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How to fix a battery in decline?

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    How to fix a battery in decline?

    52v 11.5ah PF Shark from Luna. Even though I have taken pretty good care of it, performance is clearly on the decline after just 4 months and less than 100 charges. I kept the charge setting on 90%/3 amps and rarely drained it beyond 20%, so I don't think it's abnormal use by any means.

    I get that it's months old so no refunds, but any ideas how to return it to former glory?

    #2
    Originally posted by CraigAustin View Post
    52v I kept the charge setting on 90%/3 amps and rarely drained it beyond 20%, so I don't think it's abnormal use by any means.
    Actually this in my opinion this is not good practice. Charging to 90% doesn't give the BMS a chance to balance the cells. Most BMS unit only starting balancing when the first few cells hit 4.2 volt. If you bulk charged then balanced with a separate balance charger then this would be ok. If youre not sure what im talking about then search endless sphere balance packs.

    If you can test it with a multimeter. The packs 14s 4p. Try testing each 4p to see if they're balanced. Also try fully charging the pack to %100 and try leaving it on for 8 to 9 hours.
    This is when the pack balances. Bulk charges then cycles the last few percent. The pack may need to be left on like this for a few charges but monitor the pack don't leave it alone or over night.
    Last edited by Rodney64; 07-22-2016, 01:37 AM.

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    • CraigAustin
      CraigAustin commented
      Editing a comment
      Thanks Rodney. I actually do charge to 100% every 3-4 weeks for that reason, but have not tried leaving it on for 8-9 hours. I will give it a shot and see what happens. Based on everything I had read here, the best way to prolong battery life is to avoid 100% charges at 5 amps except periodically to balance the pack; don't drain it fully all the time; and don't charge more than once a day. If that is incorrect please let me know. This battery already lacked range and can't afford to get worse.

    #3
    The pack maybe way out of balance.
    Last edited by Rodney64; 07-22-2016, 03:50 AM.

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      #4
      Try a few long charges. I would forget the 90% and now always charge to 100%.

      Comment


      • CraigAustin
        CraigAustin commented
        Editing a comment
        Thanks again Rodney, I'll try it and let you know the results.

      #5
      Thanks Craig

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        #6
        So I gave the battery a couple of 100% charges and left it plugged in afterward, as suggested, but it hasn't helped. A ride that used to drain 80% of the battery is now draining it completely. I've done this ride a lot so I'm familiar with the ranges. Also noticed my battery won't charge to 58.7v anymore, seems to top out at 58.5, is that normal?

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          #7
          That minor voltage drop IS normal. What are you getting for actual mileage? Or did I miss the number?

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            #8
            Thanks Louis. I got 14 miles on a 100% charge. Hybrid bike, rolling hills, PAS 5 but limited throttle, 20-30 mph for the most part, always pedaling. I used to get 14 miles on that route when I gunned the throttle at every opportunity.

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              #9
              What is the current mileage? Sorry I wasn't clear.

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                #10
                No problem. It's just over 1k miles.

                Comment


                • Louis
                  Louis commented
                  Editing a comment
                  I'm bad at being clear....mileage was 14 miles to a charge, what is it now?

                • CraigAustin
                  CraigAustin commented
                  Editing a comment
                  No worries!

                  BEFORE: 18 miles
                  TODAY: 14 miles

                  I used to get 14 miles on this route when I used throttle constantly, and pedaled on the downhills rather than conserve battery.

                #11
                My tentative understanding about balancing with these chargers is this:

                If your charger cycles on and off while at full charge, it can balance fully by leaving it plugged in and on a long time with 100% setting.

                If your charger never turns back on like mine (which is unusual but not unheard of), then I think it's necessary to do a few back-to-back charges at 100% to endure full balancing. Charge until it turns off, let it sit while the BMS drains the high cells, repeat. You can watch how far the pack voltage drops while sitting to see if it's draining down high cells to any significant degree. I find that repeated full charging reduces how much the voltage drops, for me, and also increases the 'full charge pack voltage' if I haven't balanced for a while. If I've balanced recently I'll see 58.7V and occasionally 58.8V right at shutoff. If not, it's more like 58.4V at shutoff.

                So, just in case your charger isn't cycling back on at 100%, try a few more charge and rest cycles and see if the voltage goes up at all, at charge termination and/or especially after resting. If so, you are balancing further.
                Last edited by JPLabs; 07-25-2016, 10:20 PM.
                Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

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                • CraigAustin
                  CraigAustin commented
                  Editing a comment
                  Thanks JP, much appreciated. Following your advice as we speak and will let you know what happens.

                • pcliteuser
                  pcliteuser commented
                  Editing a comment
                  I charged my 52v battery at 100% and let it sit overnight (roughly 9-10 hrs) at 58.2v and i noticed that what the charger does was drained the battery down to 57.4 is that normal?

                #12
                I'd guess based on how you ride, you mention riding at max speeds often, that this wouldn't be a surprise. I think it's to small of a pack. I think you'd do much better with a 20Ah pack. 11Ah is better suited to a pleasure rider. Which cell was used in your pack? is it warm or hot at the end of a commute?

                Am I wrong about you commute speeds? I'm grasping for straws, but as I mentioned, and JPLabs reinforced with more direction, you may see improvement. I'd also, since you're getting more involved in building bike, that a Satiator would be a better choice for chargers. <ducking>

                Comment


                • CraigAustin
                  CraigAustin commented
                  Editing a comment
                  Ha! Thanks Louis, you are correct and I should have bought a 20ah battery. My 11.5 PF already lacked range and now it's lost about 20%, hence the motivation for my post here. It's raining cats & dogs this morning so I'll do a few more rebalance charges and let you know the results.

                #13
                Battery is charging to 58.6 or 58.7v, so things are looking up. I'll give it a full range test once this rain lets up.

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                  #14
                  Having some bad luck here. My charger stopped working, plugged it into the wall (several different places including a hardware store) but no LED lights go on nor does the display. When I plug it into the battery, even though battery is full the display reads 51v. Fuse looks good so I doubt that's it. Any ideas?

                  I feel like a drama queen this week but an ebike is useless without a charger.

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                    #15
                    I think the Luna chargers are a weak link in an otherwise great chain. I know I had to have 3 sent to me before I got one that worked.

                    Comment


                    • Louis
                      Louis commented
                      Editing a comment
                      Unfortunately I agree. I have two. Over two and half years the only charger to NOT let me down has been the Satiator. Expensive but if the reports and information on battery longevity are true, it paid for itself in the lifecycle of one battery. VERY easy to setup on my computer and load battery profiles to the charger. I have 48V 80% and 100%, 52V 80 and 100, 36V 90%. I can change parameters and charge a 5A if i need a faster charge. It can go higher but I'm BMS limited. For anyone who may have more then one size battery it's ideal. AND it's highly water resistant and could be bike mounted.

                      OSX and Windows friendly too.
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