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HV Battery almost dead -How to charge?

Discussion in 'Gen II Prius Technical Discussion' started by MR.K, Sep 9, 2008.

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  1. MR.K

    MR.K New Member

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    I have a 05 rebuilder ..The H/V battery is at one pink bar ..I need to charge it...I have access to a 225 volt 1 amp DC charger ...a couple of hours would probably do it ....what is the easiest way to access the HV battery...other than to take it out ...This would be a similar problem to running out of gas then driving to the gas station on the battery ,only to run the HV batt dead trying to restart......thanks all.................
  2. miscrms

    miscrms Plug Envious Member

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    If you have access to one, the safest way by far is to swap it into working Prius. One pink bar should still be enough to start the ICE and recharge. Manual charging is possible, but dangerous and problematic. If you go that route, be very conservative with how long you try to charge it. I wouldn't go anywhere near full charge. There are several stories out there of people charging too long or forgetting the charger and destroying their packs (and in at least one case part of their car). At 1 bar the battery is till at about 40% SOC. Completely full is 80%. Normally its maintained by the ECU at 60% so to get 20% of 6.5Ah in at 1A would only be about 1.3 hours in theory. If you are trying to just maintain charge for long term storage, I'd maybe give it an hour every few months. The challenge will be that the Battery ECU will not recognize the charge you add while the car is powered down (or the battery is out of the car.) Plus voltage is not a very good indicator of SOC. So in a lot of ways you are charging blind.

    Rob
  3. David Beale

    David Beale Senior Member

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    One pink bar is plenty to run the car. Just get the car started. If you start trying to charge the traction battery you will likely do more harm than good. Even no bars is fine. Don't leave the car in neutral, the engine won't charge the traction battery in that state. With the car in park just let the car run for 5-10 min. The battery should charge automatically as long as the engine runs.

    To access the HV battery to use that 225V 1 amp charger you would have to take the battery box apart. There is a disconnect relay -inside- the battery box that disconnects -both- sides of the battery from the rest of the car. It's open when the power is off.

    The Toyota charger uses a special plug that activates the internal relay. If you download the schematics from Toyota (daily fee of $10 or $50 for the month) you -might- be able to figure out how to wire a connector up, but good luck getting the connector.

    As I said, best way is to get the engine running. Let the car charge itself.
  4. SageBrush

    SageBrush Senior Member

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    I hope your car is not exactly equivalent to running the battery down completely. That case can damage Prius electronics, and if I remember right, always requires a visit to the dealer to reset an ECU or two.
  5. MR.K

    MR.K New Member

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    So if you swap the H/V battery out ,would the lack of voltage be like a dead batt?
  6. miscrms

    miscrms Plug Envious Member

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    I'm not sure I understand the question, but here's how I understand things. The 12V battery is used to "start" the car, booting up the computers and getting everything ready to go. The HV battery is then used to actually start the ICE. If the HV battery is too weak, the ICE will not start and errors will be thrown. Then you're kind of stuck, because you need the ICE running to charge the HV battery. If the HV battery is showing one bar on the dash display it should have enough power to start the engine though.

    What I don't know is if the battery controller is telling you the truth. If a battery had one bar when the car was put out of commission, and then it sat for a long time slowly bleeding off charge, the Battery controller may still think it has one bar even though it could be a lot less. The battery controller SOC determination works by measuring how much current goes in and out of the battery, not by measuring pack voltage. When the battery controller is off, it obviously has no idea that the battery is discharging. I know the controller has a recalibration routine that kicks in at 242V on the high end to account for drift. I'm not sure if there is a similar thing that happens at some low voltage limit.

    Rob
  7. statultra

    statultra uber-Senior Member

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    1 pink bar will get it started
  8. richard schumacher

    richard schumacher shortbus driver

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    Turn it ON ("Ready"). Put it in "P"ark. Let it run for a half-hour. If it won't go to "Ready" or if you don't see more bars in the first few minutes turn it OFF and tow it (flatbed or four-wheel dolly) to a dealer. You can easily kill yourself or destroy the battery while trying to charge it with anything other than Toyota's charger.
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    If the traction battery SOC really is at one pink bar, then you should be able to start the Prius (if all other damage was repaired.) Then let it sit READY for a period of time as Richard indicated.

