# Powering up several devices from one charger

I need to power up 4 peltier elements (at 12vdc, approx 50W) and 2 fans( at 12vdc).

I was wondering whether a charger(like that of a laptop/mobile) that supplies 12vdc for a single device will power all of these devices up if I connect them in parallel?

If not what kind of device (preferably cheap) should I go for powering these devices?

At 12 V DC, 50 W means that it will draw 50 / 12 = 4.17 A. Multiply by 4 and you get almost 17 A. Let's provide 1 A for both fans. This means you'll need a power source that can supply 12 V at 18 A (a total of 216 W output power).

A laptop charger usually supplies 19 V at 3 to 5 A. So it is useless.

If you can get one, a computer PSU may be good for this. Just make sure the current on the 12 V rail is greater than 18 A and add a dummy load (resistor) on the 5 V rail to get it working.

Another solution is to buy from your favorite electronics parts supplier a SMPS kit with those ratings (12 V @ 18 A output).

• Does the 18A minimum limit has anything to do with permanent conduction of the switched output of the DCDC converter after the rectifier in the PSU? May 31, 2014 at 13:53
• Actually, it is not obvious (to me) that the devices must be connected in parallel. Jun 1, 2014 at 0:28
• @WhatRoughBeast when I said "devices" I was referring to the fans as well. You can't connect a fan in series with a Peltier element. Jun 1, 2014 at 8:30
• Sometimes PSUs have multiple 12V rails, that can work too but you'll need to do a bit of calculation to balance everything. Each rail will have a lower rated current but the total can be pretty high. Jun 1, 2014 at 12:51

As Cornelius has pointed out, a typical charger simply does not have the current you need, but other options exist. eBay is a good source of power supplies. You can get what you need for ~ \$20 (US). Also note that, depending on what's available in the way of power supplies, you can connect your elements in combinations of serial/parallel, to use either 12 volts/16 amps, 24 volts/8 amps, or 48 volts/4 amps. I'm ignoring the fan loads here, although I would strongly recommend a fan per element, total 4 rather than the 2 you have specified.

That said, you may not be able to drive your elements with a full 12 volts. Unless you have a proper heatsink on your cooler, with proper airflow, the Peltier will overheat and may self-destruct. So make sure you have a temperature sensor on the hot side of your elements, with the circuitry to cut off your power supply if the element gets too hot.

• Earlier I was thinking of cascading the elements, but after this I don't think I would cascade them. What kind of arrangement and power supply you would suggest so that I don't have to worry about installing temp. sensors May 31, 2014 at 19:02
• Power supply is irrelevant. The concerns are thermal. As I said, you need an adequate heat sink to ensure that your hot sides don't get too hot. If you can guarantee this, you don't need a sensor. So, for instance, if you have a fan blowing air across your heatsink (recommended) you need to be able to guarantee that the fan will not fail or that somebody doesn't block your airflow. If you cannot guarantee this, without a sensor you may lose your coolers. Jun 1, 2014 at 0:27
• It is not irrelevant because if I operate my elements at low power than I would have to deal with lesser heat! That is the only reason I posted the previous comment. Jun 1, 2014 at 4:03