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DIY High Voltage Battery Reconditioner - Grid Charger

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by tgtech, Jul 31, 2022.

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  1. Papawrench

    Papawrench Junior Member

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    Thank you for the amazing write up! The only bit I'm not sure of (no real electrical background outside of home wiring) is the resistor close to the power supply. This is to soak up current from the battery after the power supply is turned off right? Is it wired across the positive and negative leads of the power supply making a circuit? I will have the diodes after this so hopefully that protects the battery pack from feeding back into the power supply (I think) but if that is the case I'm not sure the role of the resistor and with the wiring something between positive and negative leads I'm worried about a short if I'm understanding the schematic wrong.
     
    #21 Papawrench, Oct 16, 2023
  2. tgtech

    tgtech Member

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    Yes, it is wired directly across the output of the supply. It is there as a safety measure to quickly bleed off any residual voltage from the power supply when it is turned off. When the power supply is on, about 2 ma flows through the resistor (I = V / R) and it dissipates about 0.5W, so it will get warm. I used a 3W rated resistor. The resistor doesn't affect the high voltage battery. The diodes drop the charger voltage a bit (about 0.7V per diode) and prevent "back-feeding" the power supply from the battery pack as you guessed.
     
    #22 tgtech, Oct 17, 2023
    SFO and Papawrench like this.
  3. r81984

    r81984 New Member

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    Excellent post great job designing this. I have a 2011 CT200h which is a Gen 3 prius that just started getting the P0A80 Replace hybrid battery pack and techstream shows 4 cells with lower voltage.
    But... I priced out the materials on your BOM, in today's price (2024) and they come out to almost $300 + tax using your same sources and identical items.
    Instead I bought the premade maxx volts charger for $369 with no tax. For discharging I am going to still use the lightbulb method.
     
    #23 r81984, Feb 25, 2024
  4. MrPete

    MrPete Active Member

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    Here's some info on new tools I suspect may be VERY handy for grid charging/discharging... and individual module analysis as well:

    1) TestController is a wonderful tool for managing a wide variety of smart instruments: meters, scopes, loads, power supplies, etc. See Program that can log from many multimeters. - Page 1
    2) There's some pretty amazing digital load devices out there these days. I just picked up a DL24MP load at aliexpress. Claims to handle 150W, practically speaking 100W should be no problem. One cool thing: up to four of these can be connected to handle up to 600W (reality: 400). A 450W unit would be under $70. This is a smart device, computer controllable via blue tooth. Each unit has four high power MOSFETs for handling the load.
    3) Do you need to cool high power resistors? Pick up some pure mineral oil... cheap at Walmart, Sally Beauty, or any Ranch hardware store. Nonconductive and cools just fine :)
     
    #24 MrPete, Feb 26, 2024
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