How can I build a battery box with a switch to toggle between 12v and 24v?

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    12v Battery Box
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Discussion Overview

The discussion centers around the construction of a battery box that allows toggling between 12V and 24V outputs using four 12V batteries. Participants explore wiring configurations, switch types, and the arrangement of batteries for charging and output purposes.

Discussion Character

  • Technical explanation
  • Exploratory
  • Debate/contested

Main Points Raised

  • One participant describes their previous experience building a similar battery box and expresses uncertainty about the switch configuration needed for toggling between voltages.
  • Another participant suggests a wiring diagram and emphasizes the need for non-shorting switches to prevent short circuits during switching.
  • A participant questions the placement of the negative output and discusses the implications of the switch connections, indicating that they initially believed more poles were necessary.
  • Further clarification is provided regarding the ground connections and the necessity of a double throw switch for one part of the circuit, while indicating that a single throw may suffice for another switch.

Areas of Agreement / Disagreement

Participants express varying levels of certainty about the switch configuration and wiring. While some aspects of the wiring are clarified, there remains uncertainty regarding the exact requirements for the switch types and the arrangement of the battery connections.

Contextual Notes

Participants discuss the implications of different switch types and configurations, but there are unresolved questions about the optimal setup for the battery box, including the specifics of the wiring diagram and the roles of the switches.

STUTS
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I have built these before, but have forgotten how I did it. I am making a battery box with four 12v batteries (7.5 Ah each). I will have only one pair of output terminals, one + and one -. Inside will be a switch to toggle between 12 and 24v. I do remember that in the 12v position all batteries could be charged (all parallel). I thought I used a dbl.pole, dbl. throw, ctr. off switch. I can't see how to do it now. Maybe it was a 4 pole switch. I know this seems simple, but I am drawing a blank right now.
Anyone have an answer? Thanks in advance. Stuts
 
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You would need to do this:

[PLAIN]http://dl.dropbox.com/u/4222062/12%20V%20-%2024%20V.PNG

The batteries are arranged in two parallel banks permanently wired together.

Note that the two switches are linked together and they need to be a non-shorting type so that the top batteries cannot be shortcircuited, even briefly, while switching.
 
Last edited by a moderator:
Dear vk6kro- Thank you. I could not find where the negative 'out' would be, unless it was any point along the ground leg. Also, the 'second' leg of the switch connected to the negative terminal of the lower batteries goes to an empty terminal for the 12v position. It seems to still work that way. I was convinced that I needed another pole to make this work. Thank you so much. R.
 
STUTS said:
Dear vk6kro- Thank you. I could not find where the negative 'out' would be, unless it was any point along the ground leg. Also, the 'second' leg of the switch connected to the negative terminal of the lower batteries goes to an empty terminal for the 12v position. It seems to still work that way. I was convinced that I needed another pole to make this work. Thank you so much. R.

Yes, that is right, anywhere that is shown as a ground connection can be taken as the negative output.
I have modified the diagram above to show this.

The right hand switch really only needs to be a single throw, but the other switch is double throw. So, the switch that goes nowhere is OK.
 

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