Combine 2 battery chargers to charge one battery

Discussion in 'General Electronics Chat' started by sdowney717, May 22, 2016.

  1. sdowney717

    Thread Starter Well-Known Member

    Jul 18, 2012
    I have a Minuteman 320 Pro UPS I use for the boat PC and some other things.
    I actually have an on-off-on switch so this UPS can power all boat outlets if needed. I will leave that circuit as is, but thinking I can run the UPS as a UPS for the PC.

    I modified the UPS by adding an internal cooling fan and hooked up to the boat house batteries. It works fine, with the extra fan it puts out almost 400 watts.
    This UPS sits next to my 3000 watt inverter, so just a short big wire paralleled off the 3000 watt inverters lugs gives it DC power.

    My question, I would like to run it as a true UPS, so connect the minuteman 320 AC input into my boats 120vac grid. Would be more convenient and seamless transparent, no turning the UPS on as it would always be on.

    That would mean the UPS will attempt to charge the boat's big batteries.
    I also have the onboard boat charger. So they would then be joined together, both outputting into the boat batteries, would that burn out the UPS? Or would the DC charge voltage off the UPS just fall to the level of the big charger ? I had them joined earlier like this, but don't know long term what would happen. The PDF says it is fully circuit protected.

    "Overcurrent and short circuit protected, latching shutdown on overload"
    Which I think it would just turn off if it got too hot, it would think it's 12vdc battery had an internal short idea.

    Other idea is disabling the charge ability of the UPS by using a diode which would block current flow out and allow current flow in.
    Voltage drop of 0.5, the UPS would still work, Would a Schottky diode be better?

    Ideas about this?

    pdf of device

    Pics of my mods. I made a remote on - off switch too.

    Another reason to do this, it has the beep noise every few seconds when the AC input is off and it is using the battery. I could break the beeper. under the kitchen cabinet, it is not too loud of a beep.
  2. sdowney717

    Thread Starter Well-Known Member

    Jul 18, 2012