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I'm designing a monitoring system for plants based on a lithium-ion battery and an ESP8266 (Adafruit Huzzah board). Due to the application, water may come in contact with the battery and/or electronics.

I'm considering a potting of the whole system except the usb connector for recharge purpose. The curing is producing heat than cannot create problems with the electronics/battery.

I found polyurethane based product : Electrolube UR5634RP250G (Farnell : 2476085). Do you advice this kind of solution ?

If you have cheaper solution, that could be nice too ;)

What about the thermal dissipation ? Are those kind of product corrosive for electronics ?

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    \$\begingroup\$ I believe it is not advisable to fully pot a lithium battery. If it should vent, the potting compound may prevent gas from escaping. This can cause high pressure to develop which may ultimately give rise to a high-pressure rupture. A high pressure rupture could be much more hazardous than venting. Also, the cells can swell slightly mechanically. I am not sure if it is safe to prevent this swelling. \$\endgroup\$ – mkeith Feb 7 '17 at 23:30
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    \$\begingroup\$ Looks OK. Spec sheet here. Looks bearable. Would not greatly add to ruptre pressure if thin coat used. NOTHING is truly waterproof but a void free coating of a compound with low water solubility presents mainly vapour at surface. They say UV resistant but do not trust it. It probably has an inhibitor but ALL epoxies are inherently UV unstable so avoid long term direct daylight exposure. || Be careful not to wick compound into connectors as can happen. Can insulate contacts. \$\endgroup\$ – Russell McMahon Feb 8 '17 at 1:52
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    \$\begingroup\$ Therm con in spec sheet = 0.2 W/m/K = fine. Corrosion level almost certainly low BUT you can ask Electrolube directly what compounds are liberated on setting and effects. || I said "epoxy" above but same applies to RU resins due to C-C bonds. Silicone rubbers are more UV stable. \$\endgroup\$ – Russell McMahon Feb 8 '17 at 1:54

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