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

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Discussion Overview

The discussion revolves around the configuration of four 12-volt batteries to achieve a total output of 24 volts. Participants explore different wiring cases (Case A and Case B) and their implications, including current flow and potential differences, as well as real-world considerations regarding battery performance and safety.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents Case A as their original solution for connecting the batteries to achieve 24 volts, while another suggests Case B as a possible alternative that splits the connections differently.
  • A question is raised regarding the current that can flow through a shorting wire in Case B and whether there is a potential difference between the nodes compared to Case A.
  • Another participant argues that since both cross-sections are 12 volts, current cannot flow through the shorting wire, suggesting it is redundant.
  • Concerns are expressed about the practical implications of the configurations, noting that real batteries may not all be exactly 12 volts, which could lead to large currents through internal resistances.
  • Several participants propose an alternative solution involving connecting four batteries in series, with three maintaining the same potential and one reversed, discussing the implications of voltage mismatches and overcharging risks.

Areas of Agreement / Disagreement

Participants express differing views on the viability of Case A versus Case B, with some supporting the redundancy of the shorting wire in Case B while others highlight practical issues with battery configurations. The discussion remains unresolved regarding the best approach and the implications of each case.

Contextual Notes

Participants mention limitations related to real-world battery performance, including variations in voltage and internal resistance, which are not fully addressed in the proposed configurations.

Femme_physics
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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?
 
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In case #B, what current can flow through the "shorting wire"? Is there a potential difference between the nodes it connects from case #A?
 
Oh, both crossections are 12 volts, therefor current cannot flow through there. You might say then that this wire is redundant. Yes?
 
Yes.
 
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.
 
There is another solution(which I can see) to this question. Try thinking about it...

There may be more :smile:
 
Can connect 4 in series each, 3 with the same potential coordinates, 1 in reverse :)
 
Femme_physics said:
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. :-p
 
Femme_physics said:
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.
 
  • #10
rude man said:
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).
 
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  • #11
Femme_physics said:
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.)
 

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