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Trickle Charger for 12V

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

  1. sam spade 2

    sam spade 2 Senior Member

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    Sorry. Wasn't familiar with that model. It looks good.
    NONE of the Cen-tek electrical stuff is any good......except for the little red meters which seem to do the job.

    And a 1.5 watt battery charger is pretty much of a joke.....even if it works.
     
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  2. rogerthat

    rogerthat Active Member

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    Since my job temporarily shut down this week and my car will no longer see long daily commutes, I went ahead and purchased the Harbor Freight Viking 4A charger. I found a coupon online and it ended up being under $25 out the door.

    This morning when I checked the voltage, this time with a multimeter via the jump point under the hood, it registered 10.54 volts. I still saw the red triangle on startup. After returning from the 10 mile Harbor Freight round-trip and waiting over an hour, I got a reading of 12.5 volts. Could this be further indication that the battery is not holding a charge? Anyway, I'm going to attach the charger and see what happens. From what I've read it should be fine to attach the charger as the jump point/bolt under hood and in the following order....

    Attach the negative cable/clip to a bare bolt nearby the positive jump point. Then attach the positive cable/clip to the positive jump point in the fuse box. Then plug the charger into an AC outlet (the charger has no on/off switch). Lastly, I'll select the 12V AGM mode and see what happens. For those who've used this charger, does this sequence sound right?

    How about venting, do I need to be concerned or can I just leave all the car doors closed?
     
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  3. fotomoto

    fotomoto Senior Member

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    Running a lead acid battery down very low is very bad for its longevity. Doing it to a 5 year old battery that's already considered to be undersized for optimal use is your sign to get a new battery.

    You can remove the 12v and take it to an auto parts store that offers free load testing and see where you stand.
     
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    I've always heard attach the positive first.
     
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  5. fotomoto

    fotomoto Senior Member

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    YES!

    It is not uncommon for a 12v to only last 4-5 years here in the southern USA. My last two failures in a Ford and Subaru were both @ 4.

    GOOD LUCK!
     
  6. rogerthat

    rogerthat Active Member

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    Well, I've already bought the charger so I guess I'll give it a shot anyway.

    As far order of cables is concerned, manual states for me to connect the detached negative clip/cable first, then the positive detached clip cable, and then connect the negative charger clip to the actual charger, then to plug in the charger... so I'm not sure if this counts as negative first.
     
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  7. fotomoto

    fotomoto Senior Member

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    Or if money is tight, return it for a full refund, apply to a new battery, and get a charger down the road when more funds become available.
     
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  8. bisco

    bisco cookie crumbler

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    charge it up overnight, or until the charger says complete. let it set for 4 hours, then check the voltage
     
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  9. davecook89t

    davecook89t Senior Member

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    Since the positive clamp and negative clamp are isolated until the clip is attached to the charger, it should not really matter which you connect first, but as @Mendel Leisk states, the positive clamp would normally by attached first and then the negative if attaching a jump pack, or powered-up charger, or jumper cables because if the negative clamp (ground) is attached first and the positive clamp happens to make contact with another ground point as you are attaching it to the positive terminal, you will get sparks and possible damage to the electronics. If you happen to touch another ground point when connecting the negative clamp after the positive clamp has been connected, there is no harm done as you are that clamp is meant to be grounded anyway, and if you happen to touch a ground point with the positive clamp without the negative clamp being connected, once again there is no harm because the ground is not live at that point. Disconnecting the clamps should be in the reverse order, negative clamp first then positive clamp, using the same logic of trying to avoid an incidental contact with a live ground point. I am not sure why the manual would instruct you to attach the positive clamp first, even if it is totally isolated at that point, it is better to get into the habit of connecting things in the correct order for when it really matters.
     
    #29 davecook89t, Mar 26, 2020
    Last edited: Mar 26, 2020
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  10. davecook89t

    davecook89t Senior Member

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    There should be a vent tube attached to the battery for allowing gases to escape out below the car, so it should not be necessary to leave any doors open. I believe I've heard that there should be an insignificant amount of gases produced from charging an AGM battery unless something goes seriously wrong.
     
  11. sam spade 2

    sam spade 2 Senior Member

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    What ELSE do you think a reading that low could indicate ? Unless maybe a door switch has failed, you have installed an "always on" accessory or have something plugged into the ODB port all the time.
    YES, your battery is a goner.

    Now you have a good charger.......but it is highly unlikely that it will do you any real good with the present battery.
    In fact, it might enable you to start it once at home only to have it fail completely when trying to get BACK home.

    READ THE DIRECTIONS. Some should be plugged in first, others connected to the battery first.

    Venting should not be a problem.

    Start shopping for a new battery.
     
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  12. davecook89t

    davecook89t Senior Member

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    After reading #22 a second time, I realize I misinterpreted what you were saying. The clamps are attached to a cord that connects to another cord coming from the charger (at least on the unit I have). If that cord has not yet been attached to the one coming from the charger, the clamps are isolated from one another. If the cord has been attached, I would no longer consider them to be isolated, just for the record.
     
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  13. sam spade 2

    sam spade 2 Senior Member

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    When talking about connecting a charger at the battery, it makes ABSOLUTELY no difference.
     
  14. fuzzy1

    fuzzy1 Senior Member

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    Put another way, the last connection, the one that creates the sparks, must be away from the battery.
     
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  15. rogerthat

    rogerthat Active Member

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    Well the battery is now charging. It sounds like it might be shot anyway, but I'm holding out some hope. Now once it fully charges and I allow it to sit overnight, what could I reasonably expect as a voltage drop for a functional battery.... I'll measure at the jump point with a voltmeter.
     
  16. sam spade 2

    sam spade 2 Senior Member

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    12.5 would be iffy. Anything below that is BAD.
    The charger should be disconnected at least 8 hours before measuring.

    A healthy new battery should hold 12.8 for several days.
     
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  17. davecook89t

    davecook89t Senior Member

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    It's hard to know the exact point at which it is not worth fooling with, but if it can't hold 12.5 V after being fully charged a few hours earlier, I would probably be looking to replace it as soon as possible. Are you sure you had a good connection when you measured 10.54 V under the hood? If I got a reading like that, I would probably try to measure it at the actual battery, just to be sure there wasn't a problem with the cable running from the positive post on the battery to the jump point under the hood. It's hard to see how a battery measuring 10.54 V has any life left in it.
     
  18. Mendel Leisk

    Mendel Leisk Senior Member

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    In that case, I would continue with the neg last convention, just to reinforce it in my brain cells. (y)
     
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  19. rogerthat

    rogerthat Active Member

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    Since I had left a cabin light on as described in my original post, my hope was that the low voltage may just be a function of that draining and not enough driving time to adequately recharge. However, the 10.54V reading and then a subsequent 12.5V reading is not encouraging. I measured the voltage a few times at the jump point, so I think that 10.54V reading was good. I'll probably check the voltage at the actual battery terminals if this procedure fails just in case its a cable issue. The charger display currently show 13.4V while charging.
     
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  20. Mendel Leisk

    Mendel Leisk Senior Member

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    Per post #2: if you want to know conclusively where you're at, get a Solar BA9 or siimilar.