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can I use 2 -2S lipo batteries in series to equal a 4S output?

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  • can I use 2 -2S lipo batteries in series to equal a 4S output?

    for a freewing F 22 raptor jet which takes a 4S 2200mah 40C lipo battery . is it possible to use 2 -2S batteries example[ 2S 1300mah 20C ] hooked up in series to equal out to a 4S 2200mah 40C battery ?

  • #2
    Originally posted by F22 View Post
    for a freewing F 22 raptor jet which takes a 4S 2200mah 40C lipo battery . is it possible to use 2 -2S batteries example[ 2S 1300mah 20C ] hooked up in series to equal out to a 4S 2200mah 40C battery ?
    Parallel increases capacity and series increases voltage.

    You will need 2 - 2S 2200mAh 40C in series to equal the one 4S 2200mAh 40C
    The same 2 - 2S 2200mAh 40C in parallel are equal to one 2S 4400mAh 40C
    Warbird Charlie
    HSD Skyraider; FlightLine: Sea Fury; FMS 1400: P-40B, P-51, F4U, F6F, T-28, P-40E, 1700 F4U and a Fox glider; Freewing: A-6, P-51; VQ: P-39; Dynam: ME-262, FW-190, Waco; ASM A-26; ESM F7F-3
    Incinerator Loss 16

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    • #3
      Yes you can use 2 2's lipos is ok just make sure they are both Identical in C rating and MAH.

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      • #4
        Note that the C rating is not changed in either configuration, so your 2S batteries in series would equal one 4S 1300mAh 20C.

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        • #5
          I read a while back in one of the rc forums, to say an example, two 3S 40C making it 6S 40C, than one 6S 40C is not the same in performance.

          Need to search it up, that the 6S 40C configuration is more efficient.

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          • #6
            It really depends on how well matched the cells are across the whole assembly, in ESR (often called IR). Two batteries rated with the same C rating from the makers can have big differences in ESR (meaning the true C ratings differ). To get the best performance, you have to match the batteries, using more than the C rating printed on the label.

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            • #7
              Originally posted by crankestein View Post
              I read a while back in one of the rc forums, to say an example, two 3S 40C making it 6S 40C, than one 6S 40C is not the same in performance.

              Need to search it up, that the 6S 40C configuration is more efficient.
              Not true.

              I commonly fly planes up to 12S. Try to find a 12S 6000 pack for use at 120 amps.

              High cell count packs are actually asking the packs to fail faster when under high current demand. The cells in the middle don't get ANY cooling air and have to transfer their heat out through the surrounding cells. In my high demand applications, a set of 4 X 3S packs in series will survive over 3 years when a pair of 6S in series will be dead in 6 months.
              Even with pulling the packs from the aircraft immediately, placing on a metal table as a heat sink, the 6S would still have surface temp rising for 10 minutes after the flight while the 3S packs will peak out surface temp in under 3 minutes and at a lower temperature.

              Then we get to our foam models with relatively tight fitting packs and poor cooling air flow. You want to pull the packs out as soon as possible. because they are essentially cooking themselves in your model after the flight if you put more than 10C demand on them

              If there is any performance difference between one 4S pack and 2 * 2S in series (same C and mah ratings) then its in bad connections. I've melted EC5's 5mm BULLET CONNECTORS (not the solder, though I've melted that too in a 4mm "banana" plug) in flight due to poor contact due to wear on the connector.
              FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.

              current planes from 1/2 oz to 22 lbs

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              • #8
                Interesting, I am trying to find the thread, it was on rc car forums, and this guy is a veteran with many years in the hobby.
                Its good to know, am just starting in brushless setup so really have not spent much on battery packs yet. I prefer then to buy two 3S instead of one 6S, as I have more flexibility using the 3S on cars, and in airplanes, while on the 6S, I am limited to specific models.

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                • #9
                  The harnesses needed to just use one size pack (several packs in series/parallel on the really large models) for everything is what keeps me from going to just 2S 2000 packs.
                  Too many solder joints with each being a potential failure point to bring the plane down.

                  Each cycle of plugging and unplugging packs also wears the connectors , often with tugs on the wires, and eventually leads to a failure. It was about 300 cycles on the pack that had the EC5 melt down. The pack was nearing end of life.
                  FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.

                  current planes from 1/2 oz to 22 lbs

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                  • #10
                    Isn't using LiPo packs in series akin to using unbalanced packs, since the two packs were not balanced together?

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                    • #11
                      Originally posted by Aerobob View Post
                      Isn't using LiPo packs in series akin to using unbalanced packs, since the two packs were not balanced together?
                      While this condition is possible, if you have a good balancing charger, and both packs are freshly charged, they should be close to being balanced as a set. Or, you can charge them as one pack, using a balance adapter that puts the balance cables in series as well, which is what I have done.

