since you bought it up Im still wondering what the current draw is on the one cell at 4.2 and the other 12 at 3.5. Math formula id like to know.
if they were parallel voltage would balance but being series they stay the same voltage.
The cells are in series. So yes, you add 4 volts to the overall voltage. So you have 12 cells at 3.8 volts, and 1 cell at 4.2 volts, for a total of 50 volts. That is about the same of having 12 cells at full charge, or 4.2 volts,
Look at a figure showing the discharge rate for a 4s lipo at 25C constant discharge (Battery holds ok till 3.5 volts, then the voltage goes down a clift.
I calculate with 3.7, than itâs 4.05vđ
i mean i wonder what the math is on the current that would come from each of those 13 cells with all being the same maybe at 3.5 and one at 4.2
Actually, I have the answer for that (i guessâŚ). I use a similar setup in my onewheel, but for a 14s setup. I use 2 x 6s 6000 mAh and 1 2s2p 10,000 mAh in series for a 14s at 58 volts, that is whats the onewheel needs.
After one ride, the 2s 10,000 mAh was fully charged with 3.86 Ah, almost the same as the two 6s in parallel (7.73/2 = 3.86). I have done this one many many time, always the same. Amps hrs used for the 12s and 2s are almost always exactly the same. Keep in mind that at the end of the ride, the cells in the 6s are at about 3.7 volts, and the 2s cells are at about 3.9 volts, because the 2s have a higher capacity.
starting at the same voltage that makes sense but what about when you mix the voltage as i understood you were doing with your other vehicle where you added a 4.2 volt cell onto a bunch of 3.5 volt cells. whatâs the current draw from the different cells then with the different voltage? will the higher voltage be able to put out more of the current than others? in ratio to the voltages maybe and the high voltage will put out more is my guess. but it wouldnt be much more.
Good question. My guess is that it is the same. In the onewheel setup, after some time riding we are in that situation. The 6s and the 2s cells are at different voltages, and still the amp usage seems to be the same, because at the end of the ride the total amps hrs is exactly the same for both packs.
I actually came up with the idea of reducing the battery sag in the trampa using this trick because of these results in the oneWheel. I have been using this setup in the onewheel for a long time already. Now I might try the same trick with the onewheel⌠adding a 1s2p, and going to 15s at the end of the ride. Crazy indeed⌠In the onewheel battery sag is really an issue because of risk of nosedives when the battery is very low.
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