Can i use 2 DC power supplies together?

Discussion in 'The Projects Forum' started by GARYN, Sep 5, 2009.

  1. GARYN

    Thread Starter Member

    Sep 4, 2009
    I need to make a new control panel that contains alot of DC coils and feeds many external DC solenoids. I have most of the parts in our stores but the DC power supplies that i have is not big enougth to feed the circuits. Is it advisable to use 2 of the supplies that i have in the same panel or order 1 that is electrically big enougth. i.e if i was to use 2 would i need to common up the 0volts to avoid damage caused by accidently feeding a coil with the positive of one suppply and the negative of the other? Any views would be appreciated.
  2. SgtWookie


    Jul 17, 2007
    Order a single supply that's large enough.
    If you try to connect two supplies in parallel, they will "fight" each other, generating heat and wasting power.
  3. bertus


    Apr 5, 2008

    @ alberto:
    The solution you give is partly true.
    When the voltage differ a little one power supply ( with the highest voltage ) will deliver more current than the other.
    This unbalance will probably burn one of the powersupplies and then the other.

  4. Damo666


    Aug 25, 2009
    I run some high power radio equipment using a 13.8v 10A power supply paralled with a 13.8v 25A power supply by using steering diodes. Been doing this for over 6 months without a problem.
  5. GARYN

    Thread Starter Member

    Sep 4, 2009
    Thanks everyone for the advise but instead of connecting both in parallel how about using them both independently i.e one to feed the coils in the panel and the other to feed the external solenoids (to split the load). Or is this a bad idea incase somebody in the future takes a negative feed from one and a positve from the other to feed the same load by mistake...would this destroy one or both supplies?
  6. Wendy


    Mar 24, 2008
    Yes, you can split the load between two power supplies without any issue, just be sure to track how many amps each is providing. This is routinely done in a house for it's line currents. Think a breaker or fuse for each set of controls.

    Alberto, the steering diodes help, but one supply is still going to be loaded more than the other, so one is going to be more loaded and stressed than the other. Guess which one gives up the ghost first? The OP didn't mention power supply specs, with modern power supplies with good protections are less likely to fail catastrophically than a simple unit.

    Part of the way to succeed in paralleling power supplies is to tweak them very close to each other, within a mv or so. Since individual power supplies will react slightly different there will still be an imbalance. It is better just to split the loads, the consistancy and reliability goes up.

    I recently bought two 24VDC at 6.5A that I'm thinking of putting in series for 48V, for a variable bench power supply. I'm still thinking about the kind of regulator I want to use for something like this.
  7. baberb1984

    New Member

    Apr 23, 2014
    For paralleling two DC power supplies for 2x current:
    Yeah I agree, reliability is just better if you separate the two power supplies into two separate circuits, and just try to balance the loads across the two circuits. Since I usually ground the negative DC voltage, and/or directly connect the DC common between the two supplies, there is no problem with feeding a load with the + from one DC supply with the - from the other supply

    For series connection of DC power supplies for 2x voltage:
    Putting supplies in series for double the voltage, you want a reverse-biased diode across the + and - for each supply (cathode to +, anode to - of the same supply). You do this in case they don't come on at the same time, or if one is off, the diode blocks the other supply from frying it with reverse voltage. It's not a big deal, just a bit of extra precaution; The diodes are not normally conducting, ever, and would only be conducting if there is a problem - thus routing current around the supply that is being protected.

    You can do this for any number of DC supplies, theoretically. Just size each diode for the voltage of all but the power supply it's biasing, and the current of the complete system. Remember the same current has to go through all power supplies. So if you have 10 10A 24v DC power supplies in series for a total of 10A @ 240vDC (wow), you'll want 10 diodes that can withstand at least 216vDC reverse voltage and 10A forward current.
  8. wayneh


    Sep 9, 2010
    Whoa, you just resurrected a 5-yr old thread. I doubt the OP is still waiting for advice.