What would happen if you let a full battery charge an empty

[stargazer193857]

Suppose you have a full battery and an empty one, both the same type, and you hook up positive to positive and negative to negative, and for this particular battery chemistry, the difference in voltage is great enough to commence charging of the negative one. How much current would likely travel between them? Wire melting / battery cooking current, or a more controlled rate of discharge / recharge?

 

[stargazer193857]

Well, mrBigGuy told me by PM that a similar set up would go ka-bam.
So I will not try that myself.
But I would really like to see a you-tube video of someone else doing it. I know there has to be someone who tried it, given all the skateboard crashes on you tube. But what keywords to use.
Anyone want to link me to such a video of one battery charging another and exploding?

 

[stargazer193857]

Never mind. No You-Tube video is needed. I now fully believe how dangerous it is. Probably a much safer way to do it is to put a resister between the batteries scaled to the voltage difference, and put a heat sink on the resister. I thought of that idea before, but I abandoned it because of a silly math error. Suppose the voltage difference is 1.5v and a 3 Ohm resister is used to get 0.5 amps. I then calculated the voltage drop across the resister: V = IR = 0.5 x 3 = 1.5v. I incorrectly concluded that the 1.5v drop across the resister would consume the whole 1.5v difference between them, preventing any charging. After thinking about that some more, and now realize the 1.5v drop is the same drop that was there before, and current would still be 0.5A (and decreasing). If the current were somehow zero, the resister voltage drop would decrease to zero, contradicting the assumption.

Of course I'd never play with something like this. I'm just trying to understand the physics.

 

[berkeman]

Thread is closed.

 

[alphy]

The amount of current that would travel between the two batteries depends on several factors, including the type of battery and its chemistry, the size of the batteries, and the resistance of the wires connecting them. In general, when connecting a full battery to an empty one, the current flow will be high initially as the empty battery attempts to catch up to the charge level of the full battery. This could potentially cause the wires to melt or the batteries to overheat if the current is too high.

However, most modern batteries have built-in safety mechanisms to prevent this type of overcharging. They may have internal resistance or circuitry that limits the flow of current, preventing the wires from melting or the batteries from overheating. In this case, the charging process would be more controlled and the batteries would recharge at a slower, safer rate.

It is important to note that attempting to charge a battery with a significantly higher voltage than its own can be dangerous and may cause damage to the battery or other equipment. It is always best to use batteries and chargers that are specifically designed and rated for each other to prevent potential hazards.