# Peltier Cooler connected to Power Supply, is this configuration safe?

1. Apr 26, 2012

I am building a Peltier Cooler with the circuit diagram below. The power supply will be a battery, but for testing purposes I am connecting it to a stationary power supply.

http://dl.dropbox.com/u/10419947/circuit.png

I suspect that the peltier coolers which are rated at 30A will draw as much current and power as possible once I switch the power supply on, potentially destroying the supply itself even though I do not intend to deliver anything above 10 A. Are my fears warranted? I prefer not to try my luck as the power supply costs a fortune to replace.

2. Apr 26, 2012

### Staff: Mentor

➤ Some power supplies have a current limiter so you can set the max current.

➤ Do you have manufacturer's technical data that indicates how many volts the Peltier devices need for 10A?

3. Apr 26, 2012

### vk6kro

You have the coolers in series, so each will get 3.5 volts maximum.

You can estimate the resistance of the cells by working out the resistance under full power.

R = E / I so R = 14 volts/ 30 amps = 0.4 ohms. (This is just an estimate because these devices may not be linear. I tried a lower powered Peltier and it was linear, though.)

So, if you just put 4 of these in series across 14 volts, you would get a current of 14 volts / (4 * 0.4 ohms) or 8.75 amps. So, the current switched by the MosFet should be less than this.
Much less than their 30 amp rating.
So, the Peltiers should be OK.
You could put a 10 amp fuse in series with the Peltiers to make sure the power supply is not overloaded.

Your symbol is for a NPN transistor.

Peltier devices get hot on one side and cold on the other side, so you have to have a heatsink on the hot side to carry the heat away.