hybrid battery balancing concept

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by swoll001, Mar 5, 2021.

  1. swoll001

    swoll001 Junior Member

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    [​IMG][/url][/IMG]

    So I am trying to do a cell swap. I would like to balance my cells but dont have any equipment.
    someone used this concept there they switched all the batteries so one side was all plus and the other all minus. They then ran a copper on one side and a separate copper on the other.
    the idea is that they would all end up resting at the same voltage.
    does this form of balancing work? how long would you recommend i do it for?
    it looked like this. Any thoughts. I am in a 2008 prius with about 115k miles

    [​IMG]
    [​IMG]
     
  2. Isaac Zachary

    Isaac Zachary Active Member

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    I think just doing that will give you very limited benefits. Each one of those isn't a cell, but a module of several cells. Doing what you're explaining makes all the modules have the same voltage, but not each cell inside each module.

    What worked for me is to get a hobby charger. I charged up each module individually. Then I did the copper wire and charged them together. Since they were all pretty much charged it didn't take long to get them charged up together.

    One thing to keep in mind, don't ever try to charge anything on your battery without the modules being clamped down by the black bars and white plastic ends. Otherwise the modules will puff up like balloons.
     
  3. SFO

    SFO Senior Member

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    An inexpensive HV LED power supply would be better. Be sure to keep the HV battery cool while balancing.

    DIY Grid Reconditioning Charger | PriusChat

    You could also string together a few 80v power supplies to the same effect.
     
  4. dolj

    dolj Senior Member

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    What you are describing is equalizing, not balancing. It virtually does nothing for you and is really a waste of time. There is not enough of a difference in potential for any electrons to be moved anywhere useful.

    Balancing comprises of two procedures - top balancing and bottom balancing.

    Top balancing is charging a module (or a series of modules) at a very low current (325 mA) for enough time that the lowest cell in the series gets charged to full. As each cell gets fully charged it will no longer accept the energy and will, instead, dissipate that energy as heat.

    Bottom balancing is when you discharge your module (or series of modules) so each cell is discharged to (at least) 1 volt per cell. Most commonly in PriusChat circles, the bottom balance targets are 1st discharge - 0.8V per cell; 2 - discharge 0.6V per cell; and 3 - discharge 0.5V per cell.

    A successful strategy is to top balance then bottom balance three times followed by a final top balance, and would be the most effective use of your time and energy.
     
  5. Isaac Zachary

    Isaac Zachary Active Member

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    @swoll001 's idea isn't even really equalizing. It would equalize the modules, but not the cells. If you have three cells that are 1.0V and three that are 1.4V you wouldn't know the difference than a module with all six cells at 1.2V. This is why bottom balancing these modules doesn't seem like it would work because you can't control each cell's voltage. Top balancing only works because it's impossible to hold more than 100% charge voltage.
     
  6. dolj

    dolj Senior Member

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    That is why you do a top balance first. Get all the cells up to 100%. That is also why you do shallow discharge for the first charge/discharge cycle followed by deeper discharges on subsequent cycles and then finish with a final top balance.
     
  7. Isaac Zachary

    Isaac Zachary Active Member

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    I still like the general idea of hooking all the modules up in parallel like in the pic and charging them up with a 6-cell charger. You can also discharge (if you do those steps) with a simple resistor and discharge capacity meter (the discharge meter shuts off automatically or allows you to discharge and measure each module individually if you have the time). That's what I did. Such a charger only costs $20, and the added resistor and meter are about $20 more to that price. There are no high voltages to worry about doing modules in parallel, and it would seem to me to be a better way of getting cells and modules even closer to each other in voltage. The only problem is you do have to have the battery apart and temporarily put back together in order to do it.
     
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