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12V Battery Charging Procedure

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by PriAva, Jan 13, 2012.

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  1. PriAva

    PriAva New Member

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    I have a 2008. The manual says to remove the negative cable from the battery when charging it. Why is this? Don't I lose my settings when the negative cable is removed to connect the charger?
  2. uart

    uart Senior Member

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    It's probably to isolate the battery and charger from the car, just in case the charger does anything silly with the voltage for example.

    But yeah it would cause you to lose some settings. I think that if the battery is in fair condition and the charger is sound then it shouldn't be necessary.
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  3. edthefox5

    edthefox5 Senior Member

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    Not neccesary to remove neg cable when charging. Alot of us routinely charge the battery as its very good for the battery health. About once a month I put mine on a charger mostly just to see how quickly it takes to go to full capacity which is a very good barometer of battery health.

    I have found using a regular car charger in 2 amp mode the ammeter on the charger will show 0 draw in about 15 minutes.
    This has not changed much on mine since I bought it new in 2007 and on original battery.

    But fyi if your trying to charge a battery thats gone dead the bad news is don't bother. The small AGM sulphates quite quickly when it goes dead and then even though may take a charge is really just a time bomb waiting to strand you.

    Use the jump start point POSITIVE point under the engine hood in the black plastic fuse box on right. The Positive is under the big red plastic cap. Swing the cap over and there's a metal tab thats bolted so it stands upright. That upright metal tab is where you attach the battery charger POSITIVE clamp too.
    I use a bare metal bolt right above that used to bolt on the strut for the negative clamp.
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  4. PriAva

    PriAva New Member

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    Thanks for the info!
    I hadn't even thought about trying to charge by using the connections under the hood. It sure makes it more convenient that way. I thought they were only used for jump-starting, which I did. Since you're not connecting directly on the battery, are there any extra precautions needed if done that way?
  5. edthefox5

    edthefox5 Senior Member

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    No precautions and if its good enough for jumping its gotta be good enough for charging which pulls much less current than a jump. Plus the front points are fuse protected to the battery in the trunk.
    And if you have jumped the battery already look into replacing it asap with an Optima. There's literally hundreds of posts concerning upgrading to an Optima.
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  6. Sagitar

    Sagitar Junior Member

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    My charger has a two pin connector part way down the output cable so that the battery connectors can be left permanently attached to the battery. I bring out the battery side of the cable to the interior cover over the rear light cluster so that I need only join up the two-pin connector in preparation for charging. The charger itself is on the garage wall close to the location of the rear of the car.
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  7. PriAva

    PriAva New Member

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    Well... It started OK last Saturday AM, so I went to my local dealer, had it tested and replaced it. Cost breakdown as follows:
    Battery- 183.29
    Labor- 47.50
    Batt. Fee- 3.00
    Sales Tax- 15.37

    The Toyota service manager said that I needed to drive it more often. I told him that kind of defeated my reason for having a Prius, if I have to drive it with no place that I need to go just to keep the battery charged.

    It did last 4 years under the circumstances.

    I will certainly follow the recommendation to charge it periodically.
  8. PriAva

    PriAva New Member

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    What brand charger do you have?
  9. qbee42

    qbee42 My other car is a boat

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    Four years is a normal life for a Prius 12V battery.

    Tom
  10. uart

    uart Senior Member

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    How often do you drive it PriAva? Roughly how many hours per week?

    Did you know that you can turn off the SKS (smart key) system, and that significantly reduces the drain on the battery. This would reduce the need to drive as often to maintain charge.
  11. PriAva

    PriAva New Member

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    Hard to say how many hours a week I drive it. It really varies. Sometimes it's driven every day and sometimes maybe a week goes by that it is not driven, but usually it goes out 2-3 times a week. It has about 16K miles on it. It is not our only car. As you can tell from my username, my other car is an Avalon.

    I am retired, and we do travel a lot, so it is left at the airport at times... usually about 1-2 weeks, but sometimes as long as 3 weeks. I do disable the smart key at those times. I have read that is the thing to do to help keep the battery charged. However, I am now going to start disabling it whenever it's going to be sitting for more than a couple of days.
  12. uart

    uart Senior Member

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    So it sounds like you average about 70 to 90 miles a week. Probably 1.5 to 2.5 hours per week?

    This should be enough to keep it charged, but probably only just. So yeah, if you let it get a bit run down (eg leaving doors open and door lights on) then it's probably going to take ages to regain the charge.

    Turning off SKS will probably help a lot. I think you should be ok. :)
  13. Sagitar

    Sagitar Junior Member

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    It's an Optimate4 made by tecMate.

    You can find them on TecMate International

    It was recommended by by the Toyota main dealer from whom I bought the Prius.
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  14. PriAva

    PriAva New Member

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    Sagitar... Thanks!
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