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Thread: Nissan Leaf battery testing

              
   
   
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    Seņor Member podolefsky's Avatar
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    Nissan Leaf battery testing

    Here is test data I took on a single Leaf module from Hybrid Auto Center. This is a brand new module, not used.

    Cells were balance charged to 4.2V each using an iCharger.

    I did capacity tests on each 2P set within the module. I used a CBA IV. Discharged to 3.0V at 15A (C/4). I got 58.32 and 59.1Ah. These were done after the very first charge.

    Test plots are here and here. As Hybrid Auto's site says, at 3.6V you get about 90% of the full capacity.

    Cells were balance charged again to 4.2V, then discharge rate tests done on the first 2P set.

    My setup is sort of crude, but it gets reasonable data. It is a bank of nichrome wires in parallel, a clamp ammeter (1000A DC limit), and a voltmeter. I change the number of nichrome wires, which changes the load and lets me do tests up to 600A (10C for these cells). I did each test for just a few seconds each. (The wires heat up, resistance goes up and changes the discharge rate after a few seconds.)

    Results look pretty good to me - LVC for these cells is about 2.4V, so they should be able to to well over 10C in short bursts. I didn't feel the need to test any higher (plus I ran out of nichrome wire).

    One limitation might be the tabs that connect the cells to the external terminals - they are pretty thin. The external terminals got warm, but not overly hot. They are surrounded by plastic, which looked unharmed after the tests.


    C-rate Amps Cell Voltage
    2C 120 3.96
    3C 180 3.85
    5C 300 3.75
    8C 480 3.55
    10C 600 3.50
    Last edited by podolefsky; 13 July 2014 at 2148.
    - Noah Podolefsky -
    The GSX-E

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    What was the nature of your connection to the battery terminals (bolts certainly, but of what composition and how mated to the cables)?

    Cheers.

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    Seņor Member podolefsky's Avatar
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    2AWG cable with crimped to copper lugs, bolted with stainless hardware.

    This is my discharger. Each nichrome wire pulls around 30-35A. (E.g., 2C test was done with 4 wires to pull 120A).

    - Noah Podolefsky -
    The GSX-E

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    Senior Member DRZ400's Avatar
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    I bet that would make a nice spa heater! Good info! I use a coil of 10 gauge wire with tap off points.
    2003 Ninja 250EX, Agni #95R, 6:1 Gearing, 11 Leaf Modules.
    Alltrax SPM72400, 400 amp Controller, all LED lighting
    2014 CRF450X Supermoto
    http://www.evalbum.com/1955
    http://www.evalbum.com/3337

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    Yeah that looks to be about as good as you'll manage alright - the voltage drops that can be observed across a terminal interface, particularly at high loading, and the variance that you get depending on the materials at the junction never cease to amaze me.

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    Seņor Member podolefsky's Avatar
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    Yup. The encouraging thing is that, if anything, the actual cell voltage is probably higher than the meter reading.
    - Noah Podolefsky -
    The GSX-E

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    EVangelist electriKAT's Avatar
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    Each module is a 2S2P configuration. Can you access the parallel pairs without disassembling the module, for balancing purposes? Or is the module treated as a unit?

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    Seņor Member podolefsky's Avatar
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    Each module has 3 terminals, so you can access both pairs. That's how I did my tests on one pair at a time. The center terminal is just meant for voltage sensing / balancing - but it seemed stout enough for a high discharge test (it survived 600A in a couple second burst).

    There's lots of info on the modules here.

    They say peak current 540A, but I think that is just the peak the Leaf pulls. They appear to be capable of much more.
    Last edited by podolefsky; 15 July 2014 at 0921.
    - Noah Podolefsky -
    The GSX-E

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    Senior Member DRZ400's Avatar
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    So how do they compare with your GBS as far as sag? If you were buying calles today would they be These or the GBS?
    2003 Ninja 250EX, Agni #95R, 6:1 Gearing, 11 Leaf Modules.
    Alltrax SPM72400, 400 amp Controller, all LED lighting
    2014 CRF450X Supermoto
    http://www.evalbum.com/1955
    http://www.evalbum.com/3337

  12. #10
    Seņor Member podolefsky's Avatar
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    Kind of apples and oranges - mostly because if the Leaf cells weren't a special buy, they'd probably be 1.5-2x the price of GBS.

    But, here's what I'd say. I have data for my 60Ah GBS where they sag to 2.8V/cell at 500A. I've looked down at my gauges and seen about 2.5V/cell at 650A (but that's less reliable, since I was riding when I "took that data"). That's over 10C, but it's right at the edge of those cells' capability. On the other hand, Leaf cells had lots of room left at 10C.

    (BTW, I realize voltage sag isn't the only indicator of a cell's capability - you're really worried about heat, lithium plating, etc., and I didn't measure any of that. But for burst tests, voltage will give you a good sense of how much you're stressing the cell.)

    The other place the Leaf cells are better is energy density. They're about 200 Wh/L, including the module casing, whereas GBS (and most other LiFe prismatice) are about 130 Wh/L.

    Couldn't leave out that the Leaf cells are $0.25 / Wh, GBS are about $0.40 / Wh. At that price it's no contest. But again, that's a special buy. At the same price, still no contest. If they were 2x the price, I'd have to weigh the cost/benefit - but if that were the case, knowing what I know now, I'd probably save up and get the Leaf cells.
    Last edited by podolefsky; 16 July 2014 at 1231.
    - Noah Podolefsky -
    The GSX-E

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