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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SUMMARY

This discussion focuses on constructing a battery box that toggles between 12V and 24V using four 12V batteries (7.5 Ah each). The configuration involves a double pole, double throw (DPDT) switch to manage the output, ensuring that all batteries can be charged in parallel when set to 12V. The design requires careful wiring to prevent short circuits during the switching process, with specific attention to the negative output connection. The consensus is that a single throw switch can suffice for one part of the circuit, simplifying the overall design.

PREREQUISITES
  • Understanding of battery configurations, specifically parallel wiring
  • Knowledge of switch types, particularly double pole, double throw (DPDT) switches
  • Basic electrical safety and circuit design principles
  • Familiarity with battery specifications, such as voltage and amp-hour ratings
NEXT STEPS
  • Research wiring diagrams for battery boxes with dual voltage outputs
  • Learn about non-shorting switch types and their applications in battery circuits
  • Explore safety measures for working with multiple battery configurations
  • Investigate the implications of using different switch types in electrical circuits
USEFUL FOR

This discussion is beneficial for hobbyists, electrical engineers, and DIY enthusiasts interested in building battery systems for various applications, particularly those requiring adjustable voltage outputs.

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.
 
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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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