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Thread: Battery Life

  1. #1
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    Battery Life

    So my 7200mah 2S lipos seem to only last maybe 20 minutes in my Summit before the ESC switches to half speed due to the LVD.

    Once this happens I can take the batteries out of the Summit and run them in my E-Revo for about another half hour so the batteries are fine.

    I can't change the voltage that the EVX-2 LVD cuts in at can I?

    So what can I do about this? 20 mins run time is ridiculous for 7200mah.

    Is there a solution that doesn't involve turning off the LVD and using an alarm?

    Cheers

  2. #2
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    Ive had this same problem. I think its because some evx-2's are very sensitive to voltage sag. If your lipos are used alot and tired this happens. I just got an alarm and run it in non lvd mode. As far as i know there is no way to change the cutoff setting on evx-2.

  3. #3
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    A capacitor between the lipo and ESC may help. It would smooth the power delivery, keeping voltage more stable.

  4. #4
    Marshal ksb51rl's Avatar
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    A pertinent question: what is the ERBE's LVC set at?
    Alt-241 on the number pad =

  5. #5
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    Turn off the Low Voltage Detection on your ESC and use a seperate adjustable Low Voltage Buzzer.

  6. #6
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    Quote Originally Posted by ksb51rl View Post
    A pertinent question: what is the ERBE's LVC set at?
    I THINK I remember stock Castle electronics (mmm) are set to 3.2. But of course with the Castle link you can adjust it.
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  7. #7
    Marshal ksb51rl's Avatar
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    It is. And I can tell you that such a Low Voltage Cutoff level WILL damage good cells. Not "might" but "WILL".
    Alt-241 on the number pad =

  8. #8
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    Quote Originally Posted by Jws1982 View Post
    A capacitor between the lipo and ESC may help. It would smooth the power delivery, keeping voltage more stable.
    Ksb51rl do you agree with this? Just wondering.

  9. #9
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    Quote Originally Posted by ksb51rl View Post
    A pertinent question: what is the ERBE's LVC set at?
    My ERBE's LVC is set at 3.4V

    Do you know what the EVX-2's LVC is set at? Seems like it's set at 4.10

  10. #10
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    Quote Originally Posted by clinical View Post
    My ERBE's LVC is set at 3.4V

    Do you know what the EVX-2's LVC is set at? Seems like it's set at 4.10
    I've read it's set at 3.4vpc but mine used to drop out at around 3.8vpc.
    Slugs are just naturally aspirated snails

  11. #11
    Marshal ksb51rl's Avatar
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    Battery Life

    Quote Originally Posted by roscoeP View Post
    Ksb51rl do you agree with this? Just wondering.
    That's a big, "it depends." But I believe it won't have a significant effect on run time in this case.

    Quote Originally Posted by JoelRobbo View Post
    I've read it's set at 3.4vpc but mine used to drop out at around 3.8vpc.
    I would doubt that would be 3.8V/cell dynamic. It is more likely that you were taking a static voltage reading after a bit of rebound occurred.
    Last edited by ksb51rl; 04-20-2014 at 09:30 PM.
    Alt-241 on the number pad =

  12. #12
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    Quote Originally Posted by clinical View Post
    Do you know what the EVX-2's LVC is set at? Seems like it's set at 4.10
    My sons stampede LVC cuts off around 3.8 . I'm gonna bet that Traxxas sets all the vehicles (except those with Castle esc) to cut out at the same level.

    Keep in mind Traxxas is a family - conservative company. Better to lessen the trucks run time by 5 minutes rather than kill and replace dead/puffed lipo batteries under their warranty.

    You ever see a lipo powered RC truck go up in flames? Traxxas does what it can to avoid that scenario. Not good for company image.
    Last edited by noir 522; 04-21-2014 at 12:23 AM.
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  13. #13
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    Quote Originally Posted by noir 522 View Post
    My sons stampede LVC cuts off around 3.8 . I'm gonna bet that Traxxas sets all the vehicles (except those with Castle esc) to cut out at the same level.

    Keep in mind Traxxas is a family - conservative company. Better to lessen the trucks run time by 5 minutes rather than kill and replace dead/puffed lipo batteries under their warranty.

    You ever see a lipo powered RC truck go up in flames? Traxxas does what it can to avoid that scenario. Not good for company image.
    That makes sense. $5 low voltage alarm... problem solved.

  14. #14
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    Quote Originally Posted by clinical View Post
    So my 7200mah 2S lipos seem to only last maybe 20 minutes in my Summit before the ESC switches to half speed due to the LVD.

    Once this happens I can take the batteries out of the Summit and run them in my E-Revo for about another half hour so the batteries are fine.

    I can't change the voltage that the EVX-2 LVD cuts in at can I?

    So what can I do about this? 20 mins run time is ridiculous for 7200mah.

    Is there a solution that doesn't involve turning off the LVD and using an alarm?

    Cheers
    Did you happen to check the volts on the batteries when you pulled them from the Summit? If not I would recommend a cell checker and see what the batteries voltage is. Remember the batteries will recover a little bit. I had this same issue a year ago and have many posts on the subject.

    The simplest easiest way to solve this is to disengage the LVD and plug the battery that powers the BEC in the ESC into a $5 LVA alarm. I have my LVA zipped tied to the BEC wires and plug the balancing port into the LVA. It works every time and the beep is very loud.

    A couple side benefits - You can monitor your voltage in the battery anytime (great for long trips so you have enough power to get back). You can confirm when you plug in the LVA that your batteries are fully charged. You can adjust the LVA to whatever voltage cutoff you desire. You can use NIMH batteries for backup and not hassle with turning off the LVD. You can confirm what the voltage is in the battery when you are done. Sometimes I run my lipos down to 3.8 volts and change batteries so I don't have to recharge them to storage mode.

    JUST REMEMBER WHAT ksb51rl SAID. DO NOT OVER DISCHARGE YOUR BATTERIES. YOU WILL RUIN THEM. I STOP AT 3.4 VOLTS.
    "Better Old and Devious than Young and Exuberant"

  15. #15
    RC Turnbuckle Jr. 87 GN's Avatar
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    Traxxas rep said 3.4 to 3.6, SO run an LVA until you get to know the cut out. That is what I'm doing, but haven't ran the cells down that low yet. (3.7ish) My LVA reads .02 low...
    Last edited by 87 GN; 04-21-2014 at 04:57 PM. Reason: .02
    Would you go flip my truck back over??

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