How to test a Peltier module TEC1-12705 to determine if it works as intended?

Question

Background:

The module comes from a 70W mini-cooler which doesn't really cool anymore. I took it apart and got the module out, I could read the model TEC1-12705 from the module itself. The specifications can be found here.

The performance specifications are:

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Tests I've done:

• Tested voltage at the power supply and it outputs DC 12V to the module connectors.
• Disconnected the module and measured resistance across it at a room temperature of 24º Celsius, which resulted in an average resistance of 120 Ohms .
• Connected the module to 11.30V DC from a power supply with a max output of 5A.
  • Using Ohms law the current flowing is 0.094 amps, and the power supplied to the device 1.06 watts.
  • Using and ammeter connected in series with the module and the same power supply I get a reading of 0.02 amp, which starts decreasing as soon as I close the circuit.
• After the last test now the resistance is 150 Ohms average.

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My conclusion:

The module is toast now. I don't know how these things fail, but:

• I never could get a reading of 2.4 Ohms resistance from the module.
• The increasing resistance indicates to me that the module does not handle the power supply well and must be burning the cells inside.

Question:

• Would you consider buying a new module, or does it sound to you I am doing something wrong when taking measurements?

Answer 1

It's hard to fully test peltiers by 'ohming' them with a meter. In most cases when a peltier fails it is because one of the junctions cracks, and this makes it hard to drive current through the peltier and increases the resistance. Make sure both sides are the same temperature and then check, because any thermal gradient will drive a voltage through the peltier and it's not hard to generate a voltage with a high resistance meter on the output of the peltier, sometimes meters will show a negative resistance. Also try reversing the leads with the meter and see if you get the same resistance.

It sounds to me like the peltier has been damaged.

Answer 2

Peltier are (as already said) difficult to "ohm" measure as a multimeter puts out a voltage to the circuit which in turn will trigger the electron pumåing in the peltier - resulting in incorrect values.

However all modern peltier have two- PN/NP junctions wich can be measured (assuming its a single stage peltier which the mentioned one is), it will in the forward connected configuration show a pn junction, and in reverse a negative pn junction.

A bad peltier can occasionally be baked (heated up slowly until the solder joint liqifies without destroying it). The telluride has a melting point of 449°C; well above the melting point of the solder.

Note: this will only work in rare cases and ther is no guarantee it won't DESTROY some of the pn junctions..leaving a poorly effective peltier, best option is to replace it with a new factory made product.

Answer 3

Late as always, resistance increases when Pelties heats up but should never go up to 120-150Ω, high resistance is a indicator of mechanical fracturing of the semiconductor pellets or broken soldering joint, your measurements are right and you just had a bad product that broke after some usage(should last more than 200,000h), you can just buy new module of replace it.