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Photo of damaged Peltier module

This is a 12706 module. Running in a 15 minute "on", 2 minute "off" cycle for about 3 days. I have used it another maybe 4 days max since I purchased it. So definitely nowhere near its rated life cycles.

Using 12V power supply. Clean. Pulling about 4A. Proper heat sinks on both sides. Good stable temperature differential for 3 days and then suddenly, temperature differential went away. Hot side sink was around 105°F. Cold side sink would form ice if I let it run straight without the 2 minute "off" cycles. I didn't want ice. Sorry, didn't measure temperature here, but air temperature on cold side was 45°F, when room temperature was around 75°F.

I do have to confess that I missed putting foam around it and it did have condensation and some ice around it.

My only thought is that somehow some water got in through the original RTV silicone coated heavily around the edges (as purchased, not applied by me), causing short circuit inside the module? I didn't see any cracks in the silicone before I opened this module up. It was super tight.

Any other thoughts? What else causes Peltier premature failures like this?

Thank you!

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  • \$\begingroup\$ Peltiers are very tricky to use properly. Did you use both adequate and non-excessive mounting pressure? What method did you use (torque measurement, engineered springs, etc) to measure and ensure even mounting pressure? What sort of drive mechanism (current or voltage controlled)? What was your temperature differential? What temperature did your hot side reach and what was your peltier rated for? \$\endgroup\$
    – K H
    Commented Oct 20, 2019 at 20:38
  • \$\begingroup\$ Hot side sink was around 105F. Cold side sink would form ice if I let it run straight without the 2 minute off cycles. I didn't want ice. Sorry, didn't measure temperature here, but air temperature on cold side was 45F, when room temperature was around 75F. I was using this setup: amazon.com/dp/B00M1BNXSW/ref=cm_sw_r_cp_apa_i_AJmRDbG7FJTV8 \$\endgroup\$
    – Silver Silver
    Commented Oct 20, 2019 at 20:50
  • \$\begingroup\$ And what about mounting pressure? The short circuit you show could have been caused by a chunk of bismuth flaking off due to uneven pressure rather than by moisture. If you use screws to achieve mounting pressure, it's important to check torque by doing them up with a torque screwdriver, preferably in stages, similar to when you torque lugnuts on a car tire. \$\endgroup\$
    – K H
    Commented Oct 20, 2019 at 23:58
  • \$\begingroup\$ Thanks for the idea on using a torque screwdriver. I'll try that. I did use a manual hand screwdriver and made sure I didn't overtighten the screw on the heatsink which pressed uniformly against the surface of the peltier module. Thanks. \$\endgroup\$
    – Silver Silver
    Commented Oct 21, 2019 at 0:56

2 Answers 2

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Peltiers are difficult, and that cycling may have not been right. When you say 'about', without knowing the curves and how it's set up, that might have been too much- 48watts from your numbers, meaning a passive heatsink needed about 480 sq inches.

Also appears to have shorted between first row/column and second.

I always re-potted mine with blue RTV (electronic) after sealing it to a surface.

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  • \$\begingroup\$ Hi J, if you're referring to the hot sink temperature 'about' the range was 95F to 105F. Since I was running peltier over 3 days, the room temperature fluctuated from 68-80F it was causing the hot sink temperature fluctuation. \$\endgroup\$
    – Silver Silver
    Commented Oct 21, 2019 at 0:24
  • \$\begingroup\$ Hi J, .. are you positive that the black marks are shorted? .. only reason I can think of condensation .. thanks for the confirmation on idea on repotting with RTV. I'll give that a shot! Thanks! \$\endgroup\$
    – Silver Silver
    Commented Oct 21, 2019 at 0:45
  • \$\begingroup\$ To be honest, that's appears carbon. I'd expect a bismuth 'explosion' to look more metallic sheen, but... looks can be deceiving. I'd go with the simplest explanation- water infiltration- but even then that would be rare in such a short period of time. Your cycle times don't seem obscene and there really wouldn't be that much time for heat to soak in. No, on second thought, I'd consider orientation too and make sure the wires are down next time. Just in case. Bad solder joint inside too could cause heat and arcing. Look for pitting on the surface. \$\endgroup\$
    – J.Hirsch
    Commented Oct 21, 2019 at 1:44
  • \$\begingroup\$ Hi J, my wires were facing up, so hoping that was the culprit in allowing some water to squeeze through perhaps! There could be microscopic pitting, which was hard to see, nothing apparent. Thanks! \$\endgroup\$
    – Silver Silver
    Commented Oct 21, 2019 at 2:09
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Running in a 15 minute "on", 2 minute "off" cycle for about 3 days

Peltiers are prone to rapid failure due to thermal stress if temperature cycled.
I don't know what the cycle life is for such deep stressing as you will have been giving it. The number of cycles wasn't large but the thermal cycling would be extreme.

3 days x 24 hours x 60 minutes / (15+2) = about 250 cycles.
With ice on the cold side, when you turned it off the whole device probably tended to approach 32F, then back to 105, then ... .

Do you have a datasheet for the Peltier?

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  • \$\begingroup\$ Thanks Russell. I don't have datasheet. Used the generic 12706 peltier from Amazon. I do see your point. I'll change the circuit to reduce the voltage instead of complete shut off. The only purpose of turning it off was to let the ice thaw off, since the cooling reduces drastically if the cold side sink is iced up. Thanks! \$\endgroup\$
    – Silver Silver
    Commented Oct 21, 2019 at 17:24

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