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  • li-on battery

    i have a 19v li-on battery pack. will it explode if i use it without any electronics?

  • #2
    Only if you use it as a hammer.

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    • #3
      Lithium batteries are very sensitive to being over charged or over discharged. Optimum charging is a multi-step process, and each cell has to be monitored individually. With some safer variants, like LiFePO4, explosion is pretty unlikely, but it's easy to ruin the cells.

      Ed
      For just a little more, you can do it yourself!

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      • #4
        depends how careful you are charging and discharging it.

        Putting on an industrial cement mixer and then charging it with 2 12V lead acid batteries in series = problem

        Using a voltage monitor (or ear) on a medium to low power draw tool and balance charging it with a smart charger = years of explosion free service

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        • #5
          You will also destroy it if you take the individual cells below 2.5-2.7v each.

          No sure what you mean by "without any electronics"? You need to make sure you don't discharge it beyond limits, or over charge it etc. The "electronics" are cheap and easy to implement. Why wouldn't you?

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          • #6
            you know, sometimes it's actually quite hard to do unless you're working with an existing tool battery pack. I've built quite a few battery packs and finding a high draw BMS that'll fit inside an existing case with the cells is tricky. I built a nice pack for my leaf blower, 5S1P, 15 or 20A max current BMS, built in balance charging, the works. Wouldn't run the blower as the overcurrent kept tripping. It now does duty on my drill and I built a bare pack (with balance plug) to use on the leaf blower (and kitchen handivac). It doesn't get used long enough to discharge it much and I keep a keen ear out to hear if the motor is slowing down. No problems so far. Lower current loads are much easier to deal with proper BMSs however.

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            • #7
              I have built plenty of battery packs with cells taken from old drill battery packs and laptop battery packs. As long as the cells are fairly well matched in capacity and internal resistance you can use them for quite a long while with no issues. I would wire them with two connectors - one for main charge/discharge and one for balancing the series connected cell banks. Get an R/C type charger that is capable of balance charging and you're good to go. For the stuff I use the packs in I just monitor voltage and charge the packs when it's time. For stuff that my kids use them in (Power Wheels ride-on cars) I add a small cutoff circuit that kills battery output at a set voltage so they can't over-discharge the packs.

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              • #8
                Originally posted by lakeside53 View Post
                You will also destroy it if you take the individual cells below 2.5-2.7v each.

                No sure what you mean by "without any electronics"? You need to make sure you don't discharge it beyond limits, or over charge it etc. The "electronics" are cheap and easy to implement. Why wouldn't you?
                easy? i have no idea what to do, use the board below? they are larger cells than 18650. i would have to disassemble the pack and solder on the connections (iv never done that), mechanically protect the board, get a suitable power plug etc.

                im mainly concerned with accidentally leaving the pack connected. can it explode or do anything nasty, like covering the table top with acid, if it were to discarge completely?

                btw, the pack has the power wires and only two additional wires commming out. what do these do? (10k ohm).

                https://www.aliexpress.com/item/3290...archweb201603_
                Last edited by dian; 09-28-2020, 02:09 AM.

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                • #9
                  Be careful. Different variants of lithium cell chemistry have different charge and discharge voltage limits. Lithium-iron, which is pretty common, has lower charge and discharge limits.

                  Ed
                  For just a little more, you can do it yourself!

                  Comment


                  • #10
                    Be careful. Different variants of lithium cell chemistry have different charge and discharge voltage limits. Lithium-iron, which is pretty common, has lower charge and discharge limits than older lithium cells.

                    Ed
                    For just a little more, you can do it yourself!

                    Comment


                    • #11
                      you need to be a bit more specific about what you're trying to achieve. It's like saying you want to machine something round, can I do it?

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                      • #12
                        If it is a lower current item you need to power with it and provided you check the pack voltage with a meter as you use it on a fairly frequent basis to avoid going below the safe lower voltage points then you could do this. And after a few times using the pack with the same item you would get a feel for how long you could use the pack without risk of over discharging it.

                        The same applies to charging. I don't know about you but I tend to walk away and forget about things like this. No way at all that I would even consider charging the pack without a proper Li-ion format charger. The risk of gassing and bursting becomes higher when the cells are overcharged than it is of discharging too far. So you darn well should have the proper charger at least. And that doesn't always mean a proper tool charger. Some of the tool battery packs have some of the charger control circuitry built into the packs in addition to the balancing board function.

                        The link you gave to me appears to be a balancing board. It monitors the cells and if one starts to charge faster than the others it holds it back by discharging that one cell in little amounts. That way they all come up to proper charge together. But the board shown does not actually control the charging. You still need a Li-ion cell specific charger that will shut off when the pack is up to the proper full charge voltage. If you charge the pack with the wrong style of charger, or the wrong cell chemistry option in the multi option chargers, you can still overcharge the pack and ruin the cells in pretty short order.

                        Li-ion is great stuff but it comes with a price in complexity and care to ensure the cells are used within their proper range. The metal pack cells are a lot less at risk of bursting and turning into road flares than the soft "plastic bag case" style cells. But you will find that if the metal cased cells are not still used with care to stay within the voltage limits that they will not last for many charge cycles before they are no longer up to par. Either use the pack care needed or go with a different chemistry cells. The care needed can come from either you monitoring the pack and cell voltages carefully during use and charging or it can come from using the pack management circuitry options like those voltage monitoring boards and a proper Li-ion charger.
                        Chilliwack BC, Canada

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                        • #13
                          im mainly concerned with accidentally leaving the pack connected. can it explode or do anything nasty, like covering the table top with acid, if it were to discharge completely?
                          To directly answer this.... The metal cased cells are pretty durable. And discharging by itself isn't the issue. They CAN be discharged down to 0 volts. But that will certainly ruin them completely in one go. If they discharge to the lower limit and only a little more even one time you'll likely see a 10 to 15% range of damage in terms of capacity and charge holding. And with each slight over discharge the damage will pile up faster and faster. Plus as I understand it cells damaged by even slight over discharges become more prone to gassing during the subsequent charging. And in that case if the vents do not release the gas the cells will puff out and possibly split open. If that occurs there is a small potential that the escaping gases will ignite due to the damage allowing a short circuit and the cells can turn into road flares.

                          It's more of an issue with the plastic cased flat format lithium polymer cells. But without proper care to observed lower and upper voltage limits during use and charging I would not be surprised to see that metal cased cells can do this too.
                          Chilliwack BC, Canada

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                          • #14
                            I am not a battery guru, but I can tell you that uncontrolled overcharging can result in what is laughingly called "unexpected venting with flame" by the flashlight collecting community. There is nothing like a 2 foot flame in your garage in the middle of the night to convince you to use commercial designs.
                            At the end of the project, there is a profound difference between spare parts and left over parts.

                            Location: SF East Bay.

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                            • #15
                              You tube has a bunch of videos of "venting with flames". And a number of them also include the conditions and methods that led to the "event". A lot of those will be due to charging and discharging outside of the proper limits for these cells. If you can't ensure you can stay within those limits with great zeal it's best to look at other options.
                              Chilliwack BC, Canada

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