I have recently bought TEC 12706 device from Sunrom.com; The specification says that the device can draw more than 6A current at 15.4V and internal resistance is ~2 ohms. But when I measured the internal resistance, the device shown ~6.5ohms and when I powered it using 12V PC SMPS, the device did not draw anything beyond 1.6A. I had tried connecting the device to my fully charged inverter battery (12v 120Ah) measuring a float voltage of ~13.5V. To my surprise, the device drew just over 2A max.
I was using a slightly larger heatsink with a cooling fan on the hot side and was keeping the cold side open.
- The SMPS can easily supply 10A.
- Heatsink was typically 3 times the area of the peltier device
What could be wrong in my configuration?
Datasheet: http://hackerstore.nl/PDFs/TEC1-12706.pdf
Best Answer
Thermo-Electric Cooler efficiency "is a function of ambient temperature, hot and cold side heat exchanger (heat sink) performance, thermal load, Peltier module (thermopile) geometry, and Peltier electrical parameters." And "A single-stage TEC will typically produce a maximum temperature difference of 70°C between its hot and cold sides. The more heat moved using a TEC, the less efficient it becomes, because the TEC needs to dissipate both the heat being moved, as well as the heat it generates itself from its own power consumption."
So a heat sink on the "hot side" alone isn't enough. The cold side gets cold quickly, having little thermal mass, and efficiency falls to a very low value. Also as the hot side warms up, each junction's internal resistance increases, drawing less current.
TECs are most efficient when both sides are the same temperature (and little heat is being moved.) The best overall working efficiency (in terms of pumping heat) may be up to about 13% of Imax. Beyond these currents, resistive heating losses increase greatly, and the device spends more power moving heat it generates itself.