12V battery maintenance for dummies when gone for weeks

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by Girl__wonder, Jan 4, 2026.

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  1. Girl__wonder

    Girl__wonder Junior Member

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    California
    Vehicle:
    2006 Prius
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    @Mendel Leisk and @Pdog808 thank you!

    @bisco thanks. You're right. When I pulled into Auto Zone today, an employee had just finished checking someone's battery. He then helped me. Walking in, I saw a different employee checking someone else's car. lol. It's battery day at Auto Zone.

    I had intended to buy the Noco Genius 1 there, but the website was wrong (they didn't have one in stock) so I've ordered that and the Solar BA9 charger from Amazon and will get them tomorrow. I'm curious now. The Auto Zone battery tester didn't show CCA but said my charge is now 32%. I didn't drive at all last week. My normal driving is not helping (mostly short trips around town) but I'm surprised this is even lower than the 61% charge and 73 CCA when the car sat for 6 weeks. (the AAA display, photo above. BTW, the AAA guy did not connect to the battery directly but under the hood. And his display shows the battery specs at 350 CCA, not 285 CCA).

    I had a 2006 Prius (and other cars) and never had this problem, so this is frustrating. Is there a definitive list of things to be mindful of related to the parasitic drain? I read some of long chat thread, which is a discussion (key fob bad or not?), but I'm wondering if someone compiled a definite list. thanks
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    #21 Girl__wonder, Feb 5, 2026 at 10:03 PM
  2. BiomedO1

    BiomedO1 Senior Member

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    This is why I don't like these newer algorithmic battery scanners. I consider them random number generators, made for gen-z that can't use their brain.
    The AAA test was OFF because it had the wrong CCA, so it showed only 73 CCA available. Don't know why a battery with only 73 CCA would be considered a passing grade. That would barely start a small engine on a 30F day. If it was a 6 or 8 cylinder, you would be walking.
    That Autozone tester seems to be a bit better, but not knowing it's internal algorithm - I can't really say how accurate it really is.

    I'm a bit old fashion and prefer the brute force approach of a carbon pile resistance battery tester. The battery must be fully charged (SOC) in order to pass that test and since it's an analog display needle, you can make your own judgement - If it's good enough.

    The 2025 Prime has more electronics and does more readiness testing. If your fob is on the edge range of the car; it's going to perform more testing & preparedness thinking your getting ready to use the car. You'll need to drop your fob into a tin box or Faraday bag to cut-off the fob signal. Short hops in ready mode, probably isn't putting enough power into the battery vs power expended in between trips. That why we are recommending a trickle charger during downtime.
     
    #22 BiomedO1, Feb 5, 2026 at 11:57 PM
    Last edited: Feb 6, 2026 at 12:15 AM
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