Encasing a lipo battery in hot polymer

Components & Accessories Power
1

Hi all,

I’m working on a low power prototype environmental sensor that would be encased in a polymer as part of a larger piece of equipment. The prototype I built uses a lipo battery (this one https://www.sparkfun.com/products/13854) that should be able to power it for at least a year.

The sensor would be potted in an electronics compound and then glued to the larger equipment. Hot polymer (110C) would be poured over the for the larger equipment, and the mold would be held at 100C for at least 16 hours of post cure. The sensor would not be powered during the cure cycle.

The datasheet for the battery (http://cdn.sparkfun.com/datasheets/Prot … 1.0ver.pdf) indicates it can handle 400C for 30 minutes (7.4), but doesn’t say what the long term temperature limit is. I have two questions:

  1. Will the battery survive this process?

  2. What happens if it doesn’t? Will it catch on fire/explode?

Thanks!

2

I find the specs listed in that datasheet dubious…I can’t imagine it surviving 400c

It might survive 110c-100c, if not it would likely put off fumes of the gases listed in the MSDS https://cdn.sparkfun.com/datasheets/Pro … 603443.pdf

I would suggest emailing the manufacturer to confirm/ask, however https://www.dtpbattery.com/a/Rectangula … icate.html

3

  1. Will the battery survive this process?

  2. What happens if it doesn’t? Will it catch on fire/explode?

1 - I doubt that it would survive. At the very least you will damage the battery’s ability to hold a charge / recharge, or greatly shorten it’s useful lifetime.

2 - it’s possible the battery will catch fire or explode, I’d suggest testing multiple batteries where you can deal with a possible fire.

The battery might not catch fire or explode at 400C for 30 minutes but that will most likely destroy the battery.

Give it a try and let us know but be careful!

4

Can you use a different encasing chemistry - have you looked at some of the stuff Henkel offers. We usually use epoxy-based or silicon-based and cure in oven at temps around +70C (the lower the temp, the longer the curing time). But that way it is more compatible with our electronics. - just a thought