In a simple circuit with 2 batteries and a simple load, one of them supplies 10V and the other 3V. The 3V one is reverse, in a way that the total output of batteries is 7V. Can this 3V battery be considered a resistance to the 10V?

I'm asking this cause I'm trying to get a better understanding of bipolar junctions.


  • \$\begingroup\$ No source is ideal, and this of course includes batteries. Batteries have an internal resistance that will limit current, but this will be present regardless of the polarity. However, do not do this and expect it to work well, if at all. Primary cells are not intended to run in reverse, and secondary cells might overcharge this way. You are better off adding the two and using a proper voltage regulator. I do not understand exactly how this relates to bipolar junctions. \$\endgroup\$ – BB ON Dec 3 '18 at 15:41
  • \$\begingroup\$ Thanks for the advice @BBON, but it's just theory, I'm not going to power anything. In relation to the bipolar junction, it relates in a way that a diode has a voltage drop that acts similar to a reverse battery. I'm still trying to grasp that and I really hope I'm clear enough. \$\endgroup\$ – Felipe Gonçalves Dec 3 '18 at 15:51
  • \$\begingroup\$ Also, even internal resistance is not a very real, reliable resistance, as it changes a appreciably with temperature, state of charge, and frequency. \$\endgroup\$ – anrieff Dec 3 '18 at 17:47
  • \$\begingroup\$ If current is allowed to flow in that circuit, it will flow through the 3V battery in the "wrong" direction. It will flow in the direction that tends to charge the battery rather than discharge it. What happens next depends on whether the battery is meant to be rechargeable, on how much charge it already has, on how much current is forced through it, and on how the battery is constructed. One possible answer is that hydrogen gas will be generated inside the battery, and the internal pressure will rise until the seals blow out and the battery spills its guts onto your circuit board. \$\endgroup\$ – Solomon Slow Dec 3 '18 at 18:20
  • \$\begingroup\$ 4.bp.blogspot.com/-9ZiMKYf5Q2E/T57N8gkj8wI/AAAAAAAAAEc/… \$\endgroup\$ – Solomon Slow Dec 3 '18 at 18:20

A battery isn't a resistor - it doesn't obey Ohm's law. So it's only a "resistance" in a very loose sense.

The same will apply to any other voltage source. Semiconductors aren't resistors, either.

  • \$\begingroup\$ Thanks a lot for your answer. I've been thinking about it and noted that one difference between this 3V battery and a pure resistance is that the battery doesn't dissipates power, like a resistor. \$\endgroup\$ – Felipe Gonçalves Dec 3 '18 at 16:24
  • 1
    \$\begingroup\$ But a battery will dissipate power if it is being recharged. Don't try to force ideas into categories where they don't belong. \$\endgroup\$ – Elliot Alderson Dec 3 '18 at 16:42

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