Repurposing Server PSU For Your Charging Needs

That grey box at the top of the photo is a modular power supply unit for a rack-mounted server system. [Sebastian] decided to repurpose it as a charging source for his RC batteries. He chose this HP DPS-600PB because of its power rating, efficiency, and you can get them at a reasonable price.

This is an active power factor corrected (APFC) PSU, which he says draws 40% less current than the non-APFC variety. Since he sometimes charges batteries in the field from a generator this is a big plus. But a bit of modification is necessary before it can be used as a source.

Since this is a rack device it has a set of connectors on the back. For power there are spade connectors which mate with a fin on the rack. He soldered positive and negative leads between the spades to interface with the battery chargers. The PSU won’t fire up if it’s not in the rack, so some jumper wires also need to be added connecting three of the interface pins.

With his modding all worked out he went on to use two PSUs for a 24V source, housing them to a nice carrying case while at it.

21 thoughts on “Repurposing Server PSU For Your Charging Needs

  1. Heh that’s exactly what I tried to do a couple months ago with some scrapped server PSUs. Turns out they were scrapped for a reason :)

    This idea isn’t new – there’s a nice list of PSUs RCGroups has put together for this purpose here:

    @roboman2444 – not if they’re in parallel, which they seem to be in this case. Worst you’ll get is some kind of initial (possibly large) cross-cell current as the two packs equalize when they’re first paralleled up. Not an issue if they were discharged in parallel too.

  2. @ Elias

    Sometimes you got to watch out for the cheaper cell balancers, they simply check the cell voltage and distribute whatever current is available to the lest charged cell. I learned the hard way you still need to do the “control current / control voltage” trick on the input to certain balancers because it won’t limit current or regulate input voltage on its own. A DC lab supply set to the max series charge voltage current limited to the max charge rate did the trick for my setup.

  3. mpja dot com. Local when I was down in West Palm Beach, they have some 120W rack power supplies for $4 and shipping. I love those guys! I have several repurposed PC power supplies from them.

  4. I wished I could meet with the marketing from this company that came up with “iCharger”… its such a pathetic way to communicate “We really really thought well and long about our product” to the clients. Just name is original. Call it Grizzly if you want to, but stop this stupid iX thing… it doesnt even work for apple apple anymore, but its grown and therefore they have to stick with it.

  5. Nice hack! I like how old PSU’s get re-purposed for almost everything these-days.

    However. I *highly* doubt that charging a couple of LiPos will have any significant effect on a generator what so ever, regardless of the efficiency of the power supply.

    I assume those chargers are intended to be powered by a 12v Lead-Acid battery. One fully charged car battery should provide more than enough juice to charge the LiPos a couple of time, it’s more compact than a generator and infinitely more quiet.

    So like someone else said, this is a bit of an overkill for charging in the field.

  6. Using a generator + AC power supplies to charge small RC battery packs seems like a total waste of power and way more cumbersome than it needs to be.

    Why not just charge up a 12V SLA battery before you come and use that with a DC -DC converter to charge everything you need ? It is far cheaper and less cumbersome than the AC to DC to AC to DC that is going on with the power supply solution.

  7. why is he using APFC?
    well im no generator expert, but i do know that there are three types of generator control: manual, simple govener, and computerized(uC)

    the computer control is reserved for HUGE generators > 5000w

    the manual adjustment needs adjustment whenever an appliance is turned on and off and is usless for when you need to run two different appliances at the same time when they start and stop independantly and need constand frequency and voltage. many people destroy their equipment with these… the AirConditioner clicks off and the cellphone charger(single voltage input) gets fried by 150% voltage. no matter your reaction time, you cant save your cell charger by keeping your hand on the throttle.

    now im not 100% sure, but i think most (portable consumer) gennys use simple current sensing via SERIES RESISTOR or MECHANICAL…

    the (non-uC) govener, no matter how complex or simple gets fooled by incorrect power factor draw by appliance, causing the generator to run at incorrect RPM or even oscillate RPMs, damaging the generator engine and causing possible equipment damage from incorrect voltage and frequency. (50% or 150% can BOTH damage stuff)

    any supply that rectifies the 50/60hz and filters it before using it is ONLY drawing current during the portion of the AC waveform when the voltage is greater then whats in the filter capacitor.
    the power factor of a SwitchModePowerSupply is WAY worse then a 50/60hz transformer or 50/60hz motor, even a fridge compressor.

    the power factor corrections makes SURE the generator ONLY sees a resistive load, like an incandescent lightbulb.
    (well almost, but enough for the genny to behave)

    he is probably using the batterys for when he wants to be quiet / when the high power draw is not nessary.

    imagine building or renovating a cabin without electric, need 500w – 1000w for table saw, 250w – 750w for electric drill, and only a tiny 25w – 100w for the stereo and flourecent lights (need lights to paint indoors even in day)

    so instead of running the generator for 8 hours, he uses the genny when the powertools are needed, and runs the flourecent lights and stereo on the batterys. best of both worlds

    PS: i have seen christmas parade floats destroy a 500w home stereo and then proceed to catch fire, all the while the incandescant lights flickered with the wrong voltages.
    the fuse on the darn thing(stereo) must have been bigger then the generator… must have been a tiny < 500w genny.

    either that or it was a SONY… ive seen inside sony TV's and i would NOT sleep with one plugged in!

    1. Im not sure you understand the purpose of this hack.

      The batteries he is charging are RC LiPo battery packs. They are used – as the name implies – in radio control toys.

      It’s safe to assume the hacker is an RC enthusiast who likes to fly his toys in large fields but don’t necessarily like to end the day when the plane/copter/quad’s batteries run down.

      No power factor problems or power tools here, just clean RC fun ;)

  8. I have the same charger. I would note it is rated to charge at only 300W max. I power it with a 500W ATX power supply slightly modified. I bought the PSU used for cheap.

    Modifications include easy plugs and dummy load – I used a brake light bulb for my truck. ATX power supplies don’t seem to work right without the dummy load.

    Also, I’ve read several multiple server PSU mods. There are some that float the DC ground rather than the AC which is safer.

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