Trickle Charger for 12V

Discussion in 'Gen 2 Prius Main Forum' started by rogerthat, Mar 24, 2020.

  1. rogerthat

    rogerthat Member

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    I left an interior light on overnight and the next day when I tried to start the car the MFD display was blank, the dash lights came on, including red triangle, and the car would not shift into drive, nor would it power off.

    After a minute I held my finger on the power button and the car eventually powered off. Then when I restarted, the triangle briefly illuminated, after which I was able to shift the car to drive. I've since read that the triangle coming on and then going off when starting is an indication of a 12V battery issue which is understandable as the interior light was left on. However, after driving for about 40 mins each way back and forth from work and driving an additional 30 minutes the day before, the triangle still briefly illuminated when I started the car to return home today.

    It is my understanding that it could take 10+ hours for the battery to fully recharge - can I just continue my regular 40min each way daily drive and expect the car to fully recharge after a week or do I need to purchase a charger and recharge overnight? The battery is about 5 years old, but I would prefer not to replace unless it is definitely needed.

    If a trickle charger is the best way to go, can anyone recommend a solid budget option. Would this $20 model do the trick?

    Lastly, is this a reliable procedure to give me a basic idea of the health of the 12V?
     
  2. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Just my 2 cents:

    Battery health: solar ba9
    Charger: CTEK 3300
     
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  3. davecook89t

    davecook89t Active Member

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  4. dolj

    dolj Senior Member

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    For clarity, you don't want a trickle charger, but a proper automatic charger like one of the two suggested above.

    A trickle charger will take forever (if ever) to charge a totally flat battery. A charger like the ones mentioned above will do a proper charge then revert to trickle charging to ensure it stays charged.
     
  5. rogerthat

    rogerthat Member

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    Hmm, is it possible to adjust the amperage down on that Harbor Freight charger? I had read somewhere that one should not exceed 3A?

    Also, what about just continuing to drive around - will it recharge within a week or two or am I better off using a charger?
     
  6. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Those CTEK are getting pricey. :confused: I got a 3300 at least a decade back, for around $65 (CDN), and a 4.3 for around $85. Maybe supply/demand??
     
  7. rogerthat

    rogerthat Member

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    Yeah, I'm not prepared to spend over $50 on a charger... otherwise I'd just put that money towards a new battery. However, that Harbor Freight model is affordable, so I'll wait back until someone answers my questions about amperage or if I can recharge successfully by driving, before proceeding.
     
  8. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Owner's Manual, page 373:

    upload_2020-3-24_12-30-13.png

    With a decent charger, and tester, and a bit of reading, your batteries will last longer, you'll know when they're going off, and why.
     
  9. TMR-JWAP

    TMR-JWAP Senior Member

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    If you're doing a 40 minute drive each way, that battery is going to charge, assuming the battery itself is good. At almost an hour and a half a day, it'll get better every day

    Similar to not wanting to buy a new battery if this one is still good, you also don't want to spend a lot of time or $$ if the battery is bad. Personally, I would go to a local auto parts store and have them perform a test of your battery to determine it's condition.

    After that, decisions can be made about whether it needs to be replaced or just charged.
     
  10. sam spade 2

    sam spade 2 Senior Member

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    A good 6 amp automatic charger will NOT actually charge at 6 amps in most circumstances.
    If it does, that probably is a sign that the battery is completely SHOT and continuing to pump current into it actually could be BAD.

    As for the Harbor Freight question: NO. Their chargers are generally JUNK.
    Get a tender type, true automatic charger of about 4 amp capacity or less from WalMart or any auto parts store.
    Should be able to get one for around $30.
     
  11. rogerthat

    rogerthat Member

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    Can you direct me to any good examples?

    Just reading further and it also seems that a desulfinator type charger is best? How about the 4amps - is this not too much for the Prius 12V?
     
  12. bisco

    bisco cookie crumbler

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    see posts 2 and 8
     
  13. dolj

    dolj Senior Member

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    No. The sticker on my OEM battery says no more 4.2 Amps.

    What they are warning against is fast charging with a high Amp charger. Read 15+ Amps.

    That 4 Amp HF charger will be just fine.
     
