Connecting 4 Batteries for 24V: Case A vs Case B

[Femme_physics]

Given are 4 batteries whose value for each is 12 volts. Connect all 4 batteries in such a way so you can get a general voltage o 24Volts


http://img208.imageshack.us/img208/4452/kasht.jpg


Case#A is my original solution

My classmate asked me why not case#B...I think it also possible, it just splits the corrects differently. Is that right?

 

[gneill]

In case #B, what current can flow through the "shorting wire"? Is there a potential difference between the nodes it connects from case #A?

 

[Femme_physics]

Oh, both crossections are 12 volts, therefor current cannot flow through there. You might say then that this wire is redundant. Yes?

 

[I like Serena]

Yes.

 

[rude man]

In real life you could not do this, since batteries are not all exactly 12V. So you'd be causing a large current to flow thru the internal resistances of the batteries equal to ΔV/R where ΔV is the difference in voltage and R is the sum of internal resistances.

 

[Infinitum]

There is another solution(which I can see) to this question. Try thinking about it...

There may be more

 

[Femme_physics]

Can connect 4 in series each, 3 with the same potential coordinates, 1 in reverse :)

 

[Infinitum]

Can connect 4 in series each, 3 with the same potential coordinates, 1 in reverse :)

Yep! This is the one I thought of when I saw the thread title...

And I'm not creative enough to find yet another solution. Maybe I can disprove its existence.

 

[rude man]

Can connect 4 in series each, 3 with the same potential coordinates, 1 in reverse :)

Right, and this way there's no problem with voltage mismatches.

 

[rcgldr]

In real life you could not do this, since batteries are not all exactly 12V. So you'd be causing a large current to flow thru the internal resistances of the batteries equal to ΔV/R where ΔV is the difference in voltage and R is the sum of internal resistances.

Actually the first setup (case A) shown in the OP is done with some li-po battery packs used in radio control models. There's a second set of connectors used to balance the batteries during or after charging so the voltage between cells is equalized (at least at the start of usage).

 

[NascentOxygen]

Can connect 4 in series each, 3 with the same potential coordinates, 1 in reverse :)

Sure, for a short while you can do that, but generally not advisable in the long term. The "reversed" battery is constantly being charged by the others, so expect it to object to becoming overcharged. (Both primary and secondary cells will not like being the reversed one in the string.)