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    Balance charging

    I notice on my last three balance charges on my 52V 13.5ah battery the charger has cut off at 54.6V. Today I unplugged the charger and plugged it in a second time to see if it might go higher, same result, green light came on at 54.6 again. Using the Luna charger with the three settings, 80-90-100%. Wondering if my battery is getting degraded, probably guessing I have run 200 or under charge cycles on this battery.

    Anyone have some wisdom on this?

    #2
    Checked the output on the charger with a multimeter, putting out well over 58V on the 100% setting. I read a couple older threads on balance charging which gave me a headache with all the different opinions and suggestions.

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      #3
      All it takes is one bad cell in the parallel groups to cause that group to read under spec voltage so now that one group is gonna cause the charger to down balance the rest of the group's that are in series.

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        #4
        I hope I don't don't have any bad cells, only 4 months use on this pack, likely approx 100 charges since I don't charge every day and never run it anywhere near LVC. I'll test further.

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          #5
          Have you been charging to 100% or been doing 80 to 90% charging.
          Last edited by Rodney64; 08-06-2017, 03:33 AM.

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            #6
            Originally posted by Rodney64 View Post
            Have you been charging to 100% or been doing 80 to 90% charging.
            Been charging to 80% and then charging to 100% about once a week, that likely equates to about every third or fourth charge to keep the pack in balance. Should I be running the pack down more towards LVC before charges? My understanding was full charges were harder on the battery than partial ones but I'm still learning about this stuff.

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              #7
              Originally posted by Zippy View Post

              Been charging to 80% and then charging to 100% about once a week, that likely equates to about every third or fourth charge to keep the pack in balance. Should I be running the pack down more towards LVC before charges? My understanding was full charges were harder on the battery than partial ones but I'm still learning about this stuff.
              No, your usage and charging routine is fine, that's plenty of balance cycles, and running low isn't better.

              Balancing takes a long time, even if the pack is only a little unbalanced. It's a gentle, slow process. The first time your charger comes back on after the pack is 'full', is the first balance cycle. At this point, only ONE parallel string (the highest voltage string) has been bled down and 'balanced' by the BMS. The charger turns back on, brings the whole pack up a bit until the next highest string is string is now full, process repeats. A 14S pack could take 13 cycles. Bleed resistors are only 1-5W typically. So not a fast process. Now, not all groups will be very far out, so it's not always a long process, but the older the pack, the more likely it is to take extra time.

              Maybe you aren't balancing long enough? Only when the cycling stops, is it done. Stops means it didn't come back on for a few hours, to me. I use a logging charger to see this, it is tough to catch in real time unless you watch the charger like a hawk, since the ON cycle can be very brief. Like a minute or less, sometimes.
              Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

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                #8
                Originally posted by JPLabs View Post

                No, your usage and charging routine is fine, that's plenty of balance cycles, and running low isn't better.

                Balancing takes a long time, even if the pack is only a little unbalanced. It's a gentle, slow process. The first time your charger comes back on after the pack is 'full', is the first balance cycle. At this point, only ONE parallel string (the highest voltage string) has been bled down and 'balanced' by the BMS. The charger turns back on, brings the whole pack up a bit until the next highest string is string is now full, process repeats. A 14S pack could take 13 cycles. Bleed resistors are only 1-5W typically. So not a fast process. Now, not all groups will be very far out, so it's not always a long process, but the older the pack, the more likely it is to take extra time.

                Maybe you aren't balancing long enough? Only when the cycling stops, is it done. Stops means it didn't come back on for a few hours, to me. I use a logging charger to see this, it is tough to catch in real time unless you watch the charger like a hawk, since the ON cycle can be very brief. Like a minute or less, sometimes.
                Thanks, I'll try it again and leave the charger on once the green light comes on, I did not notice any cycling at all before but I will monitor it more closely and see if there is any.

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                  #9
                  Have you ever seen you charger turn back on, automatically?

                  I have a couple chargers which don't do that with my packs, ever. If I unplug the pack then reconnect after the green light comes on, and AFTER giving the pack a few hours to balance, then it will force a manual restart. So, I can manually perform balance cycles.

