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Thread: Question for No BMS riders

              
   
   
  1. #1
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    Question for No BMS riders

    I see quite a few members who do not use a BMS. I was wondering how you make sure you do not overvoltage any individual cell during charge or undervoltage a cell while riding. I see comments stating that after charge the cells settle to a voltage which is within 0.05V of each other, but I don't see comments about where they are just before charge termination. Also I see some with 20+ cycles with no issues. Do you use some form of logger to go back and look at cell voltages during load or charge to confirm that you are staying within specs or just look at resting cell voltages and watch the pack voltage during charge and discharge?

    Seems to be a trend moving away from 18650's, GBS and CALB and an increase in Leaf and now Volt modules being used by builders, but I don't see the Leaf or Volt BMSs being used with them. Do you think that the modules are matched well enough that there is no need to monitor individual modules during charge and discharge?

  2. #2
    Senior Member Hugues's Avatar
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    Quote Originally Posted by Skahle View Post
    ...

    Seems to be a trend moving away from 18650's, GBS and CALB and an increase in Leaf and now Volt modules being used by builders, but I don't see the Leaf or Volt BMSs being used with them. Do you think that the modules are matched well enough that there is no need to monitor individual modules during charge and discharge?
    Have Leaf pack and Orion BMS,
    I really don't advise to take risk of running without BMS,
    Regards from Switzerland
    My 2.5 Upgrade Thread

  3. #3
    Member mistercrash's Avatar
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    If you have enough disposable income that you can afford one of the good BMSs available then get one and use it. If you can't even imagine how the heck you could come up with enough money to get one, does that mean you should not be part of the EV world? Because you can't afford it?

  4. #4
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    I thought I saw that even Jack Rickard (EVTV host and formerly a strong opponent of BMS) has gotten religion after the non-BMS battery fire at his business.

  5. #5
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    Quote Originally Posted by mistercrash View Post
    If you have enough disposable income that you can afford one of the good BMSs available then get one and use it. If you can't even imagine how the heck you could come up with enough money to get one, does that mean you should not be part of the EV world? Because you can't afford it?
    Just trying to understand what real users are doing, not dis anyone for their choices. When I first got mine running a while back (24 CALB 70AH, SPM72400, ME1003) I had nothing and would get the voltmeter out and go round the pack measuring V as they approached 3.55 and manually terminate when the first one got there, then watched pack V and I and stopped riding early. It got to be a pain after a few cycles so I built a cheap monitor and display with a charge terminate SSR and a low voltage LED. My observation was that even a well matched pack rose unevenly and that over 3.5 things moved pretty fast. I have no experience with Leaf or Volt packs.

    After about a year of riding I rebuilt my system to add top-balancing, improved my voltage sense accuracy and added a color, 24-cell bar chart style display. I was on a tight budget and it was the best I could do.

    I admire the work all the people on this site put in to make something useful and fun!

  6. #6
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    Either you buy a BMS, or you BE the BMS.

    As Skahle suggests above, the latter is perfectly effective if you have the dilegence to act in that capacity.

    The bottom line is that whilst battery management is absolutely crucial, how you achieve it is far more individual.

  7. #7
    Senior Member DRZ400's Avatar
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    When I had CALB cells I used the Mini-BMS and had no problems...after 500 cycles I upgraded to LEAF modules. I don't use a BMS on these cells however I'm careful to avoid the cliffs on charge and discharge. I have over 100 cycles now and they remain in perfect balance. You do give up some range ~15%, but the batteries will last longer by not charging to 4.2. Nissan uses only 80% of available capacity BTW. With 11 modules I charge to 90 volts and set my controllers LVC to 78 volts. Also I never pull more than 50 AH's from them.
    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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