Power Supply Overheated & Exploded when Powering a Peltier Cooler! Please Help!!

I am currently working on a project and making a small dehumidifer using peltier modules. I bought the modules from Sparkfun (Imax:7A, Umax:15.4, Qmax: 62.2W, Tmax: 69C, 1.7Ohm) and used 12V/6A power supply to power the module (just directly connected). Of course I attached a large heatsink on the hot-side using thermal paste and PC fan to remove the heat from the module. At the beginning it seemed like it was working fine, but after about 2 hours of operation, the power supply suddenly exploded!! :sob: Fortunatley the explosion occured inside the plastic casing, so there was no damage except on the power supply itself, but the power supply was super hot right after the explosion so I guess the overheating was the cause of this explosion.

Was I powering the peltier module in a wrong way? And is there any better way to power it without worring about overheating the power supply?? ::)

I would appreciate any suggestions.

12V/6A power supply

Post a link for the P.S.

Are we to understand there was only one 7A peltier module powered by that supply ?

7A module fed by 6A supply? I am thinking there may be something in that!

Weedpharma

weedpharma: 7A module fed by 6A supply? I am thinking there may be something in that!

Not necessarily. Maybe it was just a really humid day. SARCASM

7A module fed by 6A supply?

6A on a good day, most likely. Keep in mind that manufacturers tend to be optimistic in rating their products.

Any way you cut the cake, that setup is marginal. (maxed out). Standard design practice is load does not exceed 75% of source capacity.

mutyo051026: I bought the modules from Sparkfun (Imax:7A, Umax:15.4, Qmax: 62.2W, Tmax: 69C, 1.7Ohm) and used 12V/6A power supply to power the module (just directly connected).

I often like the idea of having adequate head-room, and enough grunt to handle the extreme situations.

So, if IMAX of a device is 7 Amp, then go with a 10 Amp supply, or even higher capacity.

Going with 'just enough' or not quite enough can potentially be problematic.

weedpharma: 7A module fed by 6A supply? I am thinking there may be something in that!

Weedpharma

Certainly is.

It is quite easy to exceed thr ripple rating of the filter caps that way.

|348x500

That works. ;D

And finally, there is no "wrong" way to hook up a Peltier device. It will move heat from one side to the other no matter how it is hooked up. If the side you wanted cold was cold, then you hooked it up correctly.

Paul

The supply might have been rated for 6A, which as we all have all pointed out is an amp short, so it was being overloaded. But a plastic case will keep in the heat and even 6A would cause the power supply to overheat and the capacitors to explode. So just a more capable supply is not simply the answer. You need ventilation and maybe forced air cooling, it depends on the power supply.

There is no ripple current on a peltier device it is a steady current. But there is a maximum temperature difference that such a device can stand across it before it breaks down and turns into a heater.

Hi, Have you tested the peltier module to make sure it has not gone short circuit. You have to measure the temperature on the hot side of the peltier to make sure it does not get near the Tmax of 69C.

Did you measure the current flowing through the peltier module.

How much heatsink compound did you apply, the usual tendency is to put too much on.

Tom... :)

Grumpy_Mike: There is no ripple current on a peltier device it is a steady current. But there is a maximum temperature difference that such a device can stand across it before it breaks down and turns into a heater.

The ripple occurs during the charging phase of the smoothing cap, more load the greater the effect. When PSU go bang it is often the electrolytic.

EDIT

Off topic perhaps but i came across this a while back.

http://m.eet.com/media/1055127/PowerTipSerieslist.pdf

May be of interest to some.

Paul_KD7HB: And finally, there is no "wrong" way to hook up a Peltier device. It will move heat from one side to the other no matter how it is hooked up. If the side you wanted cold was cold, then you hooked it up correctly.

Paul

Yes, but there is a "better" way. The connections to the external wires are subject to corrosion if they get moisture on them. It is better to wire it so that side is the hot side and the other side gets the condensation. The red and black wires on most Peltiers show you the correct polarity to achieve this.

Look up “constant current regulated power supply” and aim to find something which can deliver a current-limited 0 to 6 Amps at whatever Voltage that happens to be at the time. OFF or 12V ON is no good with Peltiers because when both sides are at similar temperature (both sides hot, for example), the thermoelectric voltage is nil, the series resistance of the cooler is pretty low, and 12V constant voltage might try to put “a lot” of Amps through it. Unless your supply burns out first. Comments here extolling bigger power supplies are not going to be good for your Peltier. Either make or buy a current limiting device, which can be as crude as a 6Amp rated npn transistor on a fat heatsink with appropriate input to its base, but there probably are better ways.

Why not use something like this:
Constant Current Electronic Load.jpg

By connecting a load between “Vin” and a Vcc (12V or whatever) instead of the DUT connection,
the mosfet will SINK the load current based on the control voltage on the output of the voltage follower.
The current sense resistor value may need to be adjusted to suit the application such that the voltage across the current sense resistor Vcurrent sense < 5Vdc.

Rcurrent sense = 0.50 ohms/40W (two 1 ohm/20W resistors in parallel) would yield 3V @ 6A.

raschemmel: Why not use something like this:

Efficiency. With a multi-amp load like a Peltier that FET's going to get roasty-toasty warm without a substantial heat sink. A switching circuit will run far cooler.

Isn't that more a function of RDS(on)

No - because the FET is running in it’s linear range and isn’t saturated.

It will get very hot…

regards

Allan