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HELP WITH GRID CHARGER DESIGN

Discussion in 'Gen 2 Prius Technical Discussion' started by Dxta, Feb 12, 2022.

  1. Dxta

    Dxta Senior Member

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    Hi guys! Been a long lurking here
    I have got four LED power supplies (48.0V 5.5A each), that i would want to combine serially, to output 196V, that i can charge some modules in a pack.

    Here are my concerns:
    1. I have done this project before, and obtain more than a 100V, which really helped me during grid charging.
    The problem i had afterwards was each time I try to connect the output terminals to the module studs, there are always sparks flying around (arches).

    2. Is there a way to prevent flying sparks each time I try connecting the charger to the pack before charging?

    3. I mistakenly reversed the output terminals of the chargers, when attempting to charge the pack, and booom! The voltage spike from the backfeed, blew and destroyed my homemade charger.

    4. Now, i got some bunch of 4 LED drive power supplies, readying them for connections.

    5. To prevent voltage spikes destroying my chargers again, cause of reverse polarity issues, would connecting some sort of inline 5A fuse at the positive output terminal, and a diode in the negative terminal, protect my charger?

    Thanks for answers.
     
    #1 Dxta, Feb 12, 2022
  2. ChapmanF

    ChapmanF Senior Member

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    The diode would help, and you can add it anywhere you want in that picture, since everything is in series anyway.

    Be sure to buy a diode whose Reverse Breakdown Voltage is high enough. If connecting the leads backward is one of the conditions you want it to protect against, then the reverse breakdown voltage had better be at least double the battery pack voltage.

    As for the sparks, are you connecting the leads to the battery while the charger is powered on, or off?

    Power supplies usually contain output filter capacitors, and if you hook up the supply to an external voltage source like a battery when the power supply itself is off, if the output isn't diode-protected, the battery will dump current into the supply input to charge the capacitors. Your added diode may alleviate that issue too.

    You could also borrow a page from the car's own tricks and use a precharge resistor with a switch around it. Make the connections to the battery with the resistor in place, power up the supplies, make sure everything looks copacetic, then close the switch around the resistor.
     
    #2 ChapmanF, Feb 12, 2022
  3. Dxta

    Dxta Senior Member

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    1. Would check if there are such diodes of higher voltage/current capacity available.
    Could you recommend any, or a link? Maybe 150-200V @5.5A or so?

    2. Yes, the leads are always connected when the charger is powered. Could that be the reasons for the sparks flying around? I haven't included an AC/DC maybe toggle switch to that set-up yet, probably that's the reasons?
    Any ideas what to do to prevent the sparks while connecting the charger terminals to the battery during charging?

    3. Could you pls explain more with using the car's strategy?
    The precharge resistor could be connected anywhere in the output charger output isn't it, or there's a specific line?

    Thanks @ChapmanF
     
    #3 Dxta, Feb 12, 2022
  4. ChapmanF

    ChapmanF Senior Member

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    I usually either go to the local electronics shop to see what they have on the wall, or look somewhere like digi-key.com. I don't know much about the option in Lagos.

    With the resistor, I was suggesting to just kind of copy what the car does with the three system main relays, where one of them (the one that's smaller than the other two) is used to bridge across a precharge resistor.
     
    #4 ChapmanF, Feb 13, 2022
    Dxta likes this.
  5. jdenenberg

    jdenenberg EE Professor

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    Chap is suggesting that you use a resistor in series with the output of your charger to limit the initial current when the charger is connected to the battery. Then use a relay to short out the resistor to start the charging cycle. Just make sure that the resistor limits the current to a reasonable level (100-200 ohms) and that the resistor can handle the power dissipation for the short time interval without getting too hot.

    JeffD
     
    #5 jdenenberg, Feb 13, 2022
  6. ChapmanF

    ChapmanF Senior Member

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    While the car uses a relay around the resistor, for a home-brew charger, an everyday toggle switch would also get the job done.
     
    #6 ChapmanF, Feb 13, 2022
  7. PriusCamper

    PriusCamper Senior Member

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    #7 PriusCamper, Feb 13, 2022
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