What is the practical difference between Peltiers of different rated current, e.g., TEC1-12706 vs TEC1-12703?

Question

I'm no expert, but from playing with Peltier modules I understand that, for a constant temperature difference between the two sides, they behave almost as a resistive load, with an almost linear relationship between input voltage and consumed current.

So, assume I have power supply flexibility to run the things at any voltage I like. That means I can make them consume any amount of current I like, below the max. So a TEC1-12706 is rated for max 6 amps, and a TEC1-12703 is rated for max 3 amps. But if I run a 12706 and 12703 at different low voltages so as to make them each consume the same total watts, will they perform differently?

From what I understand, when you run an individual Peltier module at any lower voltage than its maximum voltage, two differences are:

1. It is more efficient, in that it produces a lower ratio of waste heat compared to the useful heat pumped thru it.
2. It can only sustain a smaller temperature difference between the two sides.

Do I understand those two points correctly?

If so, still I can't understand what current rating of Peltier I should choose. There must be a difference, otherwise they wouldn't bother to make all the different ones.

Basically, in practice, assuming I have complete choice of input voltage, when are higher-current modules better, and when are lower-current modules better?

Answer 1

I am wrestling with the same question. From comparing data sheets for different current ratings for the same line of elements I can't find much difference in behaviour, except that you can push higher rated devices to higher currents. On lower currents they appear to behave approximately the same. So number and types of junctions is important for currents well below max, and maximum current is not important in that region. My guess so far...

Answer 2

Looking at the datasheets for e.g. 12705[1] and 12715[2], the only difference I can see is in Imax.

Performance curves for both are identical:

Where Th=27ºC is the ambient temperature on the hot side (this is intended to be a cooling device), and C.O.P is coefficient of performance: cooling power Qc/Input power (V × I).

So the only difference seems to be the maximum cooling capacity. With higher "rated" modules (higher number last 2 digits, e.g. 15 in TEC1-12715), one can ramp up the current to get more cooling (though the device will be less efficient) than one would be able to with lower rated modules