martin collins 1 Posted September 24, 2021 Share Posted September 24, 2021 Ideally exactly the same is the obvious answer but i have two packs here freshly charged and balanced, pack 1 reads 25.05v and pack 2 reads 25.09v is this close enough or is a meltdown on the cards? Quote Link to comment Share on other sites More sharing options...
Alan Hilton Posted September 24, 2021 Share Posted September 24, 2021 I suspect that the difference is well inside the error of the monitor ,so no problem .You will probably find more difference shown between cell voltages on a balanced charged pack Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted September 24, 2021 Share Posted September 24, 2021 Ideally, parallel charge and use them with the balance leads Y leaded but that difference is minimal. Quote Link to comment Share on other sites More sharing options...
MattyB Posted September 24, 2021 Share Posted September 24, 2021 I generally make sure they are within 0.1v when parallel charging or discharging, but 0.2V is still probably ok given the fairly meaty connectors we use. One key point when charging in parallel using a charge board is always to connect all the main connectors first before the balance leads, that way any momentary current spikes will not pass through (and potentially damage) the balance wires which are not suitable for anything over about 1A. Quote Link to comment Share on other sites More sharing options...
Mike Blandford Posted September 24, 2021 Share Posted September 24, 2021 Consider the resistance of the circuit. You have two batteries, what is their internal resistance? With 6 cells then several milliohms (say 5). Then each ground and power connection goes through a connector. Unlikely to be less than 1 milliohm each, so another 4 milliohms. This gives a total of, at least 14 milliohms. (I'm being generous here, the resistances are likely to be higher, and I haven't included any wire resistance). Your voltage difference is 40 milliohms, so the higher voltage battery will charge the other at around 3 amps (40/14). As soon as this starts the higher voltage battery will drop in voltage and the other will rise in voltage, so the current will rapidly reduce. I regularly use 2, 4-cell batteries in parallel with no problem. Other than they are fully charged, I don't check their exact voltages. I normally charge them using a dual charger, so their voltage is measured by two, different circuits. Mike Quote Link to comment Share on other sites More sharing options...
martin collins 1 Posted September 24, 2021 Author Share Posted September 24, 2021 I won`t be charging in parallel, just using them like that, i have 4 chargers (all the same make) so i don`t need to parallel charge. Quote Link to comment Share on other sites More sharing options...
Martin McIntosh Posted September 25, 2021 Share Posted September 25, 2021 It will have no noticeable effect, just the same as using a commercial Xs2P pack. The two batteries will balance the moment they are connected in parallel. I sometimes even do this with NiMh`s. Quote Link to comment Share on other sites More sharing options...
John Stainforth Posted September 26, 2021 Share Posted September 26, 2021 The Spektrum website actually recommends using several batteries in parallel as a best practice: "DO USE A SECOND BATTERY ON YOUR MOST VALUABLE AIRCRAFT. While all Spektrum 9-channel-and-above receivers have multiple battery ports, you can actually put multiple batteries into any Spektrum receiver. Simply choose two batteries of the same size and capacity with two switches." Quote Link to comment Share on other sites More sharing options...
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