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                      • #12
                        Can't see a way to put balance between cells in parallel and have it do any good.

                        The purpose of balancing is to match 2 or more cells' voltages. Cells that are paralleled WILL match voltage.

                        The standard balancing taps are for cells in series. because those can go out of balance. What we are working to prevent with balancing is 2 issues:
                        1) Highest voltage cell exceeding the pint where the cell becomes unstable and might (or will ) spontaneously ignite.
                        2) lowest voltage cell being discharged to the point that damages the cell.

                        There is a chance that a pack will NEVER go so far out of balance that there's danger of either at normal max charge level (which has a little headroom vs what the packs can tolerate if perfectly balanced) and with your LVC set high enough to prevent the low voltage issue. Even without ever balancing. I had some 3S packs that shipped without balance plugs that survived 4 years regular use and died from old age, not any issue indicating imbalance.
                        FF gliders and rubber power since 1966, CL 1970-1990, RC since 1975.

                        current planes from 1/2 oz to 22 lbs

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                        • #13
                          If mutli-cell batteries are connected in parallel, the individual cells in each pack can be out of balance, if you don't also connect the balance cables between them, so that every cell in one pack is in parallel with its mate(s) in the other. This is often done with a Y cable, so you can keep the cells in balance during both discharge and charge. This used to be more of an issue, but batteries have improved to the point that cells don't often go very far out of balance.

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                          • #14
                            Not sure if its me or what, but have noticed they get off from one another on lower C ratings.

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                            • #15
                              Lots of info on using LiPo packs in parallel, but I am asking about using them in series.

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                              • #16
                                Originally posted by bradl4648 View Post
                                Yes you can use 2 2's lipos is ok just make sure they are both Identical in C rating and MAH.
                                Aerobob; if you dont understand the above let us know.

                                JIC, yes, try to have same make, model (specs), charge/discharge/storage at the same settings as much as possible.
                                Dont fall into the habit of using one battery one say for a rc car or another airplane or any electronic device, that uses one battery and then put both in series when going flying.

                                Dont tear and wear one more than the other, have those "in series" batteries strictly for series use, NEVER use one alone. That both keep the same cycle of charge discharges. I use them all the time in series on a ARRMA Talion two 3S 4400mah 60-120c and they perform well, connectors, batteries, ESC never over heat (we are talking a esc rated at 180A). Make sure does connectors are solder well, I always apply a coat of E6000 flue over the shrink tubing for extra protection as once in a while when I pull the connectors the shrink tubing slides out, the extra glue helps me have a good grip on them.

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                                • #17
                                  Originally posted by crankestein View Post
                                  I read a while back in one of the rc forums, to say an example, two 3S 40C making it 6S 40C, than one 6S 40C is not the same in performance.

                                  Need to search it up, that the 6S 40C configuration is more efficient.
                                  Thank you

                                  Comment


                                  • #18
                                    Originally posted by WintrSol View Post

                                    While this condition is possible, if you have a good balancing charger, and both packs are freshly charged, they should be close to being balanced as a set. Or, you can charge them as one pack, using a balance adapter that puts the balance cables in series as well, which is what I have done.
                                    Thanks you for the information

                                    Comment


                                    • #19
                                      Originally posted by WintrSol View Post
                                      If mutli-cell batteries are connected in parallel, the individual cells in each pack can be out of balance, if you don't also connect the balance cables between them, so that every cell in one pack is in parallel with its mate(s) in the other. This is often done with a Y cable, so you can keep the cells in balance during both discharge and charge. This used to be more of an issue, but batteries have improved to the point that cells don't often go very far out of balance.
                                      gee never thought of the balancing plug with a Y connector ,thanks a lot

                                      Comment


                                      • #20
                                        Originally posted by crankestein View Post

                                        Aerobob; if you dont understand the above let us know.

                                        JIC, yes, try to have same make, model (specs), charge/discharge/storage at the same settings as much as possible.
                                        Dont fall into the habit of using one battery one say for a rc car or another airplane or any electronic device, that uses one battery and then put both in series when going flying.

                                        Dont tear and wear one more than the other, have those "in series" batteries strictly for series use, NEVER use one alone. That both keep the same cycle of charge discharges. I use them all the time in series on a ARRMA Talion two 3S 4400mah 60-120c and they perform well, connectors, batteries, ESC never over heat (we are talking a esc rated at 180A). Make sure does connectors are solder well, I always apply a coat of E6000 flue over the shrink tubing for extra protection as once in a while when I pull the connectors the shrink tubing slides out, the extra glue helps me have a good grip on them.
                                        wow its sure makes sense now with all this critical balancing while charging , I guess its just a easy to purchase a 4S battery to begin with , for jets especially , they like Amps, but the other guys in the club who fly giant cubs can get away with this series or parallel .thank you

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