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Topic: Whats the max external temperature a single cell lipo can take? (Read 1 time) previous topic - next topic

Seedler

Hi,

I'm wanting to shrink wrap a small board and single cell lipo with glue lined shrink wrap.

I'm worried about the heating needed for the shrink wrap.  What is the max external temperature a lipo can take?

If I use a temperature of 180 degC it shrinks to size within 30 seconds.  If I use a temp of 100 degC, it takes three or four minutes.

Is it best to do it fast with high heat, or slow with low heat?

Thanks for your help,

Dee.

Seedler


MarkT

Hi,

I'm wanting to shrink wrap a small board and single cell lipo with glue lined shrink wrap.

I'm worried about the heating needed for the shrink wrap.  What is the max external temperature a lipo can take?

If I use a temperature of 180 degC it shrinks to size within 30 seconds.  If I use a temp of 100 degC, it takes three or four minutes.

Is it best to do it fast with high heat, or slow with low heat?

Thanks for your help,

Dee.
Definitely fast with high heat, then as soon as its shrunk chill it with cold air.  That way the depth
of penetration of the high temperature will be much less.  You could pre-chill the cell in the fridge first
for extra safety.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

Seedler

Definitely fast with high heat, then as soon as its shrunk chill it with cold air.  That way the depth
of penetration of the high temperature will be much less.  You could pre-chill the cell in the fridge first
for extra safety.

Thanks, I'll give that a go.  Would you hit it with higher than 180 to get it to shrink faster, or leave it at that?

Cheers,

Dee.

Boardburner2

There is a low temperature shrinkwrap that manufacturers use to make up lipo packs.

Works around 80 C.

Google should find some.
The glue lined stuff is not used, it retains heat much longer until it sets.

Seedler

There is a low temperature shrinkwrap that manufacturers use to make up lipo packs.

Works around 80 C.

Google should find some.
The glue lined stuff is not used, it retains heat much longer until it sets.
The stuff I have will shrink at 80 C, but because its glue lined it takes a very long time.  I need it to be waterproof, which is why I am using the glue lined stuff.  I'm worried that the continuous 80 C heat over a long period would be more damaging than shrinking it fast with a high heat.

Any opinions?

Cheers

raschemmel

I don't think shrink wrap = waterproof. You may need to use silicon sealer or paint it with the blue PVC cement sold in H/W stores.

Boardburner2

How about flexible epoxy potting compound and dip it.

If you go the heatshrink route make sure the battery is discharged before you try it.

Noobian

The epoxy used for float sensors sounds like a good idea for waterproofing.

btw, what method are you using for heating? heat gun? butane lighter?

Boardburner2

The epoxy used for float sensors sounds like a good idea for waterproofing.
That,s probably too hard.

Lipo's 'breathe' over the charge discharge cycle although it only noticeable on the larger cell stacks.

polymorph

I cannot find the link now, but it seems to me the maximum temperature for Lithium Ion and LiPo cells is either 160C or 140C, above that damage to the cell occurs. Some types of Lithium Ion cells may fail spectacularly when raised above this temperature.
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Noobian

@ Seedler

How much waterproofing do you need? 1M?, 2M? or 6m? or do you need only water resistant or spash/rain proof?
What is your battery size/shape?


Note: you can always place your battery inside a PVC fitting to make it simple waterproof, or you can place it in a small jar/pill bottle and use a rubber O ring to seal it.
This way you can make sure only holes for the wires coming out of the enclosure need to be glued/epoxy and no need to worry about damaging battery. + you can always unscrew the lid/cap and remove the battery whenever you want. If the battery is a 18650 then a 20mm pipe will be good.


can you describe your project to us, and maybe we can offer a better solution. :)

Seedler

Sorry I'm only getting back now. 

This was for a small data logger project for fitting to a prawn.  Pcb and batteries are about the size of my thumb.  The setup needs to be very small and flexible, which is why I'm using heat shrink.

I ended up using a heat gun at 300C.  It shrunk it in a matter of seconds, then I blew cold air on it.  Before cooling it down I clamped the edges with plyers to waterproof.

It didn't seem to effect the batteries in any way.

Cheers,

Damien.

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