YAPiP - recreating pEEf's approach

Discussion in 'Prius PHEV Plug-In Modifications' started by jdh2550, May 23, 2012.

  1. NortTexSalv04Prius

    NortTexSalv04Prius Active Member

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    I have some questions and suggestions. Question so you disassemble HV battery pack and looked for bad cells?What criteria of bad cell below the 7.2 min voltage cell.?? Suggestion I have also seen a newer LifePo4(not pouch/tab/cylinder/or gbs style) selling on ebay from thailand or china just a thought
     
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  2. jdh2550

    jdh2550 Co-Founder, Current Motor Company

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    OK - "hotter" does not equal "hot" but I still contend that if you pack stuff more densely then they'll run hotter (they may produce the exact same amount of heat but the heat rejection will be happening over a smaller area and hence be "hotter"). BTW, the GBS cells don't run "hot" either.

    But, anyway, forget I mentioned heat!

    Next issue with pouch cells is the connections. Every connection is a potential failure point, a high resistance point or a heat point (all three are really facets of the same thing).

    JLo - do you have any pics of your interconnects? I saw Eric's other thread on interconnects. FWD - what about your installation - any pics?

    Also, I'm now contemplating starting with a 20Ah pack and then paralleling a second 20Ah pack later. If I were doing a 40Ah pack from the get-go I'd likely do 72S2P as I believe that's generally considered safer from a failure mode point of view. But doing 2 x 20Ah packs would be 2P72S. Probably not a big deal and it lets me spread the cost (with a hat tip to the Flan man).

    I also haven't ruled out RealForce cells from Enginer. These cells are higher capacity. And higher capacity means less taxing usage. OTOH, I also don't see the need to pay premium price if I don't need premium capability.

    So many options! Heck, I might even get a supercharged hamster on a wheel...
     
  3. jdh2550

    jdh2550 Co-Founder, Current Motor Company

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    On my Prius pack I had one module (each module is 6 cells) that had a voltage of 6.8V. That's all I used to decide it was bad. The pack is now back together and no more fault codes.

    In general I'd prefer to buy from a US supplier - that will either be Eric B, Enginer or Elite Power Solutions. I just need a pack that's "good value" and up to the job (230V, 100A discharge, ? A recharge, good cycle life) - I don't need the "best possible" pack. I also don't want the hassle of buying remotely - I've done it before and I'd just rather support someone in the US instead and save my headache.
     
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  4. lopezjm2001

    lopezjm2001 Senior Member

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    I consider leggo cells which use copper busbars more prone to hot joints like those used by Mr Plugin. Pouch cells can have up to three nuts/bolts and metal plates per tab connection is much safer against vibration and hot joints. My tab connections are not ideal but you can find pictures of them at Planing CanView and BMS+ conversion with lithium | PriusChat. Planetaire has a better example. You can find better examples on DIYelectriccar.com. Pouch cells probably need more labour as compared to the old traditional leggo cells. Mr Plugin has a good example as he had built a hinged cage to house the cells so he had access to the spare tyre.
     
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  5. Flaninacupboard

    Flaninacupboard Senior Member

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    The Realforce cells don't have a high enough discharge rate, they are only rated for 1C,so you need 100aH, that's 72s5p(!). A 23kwh pack would be awesome, and if you FILL the tyre well, and the whole under boot floor area (you have an advantage because you're removing the original battery) you could probably do it (I am sure three rows of 6kwh will fit under the floor, and I have seen 4kwh in the well. There was some space in the well, so 5kwh in there seems doable). This pack could still only accept 20A regen (0.2C), but, at $450/kwh (and maybe Jack will do you a good price for this project) you'd get ~90 miles of EV range for $10k. 9 miles EV for $1k is a fricking bargain compared to the official PiP...
     
  6. jdh2550

    jdh2550 Co-Founder, Current Motor Company

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    Good point - and I don't have enough for a 5P pack...
     
  7. usnavystgc

    usnavystgc Die Hard DIYer and Ebike enthusiast.

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    I know I've stated this b4 but, all this talk about cheap batts seems like a good place to restate that, I have 76 Headway 40152S cells sitting in my garage (minus the 16 on the bike that are lightly used). If you want, we can make a deal but, if not, I understand. I'm thinking $1600 (+shipping) for all of them or if you don't want the ones I used on the bike (4 cycles so far), I'll take $1300 for the 60 unused. That's only $400/kwh. The cheapest I've seen them anywhere is $23.99 per cell (plus shipping).

    This is just a thought and I don't want you to feel obliged, I just thought they might be of help to get this going. I'm perfectly fine with keeping them for my own YaPIP conversion (and I'm having fun w/ the bike too). Whatever works best for you.
     
  8. ericbecky

    ericbecky Hybrid Battery Hero

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    jdh2550,
    The options just keep coming at you. I'm glad I'm not having to make the decision :)
    If you decide to go the pouch option, I agree that a non-paralleled RealForce setup may not be up to the job on their own given their C value. For sure the A123's would work for you.
     