    If you've already ascertained that the traction battery SOC is sufficiently low enough so that the Prius will not start, then you'll have to open up the battery case in order to access the modules for recharging, since the case includes the system main relays that disconnect the battery from the battery cable terminals. However, as was previously pointed out, this can be an extremely dangerous process in terms of personal shock hazard as well as the possibility of destroying the battery. Be aware that the modules must remain under compression pressure while they are being charged - if not, the plastic module case may explode.

    I suggest that you monitor both voltage and current at all times, as well as battery module temperature. If you can current-limit the charger, then you may do well to set the charger at 0.5A and charge just for 2 hours (i.e., 1AH worth of charging). Then see if that is enough charge to get the Prius to start. If not, then repeat for another 2 hours (i.e., 4 hours total x 0.5A = 2AH total). The battery modules are rated at 6.5AH.
  10. hobbit

    hobbit Senior Member

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    To answer the original question... if you do need to get at the
    raw pack terminals, open up the left end of the box per
    these guidelines or several others that are floating around
    the net, and remove the little white covers on the "upstream"
    side of the contactors. Those terminals go straight to + and
    - and I'll leave it as an exercise to figure out the polarity.
    You don't have to remove the pack from the car or pull the top
    cover off, unless you want to go examine the connections [which
    in your case might not be a bad idea anyways].
    .
    Don't go above 235 or 240 volts on a gentle charge, and monitor
    carefully for heat. Remember, 6.5 Ah is 6.5 Ah whether it's
    one subpack or all of them, it doesn't add.
    .
    _H*
  11. bwilson4web

    bwilson4web 03 and 10 Prius

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    I'm a little confused with this posting:

    1) You have two traction battery packs and swapped one already?
    2) The 'lack of voltage' was measured where and how?

    Thanks,
    Bob Wilson
  12. MR.K

    MR.K New Member

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    Thanks Bob and you all......It's an 05 rebuilder nose hit,..I have/had a bad ABS plug(fixed) or inverter or both or something else wrong so the car doesn't run right ..after many attemps to get it to run the already weak H/V battery (down to one pink bar) is now so low I cant get the READY light to stay on... it kinda flashes...
  13. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Is it possible that one problem is a weak 12V auxiliary battery?
  14. MR.K

    MR.K New Member

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    12 volt batt is fine.....
  15. statultra

    statultra uber-Senior Member

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    the only reason you would need to charge main battery is if you get the red triangle and the screen showing the battery symbol.

    if the ready light flashes the car is attempting to start, therefore the state of charge is enough ( i may be wrong )

    when i had to charge my battery, i had completely lost all power , and it wouldnt start regardless of what i did.

    there is something else wrong with your car most likely, you should erase all DTC's.
  16. miscrms

    miscrms Plug Envious Member

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    That doesn't sound right. I've never heard of a flashing ready being caused by weak HV battery. Only a weak 12V. The 12V starts up the computers and car goes ready before it tries to start the ICE. If the HV bat were really that weak you would have all kinds of warning lights including triangle of death, HV system failure etc.

    Rob
  17. MR.K

    MR.K New Member

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    Ok.. the 3 flashs of the READY light ,upon closer inspection ,was caused by the H/V batt cable not being pushed all the way in to inverter (retainer broken and sild out a bit).......there is still the TOD and with a red main battery symbol in the screen.....the ICE will start then after about 15 seconds everything shudders then dies even in drive w/foot on pedal (I'm trying to charge the main batt)....
  18. David Beale

    David Beale Senior Member

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    So it's not a problem with the battery. Fuel? Was some sensor damaged (MAF)? I'd start with the fuel and work from there. Check for water in the fuel, for example.
  19. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Looks like you will need to invest in a code reader that is capable of retrieving the DTC logged by your car. I suggest that you look for a product that is compatible with the Toyota CAN.

    I question whether your gasoline engine actually started. It could be that MG1 spun the engine for several seconds, then gave up.

    The fact that MG1 is able to spin the engine implies that your battery has adequate charge. This won't last much longer though, if you aren't able to get the engine to remain on.
  20. statultra

    statultra uber-Senior Member

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    if the engine comes on then theres a issue with fuel, or air.

    my prius did the exact thing until the battery wouldnt power the engine.

    i suggest u check codes and get whatever needs to be fixed first.
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