Power Supplies

by Bobby Barr

Power Supply Advantages:

  • Clean Power
  • Can build very inexpensive
  • Can purchase ready to use

Power Supply Disadvantages:

  • Need a 120V source to power them
  • Best if you have a case or good way to transport

Here are some things to consider when choosing your power supply:

  • Output voltage– What voltage does your chargers need?
  • Total Power– How many watts and amps does your power supplies need to produce?
  • Price– What do you want to spend?
  • Size– Does it matter how big they are, or do you need some compact?
  • Reputation– What do you know about the store or seller you are purchasing from.

Output Voltage:

Determine the output voltage by looking at the specs on your charger. The most common are 12v, 24v, 36v or 48v. If you haven’t bought a charger yet I would recommend 24v as a good all around voltage.

 Total Power:

The total amount of power that your power supplies will need is determined by the amount that you charger/chargers can pull. Take this amount and multiply it by a factor of 1.3. Here I will use an example of powering 2 chargers. One being an 600 watt and the other being a 400 watt.

 Ex: 600 watts + 400 watts = 1000 watts

1000 watts X 1.3 = 1300 watts 

This example shows that if you want to power these two chargers, your power supply will need to output 1300 watts. Use 1300 watts as a minimum as the only real downside to having more watts is more money to purchase, room to store and weight to carry.

 Now that you have determined your total power required you will need to figure out your configuration.

For a 1300 watt system that runs on 12 volts you would either need a single power supply that outputs 1300 watts, or run multiple power supplies in parallel to achieve the 1300 watts.

 Ex: 650 watts @ 12 volts & 650 watts @ 12 volts in parallel = 1300 watts @ 12 volts

1300 watts ÷ 12 volts = 108 amps

 If the 1300 watt system was going to run on 24 volts, you may run two 650 watts power supplies in series.

 650 watts @ 12 volts & 650 watts @ 12 volts = 1300 watts @ 24 volts

1300 watts ÷ 24 volts = 54 amps

Take note of the 108 amps required on 12 V compared to only 54 amps when ran on 24 V.

Price:

Once you realize how much power your system is going to require it is time to determine the cost. Here you have three common options:

1) Purchase from a hobby supply store

  • The most expensive option.
  • The easiest, most ready to use option.

2) Buy used server power supplies and build yourself

  • The most cost effective method.
  • Requires the most amount of work and possibly risk.
  • The easiest to customize.

3) Purchase from a store or person that converts server power supplies.

  • Priced somewhere in the middle.
  • Best of both worlds.
  • Risk that the person that converted it didn’t get it right.

Size:

Size may not be a large factor in your equation if you your setup is going to be stationary. However, if your charging setup is going to be transportable then it may be a major factor. Some of the power supplies that are available are rather large, heavy and hard to find a good way of mounting in a case. Be careful here as there are some 300 watt power supplies for sale that are larger and heavier than 600 watt models.

 Reputation:

I must include this one in this list. The fact is to always do some research when purchasing electronics about the place or person you are buying from. At some point all products have issues. So check reviews to see how those situations were handled. There are good and bad sellers whether you are buying from a retail show or online auction site.

 Case:

Depending on your needs and desires this may be irrelevant or highly important. There are some amazing charging cases that people have done. This is a project all to itself for some. I have even seen Plexiglass and neon lights as well as cooling fans, fuses and switches. The choice is yours and there really isn’t a “right” and “wrong” here. If you decide to bury your power supplies under a tray or Plexiglass lid, be certain to use a fan for a constant airflow.

Summary:

Whether you decide to purchase or build your charging power system, you need to be aware that not all power supplies are designed to be ran in parallel. Check with the seller to be certain prior to purchase. When running the supplies is series, you will need to isolate the ground of one of the units. This is explained well in some of the following links.

Helpful Links: