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    Battery charging, when and how?

    I have 3 11.5 AH Luna batteries, (2 Panasonic, 1 Samsung) one in use for 100 miles, one 20 miles, and one yet to be used. All 52 volts. I also have the Luna 300 watt advanced charger. So far I have not used the 5 amp charge rate at all, just the 3 amp setting. Plus, except for once with the battery ridden 100 miles, I only charge to 80%. Is there a regime for breaking in a new or almost battery? When does the BMS balance the individual cells: all the time, or only when charged to 100%? The one time I charged to 100%, the charger seemed to hold the voltage at 58+ volts for some time, while not going higher but also still "on", or at least the green light wasn't on indicating the charge process was completed, was this time period the balancing? If so, it would seem to be a good idea to charge to 100% now and then....

    The other thing I need some input on is when to charge. Right now for example I have a battery indicating 50.4 volts, as I'm not expecting to go on an extended ride, just 1.5 miles (3 mile round trip) to the mail box the next few days, is it better practice to cycle it a bit deeper, or simply recharge if convenient to the usual 80%? I keep all the bikes and gear in my shop so it's real convenient to charge whenever I want, I'm just not sure when that is. Thanks


    #2
    https://www.electricbike.com/ebike-c...-fast-or-slow/
    http://electricbike.com/forum/forum/...r-maximum-life
    https://www.electricbike.com/%E2%80%...rs-watt-hours/

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      #3
      That answers all my questions except one:does the BMS balance the pack regardless of charge rate and percentage of charge, only when charged to 100%? Or in other words does the pack get balanced automatically, when needed, no matter how the charger is used? Thanks

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        #4
        I've read all these articles but still can't find an answer. Should I make my first few(brand new battery) charges 100%?

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          #5
          Generally speaking, for lithium-based batteries, to maximize battery lifespan:

          - Charge slowly rather than quickly.
          - Recharge early and often; frequently topping off the battery is better than using most of the power and then recharging.
          - Don't charge above 80% capacity if you don't need the juice. In terms of battery longevity, 80%>90%>100%.
          - Don't discharge below 10-20% capacity.
          - Don't charge when the pack is especially hot or cold (around freezing or below). This can damage the battery.
          - Don't leave the battery plugged in and charging for long periods of time (days, weeks) once it is full.

          You're not going to immediately kill your pack by violating these guidelines, except maybe the temperature one, but the more you go against them the more quickly you'll wear out your pack.

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            #6
            My strategy has been to immediately slow charge after every ride to 80% and then unplug. When I want to ride, I plug in and charge to 100% at up to 6a and ride as soon as I reach full charge. If I have to drive to a riding spot it might be up to an hour before I start ride, but still, the pack does not see 100% for very long.

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              #7
              Originally posted by Lance Tesla View Post
              the pack does not see 100% for very long.
              Just charging it to 100% reduces the pack's lifespan. "It's only there for a little while" doesn't change that.

              If your pack lifespan isn't particularly important to you, go ahead and charge it to 100%. You're still likely going to get quite a few hundreds of cycles out of the pack if it's good quality. Charging to a middling number and then topping it off only really matters if it's going to be sitting around unused for a while.

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                #8
                CPG,

                To your question about balancing: I have read explanations which state that the BMS works by bleeding down any parallel strings which hit target voltage before the others, in order to balance charge. Also, that this can only happen when the pack is fully charged. This makes sense to me, and I think it is correct.

                For my new pack, I elected to make a long full charge shortly after I got it, so the BMS could balance in case it was needed. Overnight, maybe 16 hours total.

                I only did the overnight charge after charging while watching it for a few cycles, just to keep an eye on it and make sure all seemed normal. 'They' always say don't charge unattended, which is good advice, but that's hard for an overnight. I also put the pack in a safe place to do the unattended charge - in my case that's a turkey pan on the garage floor. I don't mean to sound like anything bad is likely to happen, quite the contrary. It's good practice, though, just in case.
                Fabrication is fun! Build something today. Show someone. Let them help. Inspire and share. Spread the desire.

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                  #9
                  That's the premise I'm proceeding with, every now and then give it a full charge, if nothing else just to balance things out. But my charger, the "Luna 300 watt advanced", seems to shut down once the green led comes on and the fan shuts off. My amp probe shows no current flow anyway, I was under the impression it's balancing while it holds the voltage at the tail end of the charging cycle. Once I hear that fan go off and see the green light I have been unplugging everything. I have been doing my charging either in the house on the coffee table (right in front of me in other words) just so I can see how long it takes, and I never step out of the house when doing so. Unattended, I set it on my cast iron table saw top in the shop, with nothing else around it. You using the same charger I am?

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                  • JPLabs
                    JPLabs commented
                    Editing a comment
                    Yes, same charger. Mine behaves the same way. It never exceeded 58.7V at the pack, per my DVM. But some groups of cells could still be at 4.2V, and get bled down by BMS, even with no charger current. I think only a perfectly balanced pack can hit 58.8V, so this behavior makes sense to me.

                    I have never seen the charger restart after the green light. But balancing is slow, I probably haven't waited long enough to get 100% balanced. Or, maybe it doesn't ever restart, I really don't know.
                    Last edited by JPLabs; 03-20-2016, 09:21 AM.

                  #10
                  Originally posted by Arcanum View Post

                  Just charging it to 100% reduces the pack's lifespan. "It's only there for a little while" doesn't change that.

                  If your pack lifespan isn't particularly important to you, go ahead and charge it to 100%. You're still likely going to get quite a few hundreds of cycles out of the pack if it's good quality. Charging to a middling number and then topping it off only really matters if it's going to be sitting around unused for a while.
                  Lifespan is not a big deal for me: just like 286, 386, 486 and Pentium PCs, 2015 era batteries will be obsoleted long before they are used up! If I can ride a full 100% 20ah pack every other day, at 300/400 charges it will still last for a couple of years. Do you reckon there will be better cells on the market in March of 2018 compared to today to ease the pain of buying a replacement? Moore's Law says I can expect twice the performance for 1/2 the price so why try to squeeze every last electron out of the packs I have now: so in 10 years I can have a box of obsolete but still useable batteries to match the one filled with obsolete but still useable router and PC components in the same corner of the garage? You know, the one over by the bin of old phones, chargers and accessories that are also useless but still work.

                  Comment


                    #11
                    Originally posted by Lance Tesla View Post
                    Lifespan is not a big deal for me: just like 286, 386, 486 and Pentium PCs, 2015 era batteries...
                    100% agree! (no pun intended)

                    It's always good practice to look after your expensive tech, but lithium technology seems to be advancing at a significant pace now... and in two years we will likely see amazing capacity and output capability from sub-$300 packs that will make the current packs nearly obsolete.

                    In regards to balancing at the end of a charge, I would believe JPLabs. I have multiple lithium chargers for my RC planes/helis/cars. Those chargers will only start balancing upon recognizing that one cell (or group of cells in a series) reaches 4.20V (fully charged). I would imagine that is how the BMS functions on your battery.

                    In regards to charging lithium batteries safely overnight, it's not a bad idea to spend $3 for a pair of hollow concrete blocks at your local home improvement store. I stack two vertically on my concrete garage floor, away from combustibles, and place a lithium pack in them to charge. In the rare case your pack goes up in flames, pull up a chair and break out the marshmallows. (just kidding).

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                      #12
                      Agree w I4C and Tesla; hell...I already want me one of them new LC GA sharkies.

                      Power on, 5 amps, 100%....burn baby burn

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                        #13
                        0K, alright already, I'll give them hell on the charger, 100% every time! Good point on the way things battery related are rapidly changing, I mean what good is a pristine low mileage 1974 Ford Pinto? Better to use it up and move on as the technology improves and the prices drop. Now I'll have a clear conscious anyway, since they'll be obsolete by the time I finish posting this anyway. Unless in a hurry, I'll charge at the 3 amp rate though, but the first time I AM in a hurry it'll for sure be the 5 amp rate.

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                          #14
                          Originally posted by CPG View Post
                          0K, alright already, I'll give them hell on the charger, 100% every time!
                          Well, I'm sorry if I misguided you. Charging to 100% every time is not exactly necessary. Yes, charge to 100% once in a while, say every tenth charge, to ensure balancing. What you don't want to do, if it's preventable, is to discharge much below 20%. Of course it's not hugely detrimental to do so... but... If you predict that your next ride will use 80% of your battery's capacity, you should charge it to 100%. If you predict that your next ride will use 60% (or less) of your battery's capacity, charge it to 80 or 90%. Hope that makes sense.

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                            #15
                            I just got in from the shop, where I charged the bike I'm riding up to the ski area above me tomorrow morning to 100%. Then I put another battery for another bike on the charger, the one I use for running around (mostly level and short distances) town, and going to my mailbox 1.5 miles away, I'm charging that one 80%, I love that variable charge rate feature. I have all night so no hurry and one thing that seems to hold true for just about any battery, regardless of final state of charge reached, is to get there slowly if possible. I have yet to wrap my mind around the concept of "several hundred" charges, and what that will mean to me calendar wise, especially with 3 bikes I swap out riding. YEARS, I'm guessing. So when it's convenient and makes sense I'll charge to a lesser then full charge, but the rest of the time 100% and not worry about it. I like the wheelies I can easily do on a battery fresh off a 100% charge too much! It's great to get this feedback from others,

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