                  If you have never seen your charger automatically turn back on to balance, maybe you have the same situation. You could try manually restarting it for several cycles per above, and see if you start getting a higher pack voltage when the charging stops. If the voltage is coming up, you are improving the balance. Keep it up until you either see 58.8, or until the progress stops, whichever happens first.

                  The best way to check balance is by directly measuring the voltage of each cell group, not by watching pack voltage. Concluding that balance is off due to low final pack voltage is pretty solid, but not foolproof.

                  But, you need to partially disassemble it for cell measurements. Option.
                  Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

                  Comment


                    #10
                    There seems to be a batch of defective Luna Advanced chargers, based on the threass I've seen here. Same behavior as yours - won't fully charge. Open a trouble ticket if you have not already. Could be something else though (e.g., one person had a bad connection in his battery, whuch effectively turned it into a 48V pack...)

                    Comment


                      #11
                      Originally posted by JPLabs View Post
                      Have you ever seen you charger turn back on, automatically?

                      I have a couple chargers which don't do that with my packs, ever. If I unplug the pack then reconnect after the green light comes on, and AFTER giving the pack a few hours to balance, then it will force a manual restart. So, I can manually perform balance cycles.

                      If you have never seen your charger automatically turn back on to balance, maybe you have the same situation. You could try manually restarting it for several cycles per above, and see if you start getting a higher pack voltage when the charging stops. If the voltage is coming up, you are improving the balance. Keep it up until you either see 58.8, or until the progress stops, whichever happens first.

                      The best way to check balance is by directly measuring the voltage of each cell group, not by watching pack voltage. Concluding that balance is off due to low final pack voltage is pretty solid, but not foolproof.

                      But, you need to partially disassemble it for cell measurements. Option.
                      I have never seen the charger turn back on automatically to balance, that is correct. Also tried reconnecting after giving it overnight to balance (saw no cycling at any point), no change, I still end up at 56.4 (I wrote the number wrong above, it's cutting off at 56.4).

                      Comment


                        #12
                        Originally posted by Kocho View Post
                        There seems to be a batch of defective Luna Advanced chargers, based on the threass I've seen here. Same behavior as yours - won't fully charge. Open a trouble ticket if you have not already. Could be something else though (e.g., one person had a bad connection in his battery, whuch effectively turned it into a 48V pack...)
                        Hmmn........that could possibly be the case here, maybe I should buy another charger and try it? The charger indicates it's putting out full charge of over 58v though when I checked it with my multi-tester.

                        Yeah I went ahead and opened a trouble ticket hoping to get some input from staff, Gary is trying to help figure it out with some basic questions.
                        Last edited by Zippy; 08-09-2017, 08:40 AM.

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                          #13
                          Originally posted by Zippy View Post

                          Hmmn........that could possibly be the case here, maybe I should buy another charger and try it? The charger indicates it's putting out full charge of over 58v though when I checked it with my multi-tester.

                          Yeah I went ahead and opened a trouble ticket hoping to get some input from staff, Gary is trying to help figure it out with some basic questions.
                          Buying the same charger and comparing the performance of the chargers side by side would sure illuminate any problems right quick with the charger in question, and you would then have a spare on hand. Win/win!

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                            #14
                            Well upon measuring the voltage right off the battery it read 58.7 after another attempt at balance charging. For some reason my display is not indicating correct voltage (it was previously). I've got it set to UBC but looks like everything is okay. Now I've got an excuse to raid the piggy bank and purchase a Satiator from Grin and a wattmeter from Luna.
                            Last edited by JPLabs; 08-11-2017, 09:42 AM. Reason: Not edited, oops wrong button, sorry.

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                            • JPLabs
                              JPLabs commented
                              Editing a comment
                              The Satiator is a worthwhile purchase, if you have the budget, IMO. It's all the chargers I need, balances reliably, etc. But it's complex to use, and could be mis-useds with bad results. You set your own safe charge parameters, like max voltage. So it's not a safety net, all automatic system. Don't use if not capable of figuring out and verifying a safe charge profile for every pack you use.

                            #15
                            Interesting. My DP-14 shows almost a full volt higher voltage than actual. These things are not that precise and apparently can't be trusted for critical measurements. Good to take the battery out and measure the actual voltage periodically ...

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