Originally posted by crankestein
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can I use 2 -2S lipo batteries in series to equal a 4S output?
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Originally posted by WintrSol View PostIf 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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Originally posted by fhhuber View PostCan'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.
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Originally posted by crankestein View PostIts better to use two 3S t0 make one 6S, than having a 6S...
Usually the center cells suffer from excessive heat in comparison to the outside ones which cool much quicker.
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Two new same brand 2S packs may be near identical in individual cell resistance ( IR) and perform nearly the same, in series, as one 4S pack. Two packs connected in a series harness will be slightly heavier due to additional weight of connectors and series harness.
Your pack voltage right off the charger will be around 16.8 volts. After takeoff voltage tapers off to around 3.8 volts "nominal" working voltage per cell or 15.2volts. It's best to land when voltage drops to around 15.2 volts ( 3.8 volts per cell) . 3.8 volts per cell is the recommended voltage for long term storage of lipo packs for maximum pack life. It's not good to fly until speed control's low voltage cutoff occurs. Let packs cool completely before recharging also for maximum pack life.
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