Before I ask the question, these things I know: a) If a battery operated appliance, like a radio-CD-player, has weak batteries, they are all weak. Which shows that the power is drawn off the strongest battery.
b) Therefore, I’m assuming if I put in 4 new batteries and keep 4 weak ones, that while playing, the strongest ones will supply the power until they are all the same strength.
Questions:
If I have 4 weak (1/2 strength) and 4 full-strength batteries while I’m playing, will the strong ones be charging the weak ones, so they are quickly all 3/4 strength?
What if the player is not in use? Can the strong batteries charge the weaker ones if there is no current being drawn?
Mostly not but it will depend on the load of the device vs. the internal resistance of the cells themselves which will make for little charging of weak cells if any.
Cells in most devices are connected in series which makes voltage cumulative. Voltage drop depends on load and with a purely resistive load is proportional to the portion of the total resistance that segment has of the total resistance. Batteries themselves have some resistance at the same time they are a voltage source. In any case the voltage drop of any one cell will be less than the average voltage of all the cells because the device is part of the total load.
This is kind of a difficult conept to wrap your brain around I know. Put in simplest terms if I have a battery that measures exactly 6v with no load other than an high impedance meter and I connect it to a bulb, that bulb will get less than 6v. The bulb will have high resistance so will get most of the 6v but a portion will go toward the internal resistance of battery itself.
Jumping a car battery is different because they are connected in parallel where voltage is common and current is cumulative.
This one should be obvious, no. If there is no circuit there is no current flow and no chemical reaction taking place. Cells connected inseries and not to anything else don’t do anything. A car battery is in fact six-two volt cells connected in series and put in a single housing.
It’s a bad idea to mix old and new batteries. The current is flowing in the wrong direction for any charging action to occur, even with recharcheable formulations. What will happen is that the strong batteries will attempt to push current through the weak batteries, and since the internal resistance of batteries is generally low, this current can cause significant heating, possibly causing leakage or even causing the battery to burst open. Never mix old and new batteries, or mix battery types, since you could very easily cause damage and there is a slight risk of personal injury. When you change your batteries, change them all.