battery-module-internal-resistance-meter

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by pnitin, Sep 5, 2025 at 6:45 PM.

  1. pnitin

    pnitin Junior Member

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    I’ve been working on repairing the aging NiMH battery modules in my 2004 and 2012 Prius. Some cells had started failing, so I began the replacement process, slowly swapping out modules one by one.

    However, I quickly realized this approach was inefficient. Simply checking module voltage isn’t the most reliable way to determine battery health. While you can easily find used Prius battery modules on eBay or through local sellers, most only list the battery voltage—often measured right after charging—as proof of a “good” module. Unfortunately, this isn’t always accurate, and many times you discover the module doesn’t actually perform as expected once installed.

    A much better method is to measure both the module’s voltage and its internal resistance. Internal resistance is a strong indicator of battery health—low resistance cells are more efficient, less lossy, and deliver more consistent performance.

    As an electronics enthusiast, I built a simple meter that measures internal resistance. It runs on a basic 9V battery, is cost-effective, and makes it much easier to evaluate the true condition of hybrid battery modules. We’ve even launched a Kick-starter to make this tool accessible to anyone who wants to test, repair, or optimize their own hybrid battery packs.

    https://www.kickstarter.com/projects/1842571016/hybrid-battery-module-internal-resistance-meter

    sending this in hope this is helps someone like me to get battery in shape back.
    Thanks
    Nitin
     
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  2. Tombukt2

    Tombukt2 Senior Member

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    Most people are trying to clear out the junk modules that they have in boxes laying around they're not going thru all that . That's end user job .
     
  3. pnitin

    pnitin Junior Member

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    yes very true. On the other side as buyer has to be more educated in choosing what is right for him/her, and that is where I think it will help.
     
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  4. Tombukt2

    Tombukt2 Senior Member

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    Yeah. You'll have to be able to walk up to the box of modules and have at it . seems really quick to me 28 new modules would be best. As in New battery.