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    battery maintenance

    I dunno, but I feel like my battery is deteriorating faster than it should be. When I first got it, mid-june, i was getting about 18 to 20 miles per charge. (Using throttle only.) Now, only about four months later, Im only getting about 11-13 miles out of it. At that rate, I won't even get a year out of it, which is disappointing, as I spent extra on a luna battery in the hopes that it would last better, have a better BMS, etc.

    What can I do to slow this decay? I have a 48v shark from luna with a 1000w kit from amazon. its suposedly limited to 750w, though. I do ride a lot commuting to work 5 days a week and doing shopping, etc, needing to charge every day. thats still only about 90 cycles, though.

    theres two things that ive been doing that i think might be the culprit, but im not sure, and in both cases i wouldve thought the BMS shouldve stepped in to prevent damage.

    the first is that maybe ive ridden it too low. my previous ebike would turn off automatically when the charge got too low. Im not sure this build is doing that, though. when the indicator shows low (theyre inaccurate, though, i know...) itll give me a few miles, and then it starts to rev and seem like its struggling a bit while accelerating, although once im up to speed its good. itll continue on like that for at least a few more miles. i dont think ive ever continued past that point until it actually turned off, though. so it occurred to me recently that maybe it should be shutting off at the point where its revving, and by riding it past that point im damaging the battery. maybe the BMS is faulty...?

    the other thing that i thought might be affecting it is "flooring it" all the time, even from a stand still rather than starting out slow to get going before giving it full throttle. it does seem to graduate the acceleration some automatically even with the full throttle, but maybe its not enough. would trying to accelerate too much too quickly damage the battery? for now ive stopped doing it, though.

    thanks.

    #2
    That would be pretty extreme degradation, if the cells are actually losing that much capacity. Luna uses good cells, I doubt you could hurt them that badly, that fast! But, an imbalance condition can limit your pack's energy. Do you balance charge once in a while?

    Do you still see the same max voltage, at full charge, as you did new? About 54.6V? If no, could mean imbalance.

    Imbalance effect:
    One parallel group gets to 100% before the others, and charging stops to prevent overcharging that group. So some groups are left less than full. Discharging, the effect is compounded further; the lowest group will determine when you are empty, so you don't even get to fully use the full group(s).

    To balance: do a long charge at 100%. Cycle the power to restart charging, if your charger requires it for balancing. Let it sit at full voltage for a couple days so the BMS can do it's balancing routine. In a safe place.

    Search 'balance charge' for your charger type for more details.

    If your pack's BMS continuously balances, this isn't the issue, but I'm guessing you don't know that spec, so just check the above.

    Another possibility is you are just riding it a lot faster/harder than when it was new. I noticed a big effect, there, myself. I ran slower in my early days....consider this too.
    Last edited by JPLabs; 10-27-2018, 08:06 AM.
    Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

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      #3
      Originally posted by JPLabs View Post
      That would be pretty extreme degradation, if the cells are actually losing that much capacity.
      i know, which is why im kinda disappointed in it...

      Originally posted by JPLabs View Post
      Luna uses good cells, I doubt you could hurt them that badly, that fast! But, an imbalance condition can limit your pack's energy. Do you balance charge once in a while?

      Do you still see the same max voltage, at full charge, as you did new? About 54.6V? If no, could mean imbalance.

      Imbalance effect:
      One parallel group gets to 100% before the others, and charging stops to prevent overcharging that group. So some groups are left less than full. Discharging, the effect is compounded further; the lowest group will determine when you are empty, so you don't even get to fully use the full group(s).

      To balance: do a long charge at 100%. Cycle the power to restart charging, if your charger requires it for balancing. Let it sit at full voltage for a couple days so the BMS can do it's balancing routine. In a safe place.

      Search 'balance charge' for your charger type for more details.

      If your pack's BMS continuously balances, this isn't the issue, but I'm guessing you don't know that spec, so just check the above.

      Another possibility is you are just riding it a lot faster/harder than when it was new. I noticed a big effect, there, myself. I ran slower in my early days....consider this too.
      thanks for the reply. i have the luna 48v shark - https://lunacycle.com/48v-panasonic-13-5ah-shark-pack/ with the standard charger, which i think is this one - https://lunacycle.com/standard-basic...ttery-charger/. im not sure about the voltages. i do have a [cheap] multimeter, but im not super familiar with usage and since theres 4 connections on the pack im not sure which to check. (and dont want to short it by checking the wrong one. did that once when checking a light switch. mustve had it on the wrong setting or something and it sparked, melting the probes. nervous about using multimeters since then..)

      so is a balance charge just letting it sit plugged in even after its supposedly finished charging? i dont specifically do that to balance it, but it does get left plugged in for a while after finishing sometimes. im not sure whether the luna bms continuously balances, although i would hope so.

      i dont think my riding is much different, although i suppose its possible.

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      • JPLabs
        JPLabs commented
        Editing a comment
        Right, just leave it plugged in.

      #4
      Originally posted by JPLabs View Post
      Right, just leave it plugged in.
      ah, ok. so i didnt do it for balance purposes specifically, but i do leave it plugged in overnight or longer on occasion. dunno if its it balancing, but i have noticed a couple times when i happened to be around when it finished charging that the charging stopped and started a couple times at the end before it finished. i had wondered about that, but i would guess that its because of balancing.


      i just checked with the multimeter, and after sitting plugged in since yesterday afternoon, it reads 54.7 volts.


      so does that mean the battery is still fine? maybe its not the battery thats degrading, but the motor. maybe thats not running as smoothly as it was at first, so its draining the battery faster?


      also, do you think its safe to ride even when its low and 'revving'? can i ride it until the bms and/or controller cut off power because its too low, or should i stop riding if it seems like its having trouble getting enough power?


      thanks.
      Last edited by RetFor; 10-27-2018, 10:22 PM.

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        #5
        Originally posted by RetFor View Post

        ah, ok. so i didnt do it for balance purposes specifically, but i do leave it plugged in overnight or longer on occasion. dunno if its it balancing, but i have noticed a couple times when i happened to be around when it finished charging that the charging stopped and started a couple times at the end before it finished. i had wondered about that, but i would guess that its because of balancing.

        Yes, seeing that cycling is good. That's due to balancing. Pack reduces highest voltage strings to balance, then voltage drops below charger turn-on, and it cycles. When cycling STOPS, it's balanced.


        i just checked with the multimeter, and after sitting plugged in since yesterday afternoon, it reads 54.7 volts.

        If plugged in, that is still charger voltage. Leave it unplugged for 5-10 minutes, and then check the pack. If still near 54.6V at the pack, it's full and balanced, pretty well. If less, not full and balanced.


        so does that mean the battery is still fine? maybe its not the battery thats degrading, but the motor. maybe thats not running as smoothly as it was at first, so its draining the battery faster?

        Well, it means the charging is maximized, and you should get the full remaining capacity of the pack, as such. But pack could be degraded in capacity, and still balance. If your voltage is showing full per above, it means your low range is not due to imbalance. But you could have a weak pack now. We are just trying to rule out imbalance. But, it would be nice to find imbalance, that's easy to fix.


        also, do you think its safe to ride even when its low and 'revving'? can i ride it until the bms and/or controller cut off power because its too low, or should i stop riding if it seems like its having trouble getting enough power?

        It's not great for your cells if bouncing off low voltage cutoff, no. At least, go real easy on power. BMS should keep you from going too low, but I don't like to rely on that, or advise it. Then again, I push mine to keep going if I'm running out, as much as it will let me....hard not to! I go easy on it but make it give me all it can to get home.


        thanks.
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