    #13 dolj, Mar 24, 2020
    Last edited: Mar 25, 2020
  14. sam spade 2

    sam spade 2 Senior Member

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  15. rogerthat

    rogerthat Member

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    Seems like the consensus is that 4A is safe. I'll likely pick up one of those sub $50 chargers this week.

    When I drove my car earlier today I didn't see the triangle on ignition, but after stopping at a store and then starting the car up again it appeared momentarily. Does this imply that the battery does not seem to be improving by driving it over the last few days?
     
  16. davecook89t

    davecook89t Active Member

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    I will not pretend that all of the products that Harbor Freight sells are of the highest quality. I had 4 of these,1.5 Watt Solar Battery Charger, for instance and 2 of them failed within a month or 2, a 50% defect rate.

    The product I referenced in #3, on the other hand, has done the job, in my experience, and it seems the vast majority of other buyers have also been satisfied with it, if you will look at the reviews.

    The Harbor Freight unit is micro-processor controlled and will throttle down the charge rate as the battery gets close to fully charged. When I first connect the clamps to the charge points on our Gen 2 and then plug the power cord into a 110V outlet, I typically see 12.3 or 12.4 V on the LCD, a significant level of discharge for an AGM battery. Within a few seconds, the display will show 13 V or greater, as the charger begins to go through its process. A few minutes later, I will see the voltage top out at somewhere around 14.5, and following that it will start to jump around between 13 and 14 V, what I believe is its "absorption" stage. Several hours later, I will see the display holding steady at 12.6 or 12.7 V, which I believe is fully charged for my 4 year-old AGM battery. At first, I was reluctant to leave the charger plugged in overnight, not being confident that it would not to overcharge my battery, but I am now comfortable leaving it plugged in indefinitely. The charger has a "Mode" button for switching between regular Lead-Acid 6 V and 12 V batteries and AGM 12 V batteries. I have used it to charge the regular Lead-Acid 12 V battery in our Gen 4 successfully, and I have found if I hit the Mode button briefly, while it is in the midst of charging a particular battery to switch from Lead-Acid to AGM or vice versa, it will instantaneously change the level of charge it is putting on that battery, confirmation that the Mode button actually does something. It is a little pricier than the very similar looking (same manufacturer perhaps) EverStart 3A charger referenced in #14, but I believe the additional features may be worth the price difference.
     
  17. rogerthat

    rogerthat Member

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    If I take the car to an auto parts store for a check, and if the battery is bad, could the check possibly drain the battery to the point where it does not charge back up sufficiently? I am starting to suspect that the battery may be on its way out as I'm still getting the triangle momentarily at startup.... although I've been able to get the car in ready mode without issue over the last few days.
     
  18. davecook89t

    davecook89t Active Member

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    Having an auto parts store check your battery should not kill it, if there is any life left in it at all, but what they tell you about its condition may not be all that reliable, given the limitations of the test they perform. If you don't have a charger, why not take it to a shop that has one and ask them to charge it for you? They should be able to do that for a small fee ($20 or less), and they will tell you if it is not able to hold a charge. Then you will know whether to replace it or not. Even if it seems alright after driving around for several hours relying on the DC to DC converter to charge it, you are really still just guessing.
     
  19. fuzzy1

    fuzzy1 Senior Member

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    This is a good reason to preemptively change those lights to more efficient low-current LED models. If carefully selected for actual low current, not super brightness and universal omnidirectional light output, LEDs can cut the current draw by a factor of 5X to 10X, giving far more time to discover and remedy the erroneous left-on condition. With these, a battery with a reasonable charge should easily last all night, and more, and still be able to start the car.

    These LEDs also behave friendlier to the battery as its voltage drops, by reducing their current draw faster than the voltage drops. Incandescents go the other way, accelerating the battery drain.

    For best efficiency, I selected unidirectional lamps tuned for the particular directions I needed (end emitting vs side emitting). Omnidirectional lamps have a more universal fit, but waste most of their light inside the light fixture or mounting location, so cannot be made for low enough current.
     
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  20. sam spade 2

    sam spade 2 Senior Member

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    Yes. And that is normal with a worn out battery.
     
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