  9. lopezjm2001

    lopezjm2001 Senior Member

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    Here is the RFE 20ah spec sheet http://priuschat.com/attachments/rfe-f20-08180225-1-1-pdf.38819/ they can do max 2C. But you also need to look at the charge rating for regenerative braking. Also look at the difference in internal resistance rating compared to the A123 cells. The A123 cells are much superior.
     
  10. NortTexSalv04Prius

    NortTexSalv04Prius Active Member

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    Pouch cell and making a battery pack. I am considering this although with 3.2v 10ah tenergy pouch. I just am anxious about a method/process to connect tabs then make cable/temp wire leads. I have seen how the pc poster (from france) did his I fear I do not have that talent or resource to do the job correctly
     
  11. ericbecky

    ericbecky Hybrid Battery Hero

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  12. jdh2550

    jdh2550 Co-Founder, Current Motor Company

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    OK - today I need to make the decision on batteries... (well I don't need to - but I want to!)

    And the contenders are (in alphabetical order!):
    1. A123: Pros: high C, known brand. Cons: most work, lower capacity (does that indicate a "B" grade of cell?)
    2. GBS: Pros: I have experience with these cells and can get them at a good price. Cons: size
    3. Headways: Pros: I can get a good price from navy (if they're still available) Cons: will need to get more cells to complete the pack.
    4. RealForce (Enginer): Pros: capacity and packaging. Cons: C rate?, configuration?
    Now I'm off to measure my trunk space and run some numbers...
     
  13. jdh2550

    jdh2550 Co-Founder, Current Motor Company

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    And the winner is:

    ( drum roll please )

    #4: RealForce (as packs from Enginer).

    The price is right. The packaging and connections will be done for me (did I mention I'm lazy? Actually, the real reason is I'm more interested in working on the control algorithms than working on making a custom pack). I also like the idea of buying from a local MI company.

    Looking at the RealForce spec sheet the cells are rated at 2C "max discharge" (with no time component) and 5C "pulse discharge for 8 seconds". In this configuration that's 80A continuous and they can do a 200A peak.

    There are pros and cons to each approach - so I'm sure you'd all do something slightly different. But this is the one I've chosen.

    And now on with the show...
     
  14. Flaninacupboard

    Flaninacupboard Senior Member

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    In order to get 60-70mph EV mode you will want 100amps or more. Personally I would not use the Realforce cells at anything over 1C, which means a pack around 20kwh...

    If you'll be using it more like 40mph or so for most of the discharge then the cells will be a lot happier :)
     
  15. lopezjm2001

    lopezjm2001 Senior Member

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    What are you planning to use for a BMS with your RFE packs.

    Options-

    miniBMS - I use these.

    Enginer's BMS16D, Enginer | Solar Powered Prius Plug-in PHEV Conversion Kit with Lithium-Ion | Hybrid

    CellLoggers, Used by Mr Plugin and by FWD.

    Peter Perkins BMS, used by Planetaire

    Orion BMS,

    Hipower BMS - BMS - Detailed info for BMS,BMS,BMS, on Alibaba.com

    I guess that whatever you will use wil be used with your Atmel kit board. Should be able to use the Prius OEM hall effect current sensor. I would not think that your Atmel board would be able to measure 70 lifepo4 cell voltages.
     
  16. jdh2550

    jdh2550 Co-Founder, Current Motor Company

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    They're rated at 2C in their spec sheet - so that's what I'll use them at. However, most of my EV only journeys will be < 50mph. However, I'll try using them at higher speeds (and hence higher C rates) and see what happens.

    I'm curious - what data do you base your position of "nothing over 1C" on? And, of course the beauty of open-source is that anyone wanting to follow along can choose whatever power source they like. Supercharged hamsters FTW! :)
     
  17. jdh2550

    jdh2550 Co-Founder, Current Motor Company

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    I'll be using BMS from Current Motor Company's super scooter. It's a top-balancing shunt based design that interfaces with the charger. So, I'm currently trying to decide between an Elcon and a TC charger (both with the CAN control option).

    Yes, I plan on using the pre-existing current sensor and haven't decided on a voltage measurement device yet (OK, confession, I'll actually just go ask Erik what I should use! He's the EE brains behind Current Motor).
     
  18. lopezjm2001

    lopezjm2001 Senior Member

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    Yeah, can you tell us the price. I think you are getting 10kwh worth of RFE. Guessing that you are getting about 140 cells x US$30 ea. = $4200
     
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  19. Flaninacupboard

    Flaninacupboard Senior Member

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    The very significant voltage sag I've seen on my pack when running 1C. Resting voltage is 53.6V (16S), voltage at 1C drops to 48V within a few minutes, and will hover around 46-48V until one or more cells dives to <2.5V
     
  20. ericbecky

    ericbecky Hybrid Battery Hero

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    I have seen this voltage sag as well when I tested them in parallel with a lead acid setup in my EV.