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Thread: Programming controller for GBS cells

              
   
   
  1. #1
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    Programming controller for GBS cells

    Hey folks. So I'm sure this has been discussed here- but I can't seem to find the thread. Anyways, I have a 72volt GBS 60AH battery pack. I have the Alltrax 7234 controller. Should I re-program the controller to only allow 180 amps? I see the GBS cells only have a 3C discharge rating. Or, is it ok to allow the full 300 amps the controller can provide?

    Also, is it ok to immediately charge the battery pack after a ride? Or, should I wait for the cells to cool off first (they only get slightly warm, so no worries there),

    Thanks!

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    Senior Member Hugues's Avatar
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    Some of my 100 Ah GBS reach 2.8V when going beyond 200 amps. So you should start below that and monitor them before you push this up.

    I believe there is no problem to charge your batteries if they are below 25 Celsius
    Regards from Switzerland
    My 2.5 Upgrade Thread

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    Senior Member robo's Avatar
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    The cells can discharge more than 3C in short bursts. It's good to avoid sustaining discharge >3C though.

    This is assuming your motor is OK with 300A.

    I only have 20 CALB 60Ah cells and per ride, I will pull over 250A several times and it's not unheard of to pull 350A-400A if I really need (or want) it.

    Your cells will last longer of you limit to 180A, but it won't be as much fun

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    Seņor Member podolefsky's Avatar
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    3C is a continuous rating. They should be able to do 10C "burst" for under 10 seconds. 300A is only 5C and should be no problem for 60Ah GBS. I've pulled over 600A from mine in short bursts, with sag to around 2.5V.

    The fact is, even if you go full throttle, the cells will only see 300A for a second or two. Throughout the rest of the RPM range, battery amps will be less than motor amps. You have to set up a very special situation to get full motor amps for more than a few sec, like going up a steep hill with the motor at just the right RPM.

    Set your controller to full current and have fun.

    Perfectly fine to charge immediately after a ride.
    - Noah Podolefsky -
    The GSX-E

  5. #5
    Senior Member Hugues's Avatar
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    Quote Originally Posted by podolefsky View Post
    3C is a continuous rating. They should be able to do 10C "burst" for under 10 seconds. 300A is only 5C and should be no problem for 60Ah GBS. I've pulled over 600A from mine in short bursts, with sag to around 2.5V..
    mmm, your mileage may vary here,

    some of my 100 Ah GBS sag down to 2.2 V under 360 amps , those with higher internal resistance, so i would not pull 600 amps, or even less so 1000 amps from these cells. So better do this gradually and check the internal resistance of each cell.
    Regards from Switzerland
    My 2.5 Upgrade Thread

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    Seņor Member podolefsky's Avatar
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    Quote Originally Posted by Hugues View Post
    mmm, your mileage may vary here,

    some of my 100 Ah GBS sag down to 2.2 V under 360 amps , those with higher internal resistance, so i would not pull 600 amps, or even less so 1000 amps from these cells. So better do this gradually and check the internal resistance of each cell.

    Elite Power has told me the 60Ah cells are "stiffer" than the others. But 2.2V at 3.6C? I think you have some cells way below spec. You shouldn't be seeing below 2.8V at that C-rate.

    Here is discharge data for 100Ah GBS. Even at 3C, voltage doesn't dip below 3.0V except at the very end of discharge. If you're getting worse performance than that, I would complain to the supplier. The cells should have a warranty, as long as they haven't been abused.

    http://elitepowersolutions.com/docs/...g%20Curves.pdf
    Last edited by podolefsky; 21 June 2014 at 1215.
    - Noah Podolefsky -
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    Senior Member Hugues's Avatar
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    Yeah, I should send them the internal resistance values, but I bought them 2 years ago, not sure they'll want to discuss
    Regards from Switzerland
    My 2.5 Upgrade Thread

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    Thanks for the info guys! I've got the controller set to 300 amps. No problems so far- I just wanted to be sure! Thanks again!

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    Senior Member robo's Avatar
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    Quote Originally Posted by Hugues View Post
    ...some of my 100 Ah GBS sag down to 2.2 V under 360 amps...
    Hi Hugues. It's worth checking those cells. Even my 20 60Ah CALBs don't sag near 2.2V when briefly drawing 350A+. And, my pack is small (by design) compared to most here. Here are some plots from last year:

    http://www.elmoto.net/showthread.php...nce-data/page4

    Granted, those plots show pack voltage and not individual cell voltages. But 1500mi/2400km later, today the pack still seems healthy. And, that's with a few brief 250A+ draws per ride.

  10. #10
    Senior Member Hugues's Avatar
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    Quote Originally Posted by robo View Post
    ...

    Granted, those plots show pack voltage and not individual cell voltages. But 1500mi/2400km later, today the pack still seems healthy. And, that's with a few brief 250A+ draws per ride.
    well, be careful with pack voltage, mine reads 79 volts while the lowest cell is at 2.3v, i have 28 of them, so average is 2.82 v.
    Internal resistance can vary from cell to cell so pack voltage might not reliable enough when pulling a lot of amps from the pack.
    Regards from Switzerland
    My 2.5 Upgrade Thread

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