber (no voids in coating); however, it is impossible to remove.   Usually, I design a conformal coated board to have a low failure rate and low production cost and forget about the repair.

________________________________
From: EV <[hidden email]> on behalf of Lee Hart via EV <[hidden email]>
Sent: Monday, May 8, 2017 9:44 AM
To: Willie; Electric Vehicle Discussion List
Subject: Re: [EVDL] spray on PC board protectant

Willie via EV wrote:
> I'm in the process of testing a bunch of very grungy looking miniBMS cell
> modules. The good ones, I'd like to spray with something to make them more
> weather resistant. Looking for suggestions.

Hi Willie,

Most of the sprays provide pretty weak protection. In an outdoor environment
where rain, fog, and condensation are very likely, I'd suggest a conformal
coating. If nothing on the board is getting hot (no heatsinks)...

I use Dow Corning 1-2577. This is a thick silicone-based conformal coating that
is totally resistant to water and most solvents, and works over a very large
temperature range. You paint or dip the boards in it. It's clear, so you inspect
parts through it. It's soft and rubbery, and can be easily removed if you need
to make repairs.

If you want something cheap, you can also used paraffin. Melt the wax, and paint
or dip the boards in it. It too is clear, and easy to remove if necessary. The
main drawback is that it melts if anything on the board gets hot.
--
Obsolete (Ob-so-LETE). Adjective. 1. Something that is simple,
reliable, straightforward, readily available, easy to use, and
affordable. 2. Not what the salesman wants you to buy.
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com<http://www.sunrise-ev.com>
The Sunrise EV2 Project<http://www.sunrise-ev.com/>
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Re: spray on PC board protectant

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In reply to this post by Electric Vehicle Discussion List mailing list


On 05/08/2017 12:44 PM, Lee Hart via EV wrote:

> Willie via EV wrote:
>> I'm in the process of testing a bunch of very grungy looking miniBMS cell
>> modules. The good ones, I'd like to spray with something to make them
>> more
>> weather resistant. Looking for suggestions.
>
> Hi Willie,
>
> Most of the sprays provide pretty weak protection. In an outdoor
> environment where rain, fog, and condensation are very likely, I'd
> suggest a conformal coating. If nothing on the board is getting hot (no
> heatsinks)...

The miniBMS units have two large SMD resistors that dissipate up to 0.5
amps of current while top ballancing, and get quite hot to the touch
when doing so.  No heat sinks on them however, so I don't know if that
would be "too hot" or not.


>
> If you want something cheap, you can also used paraffin. Melt the wax,
> and paint or dip the boards in it. It too is clear, and easy to remove
> if necessary. The main drawback is that it melts if anything on the
> board gets hot.

The resistors would definitely melt wax.

Jay
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Re: spray on PC board protectant

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Jay Summet via EV wrote:
> The miniBMS units have two large SMD resistors that dissipate up to 0.5 amps of
> current while top ballancing, and get quite hot to the touch when doing so. No
> heat sinks on them however, so I don't know if that would be "too hot" or not.

4v at 0.5a is 2 watts; that's a lot for a surface-mount resistor. In general, I
think it's a bad idea to use surface-mount for hot parts. If you don't mind
replacing the resistors, I'd rather use a leaded 5-watt resistor.

--
Obsolete (Ob-so-LETE). Adjective. 1. Something that is simple,
reliable, straightforward, readily available, easy to use, and
affordable. 2. Not what the salesman wants you to buy.
--
Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com
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Re: spray on PC board protectant

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The MiniBMS bypass resistor is a 5w/4.7ohm power resistor (cement type with axial leads). SMD (surface mount device) was probably meant to describe the other devices on the board.   The large resistor on the MiniBMS (the version I've worked with only has one) gets hot in use, so spraying a coating on it is probably not a good idea.
Tom Keenan

> On May 8, 2017, at 2:10 PM, Lee Hart via EV <[hidden email]> wrote:
>
> Jay Summet via EV wrote:
>> The miniBMS units have two large SMD resistors that dissipate up to 0.5 amps of
>> current while top ballancing, and get quite hot to the touch when doing so. No
>> heat sinks on them however, so I don't know if that would be "too hot" or not.
>
> 4v at 0.5a is 2 watts; that's a lot for a surface-mount resistor. In general, I think it's a bad idea to use surface-mount for hot parts. If you don't mind replacing the resistors, I'd rather use a leaded 5-watt resistor.
>
> --
> Obsolete (Ob-so-LETE). Adjective. 1. Something that is simple,
> reliable, straightforward, readily available, easy to use, and
> affordable. 2. Not what the salesman wants you to buy.
> --
> Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com

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